Planetary Radio • Nov 13, 2019

A Spirited Conversation with Carolyn Porco

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Jay Pasachoff

Field Memorial Professor of Astronomy for Williams College

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Carolyn Porco

Cassini Imaging Science Team Leader for UC Berkeley Visiting Scholar

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

The outspoken planetary scientist who led the Cassini imaging team finally sits down with Mat Kaplan for a revealing, fun conversation. We also talk with astronomer Jay Pasachoff while he watches tiny Mercury crawl across the face of the Sun. Chief scientist Bruce Betts was in the Planetary Society parking lot enjoying the November 11th transit of Mercury. He joins us from there for What’s Up.

Cassini's 'Last Dance': A final portrait at Saturn
Cassini's 'Last Dance': A final portrait at Saturn In the early afternoon of 13 September 2017, the venerable and much-loved Cassini probe captured this final portrait of Saturn and its main ring system, before plummeting to fiery destruction in the planet's hazy atmosphere just 48 hours later. Using its Wide-Angle Camera (part of the Imaging Science Subsystem), Cassini snapped 75 photos: these images can be grouped into a grid of 6 by 2. Each footprint in that grid was covered with both long and short exposures via the red, green, and blue filters, plus a longer exposure shuttered through the clear filter. The veteran spacecraft took nearly two hours to collect these data: starting at 1:09 PM and concluding at 3:17 PM (all times are UTC). Only three moons—Enceladus, Janus and Mimas—can be picked out in the uncalibrated and compressed data.Image: NASA / JPL-Caltech / SSI / Ian Regan

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Mat Kaplan: [00:00:00] Our first ever conversation with Carolyn Porco and the transit of Mercury this week on Planetary Radio. Welcome. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. She is one of the best known planetary scientists on our planet. A leader of the imaging community for decades and she doesn't shy away from controversy. And it's about time she was our guest. Join me for a revealing, funny and often, profound interview. Did you catch the transit? Bruce Betts did.

I talked with my WhatsApp partner as he watched tiny Mercury crawl across the face of the sun on the 11th of November. High above Southern California, the man who may be the greatest living eclipse and transit chaser was at the Big Bear Solar Observatory that week as he did in August of 2017. Jay Pasachoff is field [00:01:00] memorial professor of astronomy at Williams College. But he travels the world studying phenomena like this transit. I reached him on his mobile phone moments after he exited his car next to Big Bear Lake.

Jay Pasachoff: All right. We're just arriving at the observatory. Well, some people have been here already. Just a second. Uh, would you, would you carry this? Yes, please.

Mat Kaplan: Are you under the dome yet?

Jay Pasachoff: Uh, no. Just approaching the dome now. And we've been meeting and organizing and some people have been here already this morning.

Mat Kaplan: That's great. How are the, how are the skies?

Jay Pasachoff: Oh, perfect. Absolutely perfect.

Mat Kaplan: You're not looking at the sun I know, not yet. Because you're too smart to do that without protection. But [laughs] you're, you're walking out on that spit of land, uh, out toward the dome?

Jay Pasachoff: Yeah. Yeah. We are on the, uh, Causeway and cameras are up there. Hello, Bryan. You have acquired the sun and just ... So to the, the porch yet. So many telescopes here. And Ben Snyder from Arizona, you know, so Arizona's here. And, and he's under way.

Mat Kaplan: It sounds like a [00:02:00] transit party.

Jay Pasachoff: Yeah. A, a dozen people at dinner last night. It was very nice.

Mat Kaplan: Well, you wait your turn. I, I assume you're going to be at an eye piece, uh, before too long. And you can tell us what you see.

Jay Pasachoff: No. No. We only have a video images at the moment.

Mat Kaplan: What do you see?

Jay Pasachoff: Well, I see a tiny dot.

Mat Kaplan: [laughs] That's good. [laughs] That's terrific.

Jay Pasachoff: Just in the right size. No sun spots today because it looks real solemn in a month. We're seeing about half of it here from California. But when we move into the big telescope, it will be many, many pixels across. It's very dramatic so that's why we're doing this from California. I do have, uh, one of my students, Christian Lockwood is at the Embry–Riddle Aeronautical University in Daytona Beach, Florida with some other, uh, cameras and telescopes to try to see the whole transit there.

And in liaison with people in, in Chile who can see the whole transit. And we're trying to compare [00:03:00] with some people in Germany. But I gather it was cloudy there this morning.

Mat Kaplan: Oh. As it is here unfortunately where I am. I'm hoping the clouds will still burn off while I, we'll have a chance to, uh, see that little black dot go across the face of the sun.

Jay Pasachoff: Well, this is good luck. I, I did arrange for the [inaudible 00:03:17] Robinson Hall the, Linde Center at Caltech to be available.

Mat Kaplan: That's great. Uh, while I have you, uh, please remind us why scientists like yourself still get so excited about transits other than the fact that it's just thrilling to see something like this happen whe- when it happens so rarely.

Jay Pasachoff: Well, uh, it is, uh, it was a conservation in 1631 when Pierre Gassendi in France saw a transit that Johannes Kepler had predicting using his new laws of orbits that really proved that Kepler was right and Copernicus was right. And now we can do other things. Ben Snyder and, and I have started looking at transits of Mercury back in 1999. [00:04:00] And Michelle, uh, for example, historically, that, uh, at the edge of the sun, you can see an effect not as a backdrop effect.

But in the past, like the people have mistakenly to think that they had discovered the atmosphere of Venus. Whereas really it was this effect that we've been setting. So we, we always try to see that and do better. And then, it's, it's time to measure the distance between the earth and the sun, which of course we've known already. But there's, we recreate this by a building from distance, uh, locations on earth.

And then the people in space craft, uh, then calibrate how, uh, how sharp their, uh, imaging is when they have a good distant object of a known size against a background that they're looking at when they look at the sun. So there are a whole lot of reasons to still look at the transits of Mercury.

Mat Kaplan: Other than the fact that it's still so exciting, you, you've still do get a big kick out of this, don't you?

Jay Pasachoff: Oh, yes. It certainly is, uh, very [00:05:00] good. And in addition to the scientific team I'm working with, we brought my daughter, Deborah, uh, Pasachoff and grandchildren, Lily Kutner and Jakob Kutner who were ages, uh, nine and seven. Uh, we hope to excite them and, uh, in the next generation to see this event and see the big telescope.

Mat Kaplan: Jay, I wish I was with you in that beautiful spot at the Big Bear Solar Observatory. Thanks for checking in with us. And, uh, I hope the skies stay clear and you get a great view from, uh, the big telescope under the dome up there.

Jay Pasachoff: Thank you very much and I hope a lot of your listeners are able to, uh, see the transit. I do have a web page. It's, INFO, .info but once you click on, there are links to the 2016 transit of Mercury. And, and then for today, we'll try to post some stuff as soon as possible. But also, if you look at the 2016, you could see the quality of what we can see with this Big Bear huge telescope.

Mat Kaplan: Excellent and we'll put [00:06:00] that link on the episode page as well

Jay Pasachoff: Good.

Mat Kaplan: Uh, Thanks, Jay.

Jay Pasachoff: Good to talk to you.

Mat Kaplan: Nice to talk to you. Bye-bye.

Jay Pasachoff: So long, so long, Mat.

Mat Kaplan: Jay Pasachoff studying and enjoying the transit of Mercury across the face of the sun on Monday, November 11. Just time for a quick look at the down link Planetary Society editorial director, Jason Davis' digest of planetary science and mission news. In honor of Carolyn Porco and the entire Voyager mission team, will start with the publication of five new research papers based on Voyager 2's passage into interstellar space a year ago. The twin space craft have now been out there 42 years. China has delayed the ambitious Chang'e 5 sample return mission.

It's now expected to leave for the moon in late 2020. And if you haven't seen it yet, check out the gorgeous panorama of the Southern sky created by TESS, the Transiting Exoplanet [00:07:00] Survey Satellite. It's made from 208 separate snapshots. This and more or at Carolyn Porco is one of those people who can make an hour or more fly by and leave you wanting more. It's not just that she has great stories to tell. Stories about her leadership of the Cassini imaging team across the Saturn Explorer's long mission.

About her earlier involvement with the Voyager spacecraft and the fascinating origin of the pale blue dot. About her colleague and friend, Planetary Society co-founder, Carl Sagan and even about the part she played in the creation of contact. The magnificent film based on Sagan's only novel. Know it's also her persona, humor and feistiness, her word that have made her such a popular science commentator. Settle in for a rollicking good time. This is more over due, this conversation than any [00:08:00] other I can think of except there's still a few other people I'd love to get on this show.

But you should have been on a long time ago. Thank you for coming to Planetary Society headquarters for a conversation.

Carolyn Porco: Well, thanks for having me finally. [laughing] I'm here. I'm here, finally.

Mat Kaplan: That's what counts. Uh, I'm a little anxious because you're a pretty good podcast host yourself. I caught you on Neil Tyson's show talking to none other than Sean Ono Lennon.

Carolyn Porco: Yeah. We were, uh, hanging out for a while. He's, was, uh, very interested in science. And, um, you know, one thing led to another and he came on StarTalk All-Stars.

Mat Kaplan: Yeah. Yeah.

Carolyn Porco: I was an All-Stars host. And he also did a StarTalk live, uh, in New York City with me.

Mat Kaplan: I heard that one, too.

Carolyn Porco: Yeah. That was fun.

Mat Kaplan: With, with him. Yeah.

Carolyn Porco: That, that was a lot of fun. Yeah.

Mat Kaplan: Yeah. He's, uh, one of these people who, not a scientist. I mean, like me, not, with all the line not. A musician much less, the son of, of an even more famous one. Uh, but he know his stuff. He obviously loves [00:09:00] talking to you about the stuff that you have spent decades doing.

