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Mars: The Interesting Bits
Doug M.
post Mar 31 2014, 09:01 PM
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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.
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vjkane
post Mar 31 2014, 09:15 PM
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QUOTE (Doug M. @ Mar 31 2014, 01:01 PM) *
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?

In general, landing site locations are driven by evidence of past water environments as well as engineering constraints (elevation, sun angles for solar panels, temperatures). Volcanoes both have relatively young surfaces (not likely to have evidence of a water environment that disappeared billions of years ago), have steep slopes, and probably mostly fall too high above the elevation datum for the parachutes to do their job.

Hellas would be nice for landing since it's so low (lots of time for the parachute to work). It is far south (solar illumination problems), and I don't know if there's any sign of past water environments.

Site(s) were proposed for the Valles Marineris system as I recall. I don't know if they were eliminated because of landing safety concerns (surface roughness) or because the signs of past water environments were weaker.

A friend of mine is a geologist who studies Mars. He has a list of sites he'd like to see rovers in to address lots of geological sites other than those that may once have been habitable. However, just good field geology doesn't seem to be enough to justify a mission.


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Explorer1
post Mar 31 2014, 09:23 PM
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There's also the aspect that these famous features are too big to be visually spectacular from the surface. Mars is a small world, and the horizon is close by. Anywhere but the narrowest parts of Valles Marineris, you can't even see both sides like the familiar canyons and valleys of Earth. At best, you'd just see a big cliff stretching away into the haze. At Olympus Mons you just see a big slope, and even the walls of Hellas are below the horizon from a landing at the centre.

Look at Earth: what do we see on the Pacific coast? Just a beach, not the whole ocean!
Let's be grateful for Mount Sharp and Endeavour, eh? wink.gif
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elakdawalla
post Mar 31 2014, 09:51 PM
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If you're interested in the considerations that go into landing site selection, read Phil Stooke's book. Odds are good that any site that ExoMars can be sent to was discussed as a potential landing site for the MERs. Or you can browse the presentations at past landing site selection meetings.


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djellison
post Mar 31 2014, 10:02 PM
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Former landing site selection meetings are fascinating. Many don't realize.... Gale was a semi-finalist for MER.... http://webgis.wr.usgs.gov/mer/images/Gale_map.jpg
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elakdawalla
post Mar 31 2014, 10:10 PM
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Probably the craziest thing I've read regarding Gale is this prescient item, from the 2001 Mars Smart Lander Science Definition Team report. It's in the section where they identify two different build options for Mars Smart Lander, which later became Mars Science Laboratory. They're describing the preferred option, the Mobile Geobiology Explorer (emphasis mine):
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4.2 Mobile Geobiology Explorer
The Explorer would be a rover capable of carrying a payload of approximately 100 kg and traversing >5 km to get to the specific scientific targets (e.g., layered deposits) that define the landing site. This corresponds to a “go-to” capability with enough reserves to explore the specific target, terrain, and materials that the rover “goes to”. The strength of the Explorer mission concept is that the Explorer can rove to and explore the sedimentary units that are relevant to the overarching program themes of life and climate. To confirm this assertion the SDT evaluated traverse scenarios for a number of possible landing sites, assuming the 5 km landing site error ellipse associated with the Smart Lander Mission. The sites included the hematite deposits that cover Noachian cratered terrain in Terra Meridiani, interior layered deposits within Gale Crater, and units within Gusev Crater. In each case it was demonstrated that a 6 to 9 km traverse (preferably 9 km), combined with detailed sampling and analysis in 3 locations, would provide data from multiple geologic units, including locations with postulated sedimentary deposits.
They had Gale all picked out from the start! (Not really, but it shows how MSL was originally conceived as a device to explore a place like Gale.)


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dvandorn
post Mar 31 2014, 10:42 PM
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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


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schaffman
post Mar 31 2014, 10:46 PM
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I think another factor is dust cover. A lot of the higher elevation areas, particularly Tharsis, are blanketed with a meter or two of dust. This would probably cause maneuvering problems for rovers and not show much geology. I remeber reading that the volcano Alba Mons, a very dusty place, was originally on a list of possible Viking landing site because the area appeared so smooth in Mariner 9 images.
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Phil Stooke
post Apr 1 2014, 04:06 PM
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Hellas is great from the atmospheric density point of view but it is often cloudy or foggy - so not ideal in other respects.

