Article,
Exchange of meteorites (and life?) between stellar systems
Astrobiology, 3 (1): 207--215 (2003)
Abstract
It is now generally accepted that meteorite-size fragments of rock
can be ejected from planetary bodies. Numerical studies of the orbital
evolution of such planetary ejecta are consistent with the observed
cosmic ray exposure times and infall rates of these meteorites. All
of these numerical studies agree that a substantial fraction (up
to one-third) of the ejecta from any planet in our Solar System is
eventually thrown out of the Solar System during encounters with
the giant planets Jupiter and Saturn. In this paper I examine the
probability that such interstellar meteorites might be captured into
a distant solar system and fall onto a terrestrial planet in that
system within a given interval of time. The overall conclusion is
that it is very unlikely that even a single meteorite originating
on a terrestrial planet in our solar system has fallen onto a terrestrial
planet in another stellar system, over the entire period of our Solar
System's existence. Although viable microorganisms may be readily
exchanged between planets in our solar system through the interplanetary
transfer of meteoritic material, it seems that the origin of life
on Earth must be sought within the confines of the Solar System,
not abroad in the galaxy.