Carolyn Porco: He's very intellectual. He's, he's hip. He's very up. It was great to, great getting to know him.

Mat Kaplan: Thank you for all the great pictures.

Carolyn Porco: Oh, those are my babies. Those are literally, those I, they feel like, I, I'm sure the way I feel about what we did with Cassini and all those beautiful images. It's the way [laughs] parents feel about their kids. It was such a joy and a privilege to do that. I felt like we were the, it was our duty to return the visual record of our travels around Saturn. And that's ho- kind of how I looked at the job, how I presented it in anything I wrote about Cassini on my website or so on. Like the, it was the romantic adventure I wanted people to, to feel in their, in their gut.

Mat Kaplan: It was romantic.

Carolyn Porco: It was. It was romantic.

Mat Kaplan: And, and your duty, I like that to get these out and to share them with the world.

Carolyn Porco: Well, yeah. Remember, I got started in this business on [00:10:00] Voyager. Voyager's where everything began as far as I'm concerned and I, uh, I've said many times I've led a charmed existence. And part of that was having as my first professional assignment right out of graduate school to be a member of the most iconic, far-reaching, historically significant, uh, I mean, on and on it goes, mission of them all and that was Voyager.

Mat Kaplan: I haven't shown you yet but just the other side of the wall behind you here are four posters. One of them is our own light sale but it was, uh, we were asked by a partner who does wonderful graphics. He wanted to determine the three most popular planetary science missions of all time. And so we helped him out. We did the polling for him. Of those three, two are Voyager and Cassini.

Carolyn Porco: Of course.

Mat Kaplan: The third being Curiosity on Mars. Not surprising, is it?

Carolyn Porco: No, not surprising at all to me. Everybody loves Voyager. Well, [00:11:00] I give a talk and I even, in a talk about Cassini and I mentioned Voyager, people clap.

Mat Kaplan: [laughs]

Carolyn Porco: I mean, they realize, they realize, it was, it was, um, God, it had all the elements, you know. And not only was the, the journey into forever and, and of course, that was underscored by the v- the record, which of course, Carl led the development of the Voyager record that had symbols of us really.

Mat Kaplan: Yeah.

Carolyn Porco: Had tokens of us in it. So it really felt like, oh, all of us in, on this spacecraft, making our way across the solar system and into interstellar space. Uh, it had that wonderful lookback of our own planet to say goodbye and then it spun on its heels and headed off into eternity. Uh, but it also was the grand adventure that really showed us in detail what our solar system was like. [00:12:00] Because if you think about it, most of our solar system resides behind the orbits of the asteroids. That's where most of the masses-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... Uh, or if you want to even talk about the volume that the planetary orbits carve out in a sense, it's all beyond the orbits of the asteroids. It's in the outer solar system. So we didn't know what our solar system looked like until Voyager passed Jupiter, Saturn, Uranus and Neptune. And it was, uh, it, it's so hard to describe what it was like to be in on that mission. Every single thing was new. And you knew, we knew, I knew. At the time, I knew that, that this was absolutely historic. I'd have these moments when I was in imaging team meetings.

And I became an official member in October of 1983 when I went to work for Brad Smith at the University-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... Of Arizona-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... Right out of graduate school. So I participated in all the planning from then on for Uranus and [00:13:00] Neptune. And I'm, just remember times when the conversation might have turned to something that I wasn't intimately involved in. And so maybe I dozed off or I was daydreaming. But I'd have these moments where I'm, I felt like I was hovering above watching this group of people talk about what was going to happen clear across the solar system.

Mat Kaplan: [laughs]

Carolyn Porco: And it was, it's something out of science fiction.

Mat Kaplan: Yeah.

Carolyn Porco: But it wasn't. It was real. And, and it was happening. And it, it was such a rush. It was a rush as it was happening. We knew as it was happening, we were doing something historic. You can only explore the solar system for the first time once, right? That only happens once. And so, just the mission itself, what it was going to accomplish, what it was going to say about us. Plus of course, it had Carl as a member of-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... The team and he just was so capable and eloquent of reaching people and letting [00:14:00] them know the significance of this mission. In a way that scientists just were not doing at that time.

Mat Kaplan: Yeah.

Carolyn Porco: I also attribute part of the love for Voyager to Brad Smith who was the imaging team leader. And he also was eloquent in the, in the press conferences and, uh, classy, uh, and it didn't hurt that he had movie star good looks. [laughing] I mean, you know, he was commanding and witty. So it had all those wonderful features and for all those reasons, people really resonated with it. So it does not surprise me that it ranks up there as the most popular mission. I think to me, it is the Apollo 11 of the planetary program.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: It has that kind of iconic stature. And it doesn't matter that there would be missions that will be more profoundly scientific than, uh, scientifically productive than Voyager. Cassini is one of them. We went deeper. We went in greater [00:15:00] detail. We went more comprehensive at Saturn than Voyager could. Uh, it doesn't matter. It was the first and it was a beautiful first. And like I said, it would, it, uh, uh, provided people such a, a touchstone into their, their cosmic significance. That it's just very beloved. And then of course, Cassini was spectacular to the nth degree.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And we carried better instruments. We were better prepared.

Mat Kaplan: Because of Voyager.

Carolyn Porco: Oh, yeah. Because of Voyager. I mean, even things like figuring out what exposure times in our cameras had to be, was a challenge. But it was nothing like Voyager. I mean, Voyager, we, you know, we didn't know, we were finding new things and figuring out what the exposures had to be was, was a big deal. You know, you didn't want to waste a lot of images taking multiple exposures. But that was a challenge but after we knew roughly what the reflectivity of surfaces were and brightness and so on, on Cassini, [00:16:00] we were much better prepared to put those, that information into models.

Put the models into our software and figure out how to command the cameras. That's the stuff that went on in my shop at Cyclops. We developed all that software for commanding the cameras. You would think that as scientists, we would be so objective and almost cold about the whole thing.

Mat Kaplan: I would not but many people do.

Carolyn Porco: And we were not. [laughing] Oh, certainly, you know, I would look at a picture and just be so amazed. The beauty of it, that's what always would knock me for a loop is just how beautiful it was-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... And how detailed. We, we had a great camera system and it just, uh, really served us well.

Mat Kaplan: Those images. We continue to get great science out of the images, out of the data from that mission. But they are simply awe-inspiring.

Carolyn Porco: Well, okay. So we can't take all the credit for that because Saturn is, you know, the most [00:17:00] beautiful system, the most beautiful planet. It's a, it's iconic, you see. You know, when, when do you see anyone like in science fiction trying to portray a planet in another stellar system and doing so without a ring?

Mat Kaplan: Yeah. [laughs] You're right.

Carolyn Porco: You know, uh, every, it always has a ring around it because it's so supernatural looking.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: That ring is so precise. It is mathematically precise. So it almost defies our concept of what Mother Nature is. Mother Nature is sort of around, on earth, it's sort of soft and, and fluffy and, you know, things aren't, everything's on a continuum. You don't see things bounded to sharp precision unless a human got in there and did it. Well, Mother Nature did this with Saturn's rings. And it's, and it's just beautiful. That, you know, they dazzle from every angle no matter how you look at them.

And so surprising, you know, we did this, deliberately, I planned this sequence to look at the rings as Cassini was passing through [00:18:00] the ring plain.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: So you got to see them. You're looking from above the rings and you got to see them. Turn over, turn over, then you're in the ring plain then you see them from below. That is one of my, it's simple as can be. But that's one of my most favorite video clips. Because you just have a hard time believing that it's natural.

Mat Kaplan: A- at one angle, they're lit from the front, from behind Cassini. I, no, wait.

Carolyn Porco: No. At one angle, they're lit directly from the sun.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Okay. And that at the other angle, when you're below the ring plain, or on, well, when you're on the opposite side of the sun, then they're, l- you see them only because light diffuses down through the rings, the ring plain. It gets scattered among the ring particles and comes out.

Mat Kaplan: That's what I was getting at.

Carolyn Porco: Yeah.

Mat Kaplan: And basically, they're back lit.

Carolyn Porco: They're back lit.

Mat Kaplan: But they're huge because the ring itself is shaping the light.

Carolyn Porco: Uh, it's scattering it and that-

Mat Kaplan: Yeah.

Carolyn Porco: ... It's like looking through a screen in some parts of the, and some parts of the rings. It's like looking through a screen. It's, when you're in that geometry, if the [00:19:00] ring is really thick, so that not much light gets through-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... It can be hard to tell the difference between a thick ring and empty space. That's when you really got to like put on your scientific hat to try to figure it all out. But, you know, what, my point is, before you even get there, it's just this smorgasbord of incredible, beautiful sights. And the public loves color. I'd, I'd like to tell a little anecdote about Voyager.

Mat Kaplan: Please, yeah.

Carolyn Porco: In Voyager days and my days were post Saturn so it was Uranus and Neptune. So this was, you know, 1983, late 1983 to 1989. I had seen as a graduate student press conferences after the Voyager Saturn fly-by's. And there was a member of the press corp who had, was also an amateur astronomer. His name was Andrew Young.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And he got on the case of the Voyager imaging team for not producing the images in true color. And I agreed with [00:20:00] him. I was kind of aghast as it was going on that, that images were thrown together so sloppily. Uh, of course, you have to understand this thing that we did, that I did with the Cassini cameras. And deliberately process images everyday for a, a long period of time. My job was to get an image out every single day and a caption to it every single day. This was like running a news magazine-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... A daily news magazine. They didn't do that on Voyager. At Voyager, the images were processed solely for press conferences. So it was only during that brief period of time like a week, 10 days around fly-by's that people were, and this I think the image processors in those days were at JPL. They were madly throwing it together.

Mat Kaplan: I know some stories about that guy. I, I've met a couple of those.

Carolyn Porco: Yeah.

Mat Kaplan: Some of them very young.

