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Mysteries of Mars's surface: a planet with a violent past

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posted on May, 3 2010 @ 03:27 AM
One of the earliest observered mysteries in the solar system is Mars's "hemispheric dichotomy." What this means is that there is a huge difference between the elevation and topography of the southern and northern hemispheres on Mars. The southern hemisphere is pitted with many crater marks, while the northern hemisphere is relatively smooth. Moreover, the elevation of the southern hemisphere is, in general, several kilometers higher than the smoother northern hemisphere lowlands.

You can see this in the map below. Its a flat-projection map of mars (similar to a map of the whole earth, for example). The color is artificial and represents elevation. The blue area in the north is generally lower than the red in the south, and it is relatively smooth, although there are two huge low-elevation "pits" in the south:

But why is this?

There have been two major theories, both involving extreme violence and trauma to Mars: 1) Something may have happened within Mars, like internal mantle convection, etc.; and 2) Mars may have been impacted by a huge external object that blew a massive amount of the planet's crust from the North out into space, creating the current terrain.

The most recent mainstream view is leaning strongly towards #2 (impact). Here is a video from 2 years ago, summarizing some recent research suggesting that a gigantic object collided with Mars perhaps 4 billion years ago:

Further evidence for an impact:
-The planet's orbit is very elliptical, moreso than any other planet...perhaps it was "knocked off course?"

-The "natural" day/night cycle of Mars should be much faster (about 8 hours) than its current roughly-25-hour day. This change could have occurred with an impact.

-The axis of Mars, like that of earth, wobbles, but at a much more erratic and wide-ranging pattern, also suggesting that the planet was hit and the axis spun in an "unnatural" way.

-There are two massive bulges on Mars: The Tharsus Bulge and the Elysium Bulge. These could be deformations from an object hitting mars and going into the mantle of the planet's interior but not passing all the way through. The bulges would be caused by shock-waves either deforming the planet or sending massive eruptions of magma up through the surface on the opposite side that then congealed to form the bulges.

-The asteroid belt between Mars and Jupiter could easily have been the source of an object or objects that hit Mars. The asteroid belt could also be the remains of another planet that actually collided with Mars and then shattered.

Although the consensus is leaning towards "collison" as the source of Mars's oddities, the type and nature of the collision is still debated. More on this below.

[edit on 5/3/10 by silent thunder]

posted on May, 3 2010 @ 03:58 AM
The video in the post above, which represents the current "scholarly consensus" most closely, suggests that the northern hemisphere was hit and sheared away by a single huge object about 4 billion years ago. This is certainly possible, but alternative theories exist.

Another possibility, expounded most popularly in the book The Mars Mystery by Graham Hancock, points to the large craters in the south as the entry-points of two or three extremely large objects. Under this "minority view" (endorsed by some academic scientists as well as popular speculative writers like Hancock), Mars was hit in rapid succession in the south by two or three giagantic objects, as well as "buckshot-style" explosions that account for the many smaller craters in the southern hemisphere. The shockwaves from this impact would have rippled across the surface of the planet, colliding on the opposite side and shearing off much of the crust across the northern hemisphere. So this is an alternative impact therory, but here the hit takes place starting from the opposite (southern) side.

One interesting thing about the southern impact theory is that it could more closely fit with the breakup of a now-destroyed possible planet tenth planet (called "Astra" in the theories of scientists Donald Patten and Samuel Windsor). In this scheme, "Astra" would have been located between Jupiter and Mars, and its remains are the cosmic rubble that now forms the asteroid belt. The destruction of "Astra" also may have taken place much more recently than 4 billion years ago (the date for an impact proposed in the "northern impact" theory of the video above).

Some scientists suggest it might have taken place as recently as 20,000 years ago, at the end of the last ice age on Earth! Could this have been connected with the end of the ice age on earth in some causal or related way? The jury is still out. We just don't know. But it would be an interesting coincidence if the Mars impact and a massive change on earth just happened to occur at the same time. Could both be results of the destruction of a tenth planet ("Astra")? Or could the change in Mars's shape and orbit somehow have altered the earth's climate? Proposed models along these and other lines have been put forth.

Whatever the case, the current scholarly consensus (endorsed by NASA among others) is that Mars once contained flowing water. This means it probably had a thicker atmosphere and was a warmer, wetter world. Considering a southern-hemisphere multiple concussion scenario, the water in the south would have flowed rapidly from its higher elevation down to the new, lower elevation in the northern hemisphere. There, it would either have been lost to space or locked in the now-frozen polar Martian ice-cap. The Martian ice-cap also contains frozen CO2, suggesting a thicker, more Earth-like atmosphere that was blasted away one way or another.

Additionally, patterns on Mars's surface point to massive south-to-north flows of water that cut deeply into the crust. The rate of flow would have been astounding: millions of cubic meters of water per second. It would have been a catestrophic flooding beyond anything imaginable thus far on Earth. An example of a surface pattern suggesting the rapid release of water and south-to-north flooding is the so-called "teardrop" pattern seen across Mars:

The teardrop-shaped "islands" in the image above would be the preserved space, with the areas surround them violently washed away in gigantic, rapid mega-flows of gushing water.

It's all still very much up in the air, but whether from the north or the south, whether 4 billion or only 20,000 years ago, evidence is coalescing that a huge impact blasted the planet and utterly changed it in a dramatic and perhaps horrific way. A warmer, wetter pre-impact Mars (perhaps able to support life?) was blown to smithereens almost instantly, most of the northern hemisphere's crust was sheared off, most of it's thicker, wetter, life-friendlier atmosphere hissed out into space, and the planet was changed forever.

I toss this info out there for your general consideration, ATS. If anyone has opinions on the pre-impact nature of Mars, the south-versus-north controversy, the presence and flows of water, the time in which the event took place, or other related matters, by all means please share with the class.

[edit on 5/3/10 by silent thunder]

posted on May, 3 2010 @ 04:03 AM
What would death valley look like under the same imaging system?

NVM on Death Valley, it's really not very far below sea level (still, I think it is surrounded by high elevation).

I'm sure there are examples of sharp elevation drops on earth though, such as if the Marianas Trench were all dried up?

[edit on 3-5-2010 by sremmos]

posted on May, 3 2010 @ 04:11 AM
reply to post by sremmos

Good questions...the area on Mars represents a much larger proportion of the planet than either of the geological features you mentioned, however. It would be like a gigantic drop in a nealy clean circle that almost belted the equator at a sligly oblique angle, resulting in a lower elevation for most of the ENTIRE northern hemisphere. You can't really compare a difference that extreme with smaller-scale geographic features. Also, look how smooth the north is in the top photo compared with the crater-pockmarked south. This is planetary-level, not local-level.

[edit on 5/3/10 by silent thunder]

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