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Holder of the Two Leashes
This thread will cover all final phases of the Dawn mission, the end of which is not certain at this point.

XMO3 was suppose to be the final orbit, but now plans have changed and it will move into a new higher altitude and higher phase orbit soon. This will be XMO4.

An interesting monthly journal for January details the plan:

Dawn Journal 31 January 2017
TheAnt
Ahuna mons have turned out to be what is called one "ice volcano"
(Used in lack of a better word in american English I guess, my native language got a word for underground water that instantly freeze as it enter the surface in the wnter which would have been very suitable here.)
Now why only a single such feature?
The American Geophysical Union put some thought on that matter and suspect there's other ones that have flattened out and started a search for potential other sites.
ngunn
QUOTE (TheAnt @ Feb 4 2017, 06:09 PM) *
Now why only a single such feature?


Another possible answer might be that the whole of Ceres is acting like a single pressure vessel with relatively fluid contents. This would require only a single relief valve (at any given time).
Gladstoner
QUOTE (TheAnt @ Feb 4 2017, 12:09 PM) *
Now why only a single such feature?
The American Geophysical Union put some thought on that matter and suspect there's other ones that have flattened out and started a search for potential other sites.


Perhaps the raised area adjacent to Ahuna is such a feature:

Click to view attachment

The elevation of this area seems to be anomalous compared to the surrounding topography. It does not appear to be associated with any crater/ basin rims or central peaks. Its association with Ahuna seems to imply a relationship of some kind. The surface of this feature is heavily cratered, which means it has been around much longer than Ahuna. Either this feature is an area of general uplift associated with the formation of Ahuna, or it is an older volcanic edifice of the upwelling that produced Ahuna (i.e. 'ancestral Ahuna') that has subsequently suffered subsidence and erosion. Or perhaps both processes were in play. Finally, it is possible it presence there could be purely coincidental.
TheAnt
@Gladstoner: You might indeed have pointed out Ahuna mons predecessor there.
But yes, it cannot be ruled out that it's associated with the current formation. We just have to wait for the verdict by the professionals.
Regardless of which two it turn out to be, I don't think it's coincidental.

What is interesting is the comparatively short timeframe for a feature like this to relax and get near invisible.
If it is lets say 10 MY, that would mean that there's some ongoing activity inside Ceres to create a feature like Ahuna mons.
The big question then will be if it's continuous or periodical.

Well this higher altitude orbit might perhaps get us a chance to catch an image of the possible fog over Occator. Backlit by the Sun would be the best way to catch it just as on Enceladus.
Gladstoner
QUOTE (TheAnt @ Feb 5 2017, 06:39 PM) *
What is interesting is the comparatively short timeframe for a feature like this to relax and get near invisible.
If it is lets say 10 MY, that would mean that there's some ongoing activity inside Ceres to create a feature like Ahuna mons.
The big question then will be if it's continuous or periodical.


Based on the features' appearances and on the (apparent) lack of extensive activity on Ceres, I'd think any volcanic processes would be episodic.
Daniele_bianchino_Italy
" Asteroid Dust Cloaks True Composition Of Dwarf Planet Ceres "

" Observations of Ceres indicate that asteroids might be camouflaged "
http://www.seti.org/seti-institute/press-r...-be-camouflaged

" Dwarf planet Ceres camouflage by asteroid dust ":
http://www.space.com/35451-dwarf-planet-ce...eroid-dust.html
Daniele_bianchino_Italy
?
Is expected to map temperatures of Ceres? I expected Already for long time :-/
Paolo
on today's Science (and behind the paywall... mad.gif )

Localized aliphatic organic material on the surface of Ceres

QUOTE
Organic compounds occur in some chondritic meteorites, and their signatures on solar system bodies have been sought for decades. Spectral signatures of organics have not been unambiguously identified on the surfaces of asteroids, whereas they have been detected on cometary nuclei. Data returned by the Visible and InfraRed Mapping Spectrometer on board the Dawn spacecraft show a clear detection of an organic absorption feature at 3.4 micrometers on dwarf planet Ceres. This signature is characteristic of aliphatic organic matter and is mainly localized on a broad region of ~1000 square kilometers close to the ~50-kilometer Ernutet crater. The combined presence on Ceres of ammonia-bearing hydrated minerals, water ice, carbonates, salts, and organic material indicates a very complex chemical environment, suggesting favorable environments to prebiotic chemistry.


