schryver@radiks.net:
NBC News at Sunrise has just announced the discovery of alien life on the planet Mars. The lifeform that became extinct more than 2 billion years ago was found as a fossil in a meteor that originated from mars and landed on earth. The fossil found was a primitive germ life form.
NASA is holding a news conference today to discuss the find. I must admit I am curious as to how they determined the meteor's origin. Most material in the solar system is similar in composition.
Using the same methods that geologists use to determine whether or not certain meteorites are from the moon, by chemical composition. Material from within the solar system actually has varied composition mainly determined by the distance of the body from the Sun (there are various theories as to why this is, an intro cosmology book will describe them all in detail), the actual percentages of various elements and compounds can be used to make a reasonable guess as to whether or not a particular meteorite was knocked off of a planet or moon to which we have sent a probe. For example, it is possible to buy fragments of "moon rocks" which are not actually samples returned from Apollo missions (which are all owned by the U.S. government) but are from meteorites which match the exact chemical and physical composition of the returned lunar samples. Such determinations are a lot easier for planets/moons which do not have active vulcanism or other events which significantly mix up the composition of the planet. At the news conference given this afternoon the fact that the meteorite was Martian in origin was probably the least controversial. It seems that exobiology may no longer be a field without a subject :) If the results are confirmed what I think will end up being the most interesting fallout of this will be in the creationism/evolution debate. It seems that life may have been independantly generated at multiple locations, barring a "space seed" debate flaring up again, and the "impossible odds" argument has become pretty weak... jim