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Thread: Tharsis Bulge

  1. #1
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    Tharsis Bulge

    Hello,

    I'm trying to figure out some basic areology. If I'm not mistaken, Tharsis is a massive area of highlands that comprises a good portion of the southern hemisphere, if not most or all of it. The highest points on the Tharsis Bulge are also the highest points on Mars, Olympus, Arsia, Pavonis and Ascraeus Mons. But areologically speaking, where does Tharsis begin and end as a distinct region?

    Cordially,

    TimberWolf

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    Well, there's no little fence with a green sign saying "Welcome to Tharsis".

    But in general terms you can see it pretty plainly from a map of the topography.

    Here's a page with lots of images that show changes in elevation:

    http://ltpwww.gsfc.nasa.gov/tharsis/global_paper.html

    And you can see the boundary quite clearly. It's the red area on the left in Figure 6.

  3. #3
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    Hello,

    Awesome link, very helpful. It looks like that the Tharsis Bulge extends from the northern Acheron Fossae to the southern edge of both Solis and Sinai Planum and the Claritas Rupes. It's staggering how deep below datum that Hellas is. Oh my. Thank you very much for the link. 8)

    Cordially,

    TimberWolf

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    Quote Originally Posted by TimberWolf
    It's staggering how deep below datum that Hellas is. Oh my. Thank you very much for the link. 8)
    Yes it is.

    I wonder if someone could take the time to compute what the air pressure should be at the bottom of Hellas? I've often wondered that, but too lazy to try to figure it out.

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    Cool pictures. Let's get those poles a meltin'.

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    I can't compute the air pressure on the bottom of Hellas Basin, but I believe the accepted number is 10 to 12 milibar. It can rise to 14 milibar in summer. This is pretty interesting because it is the only place on Mars where air pressure is consistently above the triple point of water. This means that (very) salty water can exist there at temperatures from -20 (C) to +10 (C)!
    A dark patch of soil or rock in full sunlight can easily heat up to this temperature range!
    Even better, in winter time you can see ice forming in some places. I believe this must be water ice, it's still to warm for CO2 ice. So! You have ice, you have warmth and you have enough pressure to prevent it from boiling of! There simply must be liquid water on the surface of Hellas Basin! Let's go there and get our rover wheels whet...

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    Still only 1/72 of Earth's atmospheric pressure.

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    Quote Originally Posted by Cugel
    I can't compute the air pressure on the bottom of Hellas Basin, but I believe the accepted number is 10 to 12 milibar. It can rise to 14 milibar in summer. This is pretty interesting because it is the only place on Mars where air pressure is consistently above the triple point of water. This means that (very) salty water can exist there at temperatures from -20 (C) to +10 (C)!
    A dark patch of soil or rock in full sunlight can easily heat up to this temperature range!
    Even better, in winter time you can see ice forming in some places. I believe this must be water ice, it's still to warm for CO2 ice. So! You have ice, you have warmth and you have enough pressure to prevent it from boiling of! There simply must be liquid water on the surface of Hellas Basin! Let's go there and get our rover wheels whet...
    Actually most of the northern hemisphere is also consistently above the triple point.

    Bob

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    Yes, that is true Bob. Actually my knowledge comes from this NASA link:
    http://science.nasa.gov/headlines/y2000/ast29jun_1m.htm
    (Making a splash on Mars) which I think is very instructive.

    With an air pressure between 7 and 8 milibars you are above the triple point of water, but it doesn't give you a lot of temperature range to stay liquid. As Hellas is the 'lowest' region on Mars it simply has the widest temperature range for liquid water. Although it is still not a lot, I agree.
    Another 'problem' is that night temperatures still drop to 30 or 40 degrees below freezing, even in summer. So, if there is liquid water it will be constraint to micro environments like cracks in rocks.

    On Earth we have a similar problem. A glass of cold beer seems to evaporate with incredible speed! My glass is empty all the time...

  10. #10
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    "Is that the Tharsis Bulge, or are you just happy to see me?"

    From the 1937 serial "Mae West, Princess Of Mars."

    Also starring Cary Grant as John Carter. Filmed on location in the Waterloo Lounge in Atlantic City.





    No... not really. I'm sorry. :^o

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    Hello,

    Another question: Would Tharsis be the center of ancient Martian vulcanism?

    Cordially,



    TimberWolf

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    Hello,

    Another question: Would Tharsis be the center of ancient Martian vulcanism?

    Cordially,



    TimberWolf
    Yes. Tharsis contains many volcanoes, the largest one being Olympus Mons. Scientists believe (I think) that Olympus Mons is dormant. It probably erupts on a cycle of millions of years and is now in the quiescent phase.

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    Quote Originally Posted by Brady Yoon
    Hello,

    Another question: Would Tharsis be the center of ancient Martian vulcanism?
    Yes. Tharsis contains many volcanoes, the largest one being Olympus Mons. Scientists believe (I think) that Olympus Mons is dormant. It probably erupts on a cycle of millions of years and is now in the quiescent phase.
    There is one of the major volcanoes that is not part of Tharsis.

    I think it is Elysium Mons.

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    Quote Originally Posted by aurora
    There is one of the major volcanoes that is not part of Tharsis.

    I think it is Elysium Mons.

    Correct.
    Everything I need to know I learned through Googling.

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    Since Mars has no tectonics, isn't in an orbital resonance such as Io and appears to be geologically dead. What could cause one of the volcanoes to suddenly become active?

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    Quote Originally Posted by Walter
    Since Mars has no tectonics, isn't in an orbital resonance such as Io and appears to be geologically dead. What could cause one of the volcanoes to suddenly become active?
    The same thing that caused Olympus Mons to be the largest volcano in the solar system.

    Residual heat and radioactive decay keep the interior molten (although not as molten as the Earth's core since the Earth has more mass), hot plume of material rises to near the surface.

    As the planet cools, the eruptions become less frequent, more time passes between them...

    For an earth-bound example of a shield volcano that is late in life, see Haleakala on Maui. The Island of Maui has moved off the hot spot, but Haleakala may still erupt a few times before it is done. But the eruptions may be separated by thousands of years. It is now in the "post-erosional" phase.

    There are differences between Earth and Mars, of course, but Olympus Mons may be in a phase were eruptions are now separated by 100,000 years whereas Haleakala may be only 1000 years between outbreaks.

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