see also the Science perspective article: Dwarf planet Ceres and the ingredients of life
and the JPL press release: Dawn Discovers Evidence for Organic Material on Ceres
TheAnt
This is the kind of news that could have me literally jumping up and down.
Water, ammonia, salts, cabonates and now this!
It might be quite premature to speculate if any space agency will jump at this opportunity.
But it's a fact that Ceres would provide an easy target for a lander mission.
With the very low gravity it would even be possible to have a 'jumping' lander visiting several sites for sampling.
Even the idea of returning samples might be considered.
Aliphatic organic matter - it's not any of the lighter ones, they would be long gone, from a single spectral line it's hard to say how complex those molecules are.
But I'd give an arm and a leg to have closer look at a sample here on Earth.

Explorer1
There's probably already samples of Ceres on Earth, just not yet identified as such. All those craters must have made sprayed ejecta everywhere and some meteorites must be here now, just by probability.
Otherwise a sample return mission might in fact be easier than Mars; lack of atmosphere and low gravity making up for the greater difference in orbits...
fredk
QUOTE (Explorer1 @ Feb 19 2017, 06:30 AM) *
lack of atmosphere

Doesn't atmosphere help you at Mars? You'd need a heck of a lot of fuel to brake from orbit and land without atmospheric drag. The drag would affect a launch from the surface, but with low launch speeds and thin atmosphere I'm guessing that's not a big effect.

Of course lower gravity at Ceres means lack of atmosphere won't be as important as it would've been at Mars.
Explorer1
Yes, I was talking about launching from the surface. I vaguely recall reading an article a few years ago about someone working on an engine for an ascent stage to get straight to Earth, no need for rendezvous; can't find it now. Anyway, this is a discussion for another thread, another time.
Daniele_bianchino_Italy
QUOTE (Daniele_bianchino_Italy @ Feb 8 2017, 09:53 AM) *
?
Is expected to map temperatures of Ceres? I expected Already for long time :-/


Repropose my UP question... ?

I know that Ceres has no seasons like earth. However, we can say that it is entering its warm period. Dawn was arrived to Ceres in the beginning of the cold season. Too bad the mission will end before the maximun warm season of Ceres.

PhilipTerryGraham
They're starting to publish XMO3 images on the NASA Photojournal! The first is this interesting context view of Ahuna Mons and Occator crater, taken on 11 February.

EDIT: Here's a version I uploaded to Wikimedia Commons, with annotations labelling all the discernible features in the image, per the official nomenclature by the IAU.
Habukaz
QUOTE (Daniele_bianchino_Italy @ Feb 8 2017, 10:53 AM) *
?
Is expected to map temperatures of Ceres? I expected Already for long time :-/


Some pictures showing temperature have been generated. Here's a few that I am not sure if have been posted to the Photojournal, where you can find the others. Don't know about global or other larger maps, or time series of temperature.
Daniele_bianchino_Italy
QUOTE (Habukaz @ Feb 26 2017, 01:25 PM) *
Some pictures showing temperature have been generated. Here's a few that I am not sure if have been posted to the Photojournal, where you can find the others. Don't know about global or other larger maps, or time series of temperature.


Thanks!
235 K -38C
196 K -76C
However, the VIR images are of the last year.
Ceres from this year begins to warm. The mission will not arrive to the maximum hot season of Ceres, but it could show more high temperatures in the next months....
nprev
ADMIN MODE: Moved four recent posts to the former "Water Vapor on Ceres" thread, which has been retitled "Ceres Geology". I think that discussion will continue long after the Dawn mission is completed. Thanks! smile.gif
Gladstoner
Long-range image taken on March 28:

https://photojournal.jpl.nasa.gov/catalog/PIA21401

Click to view attachment

The brightness of the Occator faculae is pretty subdued at this lighting and viewing angle.
Holder of the Two Leashes
Dawn has lost another (third) reaction wheel. But it looks like the opposition studies scheduled for Saturday the 29th will not be affected.

Dawn Status Report
Explorer1
Opposition observation data received! https://dawn.jpl.nasa.gov/mission/status.html
hendric
Man, if I ever win the lottery I'm going to work on making longer-lasting reaction wheels for space missions. sad.gif
djellison
There are many old spacecraft with great reaction wheels still working fine. But there must have been some batch - some particular hardware version rev that has hit Kepler and Dawn.
Explorer1
Movie from opposition observations released: https://www.jpl.nasa.gov/news/news.php?feature=6845
New journal soon, presumably.
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