Valles Marineris

[ElPelado]

I was yesterday in an astronomy meeting, in wich a man spoke a lot about mars, and then we saw it with an 8" telescope, at a magnification of 200x. very good, much better than with my telescope. then, we saw M31, the Andromeda Galaxy and M57, the Ring Nebula.
one of the topics was the water on mars: for example, if there was water in the past, where is it now? he also named a second theory that says that mars was always a cold planet, and many other interesting things. we also saw the "Cold War" when we saw the competition between USA and the Soviet Union to reach to mars.
he also said something that i haven't heard before: the Valles Marineris was not formed by water, but it was formed by geological activity, because in the past there were tectonic plates, like on earth. and their movment formed the Valles Marineris.
has anybody heard this theory before?

[Don. Edwards]

Yes I have. Valles Marineris is not a canyon like the Grand Canyon but a rift valley like the one that runs down the right side of Africa. Africa at the present time is tearing into pieces. This may stop in the future as the plates continue to move around.
A rift valley is where the ground splits and tears apart because of volcanic and tectonic movement. Mars per say never really had much of a chance to form plate tectonics as it is here on Earth. It being smaller and not a dense made its interior cool quicker so the heat engines that got things started with Valles Marineris didn't continue for long.
Another theory is that Valles Marineris is one of the results of the Hellas impact event. When the asteroid that hit Mars that made the Hellas basin sent incredible shockwaves through the planet. They got focused on the opposite side of the planet. The oposite side of Hellas is the Tharsis rise and the beginning of Valles Marineris at Noctis Labyrinthus. So there was an incredible amount of magma that broke through the crust that started most of the volcanoes there. It also fractured the crust enough to let it start to rift apart. But again there just was not enough heat to keep things going for long. A lot of people think the rift valley is the same as a mid oceanic trench. They are similar but they in fact have slightly different features. So in actuality when they compare the size of Valles Marineris to the Grand Canyon they are doing the Earth a disservice. The rift valley in Africa is actually they same kind of feature and easily its equal in size. Here is rough layout of the African Rift Valley system. You will see allot of it is hidden under water.

Also in the African rift valley there are not many volcanoes or any lava leaking out down the middle of the rift like an oceanic rift. Instead the volcanoes run along its sides for the most part. Although there are some that pop up in the rift zone.

Don. Edwards

[ElPelado]

I see that the red line continues to the Dead Sea, right? As i herad, the Dead Sea is the lowest land point on earth: its 500m(or km? i cant remember now... ).

An other thing i heard yesterday is that tha Olympus mount is so high because of the low gravity on mars.

[Don. Edwards]

Olympus Mons hieght actualy has several factors going for it. Thick crust at that location due to so much valcanic activity. The lower gravity does let it get higher than it would on Earth. But its also made of lighter material than say Mount Everest. Olympus Mons if made up of mostly pumis like rock so its density is lower. So it is not as heavy as if it were made of more dense materials. It also has an icredibly wide base. If layed it on the surface of the Earth it would be as wide as the the state of Colorado. Its sides do not have much of an incline so from the surface of Mars if you were at it base you wouldn't even be able to see it sumit because it would be over the horizon. It would look like a very large gently slopeing hill. Most of the big vlocanoes are like this. The only volcanoes that are more like Earths composite vlocanoes are the one around Elysium. These were most like formed the same way the Tharsis rise volcanoes were. When the impaster that hit and made the Argyre
basin it also probably caused a shockwave as well because on the opposite side id the Elysium Rise and its volcanoes. These volcanoes are a little different from the other as that they are much steeper on there sides. Elysium Mons has a very Mount Fugi look although many times bigger. Because it happens after the Tharisis event one ould sormise that Mars' magma had already gone through some changes and was more viscuse at this point. I couldbe wrong on that though.I do know what I have read and those mountains are a little different than most of the others.
Thats probably also why they never really got as big. Hope that helps answer some questions.

Don. Edwards