cosmic collisions, biological effects
An inevitable corollary of the birth of planetary systems is the formation
of numerous smaller objects, including asteroids
and comets, and the collision between some
of these bodies and larger, possibly life-bearing worlds. Thus any comprehensive
model of the origin and evolution of life must factor in the possible consequences
of such collisions. During the early, intense bombardment phase of a new
solar system, numerous, large-scale impacts may preclude the development
of life or force it to take place well below the surface of a planet where
there is some protection (see Earth, early
history). Impacts may also result in the transferance of prebiotic or
biological material between worlds (see ballistic
panspermia). Later in the course of a planet's development, occasional
collisions with objects at least several km across may dramatically influence
the course of biological evolution by wiping out many species or entire
genera (see mass extinctions) but,
at the same time, providing the opportunity for other categories of organisms
to fluorish. Such appears to have been the case at the Cretaceous-Tertiary
Boundary when, apparently in the wake of an asteroid impact, the mammals,
and ultimately humankind, filled the ecological void left by the demise
of the dinosaurs and their kin.
Archived news
Meteorites supplied
Earth life with phosphorus, scientists say (Aug 26, 2004)
Double
whammy link to extinctions (Apr 1, 2004)
Impact
caused mass extinction in 250 million BC (Feb 22, 2001)
Related entry
• potentially
hazardous asteroid
Related categories
• MEGACATASTROPHES
• ORIGIN
AND EVOLUTION OF LIFE
• ASTROBIOLOGY
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