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Headshot of Emily Lakdawalla

New views of three worlds: Ceres, Pluto, and Charon

Posted by Emily Lakdawalla

16-04-2015 15:17 CDT

Topics: trans-neptunian objects, New Horizons, pretty pictures, Pluto, Charon, asteroids, Dawn, global views, asteroid 1 Ceres

This week we've been treated to new views of three worlds: Ceres, Pluto, and Charon. As New Horizons is still quite far away from Pluto and Charon (more than 100 million kilometers away), they are mere dots. But these dots are the first color images of Pluto and Charon from New Horizons, taken by the Ralph Multispectral Visible Imaging Camera (MVIC).

New Horizons' first color view of Pluto and Charon

NASA / JHUAPL / SwRI

New Horizons' first color view of Pluto and Charon
This image of Pluto and its largest moon, Charon, was taken by the Ralph color imager aboard NASA's New Horizons spacecraft on April 9 and downlinked to Earth the following day. It is the first color image ever made of the Pluto system by a spacecraft on approach. The image was made from a distance of about 115 million kilometers.

Before you get too excited about interpreting features on the surface of Pluto from this image, you need to realize that it has been enlarged by quite a lot from the original resolution of the camera. If I've done my math right, it's been enlarged by a factor of six. Just for fun, I've "de-enlarged" the image by reducing its size by a factor of six -- these don't show you the data's actual original pixels, but it should illustrate the size of the original pixels. (They would have had to enlarge the image somewhat in order to successfully overlay the separate MVIC frames taken at different wavelengths in order to make the color photo, so there really is no original-resolution version of this picture.)

New Horizons' first color view,

In the original data, each pixel would have covered about 2300 kilometers -- just barely under the size of Pluto. So neither Pluto or Charon are actually resolved; Charon is a point source, and Pluto is basically a point source, too. All the detail that you might think you see in the publicly released image has to do with the camera instrument, not with any surface variation on Pluto. It's basically just a graphical representation of the camera's point-spread function -- a description of how light from a point source spreads out across the detector.

But there's nothing wrong with that -- it's very early in the science mission yet, and there is only better to come! The first images from MVIC that will be better than Hubble's will come at the end of June. MVIC has four times lower resolution than the monochrome camera, LORRI, so New Horizons has to be four times closer to Pluto for MVIC to achieve the "better than Hubble" landmark than for LORRI. LORRI will get better than Hubble at the end of May.

Meanwhile, Dawn is a lot closer to its target, Ceres, and spiraling closer every day. Dawn performed its sixth optical navigation observation of Ceres on April 10, just a day after New Horizons took its color picture. Dawn's perspective is down on the north pole of Ceres, so we're watching it spin beneath the spacecraft for roughly an hour out of Ceres' 9-hour day.

Dawn optical navigation sequence on Ceres, April 10, 2015

NASA / JPL / UCLA / MPS / DLR / IDA

Dawn optical navigation sequence on Ceres, April 10, 2015
This animation shows the north pole of dwarf planet Ceres as seen by the Dawn spacecraft on April 10, 2015. Dawn was at a distance of 33,000 kilometers when its framing camera took these images. The spacecraft was maneuvering toward its first science orbit, which it will enter on April 23.

It's such an unusual perspective to look down on a round world's pole like this! I'm trying to think of another animation of any other world in the solar system with a similar view -- nearly at a standstill at a very high latitude, watching it spin -- and I can't really think of any, except maybe for Cassini's observations of Saturn's poles.

Here, I've split the animation out into its 20 frames.

Dawn optical navigation sequence on Ceres, April 10, 2015 (individual frames)

NASA / JPL / UCLA / MPS / DLR / IDA

Dawn optical navigation sequence on Ceres, April 10, 2015 (individual frames)

You might notice on the right side at the beginning of the animation that there are two very bright-toned peaks jutting into space. On Twitter, someone asked me if these were Ceres' two bright spots. I couldn't figure out the answer so I asked the question at unmannedspaceflight.com and user JohnVV quickly responded to say that they were not. The territory visible in the animation is from 50 to 90 degrees north latitude; the bright spots are at 20 degrees north. But don't fear -- we'll get a closer look at the bright spots before too long!

 
See other posts from April 2015

 

Or read more blog entries about: trans-neptunian objects, New Horizons, pretty pictures, Pluto, Charon, asteroids, Dawn, global views, asteroid 1 Ceres

Comments:

Chris Radcliff : 04/16/2015 04:25 CDT

Thanks for clarifying the part about the Pluto image. When it was originally publicized, I found myself doing just as you described: peering at that blob of blurry Pluto and wondering at its odd shape and coloration. After seeing the "re-original", my brain now knows I can stop speculating until better photos are available. :)

Kim Craig: 04/16/2015 05:40 CDT

Hi Emily, MESSENGER's highly elliptic orbit may have provided similar polar views with its wide angle camera.

Tony Fisk: 04/16/2015 06:30 CDT

'We want the white spots' is hardly a proper scientific response to being able to see any part of a new world (although I can understand it!) Meanwhile, I really ought to try mapping out NH's final approach to Pluto on Port Melbourne's 1:1,000,000,000 scale map of the Solar System. (100m, and closing)

Hari Nair: 04/17/2015 09:15 CDT

MESSENGER did indeed make animations of the north and south poles of Mercury. You can see the terminator slow down, reverse, and continue back on its way due to the spin:orbit resonance and eccentricity of the orbit. They're about half way down the list here: http://messenger.jhuapl.edu/the_mission/movies.html

Messy: 04/18/2015 08:12 CDT

It's not "we want the white spots!" it's more, "are those plumes from the white spots?" which means that Ceres is an active world, which is at the moment the most exciting thing about the features. There are other white spots on Ceres, and maybe those are active too. The most important thing about the Ceres and Pluto pictures is that they prove the probes are still working.

rickray777: 04/19/2015 06:02 CDT

WOW, multicolored clouds completely covering Pluto's surface? (Sigh) Even in such a worst-case scenario, someday our species WILL find out what the surface of Pluto is really like. I mean, not us, obviously; but I AM sure our descendants will (i.e., our grandchildren, great-grandchildren, perhaps?). Yes, it would be my life's dream to see the Plutonian surface up close! The thing is, I've always been a little wary about such over-anticipation since that Titan thing back in 1980. An atmosphere, sadly, need not be very thick to be completely opaque.

Husbagm: 04/23/2015 08:00 CDT

In the latest close up picture from ceres of the bright spots there appears to be a very large round smooth black dome on the edge of the crater closest to the camera. Have you noticed that and any comment on what it could be. All the attention is to the growing number of spots but this seems to be a new and intriguing feature unless it is a trick of the light or camera angle.

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