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Earthlike Mars?
glennwsmith
post Apr 1 2009, 02:28 AM
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All, I know this isn't the right place for this post, but I've looked around and can't find an appropriate, current UMSF forum (Doug, perhaps you could give me some guidance on establishing such) -- so here goes: I think a [the] new paradigm for Martian geology is rapidly coalescing, namely, that Mars is very much like the Earth in terms of the preponderance of water -- except that it is all frozen, and covered under a thin layer of dust/regolith! See, for example, this article:

http://www.skyandtelescope.com/news/41995902.html

Hence the "seepages" found in crater walls; hence the evidence of catastophic flooding -- the result of volcanism melting huge pockets of ice. And I am going to add my own wrinkle (probably not original): that the differentiation of Mars into a rougher southern hemisphere and smoother northern hemsphere represents something like Earth's Pangea stage, ie, the northern hemisphere is a vast frozen sea covered with a thin layer of ice.
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glennwsmith
post Apr 1 2009, 02:31 AM
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Oops, of course I meant thin layer of dust, not ice . . .
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djellison
post Apr 1 2009, 07:06 AM
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New thread to move Glens posts in to.

And Glen - you should just 'edit' your first post, rather than replying to it to make a correction.
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dburt
post Apr 1 2009, 10:15 PM
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QUOTE (glennwsmith @ Mar 31 2009, 07:28 PM) *
... I think a [the] new paradigm for Martian geology is rapidly coalescing, namely, that Mars is very much like the Earth in terms of the preponderance of water -- except that it is all frozen, and covered under a thin layer of dust/regolith! .... Hence the "seepages" found in crater walls; hence the evidence of catastophic flooding -- the result of volcanism melting huge pockets of ice. And I am going to add my own wrinkle (probably not original): that the differentiation of Mars into a rougher southern hemisphere and smoother northern hemsphere represents something like Earth's Pangea stage, ie, the northern hemisphere is a vast frozen sea covered with a thin layer of ice.

Doug, thanks for moving this. And Glenn, not a particularly new paradigm for many scientists. Everyone wants to emphasize similarities with Earth, but you have spotted a major difference - that the water is all or mostly frozen. This has been speculated on for a long time; it's nice to find direct proof. Freezing/sublimating the water released all the salts that were held in solution; both rovers, plus orbiting satellites are continually finding more salts. Another difference is the extreme age of the martian crust - billions of years, owing to an apparent lack of plate tectonics on Mars since then (implying the comparison with Earth's Pangea stage may not be an appropriate one). The ancient crust has preserved the record of ancient Martian impact cratering much better than on Earth; even the hemispheric division of Mars has been blamed (by many scientists) on a giant impact.

Incidentally, the northern hemisphere is just as heavily cratered as the southern one, except that it is lower-lying, and so the ancient craters are mostly buried under a thin layer of dust and ice, as that article pointed out. Orbital studies involving detailed elevation and radar have allowed the northern buried craters to be detected (see numerous articles by Herbert Frey). The very thin atmosphere means that impact cratering is still a far more important process than on Earth - small meteorites do not burn up in the atmosphere. A final difference from Earth is that the martian crust and lavas are at least twice as rich in iron as on Earth - an important difference that probably relates to the initial degree of hydrogen loss (core oxidation) during the formation of Mars. In part, this iron-rich nature accounts for the rusty red color of Mars - and presumably accounts, in some fashion, for the prevalence of shiny gray hematite (iron oxide) spherules at the Opportunity landing site.

The big scientific question regarding Mars now is not its water-rich nature, but rather how much of, and for how long, this water might have remained liquid, rather than frozen, on ancient Mars, during and just after ancient impact cratering episode that ended about 3.8 billion years ago (age assumed from dating of Moon rocks sampled during the Apollo astronaut program). I find it easiest to relate abundant evidence for early liquid water to the impact cratering episode itself (an easy way to generate lots of heat, a temporary steamy atmosphere, and layered sediments resembling those seen by both rovers), but others prefer to relate liquid water to early volcanism, an unusual and dense atmosphere, or both. Impacts and volcanism are not mutually exclusive, of course - both were occurring at at a high rate at roughly the same time, and afterwards both continued at a greatly reduced rate.

-- HDP Don
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glennwsmith
post Apr 1 2009, 11:42 PM
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Dburt, thanks for the thoughtful summary. I think I am agreeing with you in referencing Pangea -- given the lack of plate tectonics, the uber continent never split into smaller pieces.
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MarsIsImportant
post Apr 2 2009, 01:39 PM
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Was it really ever an uber continent at all? Perhaps it is merely a remnant of the original ancient crust before Mars got hit by a HUGE dwarf sized planetary object. The idea is that Mars was struck similar to how the Earth was smashed early in its history (the Mars sized object that created the Moon). In this respect, perhaps Mars is similar to Earth.

Did a larger Moon on Mars once exist, then smashed into Mars again later in its history? That possibility of a second event could give us a false date concerning early bombardment (assumed to be 3.8 billion years ago because of the Apollo rock dating). Mars is not the Moon. It is possible that there was more than one extreme event and the evidence is mounting that this may have occurred, but it is still not convincing. Occamís razor still suggests the more simple solution.

