Valles Marineris

[dragon04]

This is a question posed to our Geological experts. Unfortunately, I need to preface the question with my extremely untrained observations.<br /><br />If Earth lost its atmosphere and water tomorrow, it (I believe) would be obvious to an observer by the structures of the continents and plate lines that there was tectonic activity as well as giant oceans.<br /><br />On Mars, I've never seen images that point to "continents" as we would recognize them.<br /><br />Other than the extremely prominent extinct volcanoes, (or is it volcanos.. I feel Dan Qualye-ish at the moment) Valles Marineris is the only other and most striking geological feature on Mars.<br /><br />I see what appear to be waterways that I would guess drained <b> into </b> the basin.<br /><br />From the image at http://antwrp.gsfc.nasa.gov/apod/ap020827.html<br /><br />you can see 3 massive volcanic mounds in the "west" of the image. And almost in the dead center of the canyon, it is far wider than at the ends.<br /><br />Now to the question. What, in your best guess, ripped Mars open? A huge impact? Sudden and massive magma discharge from the 3 volcanoes that sunk the ground to the east of them?<br /><br />I've looked at topographical images of the Grand Canyon, and with a layman's eyes, I see little in common with it and Valles Marineris.<br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[bonzelite]

i'm no expert. but you may want to revisit your initial thoughts:<br /><br />there are many striking features on mars --perhaps too many to discuss in one thread. and many of these features are of unknown or of inconclusive origin: this includes Olympus Mons, the entire Tharsis region including Vallis Marineris (for example, Tharsis is known to have been created by lava flows, but the plateau rises nearly 25,000+ feet above the surrounding terrain. and it is an anomalous structure not repeated again on mars --why? as well, the typically dark basaltic rock of volcanoes found throughout mars is not present in Tharsis, as this region is nearly entirely brightly colored, not consistent with volcanic basalt --yet is regarded as perhaps the largest volcanic-created single structure --why?). <br /><br />Vallis Marineris' origin is unknown. earlier ideas were fluvial based carving, but this structure does not seem to exhibit these traits (personally, i have never been a proponent of fluvial carving as origins of the Vallis). it is now thought to be a gaping fault opening, augmented by --but not created by-- minor later outflow to Ares Vallis, Margaritifer Terra and Chryse Planitia.

 

[JonClarke]

You are right, Mars looks nothing like earth. terrestrial tectonis are unique, there are nothing like our continents and oceans, thin crust, island arcs, spreading centres or subduction zones on any other rocky world. Even the fold belts that are so common here are rare or absent elsewhere, with the possible exception of Venus.<br /><br />We don't know what formed Valles Marinaris. Uplift, faluting and then subsidence is the best guess. Possibly related to the formation of the Tharisis bulge and the volcanoes. The valleys were then enlarged by erosion.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>