Today the 365 Days of Astronomy podcast aired my contribution, What's in a Science Meeting?, about what scientists do at big meetings like the Division of Planetary Sciences. If you want to learn more about what was presented at DPS, here's some of my posts from the meeting:
- Centaurs and Trans-Neptunian objects
- Pluto and Charon opposition surges, Nix and Hydra masses, Pluto and Eris compositions
- Triton's craters, a friendly dispute
- Friday morning at Titan's surface
- Iapetus, Kiviuq, LHB, Steins, Cherry Gary, and more
- Making Saturn's rings and moons all at once
And now for the transcript:
What's in a Science Meeting?
If I asked you to think of a space scientist, what would you think of? Maybe somebody staring through a telescope? Or someone in a low-lit office piled with books and papers, with pictures of stars or planets on their computer screens? Regardless of the environment, you probably imagine a person in solitary study. But space scientists don't always work alone. Sometimes, hundreds or even thousands of them get together in big science meetings to share and discuss their findings with each other.
My name is Emily Lakdawalla, and I'm the blogger for the Planetary Society. I recently attended one of these big science meetings, and today I'll tell you what I saw and learned there: new facts about places in distant reaches of our solar system, and stories about the challenges that space scientists face in doing their work.
In October of this year I attended the annual meeting of the Division of Planetary Sciences of the American Astronomical Society, which people usually just call "DPS." This year it was held in Pasadena, California, near Caltech and the Jet Propulsion Lab, and more than eleven hundred astronomers, geologists, physicists, and engineers were there for the five-day conference, along with students, bloggers, and other journalists like me.
I'll start by explaining how these meetings work. DPS, like most science meetings, has a combination of talk sessions and poster sessions. The talk sessions are very tightly scheduled. Each session was about two hours long and focused on one part of the solar system, like the Moon or Saturn's rings or the Kuiper Belt. Each researcher gets a ten-minute time slot. They're supposed to take only five or six minutes to talk about their work, and they usually illustrate their talks with PowerPoint slides showing their data and images. When they're done, there's a couple of minutes for questions from the audience, and then the next scientist gets up to present his or her work.
As you might imagine, it is incredibly challenging to present the results of years' worth of work in only five or six minutes. But this wasn't the only time they'd be presenting their work. Most scientists go to at least three or four of these kinds of major meetings per year. Each time, they usually just present an incremental step in the process of research that's been going on for months or years previously.
In the afternoons, there were poster sessions. Anybody who has ever done a Science Fair project would find the poster session familiar. Scientists compose detailed posters explaining their work and put them up in an exhibit hall. You won't usually see the headings "hypothesis," "materials," "procedure," and "conclusions," but if you read the posters you can often all those parts of the scientific method. The poster's presenter is supposed to stand near it for an hour or two so that they can discuss it with other scientists passing by. DPS, like other meetings, serves food and drink during poster sessions, which helps to lubricate the conversation and to make sure people will attend.
OK, that's enough explanation: what new results did I see there? DPS featured results from every part of the solar system and from every kind of research. There are 20 spacecraft out there returning data to Earth. This year, I couldn't wait to see the latest pictures from the European Space Agency's Rosetta mission, which flew past an asteroid named Lutetia in July. Lutetia is small and lumpy, but it's the largest asteroid that has ever been visited by a spacecraft. Nick Thomas talked at DPS about how Lutetia may be small but it's a whole world with complicated geology. Some places on Lutetia have very large craters, as you'd expect, while other places have no large craters, only a few small ones. There are places with deep grooves and others without, and places with enormous boulders, and other places that look smooth. They also showed huge landslides that cascaded down crater walls and spilled across their floors. The photos were beautiful, and most of them aren't available on the Web yet, and they're not likely to be for some time. That's one of the big differences in culture between European and American missions -- NASA likes to show the public what it's doing by releasing all the images very quickly, while European scientists hang on to their image data, keeping it secret as long as they can possibly get away with it.
One thing I like about going to conferences is that you can get a sense for what other scientists think of the presenter's work. I saw one talk that analyzed the topography and shape of Lutetia and showed evidence that there were incredibly steep slopes on it, where if you were standing on the surface, the angles of some slopes would be higher than 60 degrees. If that's really true, then Lutetia, or at least parts of it, has to be made of single solid blocks rather than being just a pile of broken-up rubble loosely held together by gravity. But a very well-known scientist who was sitting in front of me muttered that that work was not credible, using a term to describe its quality that I won't repeat on a G-rated show!
