APOD: Contrasting Terrains on Comet... (2014 Aug 19)

Comments and questions about the APOD on the main view screen.
bactame
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Re: APOD: Contrasting Terrains on Comet... (2014 Aug 19)

Post by bactame » Wed Aug 20, 2014 6:25 am

Landing on the object is one thing but drilling into the surface seems foolhardy. The object is obviously in a tenuous state and anything can disturb and change its behavior. The smooth spots are likely dusts or condensates and landing there will remove the material. This would interfere with analysis possibly reveal cracks which drilling will exacerbate. If you've got to land do so on a visible surface. Just because the craft has tools shouldn't imply they must be used.

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Chris Peterson
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Re: APOD: Contrasting Terrains on Comet... (2014 Aug 19)

Post by Chris Peterson » Wed Aug 20, 2014 2:16 pm

bactame wrote:Landing on the object is one thing but drilling into the surface seems foolhardy. The object is obviously in a tenuous state and anything can disturb and change its behavior. The smooth spots are likely dusts or condensates and landing there will remove the material. This would interfere with analysis possibly reveal cracks which drilling will exacerbate. If you've got to land do so on a visible surface. Just because the craft has tools shouldn't imply they must be used.
There's nothing "tenuous" about this comet. It has undergone cyclic gravitational interaction with the Sun hundreds or thousands of times, every few years, been subjected to heating and cooling, and regular outgassing. A bit of shallow sampling of its surface isn't going to have any effect on it.
Chris

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JohnD
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Re: APOD: Contrasting Terrains on Comet... (2014 Aug 19)

Post by JohnD » Wed Aug 20, 2014 4:41 pm

The shape of the comet will make the gravity field around it complex, and according to the NS, the green landing sites (bottom of first page) are where it will be most vertical to the surface. The neck will be a poor site as what gravity there is there will not be vertical to the 'ground'.

Won't the investigators want to land on a 'rocky' area? The dust that has settled elsewhere may be mainly from this comet, but could be from anywhere.

John

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Re: APOD: Contrasting Terrains on Comet... (2014 Aug 19)

Post by ta152h0 » Wed Aug 20, 2014 4:53 pm

Certaily will not be anything like Tempel 2 was . That impact would have fractured this comet, maybe rung its bell for a while
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Re: APOD: Contrasting Terrains on Comet... (2014 Aug 19)

Post by SouthEastAsia » Thu Aug 21, 2014 1:43 am

alter-ego wrote:
SouthEastAsia wrote:I'd go for landing in the center of that crater/wall-like structure in the lower-right image, on Comet's body. It might be best protected against the elements there, while also perhaps being able to study more about the interior of a circular wall on a Comet? Just my thoughts...
The landing site will need to be in sunlight a significant amount of time due to the solar cells covering the lander, Philae. The red zones (100% sunlight) are apparently not favored, while the yellow and orange zones are. The green spots mark provisional landing sites. The blue zones are in permanent shadow.

Hey, thanks for that very interesting info and link!

Based on what you gave, I'm going to make an assessment that the said walled/crater-like structure in the lower-right image on Comet's body might actually correlate to the 'Orange' coordinates on the digitzed landing analysis graphic?

And orange oasis within a sea of 100% red no-go zone?

If so, my gut would still just say; go for that neat little sweet zone (even if it's not one of the provisionals)!

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Re: APOD: Contrasting Terrains on Comet... (2014 Aug 19)

Post by stargazer » Thu Aug 21, 2014 6:54 am

What seems interesting to me:
- Why is gravel laying on the smooth surface of the neck? I mean one of the two chunks should serve as a center of gravity where the rocks fall on. Or ist this the place where the the gravity of both big pieces compensates each other?
- Close to the top edge of the picture, right below the 9 of August 19, one sees a gravel field below a cliff on a smooth surface. I magnified the picture and found a large rock with a very straight feature emanating. It's not an optical distortion because also the shadow corresponds to the shape. Would be graet if Rosetta or Philae had a closer look.

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Re: APOD: Contrasting Terrains on Comet... (2014 Aug 19)

Post by alter-ego » Wed Sep 17, 2014 4:48 am

SouthEastAsia wrote:
alter-ego wrote:
SouthEastAsia wrote:I'd go for landing in the center of that crater/wall-like structure in the lower-right image, on Comet's body. It might be best protected against the elements there, while also perhaps being able to study more about the interior of a circular wall on a Comet? Just my thoughts...
The landing site will need to be in sunlight a significant amount of time due to the solar cells covering the lander, Philae. The red zones (100% sunlight) are apparently not favored, while the yellow and orange zones are. The green spots mark provisional landing sites. The blue zones are in permanent shadow.
Hey, thanks for that very interesting info and link!

Based on what you gave, I'm going to make an assessment that the said walled/crater-like structure in the lower-right image on Comet's body might actually correlate to the 'Orange' coordinates on the digitzed landing analysis graphic?

And orange oasis within a sea of 100% red no-go zone?

If so, my gut would still just say; go for that neat little sweet zone (even if it's not one of the provisionals)!
So of 10 remaining candidate landing sites (Sep 15), site "J" has been tentatively chosen, pending final review. It is on Chury's small lobe, and is near gas jets already forming (S&T). I think I've located site J on the earlier graphic. The perspectives do not correlate exactly but close enough to show some similar features (in particular the permanent shadow zone):
Philae Landing Site J_Composite.JPG
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