HiRISE and Mars Polar Lander Options

[MarsIsImportant]

Something is not right with this image projection. So with that in mind, I will consider it possible I don't have everything completely accurate.

I need to get some sleep. Tomorrow I will look some more. So if I am wrong, then I apologize to Tim now instead of later. The truth is what we are after. It's not a popularity contest.

[djellison]

I've tidied this thread up a little - MIP, please be more careful before jumping to a conclusion so contrary to the collective wisdom, and then stating quite so forcefully.

The killer point is that if stereo imagery describes the feature as a depression, then the label is irrelevant - illumination is from the lower right. As another post ( which made no sense during clear up, so was culled ) - you must be carefull assuming that MRO is heading south, and the East is to the right. This could be an ascending observation where the geometry would be inverted.

Doug

[climber]

3) We have not yet covered the landing ellipse with HiRISE images. I think we have covered more than 50% but there is still room to believe that MPL landed outside the areas imaged so far. The HiRISE/MRO team stopped imaging the MPL area once the southern summer sun set. As Tim suggests, the lander could be a km from one of the edges of any of these images.
-Rob Manning

Hi Rob,
Looking forward to Phoenix landing, I'm wondering if the behaviour of the atmosphere at high latitude is harder to modelize or less "well known" (lack of experience) so this could give us some hope to still find MPL away from the center of the elipse?

[Phil Stooke]

MIP: "Something is not right with this image projection"

Most HiRISE images are given in a cylindrical projection, north straight up. but near-polar images like these are in polar stereographic, and north is in a different place. All the information you need is in the table with each image.

Phil

[ugordan]

Furthermore, if the dataset in question is non-map projected (NOMAP), there is no projection involved. As others have said, depending on whether the observation took place on the ascending or descending node, the illumination for these products would generally seem to come from diametrically opposite directions. If you feel the illumination suddenly "changes direction" across a single swath, that's just your brain being tricked by reverse topography (e.g. hills turning into depressions).

[climber]

The killer point is that if stereo imagery describes the feature as a depression,
Doug

Is there any possibility that this could be the crash site of MPL then?
I would go for a full MPL including heat shield etc that would have hitten the ground

[ugordan]

Tim53 said in a earlier post there's another one of those conical pits in the area suggesting this has nothing to do with MPL. If this is an impact crater, its morphology seems inconsistent with what I'd expect of a hypersonic impact into hard or rough soil. The pit itself is too large, this one is supposedly 50 meters across. I wouldn't expect a small object travelling at say 400 m/s to produce a crater that big.

If I had to put my money on it (Murphy's law!), I'd say the lander is either in the heavily clouded-over images we have now or in the rest of the ellipse that hasn't been covered yet. Other than that, anything suspicious would have probably already jumped out at the HiRISE team, at least when looking at your typical, fairly flat and dull terrain here (though I am wondering how systematic their search was so we can modify our "expectations"). On the other hand, images like PSP_005536_1030 (especially the top part of NOMAP version) have pretty big albedo variations and small-scale topography so in principle, something just might be hiding over there.

[climber]

Tim53 said in a earlier post there's another one of those conical pits in the area suggesting this has nothing to do with MPL. If this is an impact crater, its morphology seems inconsistent with what I'd expect of a hypersonic impact into hard or rough soil. The pit itself is too large, this one is supposedly 50 meters across. I wouldn't expect a small object travelling at say 400 m/s to produce a crater that big.

I agree on this but I thought may be heat would have melted the ice around the impact so the crater would have grown bigger.
Ok, if there's another conical pit around, unless MPL did a bounce as Soyuz TMA-11 did ...

[nprev]

Argh. As Gordan said earlier, "so many unknowns"! Seems as if this manifest fact will be compounded by the fact that there well might be active geology at the site; those pits sure look like something related to the CO2 geysers to me, or some other outgassing/collapse mechanism.