I also like going to meetings to get updates on work that's been going on with other space missions for years. The Cassini Saturn orbiter has produced an incredible quantity of data, and somewhere between a quarter and a third of the papers being presented at DPS had something to do with that mission. One main focus of Cassini has been Saturn's largest moon Titan, which is bigger than Mercury and has a thick nitrogen-rich atmosphere from which methane can fall as rain and carve rivers and pool in lakes. Lauren Wye presented evidence that Titan's lakes have changed size since Cassini first spotted them. Jason Barnes and Jason Soderblom showed that waves on Titan's lakes must be incredibly tiny, no more than millimeters in height. So if you could stand on the edge of a Titan lake, there'd be no waves lapping at your feet, but you would see the distant hills reflected beautifully in the mirrorlike lake surface. Feng Tian showed that earlier in Titan's history, the moon would have been colder, so its atmospheric nitrogen would have been condensed as lakes, with methane icebergs floating on top.
Several other teams argued back and forth about whether Titan has active volcanoes or not. That debate is one that's been going on since very early in the Cassini mission, and looks unlikely to end any time soon. The problem is that Titan's hazy atmosphere is very difficult to see through, and what you can see is blurry. Some scientists think they see surface changes, while others say it's just a product of Cassini viewing those spots from different angles. Another group looked at the massive dune fields that cover Titan's tropical regions, and suggested that there may actually be pools of liquid methane here and there between the sand dunes. It's not a nutty idea for sand dunes to have oases of water in between; we see such things on Earth.
Not all researchers use spacecraft. Others use telescopes. I spent one entire day at DPS in a room where one astronomer after another gave updates on their work studying the things at the edge of our solar system, like Pluto, Eris, Haumea, Varuna, and other trans-Neptunian objects. Research with telescopes has a pace that's totally different from spacecraft flybys. A flyby suddenly creates a huge pile of data that'll take scientists years to understand, but all the data is there from the beginning. With observational astronomy, scientists have to spend years adding tiny increments to their data sets.
Sometimes nature doesn't cooperate. During the first few talks in the Pluto session, by Leslie Young and Jay Pasachoff, most of the slides showed how the skies were cloudy at locations all over the world on the one night they'd hoped to catch the dwarf planet passing in front of a background star. But there are clear nights, and then astronomers can push the boundaries of what we know. One researcher reported on how his team kept looking at Kuiper belt objects repeatedly for years and have discovered that a lot of them are binaries -- there are two bodies orbiting each other. In many cases the binaries are quite close to each other, and these close binaries tend to be ones where the two bodies are similar in size to each other, just like Pluto and Charon.
The most fortunate astronomers get to fly above the weather and use the Hubble Space Telescope for their science. Dave Tholen and Marc Buie reported on years and years of observations of Pluto, Charon, and the smaller two moons that were recently discovered orbiting the ex-planet, Nix and Hydra, using Hubble. They found that Nix and Hydra were much darker than previously thought. That's important not only because we want to learn what Nix and Hydra look like, but also because astronomers estimate the sizes of these faint things from how much light they reflect; if their surfaces are darker than we thought, that means the moons are larger than we thought. The same team also found that Pluto's surface has changed and darkened dramatically in the last decade, while Charon's has not. All of these discoveries are heightening expectations for New Horizons' flyby, but we still have more than four years until the science data starts coming back from that mission.
Finally, there are scientists who rely more on physics than on data, building mathematical models to explain the formation of the solar system or the circulation of winds on giant planets, and then comparing their predictions to the real systems we can find in our backyard. My favorite of these was a talk by Robin Canup in which she explained how, when Saturn was first condensing out of a swirling nebula of dust and gas, there were probably many Titan-sized proto-moons. But all but one of these moons collided with the dust and gas and decayed in its orbit to smash into the proto-Saturn. What happened to the penultimate moon in her models was fascinating: the proto-Saturn stripped off all the outer icy material, sending it into orbit to create Saturn's icy rings, and then ate the rock-rich core. All the other scientists I talked with at the meeting were impressed with her presentation -- there's no way to prove that that's what happened more than four billion years ago, but it's a really neat story that explains an awful lot of strange details about the Saturn system.
I talked with a lot of scientists at DPS. Although the presentations and posters are fascinating, really the most important aspect of science meetings is the hallway conversations. I like to check in with veteran rings researcher Larry Esposito every meeting about whether he thinks Saturn's rings are primordial or recent (this time, his answer was "yes"). I like to have lunch with Imke de Pater to ask her about her telescopic observations of Jupiter and Saturn as well as the under-appreciated ice giants Uranus and Neptune. I like to meet face-to-face with people I have only previously met via email. I like to have a beer or two and crack geeky jokes with scientists who have been friends since we were in grad school together. And of course I love to meet people who have been enjoying reading my blog. Scientists tell me that because they spend all day focused on their research fields, they like to read what I write in order to learn about what's going on at planets other than the ones they study.
Visit The Planetary Society blog, where I write about space missions old and new. Check in regularly to see fantastic views of the surprising and strange landscapes to be found across the solar system. Thank you for listening.