[X] My Assistant

[Guest_AlexBlackwell_*]

Perron et al. have a new paper ("Evidence for an ancient martian ocean in the topography of deformed shorelines") in the June 14, 2007, issue Nature. There is also an accompanying News and Views piece by Maria Zuber. See the Editor's Summary for a synopsis and links.

See also:

Mystery Solved: Mars Had Large Oceans
By Dave Mosher, Space.com
posted: 13 June 2007
01:00 pm ET

[dvandorn]

Yes, any shoreline must follow the "areoid" because of how water collects on a planetary surface. This is a basic element of physics.

However, it is more than obvious that the "areoid" has changed over the past couple of gigayears. The Tharsis bulge was very likely emplaced *after* any such northern ocean had dried up, evaporated and/or been incorporated into underground reservoirs. This impressive pile of volcanics reshaped the very planet -- and rebalanced it, too. For example, the great canyons of Valles Marineris were formed as rifting occurred, due to the reaction of the crust to the immense amount of lava that was poured out onto the Tharsis region. The building of the Tharsis bulge is what likely caused mars to topple on its side, to place a majority of the mass now newly distributed onto the surface as close to the equator as possible.

That kind of activity, occurring over a billion years or more, would naturally crumple the crust up in some places and tear it apart in others. It is no more reasonable to expect that the areoid is the same now as it was when conditions allowed for oceans on Mars than it is to expect that the mountaintops in the Himalayas were always uplifted to the top of Earth's sensible atmosphere. Since there are fossils of seabed creatures in the rocks at the tops of those mountains, we know for a fact that those rocks once lay under an ocean. To say that there cannot be ocean-floor rocks at the top of Himalayas because the geoid doesn't allow it is just as spurious an argument as to claim that shorelines can't exist on Mars along its dichotomy boundary because the current areoid doesn't indicate them.

-the other Doug