Carolyn Porco: Yeah. So they, they were throwing together images, uh, just so the scientist would have something to present at a press conference. But I remember [00:21:00] Andrew Young. I remember his criticism. I totally agreed with him, uh, that it could be done so much better. When I was chosen to be the imaging team leader for Cassini, that was one of my cardinal things. We were going to do a far better job processing images. I was going to take great care in that. I was going to produce them in true color to the extent possible. Because that is an enormous challenge. And you never could really get there.

And I was going to take another one of my cardinal quests. Uh, in the beginning is that we were going to take every opportunity we could to produce images just because they were beautiful and also to produce video clips. We were going to have, I mean, we're going to a dynamic system. I wanted to turn the camera as much as possible into a, a video recorder.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Uh, and so, we did that, too and all that stuff was immensely popular.

Mat Kaplan: And that's still paying off. I mean, there is that feature film, which, uh, I think is out now. I actually contributed to [00:22:00] it. It's Through the Rings of Saturn, I think. I'll have to check the title. But using your images that are all genuine.

Carolyn Porco: Well, who produced it?

Mat Kaplan: I cannot remember the guy's name but I haven't been in touch with him for several years.

Carolyn Porco: Is this, is this the one where its just a, a sequence of rapid sequence of raw images?

Mat Kaplan: Uh, no. I don't think so. I don't think so.

Carolyn Porco: That's pretty cool, too. If you just look at our raw and even the, even though the, you know, the flaws of the camera were not removed, like I said, it was a visual record of our travels. That's what I felt like we were doing.

Mat Kaplan: You mentioned just in passing though you didn't refer to it this way. The image that i- is so iconic to all of us here and other people around the world. Uh, the pale blue dot.

Carolyn Porco: Yeah.

Mat Kaplan: Because you apparently had a part in that.

Carolyn Porco: Yeah, I know. It's, it's not often, uh, mentioned. But that's why these days are making it clear that it w- it was, Carl deserves absolutely full credit for making it happen. But, but I know that I, as soon as I was added to the imaging team in late [00:23:00] '83, was starting to hawk around the idea that we should turn the spacecraft around and take a picture of the earth and the other planets.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Just because it would be a wonderful thing to see our planet from afar and I also thought, wouldn't it be cool to show what our solar system would look like to an alien coming in from outside?

Mat Kaplan: Yeah.

Carolyn Porco: You know, new perspective. It's, it's all about perspective. I remember vividly walking into Brad Smith's office. So this could have been late '83, early '84 and saying to him, "You know, I think it would be really good to take a picture of the earth and the other planets." And he said, "Well, if you got," right away, right off the bat, it wasn't, "Oh, what a crazy idea. It was, oh, I don't know if they'd let us-

Mat Kaplan: Huh?

Carolyn Porco: ... Do that? He said, right off the bat, he said, "Well, you know, if you're going to do that, you have to turn the space craft so that you put the sun from the point of view of the cameras. You put the sun behind the high gain antenna. So that [00:24:00] you don't get any sunlight on the camera detector. Because if you're going to image the earth from the outer solar system, the earth is going to be very close to the sun."

Mat Kaplan: Yeah. Yeah.

Carolyn Porco: ... "And, and you burn the cameras out." So as far as I'm concerned, he's the one who came up with that idea. And then, I started probably in '84. You know, our imaging team meetings were three times a year. So it could have been early '84 like the next team meeting I went to that I went around talking to people. Seeing if this was possible and I know there was tremendous skepticism and I know-

Mat Kaplan: The resistance, right?

Carolyn Porco: Well, it wasn't at the level, uh, that, a resistance, yeah. I mean, just-

Mat Kaplan: [laughs]

Carolyn Porco: In a word, I'll say, there was resistance to it. And I was surprised but even Ed Stone said, in his very gentlemanly way, he said, "Well, you know, you, you're probably not going to be able to do that unless you could find any science in it."

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: You know, just to take a picture of [00:25:00] earth, they wouldn't, uh, allow that to happen. The, the project wouldn't allow that to happen. Now let me s- let me just parenthetically say here. Voyager was one of those missions and it's early enough that it was just absolutely sacred that you always kep the high gain antenna pointing to the earth and had a constant link with the earth. Because if it was feared the spacecraft was taken off for its line, you might not be able to get it back.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: So it wasn't like we're going to take the spacecraft off for its line. Just for something like this. You better have a really good reason for it. I was a new team member. And I wasn't in the, the mode of like trying to be the little, uh, David to the big Goliath.

Mat Kaplan: [laughs]

Carolyn Porco: So I went off and thought, well, I, I thought about science taking a picture when I knew the earth was going to be a pixel. Actually now, there could have been science in it. But, uh, I, I couldn't think of [00:26:00] anything then until I went off and came up with the idea to try to get, capture the dustpans, the, the dustpans-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... That had just been discovered in the asteroid belt by the IRAS spacecraft. Uh, and so, that's what I ended up doing. That's the observation I ended up doing. But I guess it was the asteroid belt was far enough away from the sun that it wasn't a problem. All I'm saying is, I come up with this idea. Tried to get people interested in it and it didn't work. So sometime in 1988, I hear that Carl is, is hawking this idea around, too. He could have thought of it long, long before. But I'm hearing that he's pushing this idea now.

I think I might have written him a letter, uh, that said, I learned that you're trying to do this. I tried to do this a while ago and didn't get anywhere. I really think this should be done. And he responded basically, "Great. Help me." [laughing] You know, why don't you come aboard and help? [00:27:00] So he put me in charge of figuring out what the exposure times for the-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... Images should be, uh, and I wrote him back. I, I did some calculations, uh, and wrote him back. Uh, sent them to him. It was a lot of work for him to do it. He had the cloud, uh, and he could maneuver politically to get it done. He had to-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... Go all the way to NASA headquarters.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And I, I just learned recently that Ed Stone accompanied him. So he was successful convincing Ed Stone.

Mat Kaplan: Oh.

Carolyn Porco: And they went to NASA headquarters to, to basically get NASA to direct JPL to do it. But, uh, it was, you know, we waited until the whole entire planetary part of the mission was over. So this was, it happened in February of 1990. So the mission, Neptune encounter was over in August of 1989. And as you know, it became an incredibly popular image. Even though it's not much of an image to look at, uh, it was incredibly popular [00:28:00] and even the phrase, pale blue dot has become-

Mat Kaplan: Yeah.

Carolyn Porco: ... Now synonymous with planetary brotherhood and protection of the environment.

Mat Kaplan: I use it all the time on, on this show.

Carolyn Porco: That phrase.

Mat Kaplan: Yeah.

Carolyn Porco: Well, you're not the only one.

Mat Kaplan: No. [laughs] We've got much more of Carolyn Porco including that time we all waved at Saturn. Stay with us.

Kate Howells: The Planetary Society is building the ultimate list of life goals for space fans. And we need your help. Hi. I'm Kate Howells, Community Engagement Leader for the society. What's on your list? The must see objects in the night sky, the most awe-inspiring destinations, the experiences of a lifetime. Tell us about them at We'll share them with your space soulmates around the world. That's Thanks.

Mat Kaplan: On the back of my old business card, I have that other iconic image that you had even more to do with-

Carolyn Porco: Oh.

Mat Kaplan: Of earth [00:29:00] seen-

Carolyn Porco: Seen from Cassini.

Mat Kaplan: ... From Cassini, exactly.

Carolyn Porco: With the rings.

Mat Kaplan: With the rings.

Carolyn Porco: The zoomed in version I hope, which is the real beautiful one.

Mat Kaplan: Yes.

Carolyn Porco: Yes.

Mat Kaplan: And I, I mean, for that matter, I was also at JPL waving at Saturn and smiling-

Carolyn Porco: Okay.

Mat Kaplan: ... When you did that one.

Carolyn Porco: Yeah.

Mat Kaplan: This stuff strikes a chord with pretty much everybody. Whether they follow missions like this regularly or not.

Carolyn Porco: Well, I couldn't agree more and I've, and I learned just how much a chord it strikes with people. I mean, I learned of course in Voyager but when I was selected to be the team leader on Cassini, I, um, another one of those things on my to-do list. Right away was to redo the pale blue dot Voyager picture, only do it better. Now it's not generally known that in the proposal that Carl wrote to the Voyager project, urging them to get this picture done, he wrote that the purpose of the picture was to take an image of earth [00:30:00] awash in a sea of stars.

So the Voyager pale blue dot picture didn't quite turn out like that. You can't see any stars. Actually, the earth is sitting on a beam of light that was scattered in the optics of the canvass. So it's not the most beautiful picture. Of course, it, it's what Carl had to say about it and the way he romanced it that made it so, uh, iconic and really struck, people, people got it. They heard him say that and they got it, why this was an important image. So I wanted to redo it. So busy. Never got a chance to work on it until about, I don't know, when we were in our second extension of the mission.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: When it, I think I probably started thinking about it again, 2010, 2011 and figuring out where to put it in the timeline of images that we were going to take. And I had to piggyback another scientific instruments. Mind you, you can't just go and say, "I want to do this just to do it." [00:31:00] I, I, maybe I was able to do that one or two or three times in the whole mission. It was really a, a difficult sell. I thought a piggyback on someone else's observation. So there was going to be a mosaic made of Saturn when Cassini would be in eclipse.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Right? So instead of needing a high gain antenna to shield the sun, we had Saturn to shield the sun, that would be perfect. I managed to convince the, the originators of that mosaic to let us piggyback. But w- you know, while I'm doing this, you know how good ideas just come. They, they just arrive.

Mat Kaplan: Yeah.