[ugordan]

I might be wrong about this, but if you're thinking about heat shield heat, there might not be that much heat at all. If the heat shield is ablative, the part that heats up is the part that's ablated away, which is a mechanism for keeping the shield cool. The shield material is a very good heat insulator so it doesn't store too much heat during reentry. If you're talking about impact-induced heating, my gut feeling tells me there isn't that much produced. A Mach 2 impact is likely to compress/scatter soil rather than heat it up significantly. Also, keep in mind that water ice (if it's water) has a high specific melting heat so it would take a LOT of heat to melt that large a volume.

[climber]

Yes, I concur. Ablative material (sort of "cork" as they say in Phoenix video) won't let heatshield very hot.
So, we're back on the search

[tim53]

Yes, I concur. Ablative material (sort of "cork" as they say in Phoenix video) won't let heatshield very hot.
So, we're back on the search

I thought about the possibility that these pits might indicate sublimation of loose ice by a warm lander and heatshield landing on it (there are two in this area, IIRC - the one that Marsisimportant posted, and a smaller one some hundreds of meters away, again IIRC). But it would have to be pretty loosely consolidated, and ice has a tremendous capacity for absorbing heat. Then, perhaps the real clincher is that other regions of polar terrain show similar pits in abundance.

They are intriguing features in their own right, though.

-Tim.
P.S. Hi Rob!
PPS. Emily - I thought I was wrong once, but apparently I was mistaken!

[hendric]

What kind of effect would the downed lander have on the surrounding area over time? There are a ton of possibilities here I imagine, anything from growing a pit in the ice to growing a hill of dust.

[remcook]

A friend of mine went to Greenland a while back and he showed this fascinating, yet depressing, picture of a big hole in the snow made by a single Mars bar wrapper. MPL is not that dark though I would think.

[MarsEngineer]

Hi Climber,

You are correct. There was and continues to be a lot of uncertainty in our knowledge of the density variations in the altitude range that the entry vehicle does most of its deceleration (mostly between 20 and 50 km). Given that these machines enter at very shallow entry flight path angles - around 13.5 degrees for MPL - only a few percent uncertainty in our estimates of the atmosphere density means the difference of many 10s of km on the surface. The ellipse shown on the HiRISE site (made by Tim) is based on our best guess of where the vehicle was when it reached the top of the atmosphere (based on our radiometric tracking data taken in the hours and days before landing). We think these estimates were pretty good and do not depend much on what failures may have happened to the vehicle. We then use computer simulations to model entry, descent and landing using one atmosphere model (as well as slight variations in the entry initial conditions), we then do the simulation again and again using slightly different models (correctly selected statistics-wise) and then we look to see how these are scattered on the surface. The ellipse that Tim placed on that HiRISE map at the HiRISE site represents about a 2-sigma ellipse (see Emily's Blog from yesterday). So we believe that there is about an 86% probability that MPL is inside that ellipse.

Of course, people ask me; What if the cruise stage never came off? or What if the parachute did not open? What if it tumbled during entry? Well it turns out that these cases do not make a huge difference in the position and shape of the 2-sigma ellipse. It makes it a tad longer (probably moves it further south a few km as well ). As you suggest Climber, one place that we could be very wrong and would make a bigger difference in the ellipse is the atmosphere. You will also notice that the HiRISE images do not cover the right side of the ellipse. That was due to a mistake I made (an unfortunate change of longitude definitions occurred just after the post-MPL trajectory reconstruction that I was not aware of ... it resulted in our estimates of where the ellipse was painted on the surface moving a few km to the east after the HiRISE image "campaign" was well under way).

As I said before, it is there somewhere and I have some faith that it will eventually be seen. While I could be wrong (I have been many times in this biz), I doubt that it would have made a crater that did not leave equipment visibly scattered on the surface (unless subsequently covered by dust or other Mars material). Even without a parachute, it would have slowed down to very nearly it's Mars "terminal velocity" which for this vehicle is around 220 - 300 m/s (depending on tumbling attitude). That is fast but not fast enough to poke a deep hole in Mars!

If it is a needle in a haystack, I *think* it will be a bright needle. (My friends think I am an optimist.)

Cheers!

-Rob M

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These comments and opinions are solely those of the author and do not reflect the views of JPL, Caltech nor NASA.