Iím keeping my mind open because there is still so much that we donít know about Mars. Answers wonít come as quickly as we might want. But look at the speculation of frozen water on Mars! It has taken almost 30 years for it to now become established fact. Just a few years ago, I was almost laughed at because of my suggestion there might have been large numbers of glaciers on Mars at one time. Few are laughing at that idea now.
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glennwsmith
post Apr 4 2009, 03:41 AM
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Marsisimportant, thanks for adding the primeval collision to the overall picture -- you and Dburt have covered all the important bases, and in doing so, you have clarified for me what I was hoping to do with my original post, which was to paint a picture -- at which I will now, thanks to the infinite patience of Doug Ellison and all you other UMSF members, take another whack. To wit: I have been looking at the global pictures of Mars for some years now, and I have never been able to make sense out of what I am seeing. Yes, it is Earth's sister planet, but it just hasn't made any sense to me. But suddenly -- seeing the Hirise photo of a recent meteor strike on the Northern plains throwing out rays of ice -- it has all become clear. Imagine Earth at the Pangea stage with its seas frozen, and the entire planet covered with a thin layer of dust -- it would look very much like Mars today (allowing for the fact that the dust covering Mars is rich in iron oxide). I hope I am not beating a dead horse, I am just trying to explain my eureka moment. But maybe I'm behind the curve, and all of this has been obvious to most UMSF members for some time . . .
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imipak
post Apr 5 2009, 06:49 PM
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A picture of Mars with somewhat ubiquitous sub-surface ice seems to be emerging (for some value of "ubiquitous" yet to be firmly established, but certainly less than 1), and this is relatively new. I haven't seen any informed speculation about, or estimates at upper and lower bounds for, the thickness or volume of these layers (and would welcome some pointers, if anyone has any?) I like your "eureka moment" image, though, I just think it'll turn out to be a bit less dramatic than ocean-basin scale volumes.


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Fran Ontanaya
post Apr 5 2009, 11:17 PM
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There's the Medusae Fossae radar profile.

http://www.nasa.gov/mission_pages/mars/new...s-20071101.html

QUOTE
The radar observations found the Medusae Fossae Formation to be massive deposits more than 2.5 kilometers (1.4 miles) thick in places.


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glennwsmith
post Apr 5 2009, 11:48 PM
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Imipak and Fran, thanks for the excellent additions to this thread. And I'm wondering inf anyone else out there has been as confused as I have been in trying to decipher the big picture of Martian surface geology?
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glennwsmith
post Apr 6 2009, 02:16 AM
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On behalf of all who have joined this thread, I am adding for discussion purposes an image (with which I have taken some BIG liberties) showing 1) an early, "earthlike Mars", 2) Mars with its "seas" frozen, and 3) the seas covered with a thin layer of [red] dust -- voila, current day Mars! But I am not nearly so good a graphic artist as many of you . . .


Attached Image


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Geert
post Apr 6 2009, 05:48 AM
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A very interesting picture and discussion.

However, how much evidence is there really that all of the water was liquid at the same time? Would it not be possible that the effects were more local, resulting from various causes and not one 'tropical period'.

Lacking a large moon, precession, nutation, and polar motion of Mars rotational axis will probably be larger then on Earth, resulting in several cycle's of 'super seasons' imposed on the existing seasons (which are already stronger then on earth due to Mars more elliptical orbit). Area's with exposed ice around the poles might receive more solar heating due to this, resulting in the ice sublimating (increasing air pressure) or possible become liquid for a short while, however at the same time other area's might 'cool down' due to the same effect, and ice might start building up again on these area's (reducing air pressure again). So the ice would more or less shift from one area to the other and this might even be possible without a liquid phase in between??

Local effects might be vulcanism (volcanic heat might rapidly heat a layer of ice, resulting in the ice sublimating and possible a short local liquid period if the air pressure rises sufficiently locally during a short period) or impacts (same effects, local heating). So you might have local 'flood-waves' during short periods without the need for a planet-wide 'tropical period'.

How much prove do we have that we are looking at a planet-wide 'tropical period' instead of just a series of (more or less unrelated) local events?
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djellison
post Apr 6 2009, 07:27 AM
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So basically, it's Tim Parkers old Northern Hemisphere Ocean idea. I saw it mentioned in a few books, but the evidence wasn't water-tight at the time.


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Phil Stooke
post Apr 6 2009, 07:42 PM
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Glennwsmith, your map is OK ( and similar to other visualizations of this concept) except for one glaring error.. the ocean, if it existed, would be confined to low elevation areas, so you need to make its outlines fit contours, not albedo markings. The bright central part of your image, Arabia Terra, is actually highlands.

Doug, the first person I am aware of to promote this idea of a northern ocean was Victor Baker (U. Arizona). He called it Oceanus Borealis, I think. There was a paper in Nature about it. Tim Parker mapped possible shorelines of that ocean.

Phil


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glennwsmith
post Apr 7 2009, 12:02 AM
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Geert, you are certainly justified in bringing up local constraints on ocean formation -- my simple-minded conception of a Mars ocean is like talking about "liberal" or "conservative" voters as if they have a uniform profile. And I stand properly corrected, Phil, for my simple-minded map-drawing technique. But it is the Dougmeister who has really got this thread unspooling into a nice, fat pile, with his mention of Tim Parker, the real pioneer of the northern ocean theory. I've done some quick (and belated?) research, and the theory of Dr. Parker and his colleagues is all over the web -- not to mention a lengthy discussion thereof on UMSF back in June of 2007! (And not to mention, as per Phil's comment, several scientific depictions of same.) Despite my discomfiture, the point remains that these photos of fresh, ice-penetrating craters will bring roaring back into well deserved focus the thought that oceans -- whether large or small -- lie frozen beneath them. Dr. Parker, we would love to hear from you!!!
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