Tuesday, March 04, 2008
History Channel: Cosmic Collisions: how asteroids can get flung into the inner solar system
On March 4, 2008, the History Channel aired the “Cosmic Collisions” episode in its “Universe” series. This program surveyed the possibilities of collisions among all kinds of astronomical entities, including galaxies themselves. The Milky Way is actually absorbing two small galaxies now, and will one day collide with the Andromeda Galaxy, in billions of years.
But the part of the program of practical significance was that dealing with “families” of objects in the Kuiper Belt (beyond Neptune) and Asteroid Belt, mostly between Mars and Jupiter. The Kuiper Belt tends to consist of icy objects and comets; the asteroids are metallic and rocky. There is a tendency for them to collide among their groups, and also to get into some kind of synchronicity with Jupiter that flings many of them into the inner solar system, setting up possible strikes on Earth.
The two biggest strikes on Earth happened 250 million years ago, when the Earth’s land mass was one continent Pangea, and 65 million years ago. The strike 250 million years ago seems to have been an asteroid of several miles width and the evidence remains in the plateau desert terrain of northwestern Australia. That strike provoked “the great dying” with a “nuclear winter” and killed off 90% of species, allowing the dinosaurs to evolve. The second strike was off Yucatan and gave mammals a chance to evolve. It may have been more like a chondrite, and it was not as large as the earlier one.
A major asteroid hit, if undetected and unintercepted, could wipe out civilization as we know it, although in some areas men would survive and start a tribal existence again. Sounds like a good topic for a movie. Screenplays anyone?