Lecture #20: Weird Science

I. FYI-- -- Cassini is orbiting Saturn
II. Science and Philosophy -- meteors are seen in the atmosphere, hence the connection to "meteorology", which has to do with weather not meteors! -- meteors are the same as "shooting stars", which is a romantic name but obviously an erroneous one! -- history of discovery of meteorites -- Chladni (1794) and Biot (1803) -- imperfect science vs. nonscience and conspiracies -- metals from space -- roles of science and beliefs III. Meteors: -- fireballs and UFOs -- Antartica finds-- SNC meteorites IV. Classification of meteorites -- stones and irons: falls and finds -- chondrites and chondrules V. Origin of meteors -- large parent bodies would have melted, differentiated, but smaller ones leave meteoric material unchanged since solar-system formation: "carbonaceous chondrites" -- most parent bodies in the asteroid belt, about 100 km is size (such as Ceres, see here for the latest images from the Dawn mission) -- comets -- planets: Moon and Mars (SNC meteors) -- meteors from the asteroid belt were probably formed by fragmenting larger bodies. Neary Jupiter is likely responsible for the creation of the asteroid belt-- it perturbed the orbits of nearby planetesmals and sent some crashing through the asteroid belt, causing fragmentation and preventing a planet from forming there. VI. Large Events -- Tunguska, Siberia in 1908: 30-60 km meteor exploded 6 km in the air, made a huge fireball and sonic boom, no crater -- meteor explosions in the atmosphere are actually pretty common, about every few days, but rarely near cities -- in 1972, a large meteor skipped off the atmosphere over Montana and did not explode, would have been as bad as Hiroshima if it had exploded over a populated area -- still, the only recorded human death was an old man near Tunguska VII. Organic Molecules and Amino Acids -- found in carbonaceous chondrites in meteors formed in early solar system -- probably got there as a result of cooking the meteor at fairly low temperatures, plus having lots of carbon monoxide and ammonia around -- amino acids show both "handedness", unlike when made by life -- early ogranic compounds formed in solar system, not just "primordial soup" on Earth VIII. Meteors from the Moon and Mars -- Antartic meteors from Moon, and "SNC" meteors from Mars -- possible evidence for life, but very controversial and probably unlikely