Dawn at Ceres Thread

[-ctn-]

So does anyone know how those radial ejecta (?) lines would form? Don't they usually spider outwards from an impact crater? They look almost parallel to eachother. Or is that specific type of surface feature not uncommon? I'd never seen it before, that I can recall.

[Scotius]

Similiar structures were found on the surface of Callisto and Ganymedes. Astronomers theoretise they were formed by chain-impacts by comets\asteroids ripped to pieces by Jupiter's gravitation - like comet Shoemaker-Levy 9 was.

https://en.wikipedia.org/wiki/Crater_chain

[-ctn-]

So if I understand correctly, those are theorized to be caused by intense gravity - so on such a small gravity world, would those be caused by Ceres' own gravity? Or just chunks that happened to fall into place like that?

[Scotius]

We don't even know if they are real chain craters. Maybe they're old, mostly eroded cracks created when Ceres was cooling (and contracting because of loss of heat).

[Newt]

At least some of the lines that I beleive you all are reffering to, appear perhaps to radiate from a large basin. These would be, from my understanding, either cracks of some sort (as on Vesta), or strings of secondary craters (as occur on the Moon).

[PB666]

Looking at this picture, i can't shake the feeling i'm looking at a very old surface. Flat, eroded craters, no mountains worth mentioning except that solitary peak. Compared to Ceres, Moon looks sharp and well defined. Mercury too, for that matter. Did Late Heavy Bombardment missed Ceres completely?

Ceres may have been hit by larger numbers of small impactors causing the earlier craters to loose their distinction. The sun has also been increasing intensity and this may have caused degassing of lighter element deposits on the surface.

[Exoscientist]

Same old spots from same old altitude (13600 km) on May 7th. Yesterday, Dawn reached its new orbit at 4400 km of height above the surface. That's 3x the resolution in this image! Can't wait for the photos.

http://3.bp.blogspot.com/-fFAGp6e-xh8/VXCQSX4eQLI/AAAAAAAAEXE/L7oc2NrJefM/s1600/PIA19557.tif

You added an extra 0 to those distances.

Bob Clark

[Wallygator]

Looking at this picture, i can't shake the feeling i'm looking at a very old surface. Flat, eroded craters, no mountains worth mentioning except that solitary peak. Compared to Ceres, Moon looks sharp and well defined. Mercury too, for that matter. Did Late Heavy Bombardment missed Ceres completely?

At first I thought the same, however on reflection (get that?) I would think that the specular reflection creates a very low contrast in the upper hemisphere which might seem like a smooth surface but when I look at the terminator there seems to quite a bit of relief. Only a proper altitude map will give a conclusive answer.

[Frida Space]

You added an extra 0 to those distances.

Bob Clark

Do you mean it should have been 440 km instead of 4400? No, 4400 was correct. Actually, if you want to be very precise, it should have been 4300 km and not 4400 as I wrote, but the number of zeros was already fine.

[Exoscientist]

Do you mean it should have been 440 km instead of 4400? No, 4400 was correct. Actually, if you want to be very precise, it should have been 4300 km and not 4400 as I wrote, but the number of zeros was already fine.

You are correct. I was mixing up distance and resolution. Here is a chart showing the mission schedule; notice there is about a factor of 10 difference between the distance and resolution for the metric units:

Dawn just entered into the Survey portion where the resolution will be at 410 meters per pixel. Looking forward to the next image release at this improved resolution.

The best will be in December though at only 35 meters per pixel.

Bob Clark

Edited June 7, 2015 by Exoscientist

[Frida Space]

A truly glorious aerial tour of Ceres.

[Findthepin1]

what is the object in the profile picture

is that ganymede

[Frida Space]

what is the object in the profile picture

is that ganymede

Me? It's Saturn's moon Dione as seen from Cassini on May 9th, 2015, colorized. https://www.flickr.com/photos/lunexit/17335037590

[Frida Space]

Ceres from 5100 km away on May 22, 2015. Resolution is 480 m/pixel. Great tweet from Dawn: "Just started taking images in my new orbit. The team will share a new view of the bright spots soon. Stay tuned!"

[Scotius]

Those "scratches" definitely do not look like impact features.

[Robotengineer]

Is it just me or do they seem to go in the same general direction?

[-ctn-]

It looks like someone scraped a gardening tool across it, haha.

If if you look closely, they are tiny, successive craters. Like if you rolled a heavy rock across the surface. Wonder what they actually are and how they formed.

[SnakyLeVrai]

A truly glorious aerial tour of Ceres.

All we need now is to ask the DLR if they can give us the elevation files so we could put it in KSP

[Nibb31]

It looks like someone scraped a gardening tool across it, haha.

If if you look closely, they are tiny, successive craters. Like if you rolled a heavy rock across the surface. Wonder what they actually are and how they formed.

They could be caused by meteorites that disintegrate into many smaller parts and crash while the planet rotates. Maybe a phenomenon similar to the Shoemaker-Levy 9 observations could cause something like this.

Edited June 9, 2015 by Nibb31

[Frida Space]

Again, from 5100 km.

[-ctn-]

They could be caused by meteorites that disintegrate into many smaller parts and crash while the planet rotates. Maybe a phenomenon similar to the Shoemaker-Levy 9 observations could cause something like this.

But Ceres' gravity is surely not nearly strong enough to rip apart meteorites?

[AndrewBCrisp]

Not necessarily: as I understand it, it's tidal forces that can tear apart objects bound together by gravity, and then only when they fall inside a given body's Roche limit. A basic rule of thumb is that Roche's limit is approx. 2.4 x the radius of a given body. For Ceres, this works out to 1,125 km. So, if you get a small asteroid passing close to Ceres, it could conceivably break apart. Once outside of Ceres' influence, the fragments might re-coalesce, or depending on the path, diverge widely. This would probably work best with asteroids that are less dense than Ceres - so water-ice and rock would shatter, but solid iron-nickel might survive intact.

That's as I understand the principle, anyway. Any errors are my own.

[Frida Space]

Wow. The spots from 4400 km on June 6th.

And part of the southern hemisphere too:

Edited June 10, 2015 by Frida Space

[vixr]

I just looked over an article on flipboard about what those shiny spots on Ceres could be (obviously alien tech) and included was a short flyby video clip produced by NASA... as I watched the vid, I kept making mental notes of the most desirable flat spots to land on... KSP has ruined me.

Edited June 10, 2015 by vixr

[Frida Space]

Am I the only one to think that the bright dots are overexposed? I mean, if they reduced a bit the exposure time of the Framing Camera maybe the rest of the surface would look very dark, but maybe we could get a few hints on the structure and features inside​ the dots.