ALH84001 is the designation of a
meteorite fragmented, generally regarded as originating on
Mars. It was discovered in December
1984 in
Antarctica by a meteorite-search expedition of the
ANSMET[?] program, as one of 7000 others. On discovery, its weight was 1.93
kg. According to
NASA, it was formed on Mars from molten
lava about 4 billion years ago, then came to earth as another meteorite impacted on Mars, throwing ALH84001 off Mars' surface as debris, about 3.7 billion years ago. Roughly 13000 years ago, ALH84001 impacted on earth.
ALH84001 became known because of certain
microscopic structures that were for some time considered the remains of
bacteria-like lifeforms. This would have been the first proof of extraterrestrial life and, eventually,
panspermia theory. Today, the actual origin of the tube-like structures is still subject of disputes.
