Unlocking Secrets of Martian Life - Brief Article

USA Today (Society for the Advancement of Education), June, 2000

METEORS

Research by scientists at The University of Texas at Austin and NASA's Johnson Space Center on a 4,570,000,000-year-old Martian meteorite has established the age of 3,900,000,000 years for a carbonate vein deposited inside it. This carbonate vein contains odd formations, resembling terrestrial bacteria, that might prove to be evidence of ancient Martian life.

At least two models have been proposed for the formation of the vein. One suggests that water passed through an existing fracture, depositing the carbonate minerals. An opposing view suggests that it formed from a high-temperature, carbon dioxide-rich fluid during massive fracturing caused by an asteroid impact on Mars. Because water is considered essential for the existence of life, the presence or absence of water on Mars when the carbonate vein formed is central to the issue of life on the planet as well as to the formation of the vein.

Independent evidence suggests that early Mars had a warm, wet climate. Surface water, though, has not existed on Mars for 3,500,000,000 to 3,800,000,000 years. A date of 3,900,000,000 years for the carbonate vein, as well as for the strange shapes inside it, places them within the time range when surface water is thought to have existed on the planet.

The 4.2-pound, grapefruit-sized meteorite is believed originally to have been an igneous rock ejected from the Martian surface after a large object, such as an asteroid, crashed into it. Martian material was thrown far out into space, floating as space debris for about 16,000,000 years. Scientists believe the meteorite fell to Earth about 13,000 to 15,000 years ago. The object was discovered in Antarctica in 1984 during a scientific expedition to collect the meteorites that regularly emerge from the eroding ice of Antarctica's Allen Hills. It was identified as Martian in origin in 1994. The meteorite is one of 13 so far identified as Martian because they contain inclusions (minute bubbles) of gas with the same distinctive composition found in the Martian atmosphere. Information on Martian atmospheric gas was transmitted back to Earth in 1976 by unmanned vehicles that landed on the planet during NASA's Viking program.

In 1996, the Johnson Space Center announced the carbonate material contained slender, squiggly formations that could be fossils of organisms resembling bacteria. James N. Connelly, assistant professor of geological sciences at the university, and research scientist associate Kathryn Manser dated the carbonate samples using techniques roughly similar to Carbon 14 dating of artifacts by archaeologists.