Carolyn Porco: And I just thought, "Wow." Instead of doing what every mission has done since Voyager and what, of course Voyager did was take the picture of the earth and then a week later, two weeks later, release it to the public and say, "Hey, world. While you weren't looking, guess what we did?" I thought, wouldn't it be great if we told the people of the world ahead of time-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... At such and such a [00:32:00] time, such and such a date, we are going to take your picture. Take a picture of all of us from Saturn and invite them to go out at that time and as the picture taking window opens and just contemplate this whole thing. Contemplate being on a planet, a small planet and everyone else on it, all living creatures. How connected we are to all of them and think about their own existence. Think about how unique our planet is in its lushness and its life-giving properties.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And just, you know, smile at the sheer joy of being alive on a pale blue dot. That kind of thing and that's exactly what we did.

Mat Kaplan: W- where were you at that moment?

Carolyn Porco: It's am- it's amazing to me. I was in Colorado and I was being filmed by the BBC.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: They wanted to come out and capture me while the thing was going on. I have to say that while I was being recorded, [00:33:00] I completely lost track of the fact that I was being recorded, you know. It can be very, I got completely swept up in the whole thing. Like, I just forgot I was being interviewed. And I was as amazed myself at this whole thing as I'm sure everybody else who participated in this was. That I'm looking in that direction. It was daylight but I knew where Saturn was. And I'm thinking, "My God. There's a camera out there. And it's taking a picture of me and it made the solar system so much smaller."

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And I felt so connected to that thing, not only having been the originator of the idea but just that, that was something humankind had made. A machine out there was taking our picture. So I was amazed by that. I, I really did feel what I wanted everybody else to feel, the sense of connection with everybody else. How important life is, how unique it is in our solar system, how [00:34:00] we have to protect our own planet. All those feelings just washed over me. And it was really a, a great, great moment. We had set up in my shop, Cyclops, had set up a website for people to write in. And tell us what happened.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And I got lots and lots of responses from people in Asia, in Canada, in South America, in Africa. I mean, just all over and, and it worked just as I had wanted it to. People felt so, um, I don't know, inspired. And one woman called it transcendent. Uh, another guy described how he and his 10-year old daughter did this together and it was, uh, th- they loved it. Everybody just loved it. So, you say strike a chord, it was like the biggest piece of cosmic performance art.

Mat Kaplan: [laughs]

Carolyn Porco: In fact, Brian Eno, uh, gave a talk after me.

Mat Kaplan: [00:35:00] Brian Eno, the great music, uh, uh, musician, producer, composer, yeah.

Carolyn Porco: Yes. He gave a talk after me at this conference called Starmus. And I, I described this thing to him. And it, he who came up with this in, in saying, "Well, that was a great talk. And that must have been the greatest piece of performance I ever," it, I was so glad we did it. And, and it resulted in a beautiful picture of earth and there are stars in the picture. When I first released this picture to the public, I did so at the celebration for Carl Sagan at the Library of Congress-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... That was held in concert with his papers being archived by the LLC.

Mat Kaplan: I am rereading about that right now because I'm talking, I'm reading for the second time. It's not just Sagan's book because I'll be interviewing you as, as I told you-

Carolyn Porco: Mm-hmm [affirmative]

Mat Kaplan: ... In just a couple of days as we speak. And she talks about that ceremony and how overwhelming it was.

Carolyn Porco: Oh, really?

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Does she mention the pale blue dot picture?

Mat Kaplan: I'm [00:36:00] afraid not.

Carolyn Porco: No, okay.

Mat Kaplan: But, but it does come up elsewhere in the book.

Carolyn Porco: Okay. So anyway, I, I mean, I'm sorry I'm talking so long about it but it was a very, very-

Mat Kaplan: Obviously, very meaningful to you.

Carolyn Porco: It-

Mat Kaplan: But it is to so many of us.

Carolyn Porco: Yeah.

Mat Kaplan: I told you. I was standing heavily biased, proud admittedly but not so different-

Carolyn Porco: Where? Where?

Mat Kaplan: At JPL.

Carolyn Porco: Oh, okay.

Mat Kaplan: I was standing in the patio with hundreds and hundreds of people who would all come out, uh, doing the wave and smiling and laughing and listening to music and it was glorious. Yeah. We were told when to look up and roughly where to look. [laughs] But, and, uh, and then of course, to see that image later, itt, it, it's, uh, thrilling still.

Carolyn Porco: It took us, it took us a long time to process that. It was really a lot of work because it's a lot of images that had to be pieced together. But it, it turned out beautifully.

Mat Kaplan: Back to doing science out there at Saturn and why we should go back. I mean, I'm going to, I'm going to ignore Titan and maybe I'll ask you a little bit later about the Dragonfly mission and what you think of that. Why do we need, why else do we need to go [00:37:00] back to Saturn after being out there and seeing this and amazing success of the Cassini mission for so many years?

Carolyn Porco: Well, that's actually a very reasonable question.

Mat Kaplan: Hmm.

Carolyn Porco: And it really, no. It, it really gets to a, an issue that I've been thinking about a lot. And that is, you know, how much, how much longer are we going to continue to exploit the solar system? I mean, how much do we really need to know? These are good questions, you know.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Lots of resources go into this. And we need to have good reasons. I mean, I think there's lots to continue to do in the solar system. We have to go back to Neptune for example, an ice giant. We, and do-

Mat Kaplan: Yeah.

Carolyn Porco: ... What we did at Cassini at a place like Neptune. But these are good questions. Why go back? And at Saturn, one of the most profound discoveries we made was this moon, Enceladus. Enceladus is a small moon of Saturn that has, [00:38:00] uh, we found out from 13 years being there has a global ocean with a salinity not too different from that of the earth. By flying through the plume, we also found it had, uh, there's evidence for, uh, large organic compounds. We couldn't measure the organic compounds themselves.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: We didn't have instruments that could do that. But you could work backwards to show that the compounds that were detected actually came from larger compounds. And that's important because you know, the, the, the compounds, the organic compounds of biology like amino acids, they are relatively big. They're not like methane. They're not like acetylene. They're relatively big. So there are relatively big organic compounds in, in the material that is gushing out from Enceladus, uh, forming a, a plume of material.

And that plume is, is fed by geysers [00:39:00] about 101 geysers on the surface. This was actually stuff that my research group and I did to figure out all those geysers. And where they were and what connections they have to the other observations.

Mat Kaplan: And coming out of those tiger stripes. Great, great turn.

Carolyn Porco: Co- they're coming out of four fractures-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... That cross the South Pole terrain, so the South Pole region. I don't want to say it was a surprise. Anyone who says that scientists were so surprised to see this, uh, that's not the correct historical history.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: The narrative really is that people knew there was something going on with Enceladus. Either charge particles were hitting its surface releasing them to form the E ring of Saturn-

Mat Kaplan: Mm-hmm [affirmative] Mm-hmm [affirmative]

Carolyn Porco: ... Which Enceladus is embedded in. That was the common wisdom but there was a paper in 1984, post Voyager. 1984 that said the E ring could possibly be produced by a geyser material that was in the form of a geyser coming from its interior.

Mat Kaplan: [00:40:00] Wow.

Carolyn Porco: So we planned our observations from the beginning to look at the, in the proper orientation so that we would see something like a geyser. And that's what we found. Early 2005, we discovered the plume. And other instruments of course confirmed later there was organic compounds in it or they found later there was organic compounds in it. And they did the whole chemical analysis. But, um, the imaging team and the magnetometer were the instruments that first had anything to say about the existence of the plume.

Mat Kaplan: Do you wish, I mean, Europa Clipper seems to be on track for that other ocean moon, the one going around Jupiter. Do you wish there was a, an Enceladus clipper? Or maybe we should have gone to Enceladus instead of Europa?

Carolyn Porco: Clipper is going to do at Europa what we did with Cassini at Enceladus.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: That's what it's going to do. It's going to bring, uh, the knowledge of Europa up to the same level [00:41:00] of our knowledge on Enceladus. So a lot of what is said about Europa is actually speculation. They don't quite know. We do know on Enceladus because we spent 13 years studying it. So I think the Clipper is going to do very important stuff. It needs to be done.

Mat Kaplan: Yeah.

Carolyn Porco: Um, I'm not this, I will a- I was, you know, years ago, I was saying we should go back to Enceladus because it's so urgent. Uh, I'm not really disappointed that they're going to go back, uh, Europa with the Clipper mission. But next, we need to do a series, deep dive on Enceladus because Cassini didn't have the instrumentation that could tell you whether or not there was life in Enceladus. And that's the reason why Enceladus was so profoundly interesting and our results were so profound period.

And that is that it points to an ocean that could possibly support life. There was even evidence of hydrothermal activity in the plume-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: If you'd buy one of the insi- instruments. So, [00:42:00] there's tantalizing clues and how long has it been that NASA has set as its goal to find life in the solar system? To find habitable zones? And to determine if life got started? I, I'll tell you. It goes all the way back to the 1958 charter.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: They had in mind to survey the solar system and see if life got started anywhere else. So here we are, this incredible time when we now know there's a moon out there that yes, has a sub surface ocean like many, not many but several do. But it is unique in having that ocean being expressed into space. And it's relatively trivial to just go sample it. We could next ask very pointed questions about whether or not there are any signatures of life in the plume of Enceladus. If we had a mission that could go there and at least go into orbit around Enceladus and, and even better, land on the [00:43:00] surface.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And instruments that could do better than we could do with Cassini. Like, you know, measure, detect directly if possible large molecules and determine what molecules those are. Not, oh, this one has, you know, is, is 250 atomic mass units. I mean, just really determine what those molecules are. We want to know chemically what's there. Uh, I've been the one pushing this idea for a long time. I think some people think I'm crazy. But I don't and that is that there could be microbes in the f- the frost particles that are in that plume.

