Maps Show Mars Was Once More Like Earth

vrioux writes "NASA scientists have discovered additional evidence that Mars once underwent plate tectonics, slow movement of the planet's crust, like the present-day Earth. A new map of Mars' magnetic field made by the Mars Global Surveyor spacecraft reveals a world whose history was shaped by great crustal plates being pulled apart or smashed together. ."

Comments

probably more common than we think

[BushCheney08]

I wouldn't be surprised to find that the majority of solid planets that we examine undergo the same basic geologic mechanisms. Tectonics, subduction, spreading, etc, are probably far more common in the universe than we think.

Re:probably more common than we think

[J'raxis]

Tectonics might not be. One of the prevailing theories of why we have tectonic plates is that a sizeable chunk of the earth's crust got sheared off by a massive impact, leaving the remaining chunks of crust to slowly slide around the surface of the earth. The impactor that struck the earth hit at a particularly fortuitous angle; a little bit off and it would have destroyed the planet instead. Whether or not these kinds of impacts are improbable or not is still an open question -- one theory is that the impactor formed at one of the earth's Lagrange points, and it wasn't just a "random" blow from an asteroid, so it may be more common than it at first sounds.

Incidentally, the impactor blew that crustal material clear into orbit, which ultimately coalesced into the moon. See the giant impact theory entry on Wikipedia.

Based on the site photos...

[Pomme de Terre!]

... it also appears to have been ruled by giant purple spiders.

Mars' orbit once crossed Earth's?

[Anonymous Coward]

I once read an interesting story about some astonomer who believed that a long time ago Mars' orbit once was highly eliptical and crossed Earth's orbit and there was a near collision. Mars used to have oceans that alternatively froze solid and melted & boiled during it's highly elliptical orbit around the Sun until a very close encounter with Earth, where the two planets' gravities caused them to do a quick dance around each other during the near-collision, slinging off most of Mars' water which then was captured by the Earth's gravity and eventually fell into our own oceans, then Mars itself got slung outward towards it's current orbit where it collided with another small planetoid, the collision resulting in the formation of the asteroid belt and Mars' current stable orbit that is vastly less eliptical that before, but still not "almost circular" like Earth's orbit..

Best evidence for water

[Council]

To me, the best evidence for water is this map, which they always show at NASA presentations on Mars. It's a topographic map colored by altitude, and you see that the areas below a certain depth are almost completely crater-free, contrasted strongly with the areas above that depth. This, to me, is a really, really strong argument that it was once covered in water and had a coastline.

Looking at that map always makes an Earth-like Mars seem much more real to me.