RedEaredSlider (1855926) writes "NASA's Mars Reconnaissance Orbiter has found a giant buried deposit of dry ice, which could be evidence that Mars once had a thicker atmosphere and was able to have more water on its surface.
The orbiter's ground-penetrating radar found the dry ice, which is frozen carbon dioxide, near the planet's south pole. The scientists think that when Mars' axial tilt increases, the carbon dioxide turns into a gas, thickening the atmosphere. The result would be more intense dust storms, but also a wider range of areas where liquid water could exist."
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