[X] My Assistant

[Doug M.]

Inspired by the recent story about ExoMars site selection. So they want to land someplace that has evidence of water, someplace with sedimentary rocks, someplace ancient... and someplace safe. Oh, and also low latitudes. That's not explicitly stated, but ExoMars is using solar panels, so they're not likely to pick a spot at 50 degrees north.

Here's a thing: if you're just casually looking at a map of Mars, what jumps out at you as interesting-looking places to poke around? I'd say three: the big volcanoes, the Valles Marineris, and the Hellas Basin. But Hellas seems to be a perpetual also-ran, and the volcanoes and the VM don't even get a mention.

Is there any prospect of a mission to any of these regions? Is the main constraint that it's too dangerous, too rugged, or that those areas are less scientifically interesting?


Doug M.

[dvandorn]

Just as sort of a summary...

Olympus Mons is both a difficult landing area (nearly sticks completely out of the sensible atmosphere, meaning you get a lot less braking from heat shield and parachutes) and represents in landforms just the final volcanic period of Mars' history. Water doesn't ever appear to have run down its slopes, nor of any of the other Great Volcanos of the Tharsis Plateau. We can investigate this mineralogy nearly as well from orbit as we can from the surface.

Hellas would let you land a larger vehicle, as it is well below the Martian mean surface altitude and parachutes would be very effective, moreso than at other places on Mars. However, it appears from orbital data to be deficient in hydrated minerals as compared to the southern highlands within which it resides. My best guess is that Hellas was formed after the time of a mostly warm, wet Mars and the enormous basin was likely dried out by the impact event. On the other hand, you do see some odd, unusual landforms in Hellas, but most people seem to think this is due to higher air pressure causing greater and different forms of wind erosion.

Finally, Valles Marineris is a rift valley, the bottom of which seems to have been primarily covered by large-bock talus and after that a thick layer of dust. And it primarily cuts through the great volcanic pile of the Tharsis Plateau, which again all seems to have been emplaced after Mars' warm, wet period. So, while interesting from a perspective of detailing the volcanic history of Mars, it's not a great place to land safely, and it doesn't preserve much signature from the warm, wet days. It's also nearly impossible to exactly locate a block in a talus field to the strata from which it fell...

-the other Doug