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Headshot of Emily Lakdawalla

Ceres: Just a little bit closer (and officially better than Hubble)

Posted by Emily Lakdawalla

27-01-2015 18:26 CST

Topics: pretty pictures, amateur image processing, asteroids, Voyager 1 and 2, Dawn, asteroid 1 Ceres, Uranus' moons

Last week's Dawn images of Ceres were just slightly less detailed than Hubble's best. This week's are just slightly more detailed. Detailed enough to be dangerous. It's very tempting to talk myself into interpretations of the various light and dark splotches visible in this latest animation -- I see double-ringed craters, arcuate ridges, and a smattering of bright dots that I want to call fresh impact craters. But since Dawn's getting closer every minute, I'm going to refrain from drawing any conclusions for a little while! In the meantime, let's just enjoy the images.

Here's the animation more or less as released by the Dawn team -- I aligned it and tweaked the levels a little bit:

Dawn's view of Ceres on January 25, 2015 (animation)

NASA / JPL / UCLA / MPS / DLR / IDA / Emily Lakdawalla

Dawn's view of Ceres on January 25, 2015 (animation)
This animation is composed of 20 images gathered over a period of about an hour for optical navigation purposes. Dawn was 237,000 kilometers from Ceres at the time.

Just for fun, let's compare it to the view from January 13:

Dawn optical navigation sequence on Ceres, January 13, 2015


Dawn optical navigation sequence on Ceres, January 13, 2015
Dawn took the 20 images for this animation on January 13, 2015, in its first lengthy optical navigation sequence on asteroid 1 Ceres. Dawn was 383,000 kilometers away at the time. The images in this animation have been aligned and contrast-adjusted.

As he did last week, Björn Jónsson took a subset of the frames from the animation, reprojected them to a common map projection, stacked them, and then reprojected the result to give a super-resolution view of the globe. It's lovely work. But I think I'm still going to put off expressing opinions about what I see. We'll get to watch these features grow and come into focus over the next few weeks. I can be patient for that much longer!

Dawn's view of Ceres on January 25, 2015 (super-res stack of 9 images)

NASA / JPL / UCLA / MPS / DLR / IDA / Björn Jónsson

Dawn's view of Ceres on January 25, 2015 (super-res stack of 9 images)
This image of Ceres is composed of 9 frames from the January 25, 2015 optical navigation movie, stacked and then sharpened in order to reveal sub-pixel detail.

If the images look blurry to you, it's because they've been enlarged. The Dawn team did release still images, one each from January 13 and January 25, showing just how much of the Framing Camera's field of view Ceres presently occupies. It's not much: 27 pixels in the first, and 43 in the second. In both cases, that beacon of a white spot on Ceres is essentially just one pixel. That means it's rather small, and really shockingly bright by comparison to the rest of Ceres' surface.

Shortly after these images showed up online, Ted Stryk pointed out an interesting similarity, which I shared on Twitter:

Pretty striking similarity, eh? To be fair, a lot of things in the solar system look similar when they occupy less than 50 pixels' width on your camera detector. The comparison does make me wonder whether Ceres will continue to look like Umbriel. Whether or not it does, I wonder what Umbriel would look like if we sent a modern camera on a spacecraft that could enter orbit at Uranus to photograph it. We need a mission to an ice giant!

Umbriel (2013 version)

NASA / JPL / Ted Stryk

Umbriel (2013 version)
This view of Umbriel was composed by stacking Voyager 2's best two images of it, and coloring it using images taken from a greater distance.
See other posts from January 2015


Or read more blog entries about: pretty pictures, amateur image processing, asteroids, Voyager 1 and 2, Dawn, asteroid 1 Ceres, Uranus' moons


alan: 01/28/2015 05:48 CST

Can't wait for the high res images, just speculation, but assuming the white spot is ice within a crater, unless it is really recent, would there not be sublimation, or some form of deposition that would have made it less prominent? Alternative explanations?

jody: 01/28/2015 06:23 CST

XKCD has an alternative explanation.

alan: 01/28/2015 08:56 CST

Only serious alternative explanations need apply

Steven Taylor : 01/28/2015 02:53 CST

I also am finding it difficult to wait for higher resolution images. Re White Spot. I read that it still is contained in a single pixel, so its true size and albedo is still uncertain. Perhaps we are looking at the underlying surmised ice layer. It would be good to know the latitude of this feature. As the tilt of Ceres is low, and if the albedo is high, the temperature would surely be much lower than the often quoted figure of -40 Celsius.

rickray777: 01/28/2015 03:26 CST

Very interesting! I can almost see what looks like hummocky cratered terrain. And the white spot: I once saw a cartoon that depicted it as a small tag saying "Inspected by No. 6"! But in reality, I would have to say that it's probably a small, white-floored crater on Ceres (the rest of the surface being covered in rather darkish material). Kind of like the Uranian moon Umbriel; except that it's rather unlikely to be another "fluorescent Cheerio"!

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