Martian Fossils On Earth: The Story of Meteorite ALH 84001
materials These burn up entirely when they enter the atmosphere leaving only vapor and bits of dust A few meteor causing bodies are large and fall to the ground as meteorites How do scientists recognize a meteorite First the outside of a meteorite shows signs of its fiery trip through the atmosphere It is often oddly shaped and its surface is smooth or glassy Second the rock is out of place It is made of minerals unlike the other rocks around it Sometimes the original meteorite is so huge that it leaves a visible crater on Earth About 10,000 years ago a large rock composed mainly of iron and nickel struck the ground about 50 kilometers 30 miles east
of the present day city of Flagstaff Arizona It blasted out a huge hole about 1 kilometer more than half a mile across It is commonly called Meteor Crater although its official name is the Barringer Meteorite Crater Many nickel iron meteorites have been col lected from that site Scientists classify each meteorite as a member of a family according to its physical appearance and mineral makeup A meteorite family is often named after the location where the first such meteorite is found ALH 84001 is a shergottite meteorite The first known shergottite meteorite fell in Shergotty India on August 25 1865 ANSMET scientists have since found many more shergottite meteorites including the small black crusty one pictured here designated QUE 94201 It was found in the Queen Alexandra Range during the Antarctic summer of 1994 1995 A meteorite that fell and killed an unfortunate dog in Nakhla Egypt on June 28 1911 was the first to be classified as nakhlite Another fell in Chassigny
France on October 3 1815 and was designated chas signite Later other nakhlite meteorites were found in Lafayette Indiana in 1931 and in Governador Valadares Brazil in 1958 Together the shergottite nakhlite and chassignite meteorites are known as SNC meteorites Meteorite ALH 84001 was first identified incorrectly incorrectly as a rare form of another mineral family the diogenites In 1993 meteoriticist meteorite scientist David Mittlefehldt caught the error He announced that meteorite ALH 84001 was the tenth known member of the SNC class Scientists now know of well over 100 SNC meteorites Those rare rocks are very special indeed for scientists now believe that the SNC meteorites are pieces of the planet Mars On August 7 1996 meteorite ALH 84001 became the most famous rock on Earth That day a team of scientists led by David S McKay of JSC made an astounding announcement They believed that meteorite meteorite ALH 84001 contained chemical evidence and fossils of ancient Martian microbes Life may have begun on Mars at about the same time as on Earth
2 HOW WAS METEORITE ALH 84001 DISCOVERED Who would want to live for months in Antarctica where it snows even in the summertime Thousands of scientists from around the world that’s who Among them are the researchers of the Antarctic Search for Meteorites ANSMET project Although meteorites are no more likely to fall on Antarctica than on other places they are much easier to find there And the meteorites found in Antarctica are in better condition
