Dawn, Vesta AND Ceres! :) Options

[Patteroast]

I just figured, since people here seem to have an inside track on the happenings of upcoming missions, we should have a thread prepared for this mission. You know, since it's so pressing.

I have to say Dawn is one of the most exciting missions planned in the near future for me. How's it coming along?

[Guest_Sunspot_*]

You probably have it already but: http://www-ssc.igpp.ucla.edu/dawn/

[Chmee]

This is a very exciting mission. I am very interested in seeing how Ceres looks, being the largest asteroid. It is big enough to even a spherical shape.

[Bob Shaw]

Oddly enough, the Hubble images suggested that it's flattened - a bit like a tangerine, so it looks like a sort of half-way house. There's also hope of finding some Mars-like surface features as a result of the high water content...

[Mongo]

There's also hope of finding some Mars-like surface features as a result of the high water content...

There is also a chance, according to the Dawn website linked a few posts above, that Ceres may have a (very) thin permanent atmosphere.

Bill

[Decepticon]

This is a very exciting mission.  I am very interested in seeing how Ceres looks, being the largest asteroid. It is big enough to even a spherical shape.

I'm surprised that even at Hubble's resolution Ceres pics look so bad. Compared to the Vesta images.

Example of ceres picture. http://www.planetary.org/html/news/article...ceres_spot.html


Does anyone know the closets Ceres comes to earth?

[hendric]

I'm surprised that even at Hubble's resolution Ceres pics look so bad. Compared to the Vesta images.

Vesta has a much higher albedo, 0.38 vs 0.1 for Ceres, it is somewhat closer (it's the brightest asteroid in the sky, and at the right time in dark-skies should be visible naked-eye).

Also, you might be confusing the Vesta images with a Hubble-based 3-D model. Check out this:

http://www.solarviews.com/eng/vesta.htm

Another possibility is that with the low albedo, more stretching is necessary in the raw images to bring out brightness differences.

I'd also bet alot more telescope time is spent on Vesta, because of the large "volcanic" markings, vs Ceres' relatively homogenous surface.

Other than those, no clue.

[Decepticon]

Ahh I see. Thanks for clearing that up.


When we finally see Ceres close up will be a a life long dream for me.

I consider this little rock the precursor to a rocky planet.



I've always wondered if Ceres contains Subsurface Ice and past geological activity.

[Jyril]

IMO Vesta is more interesting, since it seems to be the only clearly differentiated body in the asteroid belt. Ceres is more like a giant-sized primordial asteroid (which, of course, is interesting in its own right).

BTW, is Dawn going to make any other asteroid flybys?

[Guest_BruceMoomaw_*]

When Dawn was first acepted, C.T. Russell told me that they had in mind as many as a half-dozen flybys of other asteroids planned for the mission in addition to the rendezvous with Vesta and Ceres -- with a wide variety of possible targets, depending on how efficient its SEP drive was. Of course, since then, they've had to downsize the mission and radically change its trajectory; it's time I checked with him again.

As for Ceres, there's been an awful lot written lately on the serious possibility that it may have water-frost polar caps and a substantial amount of aqueous mineral alteration on its surface. (One major disapointment for the Dawn team is that they had to remove the magnetometer, which could have looked for a subsurface liquid-water table on Ceres.) Also, at the 2003 DPS meeting a team using the adaptive-optics Keck telescope released by far the best Ceres photos ever taken (50-km resolution; much better than Hubble's), which very clearly showed two round features 130 and 190 km wide -- almost certainly crater floors -- with albedos 5-10% darker than their immediate surroundings. The bigger one had a very big bright spot inside it, so that it was actually a dark ring -- and it showed unusual spectral characteristics. This suggests some very interesting modification processes on Ceres' surface. (The same photos, by the way, totally failed to show the much bigger "Piazzi" spot supposedly seen by Hubble -- which suggests the possibility that it was an artifact of those images' lower resolution.) I'm surprised that there has apparently been no publicity for those photos since, and am about to do a Web search on them.

Combine this with the puzzle of the huge lava flows on an object as tiny as Vesta -- and the continuing puzzle of how asteroids in not-too-distant orbits can be so radically different in composition -- and Dawn promises to be a very interesting mission even with its downsized science payload.

[Guest_BruceMoomaw_*]

Bwah-ha-ha! Here they are ( http://www.cfht.hawaii.edu/Instruments/Ima...pueo-nui-ss.pdf ; pg 13). Feature B is the dark crater with the big light spot inside it, although at the meeting he showed a few other photos clearly showing feature B marching across Ceres' disk as it rotates. All of Dumas' other abstracts on this subject seem to have been yanked off the Web, which suggests that he's about to publish an official piece on the subject. Also note the photos on pg. 14 showing the extremely irregular shapes of Juno (the asteroid, not the space probe) and Davida -- which he also showed at that conference -- and some neat views of Vesta and a whole series of asteroidal satellites (which I have NOT seen before; pg. 6 and 20).

However, another odd twist: while looking for these, I also found some 2004 Hubble photos of Ceres which seem even better ( http://www.boulder.swri.edu/AR2004/ ) -- and, by gum, they very clearly show the huge light Piazzi Spot. I don't know what to make of all this yet. (Once again, Joel Parker's official paper has yet to be published, although it's been submitted to "Advances in Space Research".)

[Guest_BruceMoomaw_*]

Screwup on my part: I hd forgotten that the Piazzi Spot was supposed to be dark, not light ( http://www.geocities.com/zlipanov/selected...es/1_ceres.html ). Actually, Parker's one abstract on his new observations say that the improved 2004 Hubble photos showed "one light spot" (which is what stands out blindingly on the photos in the SwRI report) and "one dark spot". And, on looking at Hubble's original views of the Piazzi Spot, they're so extremely fuzzy that maybe it IS one of the two dark spots identified on the Keck photos. Anyway, there's obviously some interesting stuff there.

[hendric]

I sent an email to their "Ask a Scientist" link and got this response:

I tried to reply at the website but it seems that I need a user account and password. If you could please let people know that Dawn is doing fine. The Xe tank etc. was assembled at JPL several months ago. The remaining assembly is taking place at Orbital. Some 90% of the parts have been delivered. Launch is scheduled for June 17th 2006.

The trajectory will not be finalized until sometime in July. I can tell you that targets of opportunity are being explored. There will be opportunities to test the instrumentation as well. It is too early to go into detail about an extended mission, but a discussion about that is in people’s minds.

Updates and pictures are available at: http://dawn.jpl.nasa.gov

Let me know if I can be of any more assistance.

J. A. Wise

Dawn E/PO Manager

I'm going to ask about their image release policy...

[Bob Shaw]

Bruce:

Ver-r-r-r-r-y interesting asteroidal images - I swear there are some stereo pairs in the HST Ceres images at SWRI!

Bob Shaw

[AndyG]

Does anyone know the closets Ceres comes to earth?

1.7AU. About 14 light-minutes.

Andy G