Mat Kaplan: Why would that be crazy? I mean there-

Carolyn Porco: Well some, because, bec- because it sounds crazy. Like, i- it sounds maybe like it's, it's stretching too far. But my argument is this, that on earth, just about every frost particle you run into on earth, even in the stratosphere, has a bacterium at its center. Bacteria nucleate [00:44:00] ice particles.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Uh, you know, frost particles. So-

Mat Kaplan: They actually help to form the ice particles.

Carolyn Porco: They actually help to form the ice particles so it's not-

Mat Kaplan: Wow.

Carolyn Porco: ... Crazy that you could ha- and, and there's reasons why you could have microbes if there exist at the hydrothermal vents on the sea floor of Enceladus. How they would get themselves attached to any bubbles that come up, uh, through the water column. That's a common process here on earth. It's called bubble scrubbing.

Mat Kaplan: Hmm.

Carolyn Porco: So it's not out of the question that you could have microbes in the plume probably at the center of the ice particles. So my thing is not only do you want to bring chemical instruments. I doubt they could give you, uh, 100% confidence level that you'd found life. But also, bring a microscope.

Mat Kaplan: Yeah.

Carolyn Porco: Because if you could get a picture of a, of an organism, even better if they're still alive, a little video, I mean, talk about knocking people's [00:45:00] socks off. So we want to go back to Saturn because we want to go back to Enceladus to see if it is a moon that is forthcoming in telling us where the life got started in, uh, any other place. And it's not, I have to be honest. It, there's a camp of people who think you can't get life started in an ocean. But there's others who say, you know, that you could. Metabolism probably got started in the ocean.

At least that's what they say. So, so, who knows? But, you, you know, this is all about exploration. It's not like-

Mat Kaplan: We won't know until we look.

Carolyn Porco: Uh, right. And if we knew the answer, maybe we wouldn't need to go back.

Mat Kaplan: [laughs]

Carolyn Porco: But we don't know the answer. The clues, the hints are there and it's just like, you know, running the program now, let's get back.

Mat Kaplan: I guess we should move on. Before we leave the Saturnian system though, oh, how do you feel about Dragonfly?

Carolyn Porco: Oh, I was very happy that Dragonfly got selected. Because it's, it's a cool mission design. I had been criticizing the Titan [00:46:00] people for, you know, when they, they talked about missions going back to, to Titan, like we were talking about missions going back to Enceladus. The, their mission seems so ho-hum like it was just a redo of Cassini. But this group came up with a really cool idea, which is this drone basically-

Mat Kaplan: Yeah.

Carolyn Porco: ... Of putting it in the atmosphere, uh, hopping like, you know, on the surface sampling something.

Mat Kaplan: Very cool.

Carolyn Porco: Get a, oh, very cool. Very cool mission design.

Mat Kaplan: We've talked as if we've heard about it as well. And of course, she's [laughs] uh, very enthusiastic about her project.

Carolyn Porco: Yeah, of course. Of course and, and, um, and it's good. It's good that it's being done by APL and, uh, so, I, I liked it. I was a bit disappointed though that they're not going to get to the lakes and the seas in the north, you know. That's, I mean-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... To, to be able to sample the hydrocarbons that are ponded there in the, in the north, well, there's some in the south, too that we found early on in the mission. But, you know, that would have been really glorious. But I think already, it's somewhat of a [00:47:00] risky mission. So-

Mat Kaplan: Yeah.

Carolyn Porco: ... I don't think they, they thought they could pull it off. But they're going to sample those areas as I understand it, uh, that you know, our pictures are dark. And we think that that's the hydrocarbon material in the atmosphere just raining down on the surface. So, it'll be interesting to see, you know, what they find. They claim they're going to be going looking for life at least I've heard some of them claim that. I, I think it's a stretch. I think it's a stretch because the temperature's on the surface. There's something like 350 degrees below zero Fahrenheit.

They could have a major problem with kinetics getting biotic chemistry going on a place like that. But-

Mat Kaplan: Although I know there are people thinking about this. Like, what kinds of processes could drive biology in that kind of, it does seem far-fetched but yeah.

Carolyn Porco: Well, what I, why I'm excited about it even though I think it's far-fetched to find

Mat Kaplan: [laughs]

Carolyn Porco: ... Evidence of life, I think it's covered with [00:48:00] native organic compounds. Organic compounds that are native to the tiny system. If it never got to life, they could just answer the question. What do organic compounds do in an environment like this? Even that would be extraordinary to know and very helpful. And for people to think about what happens in the run up to life, prebiotic chemistry. So, I was very excited about it.

Mat Kaplan: I can't wait to see the pictures.

Carolyn Porco: That's going to be absolutely fascinating. I hope they have a camera that will be able to take the picture of Saturn through the atmosphere of Titan.

Mat Kaplan: Boy, oh, boy.

Carolyn Porco: Ah.

Mat Kaplan: I've seen artist's concepts like that. But my God.

Carolyn Porco: Oh well then, going back to Chesley Bonestell, yeah. [laughs]

Mat Kaplan: Yeah, right.

Carolyn Porco: Yeah. He didn't know the atmosphere of Titan was opaque. [laughs] But, I mean, not completely opaque-

Mat Kaplan: Yeah.

Carolyn Porco: ... But very hard to see through.

Mat Kaplan: We're back to images, which have dominated so much of your life and the exploration that you've conducted. What's the right way to manage images? Because I, I, I know that you [00:49:00] have strong feelings or at least you used to about the images that come back that you've worked so hard to create. You talked about some of these challenges with Cassini but also with Voyager. There are, it seems now, a couple camps one that says, no. Put them out raw. Send them all out. And then, another camp that says, no. These need to be studied.

They need to be, they need to be worked with before they are simply released. I mean, where do you come down in this?

Carolyn Porco: Well, this, this was a painful story in, in the development of Cassini, uh, because my team and I thought we were going to have a nine-month proprietary period like everybody else.

Mat Kaplan: Yeah. That's what I've heard.

Carolyn Porco: And then, I think it was 2003, we were told you're going to be releasing your, all your images to the public. And-

Mat Kaplan: Uh-huh.

Carolyn Porco: I had-

Mat Kaplan: So that came from on high.

Carolyn Porco: Oh, yeah. I, okay. Well, again, let me, maybe I should back up even more and say, I had plans for, you know, [00:50:00] releasing images. We were going to release images. I was going to c- you know, turn them into true color. And we were going to release them. And I knew I'd be doing that but I didn't know then. No one that came up with this crazy idea that we're going to release the raw images to the public. It really created a problem on my team. That Europeans were the ones who were most upset. They felt that they had been promised-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... A nine-month proprietary period. They were afraid people wouldn't get the images and we're going to scoop them after they had put in all this work.

Mat Kaplan: Years of work in case.

Carolyn Porco: Ye- uh, both came. By the time we got into orbit at, at Saturn, it was 14 years of work.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And the way this all was done was done in a very uncollegial way, I must say. Just, for us to be ordered to do this. So it was, it did not go over well on my team. I personally was not worried about getting scooped from the outs. I was doing planetary rings then and I wasn't so much getting [00:51:00] scooped. I worried about getting scooped from the outside by my, by members of the public or by outside scientists. Because all my competitors were already on the im- on the-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... On, on Cassini.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: I was just concerned that, you know, everyone else was, on Cassini was going to have our images and, and that would be a big problem for us. I had not anticipated that people from the outside would want to process our images just to, for the sake of processing them to make a nice picture. That, that came later and that also surprised me. In the end, the public very much appreciated it. We managed to work out a, a scheduling so that we did get to process things nicely.

And I was very, very pleased that the press ended up being either they would deliberately respectful or they didn't want to see or care about what the members of the public were processing before they actually made a big deal about any image from [00:52:00] Saturn. They waited until we released it. So that was, that was okay. And I was a, as I said, I was happy to see in the end that it did engender a lot of affection in members of the public for Cassini. But w- I will say this.

That we did have enormous problems because those images were also available to our colleagues who used them to help them make discoveries that we, or, or claim they made discoveries.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And there was no quid, uh, no quid pro quo. There was no reciprocity in that. And that was a very bad thing. And I hope that, um, other projects deal with it better than they dealt with it in, in our case. It, it created a lot of resentment.

Mat Kaplan: Hmm?

Carolyn Porco: A lot of resentment. And it was not a way to treat a major team on a spacecraft mission. The team that was shouldering a lot more work and certainly a, uh, shouldering a lot more of the responsibility of keeping the [00:53:00] mission in the eyes of the public. That was like a big slap in the face.

Mat Kaplan: Very understandable. A big jump back in toward the center of the solar system to Mars. Lots of great stuff happened there. Lots more to come. Uh, including plans to send people there. Uh, we talk every now and then on this show about Elon Musk building his big spaceship. And wanting to establish a human community, a colony if you will, uh, on that planet. You have strong feelings about this.

Carolyn Porco: Oh, you know I have strong feelings about this.

Mat Kaplan: [laughs]

Carolyn Porco: Have you heard me?

Mat Kaplan: A little, a little bit.

Carolyn Porco: Express my strong feelings? Yeah. I think the guy's on drugs.

Mat Kaplan: [laughs] Well, that's a proven fact in at least one case. But, uh-

Carolyn Porco: [laughs] I, I, no, seriously. I think he, maybe he can afford fact checkers but he's not going to terraform Mars. It's not possible.

Mat Kaplan: Well, you agree with our boss about that, Bill Nye. I have a bet with him. I said, "You, you don't think terraforming, maybe in 10, within 10,000 years?" He said no.

Carolyn Porco: Here's, let's, let's [00:54:00] say, let me, let's just get to the facts and I have been informed by people who are on Mars orbiting missions. Recent results show that there are, there is an insufficient amount of CO2 in reservoirs that are not atmospheric to ever get the atmosphere to the point where terraforming would even be possible. So, you know, you've, you've got CO2 already in the atmosphere. We know that's insufficient. But even if you could take the CO2 and the reservoir's under the ground, or on the surface in, I guess the ice caps.

