This is an image of Mars.
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Image from: NASA
The Earliest History of Mars
The terrestrial planets formed about 4 Billion Years ago. As the process which formed them came to an end, the planets may have been left in either of the following two states:
- very warm, with a softer & pliable interior. There is probably abundant water on the surface. Heat from inside Mars probably caused volcanoes, as well as continental drift.
- cold and rocky, needing to be warmed from the inside.
With Mars, the second case is probably more likely.
Nevertheless, during this time, the surface continued to be bombarded by the remainder of planetary material available nearby, which heated the surface (not the interior) of Mars. This heating was accompanied by hydrothermal activity, or circulation of water within the ground. These conditions are very favorable for certain forms of life.
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