Wednesday, March 10, 1999 Published at 17:07 GMT
Magnet theory to life on Mars
Globules of complex carbons molecules in a rock from Mars
By BBC News Online Science Editor Dr David Whitehouse
Scientists are about to reveal what may be the best evidence yet for past life in a rock from Mars. They hope it will cause their critics to pause for thought instead of dismissing their controversial claims.
For many years, several lines of research have hinted at the possibility of past life in one of the 14 known meteorites from Mars. Each line of research, such as the presence of complex carbon molecules, was interesting but not enough to prove the case.
They were found in a Mars rock picked up in the Allen Hills region of Antarctica.
Since then, the jury has been out. Most scientists are fascinated but unconvinced, pointing out that there are other explanations for what has been found in the Mars rock.
But new findings will be revealed next week at a conference in the US. They centre on discovery of tiny magnetic grains found in the rock.
Some terrestrial bacteria have evolved the ability to sense the Earth's magnetic field. They do this by making tiny magnetic crystals of iron inside themselves and arranging them into chains called "magnetsomes".
These tiny grains, made of a material called magnetite, have a very specific size and shape. They are also very pure - far purer than magnetite grains that occur naturally.
Professor Joe Kirschvink of the California Institute of Technology, an expert on biological magnetism, will point out next week that magnetsomes have unique properties. If they are present in the Mars rock then they could certainly be identified, he will say.
Dr Kathie Thomas-Keprta, of Nasa's Johnson Space Center in Texas, will describe research that she believes shows that magnetite produced by bacteria-like microorganisms is indeed present in the Allen Hills meteorite.
The presence of magnetite in the Mars rock has been known for some time. The grains of this magnetic material seem to be located in the rims of globules of complex carbon molecules. This is just what would be expected if they were fossils of ancient Martian bacteria.
In the most detailed investigation of the composition of these magnetite grains, Dr Thomas-Keprta will conclude that they were indeed formed by past Martian life.
Joe Kirschvink says these results are "very exciting" and that he is convinced this is definite evidence for life on Mars.
This new research is sure to re-ignite the debate that has been rumbling on for more than two years.