And put them into the atmosphere, it still wouldn't work. So you can't terraform Mars. And besides, why would you want to?

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Here's where I'm becoming very critical of commercial space. I hear things like mining asteroids will save the earth. Or we need to go to Mars because we're in danger here on earth. We've screwed things up. We're going to get hit [00:55:00] by asteroids. We need another place to go. And of course, the same motives are given for this even crazier notion that we're going to actually colonize another stellar system. Uh, it's not going to happen. These are lovely thoughts. I, I empathize with the people who put f- them forth because they, some of them are younger than me. But some of them are about my age.

I grew up in the '60s. I, it was a Star Trek fan. I love the whole concept of us being a f- a, you know, space fairing civilization, being on the Starship Enterprise. I love the whole thing. It's a wonderful fantasy. It's inspiring but let's get real. It can't happen. It can't happen. And, but we're hearing things like again, Elon saying terraforming Mars. And he's going to, people are going to be living on Mars. People will live on Mars in the same way people live on Antarctica now. There is an outpost there. It's continuously inhabited. It's not continuously [00:56:00] inhabited by the same people.

People aren't living there. They're not giving birth to the next generation there, raising, it's not going to be a multi-generational thing in the Antarctic. And that's the way we will make our way across the solar system. There will be outposts. I had been calling them colonies. I think now, it's better so you're not, don't get confused with the idea of a colony where people live out their lives. And you know-

Mat Kaplan: Yeah.

Carolyn Porco: ... They, they don't, they don't make their living there or they don't give birth to the next generation. We will see outposts. We could on the moon. Maybe on Mars, I could see it for reasons of scientific research. But to have this idea that humans are going to move off the planet, and that's the way we're going to survive is in fact, irresponsible.

I say these days, Elon Musk, Jeff Bezos, if you have so many resources that you could talk about putting thousands [00:57:00] of satellites into low earth orbit to connect the remaining four billion people onto the internet, uh, why don't you spend those resources down here? Because we are at a crossroads with regard to our own planet. We are in really very serious trouble. And we could use a little love.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: You know? I, I don't see why they have, those people have to make even more money that anything they do, they want to have it be profitable. It's time to give back. Going to Mars for research purposes, going there because I come to the, the, the Apollo 11, but the Apollo program how inspirational it was.

Mat Kaplan: Human skill in addition to complimenting robots going to these places and establishing perhaps these outposts that you've talked about. Much better word because colony also has political and cultural connotations-

Carolyn Porco: Oh, good. Yeah.

Mat Kaplan: ... That a lot of people don't like. [00:58:00] But you do believe that humans have a place out there.

Carolyn Porco: I think they have a place out, uh, certainly scientifically. Uh, you know, the point has been made by others. W- we have tremendously capable robotics. And we, they'll get better and better with AI. But, you know, there's something about having a human there to pick up our lock and say, "Oh, I see this." Or, I, I think there's, there's place for it.

Mat Kaplan: Yeah.

Carolyn Porco: But I would even say before we do that, let's make sure the earth is secure. It may be time to just rethink this whole thing and, and just clean up our act at home first. You know, there's no, there's no Planet B. The idea that there's a Planet B is just, uh, you know, it's fantasy. We are part of our planet. It is part of us. We evolved here. We are intimately woven into the web of life that is here. And to even undertake, physically undertake, physiologically undertake [00:59:00] any of these things we're talking about is a strain on the human body. Here's another thing that I laugh at.

I just went on and on about true color and how important it was to me to process our images in true color to give people a sense of what it was really like. Even in doing that, by the way, you have to cheat a little. But, uh, put that aside for the moment. I'm wondering if Elon Musk thinks it would be great to go to Mars because he's seen the pictures that people have produced of Mars. And they are extremely processed. The contrast is enha- is, is enhanced. The colors are enhanced. They look like Sedona.

Mat Kaplan: Yeah.

Carolyn Porco: If you were really there on Mars, it would be very low contrast. Even on a good day, the atmosphere would be very hazy. You know, Elon might not like it so much.

Mat Kaplan: [laughs]

Carolyn Porco: So, let's get real about this and, and please, you know, love your fellow earthlings. Love the earth. That's my motto these days. Love the earth.

Mat Kaplan: I couldn't agree more. I just hope that we can continue [01:00:00] to explore the solar system as we fix the terrible things that, uh, are happening down here on this planet. And, and what you said I think made me think of your, your friend, your colleague, maybe even your mentor, Carl Sagan.

Carolyn Porco: Yeah?

Mat Kaplan: I want to come back to him in a second.

Carolyn Porco: Yeah.

Mat Kaplan: But I got one more before we bring in all the way back home to Carl. You think Pluto is a planet?

Carolyn Porco: [laughs] No.

Mat Kaplan: Oh, yeah. We're going there. You'll want to stay for Pluto and Carolyn Porco's view of the great planet debate along with her memories of Carl Sagan.

Casey Dreier: I know you're a fan of space because you're listening to Planetary Radio right now. But if you want to take that extra step to be not just a fan but an advocate, I hope you'll join me, Casey Dreier, the Chief Advocate here at The Planetary Society at our annual Day of Action this February 9th and 10th in Washington DC. That's when members from across the country come to DC and meet with members of Congress face to face and advocate for space. To learn [01:01:00] more, go to

Carolyn Porco: No. Pluto is not a planet. Never was a planet. It just was, you know, it suffered a mistaken identity for a very long period of time. And people got so attached to the idea that it caused this big commotion but, no. It's not a planet and that doesn't make it any less interesting, uh, than it is or it should be. He- here's the thing about this whole, this whole debate. The word planet as shown by several people but the latest really detailed work, the one that really kind of cleaned up the slightly misbegotten IAU attempt at this-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... Uh, at this topic was worked on by Jean-Luc Margot at UCLA. He showed that the bodies that we call the planets now, the eight of them in our solar system are the ones that have sculpted our solar system. They're the ones that have-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... Cleaned out their orbital corridors [01:02:00] and that's why we see eight distinct objects and not a disc of debris. He also showed and, and the exoplanet people were waiting for something like this. He has shown that if you use the same criterion that produces, shows that eight of our planets are those, um, sculptors. You take that same criterion and you apply it to other stellar systems, you show that, that some large, very large number, 95, 99, I forget, percent of the exoplanets are also, uh, also fit that criterion.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: So here's the thing. What this really means is that when the Greeks thousands of years ago looked up at the sky and they saw this wandering, stellar-looking things, uh, and they called them planets, what they really were seeing were bodies that were dominant in the chronology of the solar system.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And that's why they saw only eight of them. [01:03:00] And now, we are like the Greeks looking out at the exoplanets. All we see are little planets so we don't have any detail on them yet. So we're equally ignorant about them as the Greeks were about our planets. And what do we, what we're seeing are those objects that have sculpted out their solar systems. So, even if there was no word for this class of bodies that has been dominant, dynamically dominant in their solar systems. Even if there was no word, we'd have to invent a word for them.

Because whenever anybody on a computer tries to simulate the evolution of a solar system or a stellar system, this concept of a body that clears out its orbital corridor is central. So we would need a word anyway. But we have that word, it's called planet.

Mat Kaplan: [laughs]

Carolyn Porco: So there's no sense in trying to extend planet to other criteria like roundness or anything. [01:04:00] This category needs to remain the same.

Mat Kaplan: What about the sort of compromise term? That a lot of people have adopted? A dwarf planet? Not just for Pluto but Siri's and some of those other objects that have been found in the Kuiper belt.

Carolyn Porco: Well, dwarf planet makes no sense when you think about it. Because how can anything be a dwarf of a category that it is not a member of? Right? Another word needs to be created but here's another thing. I don't think the roundness is a sensible criterion. Because you never really know if it's round. And whether it's round, whether it's in hydrostatic equilibrium will depend on its composition. There's other ways to look at categorizing bodies according to their geophysical properties. Uh, and I think of s- someone I know is, is going to be working on this.

So I won't make any mention of it yet. On one hand, I'm sort of sympathetic that people want to be able to talk about [01:05:00] large-ish bodies. But I'm not sympathetic to a lot of justifications that I've heard. Some of them go like, look at Pluto. Look how complex its surface is. Well, complexity is not something that you can use to categorize anything because there's complexity on every spatial scale. Complexity is an outcome of our universe. It's everywhere to be found. So its scale and variant, you can't use that. Another is look at Pluto. It's got satellites.

It looks like a miniature solar system. Well, asteroids have satellites. That's another scale and variant pro- problem, uh, process. So you can't, you can't use that to say it's got to be a planet. So, I just think if this group of people, uh, interested in natural or inherent geophysical characteristics, uh, wants a word, they just, should invent another word. But planet is taken and it's already well-justified.

Mat Kaplan: So you know I'm going to hear from people, of course. And I suspect the debate [01:06:00] will continue. Uh, here and elsewhere with excellent people on both sides. But I know that you in spite of all of this have marveled at those gorgeous images of Pluto returned by New Horizons.

Carolyn Porco: Oh, I love them. I mean, it really was, I was, I was, of course, eager to see was it going to look like Triton?

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Because they're kind of kissing cousins. Uh, Triton was captured from the outer solar system into orbit around Neptune. Uh, excuse me, from a heliocentric orbit into orbit around Neptune. So I was expecting that it would, uh, it would look like but I was half hoping it wouldn't because then it would be more exciting. And it kind of like split the difference because there are ways in which it looks like Triton. There are, of course, because it's also an icy body. It's in a cold place. It's got nitrogen on the surface.

It has things in common with Triton but it also had a lot of really, really unusual features like the conve-

Mat Kaplan: I'll say, yeah.

Carolyn Porco: ... The convective pattern in, I, I don't know that [01:07:00] terminology. But there was a big flat area. It had these things that look like the top of convection cells. It's really the convection of the ice. And, and the pictures were just really, really beautiful. They did a beautiful job with the instrumentation and so on.

