Martian Yellowstone

The script that follows aired in lightly edited form on the Earth & Sky radio program on Sunday, September 27, 1998.

Teaser: The hot springs of Yellowstone National Park contain clues which could help future Mars explorers find the fossil remains of martian microorganisms. Martian Yellowstone, after this, on Earth & Sky.

Byrd: This is Earth & Sky. I'm Deborah Byrd with news on the hunt for life on Mars.

Block: And I'm Joel Block. Carbonate minerals on Earth include limestone, usually laid down on sea bottoms, and travertine, formed when hot water dissolves limestone then re-deposits it.

Byrd: So far, no one has found large carbonate deposits on Mars. But scientists found small carbonate globules in ALH 84001, the meteorite some think contains microscopic fossils of ancient martian microbes. Scientists found the possible fossils around the carbonate.

Block: Three billion years ago, scientists say, hot water containing primitive martian microbes percolated through ALH 84001 carrying dissolved carbonates. The carbonates condensed, forming the globules and preserving the microbes. But others think the water must have been too hot for life.

Byrd: NASA scientists answered this challenge by studying Mammoth Hot Springs in Yellowstone National Park. There, hot water dissolves underground limestone and carries it to the surface. Just centimeters from the hot spring vents they found living bacteria threads in water hot enough to cook meat.

Block: What's more, they found dead bacteria threads that had recently been encased in carbonate. Fossils nearly identical to these are found in Earth rocks that are 360 million years old.

Byrd: The hot springs bacteria suggest that, even if the carbonates in ALH 84001 formed at a high temperature, some kinds of living martian bacteria might have been present. They also suggest that explorers should seek out rocks formed long ago in hot springs on Mars, for they might contain fossilized bacteria. Our show is made possible by the National Science Foundation. We're Block & Byrd for Earth & Sky.