Earthlike Mars? Options

[glennwsmith]

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.

[Phil Stooke]

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

[tim53]

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

My ears just burst into flames! (actually, a friend told me about this thread).

No, Phil. Vic Baker's work post-dates and is based loosely on mine...

"I started out as a child"...

Seriously, my own ruminations about a possible northern plains ocean on Mars began in 1985. Baerbel Lucchitta of the USGS and Heins-Peter Jons of Germany and I were looking at the same curious plains boundaries around the northern plains and interpreting them somewhat differently, but as indicating an ocean at that level of some sort or other. Mine was happy and "tropical" (as described above), with waves responsible for the erosional and arcuate constructional features along the margin. Lucchitta's was frozen over, with comparisons made with morphologies she saw around the Antarctic coastline. Jons' described his ocean as a "mud ocean", with the margins being flow fronts of freezing mud transgressing up the margins of the plains as catastrophic flooding dumped water and sediment into the plains.

With all the new high resolution data available now, I'm looking at the problem anew. Instead of a tropical early Mars, I think it's more likely that the planet has always been cold, modulated by pulses of greenhouse warming in a thicker atmosphere and possibly by higher internal heat flow. Most (but very interestingly not all) of the features I mapped as shorelines based on Viking data appear to exhibit debris-flow or even lava-flow front morphologies. But it's very interesting to note that these boundaries are still elevated, sometimes by hundreds of meters, with respect to the plains immediately interior to them. Tens or even hundreds of millions of cubic kilometers of water is "easier" to get rid of than the equivalent volume of lava, so I think it's more likely that these are some sort of ocean shorelines rather than volcanic plains margins.

I think it's likely that, if Mars had an ocean, that it was ice AND debris covered most of the time (not just dust, either, because the northern plains surface is rather rocky in MOC and HiRISE images). Also, if the marginal features are shorelines, Mars has lost a lot of its original water inventory over geologic time.

...subject to revision!

-Tim.

[Geert]

But it's very interesting to note that these boundaries are still elevated, sometimes by hundreds of meters, with respect to the plains immediately interior to them. Tens or even hundreds of millions of cubic kilometers of water is "easier" to get rid of than the equivalent volume of lava, so I think it's more likely that these are some sort of ocean shorelines rather than volcanic plains margins.

I'm an absolute amateur in this so hopefully this isn't a too dumb question: but if these are ocean shorelines, does this imply that the water had to be liquid at that (or any other) time? What happens if the lava flows at the time just ran into ice instead of water, would we see the difference?

Giving the precession of the rotation axis, moving fields/glaciers of ice seem to my simple mind the easiest answer, the ice caps wonder around the surface pending the direction of the rotation axis at the time, without ever resulting in large liquid oceans. Ice sublimates in one spot and builds up again in another with at the very most only very short local periods of liquid water (due volcanic activity or impacts).
In an other threat on this forum we discussed already the theorie that the deposits we see at Meridiani could have been formed inside ice fields instead of in liquid water, so instead of a shallow liquid ocean the area might also have been covered by an icefield which later disappeared.