Life in a Martian Meteorite
LIFE IN A MARTIAN METEORITE?
In 1996 a team of scientists proposed a very intriguing hypothesis regarding the possible biological origin of about a half-dozen features observed in a Martian meteorite, ALH 84001. In part, the hypothesis involved tiny grains of the naturally magnetic mineral magnetite, which is commonly found in basalt (a high-temperature volcanic rock that makes up oceanic crust). While most magnetite on Earth is inorganic, some bacteria have discovered ways to make minute grains of geochemically pure, low-temperature magnetite, which they organize into chains within their cells to use as a kind of directional compass. This enables cells to better control their movement in the environment and to track favorable environmental conditions. Some of the magnetites found in the Martian meteorite bear a strong resemblance to the magnetites formed by terrestrial bacteria. But is the population of magnetites in the meteorite a reliable indicator of life? Scientists are still debating this question.