HOW WERE THE LARGE CANYONS ON MARS THOUGHT TO HAVE BEEN FORMED?

Since this is not my area of expertise, I searched Google under the key words "Mars canyons formation" to get these possible sources:

http://www.lukew.com/marsgeo/tectonic2.html
http://www.webspawner.com/users/theory/
http://mpfwww.jpl.nasa.gov/education/modules/webpages/module3.htm
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-4D4PR3P-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7210c6a684af60e597051904a754b8b0
http://books.google.com/books?id=uLHlJ6sjohwC&pg=PA110&lpg=PA110&dq=mars+canyons+formation&source=web&ots=NgFX9mHC3W&sig=_7cB8RcLgmgaMKv0Tg9wuMyPwtA

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.

I hope this helps. Thanks for asking.

BY CHANGING

The large canyons on Mars, such as Valles Marineris, are thought to have been formed through a combination of tectonic and erosional processes. Here's how the scientists have arrived at this understanding:

1. Remote Sensing: Scientists have used various instruments and remote sensing techniques to study the Martian surface. Orbiting spacecraft, such as the Mars Global Surveyor and the Mars Reconnaissance Orbiter, have provided high-resolution images and data that help us understand the geological features on Mars.

2. Tectonic Activity: Valles Marineris, the largest canyon system on Mars, stretches over 4,000 kilometers in length. Scientists believe that the canyon system was formed primarily as a result of tectonic activity. Mars had active tectonic processes in its early history, similar to those on Earth, which caused crustal stretching and fracturing. This stretching could have led to the formation of a large graben—a depressed block of crust—creating the foundation for Valles Marineris.

3. Erosion: In addition to tectonics, erosion has played a significant role in shaping the Martian canyons. The erosional processes on Mars, including wind action, water flow (in the past), and possibly volcanic activity, have helped to shape and deepen these canyons over time. For example, scientists believe that flowing water and catastrophic flooding events may have further carved and modified the channels within the canyons.

4. Lava Flows: Some Martian canyons, such as Ma'adim Vallis, show evidence of extensive lava flows. These volcanic activities are thought to have occurred after the initial formation of the canyons, filling and modifying the existing channels.

In summary, the large canyons on Mars were most likely formed by a combination of tectonic forces that created the initial depressions, followed by erosional processes like water flow, wind erosion, and possible volcanic activities that shaped and further deepened the canyons over time.