Mat Kaplan: Gorgeous, yeah.

Carolyn Porco: Uh, yeah. So, so I get it. But it, but you don't look at something like that and say, "Oh, it's so beautiful. It's so complex. It should be called a planet." That is not the way we do things in science. We don't base it on, "Oh, it's so beautiful." Then I hear this, these inane things. I'm sorry. You know, I, I'm on, I'm on my roll now.

Mat Kaplan: [laughs]

Carolyn Porco: Like, like, oh, we don't want to disappoint the members of the public. Well, a- as you know, I am all about informing the public of what we do and getting them inspired to feel a part of it. But the members of the public should not be telling scientists how to do their science any more than a member of the public should stand behind your dentist while she's drilling in your mouth and [01:08:00] say, "I think you should go a half inch back and three inches down." They shouldn't be telling us how to categorize things. We love them. We want them to, you know, to enjoy what we do.

But when push comes to sh- shove, scientists are scientists for a reason. You got to let us do our job.

Mat Kaplan: Keep those cards and letters coming, everybody. And you have done more than your share of communicating what our boss calls the passion, beauty and joy, the wonder of our solar system. We open this conversation talking about you doing stuff with, uh, StarTalk. You clearly believe very strongly in this. And you also said Carl Sagan was a pioneer in doing this. As a scientist who cared about communicating the passion he felt to the public, you were a friend, a colleague. What were the most important things that you got out of your relationship with, with Carl?

Carolyn Porco: Well, out of my relationship with Carl, I, [01:09:00] I was somewhat of a mentoree of his. Not, not, I wasn't a student of his. I never did any research with him.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: But I felt, we were on the Voyager imaging team together.

Mat Kaplan: Yeah, as you said.

Carolyn Porco: Actually, I first, I first met him when I was an undergraduate and he came through our university. This is Stony Brook University to give a talk about, um, Mariner 9. And the students got to meet him. I got to meet him then. But then of course, I met him later on as a, when I was a graduate student at Caltech. And met him at conferences and then of course we ended up on the imaging team together. And I felt that the man had my back. There were times when I, I think he felt someone was rude to me or said something to me that was really inappropriate. This is at a meeting.

In his very Carl way, you know, very gracious, very maybe even witty, very calm, very measured way but he would defend me. And basically, not tell the guy, "Oh, you're being such a [01:10:00] jerk." You know that's [laughs] that's something I might do.

Mat Kaplan: [laughs]

Carolyn Porco: He would just, he would just, you know, make it clear that that was a, you know, uh, not an appropriate statement, wasn't even accurate. So that was wonderful. And he, he would, uh, also compliment me when, you know, he thought I had done something well. So that was lovely to know that Carl Sagan's looking out for you. I also learned I just watched the way that he conducted himself as a scientist in combat. Sitting around a table when there's like heated discussion, he was always very measured there and very calm. And he would be the guy that would, I don't know if it was his voice, his bearing.

I don't know but he just had that thing he could bring tempers down. He just was very principled in the way he conducted himself. And so I use him as an example of what a scientist really should and could be. Kind of like the, there's this phrase, the [inaudible [01:11:00] 01:11:00]. Like the beautiful ideal, you know.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: That, that shiny thing that-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... You know, you aspire to or that, that's what Carl was like. And he wasn't, he, he was pretty much that way personally, too. Like what you saw on television is what you got. Not that I didn't see him like, you know, get irritated with his daughter or whatever. So he was human but he was also just a wonderful, wonderful man. And I think he deserves all the affection and accolades that he's received, uh, during his life and since. Because he was, um, he was that. He was, he was the, the real McCoy.

Mat Kaplan: So it must have been quite an honor when you were asked to help out with the production of the movie, Contact based on his book, well on the character of Ellie Arroway, the, the central character in the story.

Carolyn Porco: Oh, it was, it was a, a complete surprise. I, I didn't realize it until later that there was, I was at Cornell for an imaging team meeting [01:12:00] that I was holding there. Because I had team members at Cornell. And he invited me to have dinner with him and, uh, Annie at their house. And you know, you could-

Mat Kaplan: Andrew Ying, of course. Yeah.

Carolyn Porco: ... Andrew Ying. In fact, oh, gosh. A- uh, Carl wanted me to meet Annie, you know. He said, "I think you two are going to like each other." And it turned out, we're still friends. It was great. He was very, very right about that. So we were having dinner and as you can imagine, the conversation was very wide-ranging. Everything from, you know, uh, SETI and, uh, the pale blue dot and women in science and so many things. It wasn't until after he had invited me to be a consultant on the main character, Ellie Arroway in the, the movie that I realized I was probably being interviewed-

Mat Kaplan: [laughs]

Carolyn Porco: ... At that dinner.

Mat Kaplan: Yeah.

Carolyn Porco: He probably wanted to know, you know, would she be good at this? And, and I'll never forget. He called me up and he said, "Out of all the people we know, out of all the women scientists we know, we think that you come closest to [01:13:00] being what we want to portray-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... On the screen." So, uh, I was of course delighted. It didn't take me a microsecond to, to agree to that. So, I've read the book again because I had read it long ago. And then I went to this, this meeting of the director at the time, they ended up getting a different director. But the director at the time, George Miller, the executive producer, Lynda Obst and Carl and Annie and someone to take notes. It was great. They just peppered me with questions. You know, if you were in this kind of a situation, how would you feel? What was your life like?

Uh, why do you, did you get into science? Why do you have long hair when all of the women have cut their hair?

Mat Kaplan: [laughs]

Carolyn Porco: Obviously, what they were trying to do was just lend authenticity to what they were, were making, this film that they were making. Uh, so everyone had a great time. I was told it really inspired them. And the plan was, for me to [01:14:00] meet with Jodie Foster. She was going to kind of shadow me for a day or two. And get and talk to her, she was going to pick my brains. And so there was about a year when the people at Warner Bros would call me up and say, "Oh, quick. Give us your schedule for the next two months."

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: Because we want to find a time when we can hook you up with-

Mat Kaplan: Yeah.

Carolyn Porco: ... With Jodie. And so, I do it and then two months would go by and nothing and would happen. And then they'd call me again, same thing. And this went on about three or four times. And I remember calling Carl up and saying, "Carl, what's going on here?" And here's another thing I'll never forget. He'll say, how did he put this? It was just so Carl and just hysterical. The section of the American Astronomical Society that's devoted to planetary scientists is called the Division of Planetary Scientists.

Mat Kaplan: DPS.

Carolyn Porco: The DPS. He said to me, "Hollywood makes the DPS look like the paradigm of fascist order." [laughing][01:15:00] So, so anyway, I never got to be with Jodie Foster but I was told by Lynda Obst that she in the end used Carl as her role model. And she did a fa-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... They did a fabulous job.

Mat Kaplan: I thought so. I, and I, I can certainly see some elements of, of your character in what Jodie Foster brought to that wonderful character at the center of that movie.

Carolyn Porco: Okay. So you tell me what? What characteristics?

Mat Kaplan: Oh, her independence. Uh, the enormous curiosity, the passion that she brought to her work.

Carolyn Porco: Her feistiness.

Mat Kaplan: Her feistiness, absolutely.

Carolyn Porco: Yeah.

Mat Kaplan: Yeah.

Carolyn Porco: Yeah. So I think that's probably what they wanted. Um, I love that film so much. It wasn't of course, it didn't capture everything that was in Carl's book. As far as the story-

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: ... What's in Carl's book was better. But uh, and I regretted that they didn't, we talked about this. I asked him, "Are you going to, how are you going to deal with the, the pi? The, the, you know-

Mat Kaplan: At the end [01:16:00] of the book, right.

Carolyn Porco: ... At the end of the book, pi and the message.

Mat Kaplan: Yeah.

Carolyn Porco: Please, you've got to put that in the movie. And they said, "We just don't think anyone will get it."

Mat Kaplan: Yeah.

Carolyn Porco: So they didn't put that in the, in the movie.

Mat Kaplan: And I, I love the end of the book with that and I won't give it away because I'm sure there are a lot of people out there who've seen the movie but not read the book. So read the book.

Carolyn Porco: Oh, read the book. Really read the book. And it's so obviously Carl. I asked Carl directly, like twice. Now once he offered and another time I asked him, who is this character based on, you know?

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And he said, "Well, i- it's really based on me," meaning himself. You know, the voice of Ellie is Carl's voice in talking about the approach to science, of the conflict between religion and science. And all that stuff that is said in, that she says or what she espouses is all Carl. That's his voice. But I think what he did was he just pulled [01:17:00] together like, you know, bits and pieces of various people-

Mat Kaplan: Little of Jill Charter, little of you, a lot of his own voice. Some of Annie as well, Annie.

Carolyn Porco: Oh, I think it's mostly Annie.

Mat Kaplan: Yeah.

Carolyn Porco: I think it's mostly Annie. Um, but I think the, I don't know what you would call it, the accoutrements, you know, like I went to graduate school at Caltech and I have long hair and I'm feisty. Uh, Jill's father died when she was young apparently. I think he got that from her. I know that there are scenes in the book that, uh, come out of Annie's life, you know.

Mat Kaplan: Mm-hmm [affirmative]

Carolyn Porco: And I think the relationship between the two in the book, they, they took a lot of their own relationship and put it in the book. So I think of Ellie as kind of a composite character. But really, if you're hellbent on thinking of Ellie Arroway as a single person, then she's Carl Sagan and drag.

Mat Kaplan: [laughs] That's great. Um, [01:18:00] this conversation has been more fun and every bit as feisty. Maybe more so-

Carolyn Porco: [laughs]

Mat Kaplan: ... Than I had hoped. Thank you. You need to hit the road. I know you're headed up north here in California.