Valles Marineris sites are fantastic in many ways and there are good water-related sites, but winds are a problem there during the parachute phase.

As for places like Olympus Mons... landing on a volcano, even if possible, would tell you little except the composition of the lava and maybe its age (with new techniques) ... interesting in itself but not really very enticing compared with other sites. what we really want to find is a single site with many goals. Think of Apollo 17, able to examine the floor of its valley, and the mountains north and south of it, and a landslide off the top of the southern mountain, and a dark-halo crater, and a fault scarp. Gale was a great site because within 10 km or so of driving we had access to the crater floor material, an alluvial fan, and multiple layers of rock of different composition - with hematite, sulfates, clays etc.

If I were to go to a big volcano, first I would want one at lower elevation than Tharsis, and second one with other features of interest around it. Apollinaris Mons north of Gusev may be a good candidate. I wouldn't land on its top but at its base where plenty of evidence of other processes including volcano-ice interactions should be present, as well as the edge of the volcano itself. Arsia Mons is a good alternative but even its base very high.

Phil


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Tom Tamlyn
post Apr 2 2014, 12:40 AM
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In Roving Mars, Steve Squyres writes that Melas Chasma, a site on the floor of Valles Marineris, was one of the final three candidates for the MER mission. As Phil mentioned above, the likelihood of high winds was considered a fatal problem ("all the spectacular topography at Melas could lead to some powerful winds"). The other was that 30-40 percent of the proposed landing ellipse was covered with sand dunes, leading to the risk that the rover "would see nothing but sand the whole mission." Roving Mars at 121-22.
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machi
post Apr 2 2014, 02:15 AM
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Unfortunately ExoMars is pretty limited in terms of safe landing. He can land only between -5 to 25° latitude and surface must be at least 2 kilometers under zero altitude.
My favorite place from candidates under consideration is southern Isidis (image below with approx. landing ellipse size). Hydraotes Chaos is not between candidates but it definitely looks interesting and it's place with detected hydrated minerals.
My other (realistic?) suggestions for some future missions are southern Argyre near Charitum Montes, vicinity of Anseris Mons and I agree with Phil that Apollinaris Mons is very good candidate from bigger volcanoes.
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jamescanvin
post Apr 2 2014, 07:57 AM
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QUOTE (machi @ Apr 2 2014, 03:15 AM) *
Unfortunately ExoMars is pretty limited in terms of safe landing. He can land only between -5 to 25° latitude and surface must be at least 2 kilometers under zero altitude.


Peter Grindrod has a great GIF on his blog showing this.



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Explorer1
post Apr 9 2014, 05:20 PM
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Potential improvements to both altitude constraints and landing accuracy. Looks very interesting...

http://www.nasa.gov/mission_pages/tdm/ldsd...ml#.U0WAclcTVJI
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AndreaMacha
post Apr 10 2014, 09:08 AM
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QUOTE (Doug M. @ Mar 31 2014, 10:01 PM) *
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.


You will not find any other place than Earth.. Your project sounds awesome but it could merely turn out into wastage of money..
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TheAnt
post Apr 21 2014, 12:48 AM
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I really would like to see Hellas explored in one way of other in my lifetime.

But yes, it is quite too far to the south for any solar powered mission, and in many places the terrain is not well suited at least to a rover.
Though I don't know if this example here could be said to be caused by wind.

The image is from ESP_016022_1420
And the caption state that "Materials appear to have flowed in a viscous manner, like ice." In some other images from the area the caption is more outspoken and talk about "glacial like" and "glacial flow features" (ESP_022494_1385), which hints that some of the channels that have been considered to be flows of water, might instead be glacial.
Alluvial fans and inverted channels are also found in Hellas, though they might indeed be from a somewhat later time than the hypothetical 'warm epoch'.
Terby with the layered terrain is also very interesting, though it might require one very agile alpinist rover to carry out a good study there. smile.gif

Now serious, with the restrictions we have, I agree with machi on Argyre, especially since I know have talked about finding layered rocks.

This area have a promise to give interesting results in more than one academic discipline.
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