Two recent studies have enlivened the argument that an ancient meteorite contains fossils of bacteria from Mars. But several scientists say the reports fall short of proving that the Mars rock, ALH84001, harbors biological remains.
The rock became famous in 1996 when researchers reported several lines of evidence indicating that it harbors relics of life. Most dramatic were tiny worm-shaped features that the team suggested could be fossils of bacteria (SN: 8/1/96, p. 84). Other lifelike features within the meteorite include carbonate globules and mineral grains of magnetite within those globules. Although magnetite can form inorganically in geologic settings, some bacteria on Earth make magnetite cry