Life on Mars

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The case for fossil Martian bacteria in the now famous meteorite ALH 84001 (Shown below, images courtesy NASA/JPL and Wikipedia) was strengthened over the long holiday weekend as new evidence was announced supporting the findings of the original researchers. The rock in question is an achondrite meteor fragment which is believed to have been blasted off the Martian surface over a billion years ago. After a long trip through interplanetary space it fell to earth in Antarctica in a region called Allan Hills and was recovered in 1984. Subsequent examination in the mid 1990s by a team of astronomers and biologists found chemical residues associated with life as well as odd shaped microscopic structures resembling terrestrial fossil bacteria. The 1996 announcement ignited a heated debate over the origin of the chemicals and structures, with some scientists saying they could have been created from non biological sources or as a result of contamination by terrestrial microbes. But a new study said to be available in the next few days supports the Mars biological origin theory:

The new work centers on so-called magnetic bacteria that on Earth, and apparently Mars as well, leave distinctively-shaped remnants in the rock. In addition the features test with a high chemical purity more like a biological feature than geological. These are just like the magnetite-related life forms found in the meteorite believed to represent Martian life forms, says Dr. Dennis Bazylinski, who peer reviewed the new findings.

In the past decade, since the initial announcement, new discoveries have strengthened the circumstantial evidence for ancient Martian life. Ancient seas and rivers are now virtually confirmed. And similar structures to the possible nano-bacteria of the size indicated in the Martian sample have been found on earth (Including even weirder, possible tiny life forms called nanobes). This newest evidence is, alas, not a smoking gun. But the weight of all the evidence taken together might give scientist just enough leeway to state, tentatively, and for the first time that Mars supported life billions of years ago.

Above: ALH 84001 Weight: 1930 grams;   Dimensions (cm): 17 x 9.5 x 6.5;   Type: Achondrite

Below: Structures on ALH 84001 revealed by scanning electron microscope which resemble terrestrial bacteria.