[X] My Assistant

[tuvas]

Okay, we now have definitive pictures of VL1, 2, Spirit, Opportunity, and a Pathfinder coming up soon. So, now, what would the lost landers look like, starting with Beagle, MPL, and Mars 6, which will be the easiest to find of the landers. Just curious to hear your thoughts. Thanks!

[dvandorn]

Let's see, a couple of responses, here...

Doug, I'm not sure we have a really good idea of what the MPL remains might look like. The greatest rate of landform change observed on Mars is in the polar regions; an awful lot of material moves around every Martian year when literally trillions of tons of solid CO2 gets laid down and then sublimates off.

Just for starters, I have to wonder what the simple weight of the dry ice built up on and over the crash (and the backshell & heat shield, for that matter) might have done to them. Just how deep does the dry ice layer lay down at MPL's latitude, anyway? Even if it wouldn't cover over MPL entirely, I'd think you would see some serious effects from being buried in dry ice.

Ditto for the 'chute. I don't know what was used to pigment MPL's 'chute, but I know a lot of dyes fade in extreme cold. After three winters, and dust deposition from the winds during sublimation season, I'm thinking that the 'chute may not be recognizable anymore.

And, yes -- the winds. We see that polar latitudes sublimate somewhat unevenly, with "warm" spots (thinner ice layers or rocks which receive more insolation through the dry ice cap and sublimate the frozen CO2 from below) clearing off and blowing dust onto adjacent dry ice surfaces, which creates more preferential sublimation, which creates more clear spots, until the whole surface is clear. The lander and any of its related EDL equipment might have created warm spots and been the sources of early clearing spots -- which means they might have been exposed to pretty stiff winds as pent-up CO2 gas blew through the ice ceiling. Hey, we *know* they blow through energetically enough to spray dust out onto adjacent dry ice-covered surfaces. What would such events do to the 'chute fabric (especially if it's super-cold)? What would they do to the wreck of MPL itself?

I mean, it's even possible that some pieces of MPL have been blown several meters away from the main crach site.

And to Bob, I'm on the fence as to whether the DS2 impact points would be obvious. We know that Spirit's heat shield drew a gouge into Bonneville's rim, which was extremely dark and contrasty with the surrounding materials. It was quite obvious in both MOC imagery and in the ground-level images from the far rim.

However, while MRO's view of Bonneville shows the heat shield, the albedo difference seems to be almost completely gone. I'll grant you, wind smoothing is probably at its peak effect at crater rims, but this would seem to argue against there being much in the way of identifying marks on the craters made by the penetrators. It might well be possible to identify the impact sites in other ways, but (especially after three Martian winters) I'm not all that sanguine that we'll be able to find them.

-the other Doug

[mcaplinger]

Just how deep does the dry ice layer lay down at MPL's latitude, anyway?

About 40 cm, based on http://ltpwww.gsfc.nasa.gov/tharsis/snow_paper.html -- it would take 3x that much to cover the lander over.