More Moon and Mars

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Mars and the Moon put on a nice display tonight. They huddle close together as darkness falls, and move even closer during the night. At their closest, in the early morning, they'll be separated by about the width of the Moon itself.

Although Mars looks orange, scientists are interested in a patch of white beneath its orange soil. The white is almost pure silica -- the mineral that's used to make glass. It's exciting because it probably formed in a watery environment. Similar environments on Earth are crawling with microscopic organisms, so the Martian silica could contain the microscopic fossils of ancient life.

The silica was discovered last year by Spirit, one of the Mars rovers. While driving through the Columbia Hills, its wheels dug into a deep layer of soil. When Spirit pulled away, its cameras revealed the white patch just below the surface. Its instruments found that the white stuff is made of silica.

Planetary scientists say the silica probably formed around a vent of steam that contained a lot of acid. The acid eroded everything else, leaving behind only the silica. But it's also possible that it formed in a hotspring. Such environments are common on Earth, and they're good homes for microscopic life.

Spirit can't see anything as small as a microscopic fossil, so we'll probably never know if it dug up some. But the discovery at least shows that, in the far-distant past, conditions could have been favorable for Martian life.

Script by Damond Benningfield, Copyright 2007

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