New report offers compelling evidence of Mars life

Close-up view of a meteorite that has provided tantalizing evidence of fossilized life on Mars

By Richard Stenger
CNN.com Writer

(CNN) -- The presence of extraordinary magnetic fossils in a meteorite from Mars suggests that the planet once hosted primitive life, scientists reported this week.

The only known sources of such microscopic magnetic crystals on Earth are certain types of bacteria that produce them to seek food and energy.

Magnetite, the mineral form of black iron oxide, is created through natural forces on our planet. But magnetite crystals like those produced exclusively by a class of aqueous bacteria are different. They are chemically pure and free of defects.

"The process of evolution has driven magnetotactic bacteria to make perfect little bar magnets, which differ strikingly from anything found outside biology," said Joseph Kirschvink, a geobiologist who took part in the NASA-funded study.

"In fact, an entire industry devoted to making small magnetic particles for magnetic tapes and computer disks has tried and failed for the past 50 years to make similar particles," he said in a statement.

The microorganisms arrange the magnet crystals in their cells as miniature compasses, which direct them along naturally occurring magnetic fields towards hospitable environments.

The magnetic samples came from the oldest identified red planet meteorite, a potato-sized igneous rock with an estimated age of 4.5 billion years. Life could have thrived on the planet at the time, scientists theorize.

"Mars is smaller than Earth and it developed faster. Consequently, bacteria able to produce tiny magnets could have evolved much earlier on Mars," said Simon Clement, another scientist who investigated the meteorite.

Kirschvink, Clement and other planetary scientists published their findings in the December issue of Geochimica et Cosmochimica Acta, the journal of the Geochemical Society and the Meteoritical Society.

The meteorite landed more than 13,000 years ago in Antarctica, according to researchers, where it remained buried in ice until its discovery in 1984.

NASA scientists created a stir in 1996 when they announced they had discovered microscopic fossils of life in the meteorite, known as ALH84001.

Critics have countered that terrestrial life could have contaminated the rock after it reached Earth. But later research demonstrated that the samples came from an uncontaminated section of the meteorite, the report authors said.

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Mars Meteorite Home Page
NASA site: Life on Mars?
Geochemical and Meteoritical Societies journal
The Meteoritical Society

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