Planetary Science Research Discoveries

pdf version  PSRD-LifeonMars.pdf

HOT IDEA HEADERposted October 18, 1996

Life on Mars?
Written by G. Jeffrey Taylor
Hawai'i Institute of Geophysics and Planetology
People have long wondered if life could have existed or even still exits on Mars. The Viking landers in 1976 searched for signs of life in the red soil, but found no clear-cut evidence. Future missions are planned to search other terrains on Mars, such as areas where water must have flowed in rivers and formed lakes that eventually dried up. But the search has already started. A group of investigators at the Johnson Space Center and Stanford University has revealed evidence from an intense, careful study of a meteorite from Mars that tiny bacteria-like creatures may have lived in cracks in the rock.

In this first issue of PSRD, we describe evidence the researchers have assembled, and present some of the nonbiological alternatives other scientists have proposed. We intend to follow the debate as it unfolds during the coming months or, perhaps, years.

Begin your discovery here. Investigate the type of evidence of most interest to you or simply go through the list in order.

Hot Idea Contents

Mars Meteorite ALH 84001 Meteorite from the Ancient Crust of Mars. ALH 84001 originated as a slowly-cooled igneous rock in the Martian crust, was excavated by an impact, altered by fluids, and finally sent to Earth by another impact.
Tubes with segments The Evidence and the Debate. The NASA-Stanford group cites four lines of evidence for fossil life in ALH 84001, all of which are found associated with unusual globules of carbonate minerals: (1) formation before arrival on Earth; (2) concentrations of organic chemicals; (3) tiny grains of iron oxide and iron sulfide; and (4) tubular, fossil-like objects. Alternative interpretations appear in pop-up windows which you open with a click of a button (a JavaScript enhancement).
Martian river channel Ancient Hospitable Mars. Before about 3 billion years ago, Mars may have had a more clement climate than now, perhaps allowing life to develop.
The Researchers The Researchers.
Reference: McKay, David S., and others (1996) Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001, Science, v. 273, p. 924-930.

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