Carolyn Porco: I'm headed up north, yeah. But this was fun. I'm glad I did it.

Mat Kaplan: Oh, me, too.

Carolyn Porco: It's true. I haven't, I haven't-

Mat Kaplan: Come back.

Carolyn Porco: We've, I've come back. [laughs]

Mat Kaplan: Thank you, Carolyn.

Carolyn Porco: Well, thank you, Mat. This was fun.

Mat Kaplan: It is time for What's Up on Planetary Radio. And, uh, we are joined by the chief scientist for The Planetary Society. Bruce Betts is in the parking lot of the Planetary Society. Hey there. There's a little black spot on the sun today.

Bruce Betts: There is a little black spot on the sun.

Mat Kaplan: [laughs]

Bruce Betts: Sorry. Sorry. I told people I wouldn't sing. Um, okay.

Mat Kaplan: Especially on the phone.

Bruce Betts: Yeah. We're, we're out here looking at the, uh, Mercury transit using our proper safety filters. So some, uh, great Planetary Society volunteers. And we've, uh, checked out that indeed, there is a little black spot on the sun today. And it is moving across the [01:19:00] sun as Mercury moves between, oh, there's a bus. That's not in front of the sun though.

Mat Kaplan: [laughs]

Bruce Betts: As Mercury, uh, has moves across our vision, as we look over to, uh, the sun from earth.

Mat Kaplan: Glad to hear that you're out there joined by other folks. Uh, take a look at this. And it's no wonder I couldn't see it in my solar binoculars because it's really tiny.

Bruce Betts: It is. It's, it's, very tiny. I've been trying to take pictures just with my camera with a proper solar filter. And it's right on the, on them yet. I get a black smudge go with the bigger cells go so it's quite clear. Could you see it through your telescope?

Mat Kaplan: Yeah. I could, I could. It's just really tiny. [laughs]

Bruce Betts: Small planet, really far away.

Mat Kaplan: What else is up in the night sky? Or the day sky?

Bruce Betts: We've got to mean night sky. We're in the early evening. We're getting super bright Venus starting to rise, uh, low in the West shortly after sunset and above it is bright Jupiter. Uh, they'll be closing in on each other. And we've [01:20:00] also got Saturn still to the upper left of those. And then in the morning sky, in the East, we've got, uh, Mars looking reddish but not super bright. Mercury's hard to see in the middle of the night right now because [laughs] it's right in front of the sun, man.

Mat Kaplan: [laughs] I'm going to wait for that Mars transit. When's that happening again? [laughs]

Bruce Betts: Well first, you're going to have to get us someplace farther out than Mars.

Mat Kaplan: [laughs]

Bruce Betts: And so, you can do that. Uh, if you have a Siri or, uh, towards Jupiter and then, uh, it's not happening. No. Sorry.

Mat Kaplan: [laughs]

Bruce Betts: So we move on actually to this freaking space history. And it was 50 years ago that Apollo 12 launched and landed on the moon, becoming a second mission to land humans on the moon.

Mat Kaplan: We heard from Jason Davis about that last week.

Bruce Betts: And you can check out his web page on our website at that, uh, on the Apollo 12 mission. So we've got a gang in the parking lot ready to help [01:21:00] me out. Here we go. One, two, three.

Jay Pasachoff: [inaudible 01:21:02]

Bruce Betts: All right. It's good. That was really good. [laughs] Thank you.

Mat Kaplan: Tell everybody I say hi.

Bruce Betts: Mat says hi.

Speaker 7: Hey, Mat.

Speaker 8: Hey, Mat.

Mat Kaplan: [laughs]

Bruce Betts: So the next Mercury transit, next Mercury transit is 2032. The next one visible from the US, 2049.

Mat Kaplan: Wow. All right. It's a date.

Bruce Betts: There's about 13 or 14 per century but they come kind of clumped. But hey, it's better than the next Venus transit being, you know, like 2117. We move on to the contest and I ask you what comet did Mariner 10 about in 1973. How'd we do, Mat?

Mat Kaplan: Oh, we did great, I think because, uh, that Sasha Sagan interview of a couple of weeks ago was so popular. We heard from a lot of, uh, first time listeners and, and first time inference as well. And what a lot of them told us was, that you were [01:22:00] off by a little bit. Said apparently, that data came back a month later?

Bruce Betts: People often say I'm off.

Mat Kaplan: [laughs]

Bruce Betts: But it's usually by more than a little bit.

Mat Kaplan: [laughs]

Bruce Betts: So I'll take it as a victory.

Mat Kaplan: [laughs]

Bruce Betts: I don't know. I trust our listeners. So, uh, I was using the Trajan calendar. A little now-

Mat Kaplan: Oh, of course.

Bruce Betts: ... Uh, Trajan calendar. Uh-

Mat Kaplan: Yeah, which is why it's, it's, so, which is why it's so hard to make an appointment with you. [laughing]

Bruce Betts: No. That's not why, Mat.

Mat Kaplan: [laughs] So I bet you want to hear about our winner.

Bruce Betts: What, what a, yeah. What else did we learn?

Mat Kaplan: Chosen by, our winner and he's a first time winner, first time entering the contest, too. Eric Robertson in Cleveland, Ohio where the Cuyahoga River burns slowly to the sea.

Bruce Betts: [laughs]

Mat Kaplan: Indeed said [laughing] that it was comet C/1973 E1 Kohoutek.

Bruce Betts: Yup. Yeah. And it was, uh, Carolyn says, may have also said it was the first comet [01:23:00] a spacecraft returned a data about.

Mat Kaplan: And we did hear that from a lot of people. And a big disappointment to a whole lot of people who are, uh, alive and looking up at the time. Because it was supposed to be put on this big show and it just did not.

Bruce Betts: Yes. I, I was one of the ones disappointed. And, uh, it, but it helps them teach an important lesson, not to over hype things when you really don't know what's happening. And I'm guessing it was not the astronomers who did that.

Mat Kaplan: Yeah. I, Eric, you are going to receive that copy of Sasha Sagan's book, For Small Creatures Such as We. It's a terrific book along with a 200-point iTelescope.Net astronomy account. So congratulations, Eric. Daniel Sorkin in New York. Comet Kohoutek may have disappointed but Planetary Radio never does. Ad astra.

Bruce Betts: Yeah. [laughing]

Mat Kaplan: Mark Little. Mariner 10 discovered that Mercury has a helium atmosphere but he really wants me to say it like this. Mariner 10 has a helium [01:24:00] atmosphere. [laughs]

Bruce Betts: I don't think it's thick enough to really alter your voice but okay.

Mat Kaplan: [laughs] No. I'd be lucky-

Bruce Betts: I mean, maybe.

Mat Kaplan: ... If it sounded that way. Uh, Zachary Lupin, last week's winner, he mentioned that you did a couple of weeks ago and you put this question out there. I think you did anyway. Don't forget to mention the science team was led by Planetary Society co-founder, Bruce Murray.

Bruce Betts: Indeed. Uh, he was, uh, behind the imaging on Mariner 10. And he had done on some of the, uh, Mars missions.

Mat Kaplan: Your, your mentor we should add a- also at, uh, Caltech.

Bruce Betts: Yeah. My PhD adviser.

Mat Kaplan: Yeah. From our, uh, poet laureate, Dave Fairchild, he's back. Comet Kohoutek was thought it to be a comet of brilliance. It wasn't, you see. But Mariner 10 thought it still pretty grand and watched it in the ultraviolet band. [laughing] I, ultraviolet band, that, that was my favorite, uh, rock group of the, uh, of the '70s as well. Pure coincidence of [01:25:00] course.

Bruce Betts: [laughs]

Mat Kaplan: All right. We're done unless you've got a new question for us.

Bruce Betts: You know I do, Mat. This time, I do have a new question. And we're going to talk about planetary transits. What spacecraft observed a planetary transit from the surface of another planet? Go to

Mat Kaplan: Wow. Okay. That is extra cool. We have a very special price this time. Our friends at the Yugen Tribe who make this terrific cosmic jewelry are now selling that jewelry through another of our partners, ChopShop, and, uh, isn't this perfect? Just at the start of the, uh, Christmas or holiday shopping season, we're going to give away a necklace and earring set from Yugen with interchangeable images of LightSail, of LightSail 2. So, uh, pretty thrilling.

Bruce Betts: Cool.

Mat Kaplan: [01:26:00] Yeah. Isn't that great? So that's the price.

Bruce Betts: Buy them from?

Mat Kaplan: Yeah. Well, yeah, you can if you go to and put in your credit card.

Bruce Betts: Oh, okay.

Mat Kaplan: [laughing] But anyway, we're, we're going to have a free set for somebody out there just in time. You have this time until the 20th. That will be November, 20 at 8AM, Pacific time to get us your answer. All right, Bruce. It's still going on, right?

Bruce Betts: It is. It is for a few more minutes. Still in front of the sun. So I want to go watch it some more.

Mat Kaplan: Yeah, enjoy.

Bruce Betts: All right, everybody. Go out there. Look out at the night sky or the day side sky if you're using appropriate filters. And think about whether you prefer a Mercury transit or public transit.

Mat Kaplan: [laughs]

Bruce Betts: Thank you and good night.

Mat Kaplan: [laughs] That's an easy question to answer but I'll leave it to the listeners. Uh, that's our friend, chief scientist for The Planetary Society, Bruce Betts. He's in transit as he joins [01:27:00] us here on What's Up. Planetary Radio is produced by The Planetary Society in Pasadena, California. And is made possible by its members who love every world in the galaxy, large or small. Learn how to become a member of the society at And please, leave us a rating or review on iTunes Apple podcast. Mark Hilverda is our associate producer.

Josh Doyle composed our theme which is arranged and performed by Peter Schlosser. I'm Mat Kaplan. Ad astra.