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Did
It Happen?
The image above shows an expanding supernova remnant blazing
over a barren Earth landscape--the possible result of a nearby explosion.
Composit image: Chandra X-Ray Observatory
image of Cassiopeia A courtesy of NASA. Landscape courtesy © 2000-
www.arttoday.com
Several
possible effects of a nearby supernova on Earth have been proposed.
1. If the amount
of infalling radioactive material is sufficient, plants and animals
would die directly from radiation sickness.
2. In certain
types of supernovae, huge quantities of tiny particles called neutrinos
are released. The flood of neutrinos would pass through plants and
animals causing genetic mutations and cancers.
3. Infalling
radioactive matter from supernovae are like cosmic rays, which some
scientists think may cause increased cloud cover. If enough clouds
are created by particles from a supernova, a super-cold "cosmic-ray
winter" may occur, causing widespread starvation.
4. Increased
radiation from a supernova may destroy Earth's protective ozone
layer for centuries. If the ozone layer were gone, ultraviolet rays
from our own Sun would reach the surface, killing land plants and
ocean plankton. Earth's food chains would collapse from the
bottom up, causing starvation and extinction.
Now the question
is: Did a nearby supernova kill the dinosaurs? Unfortunately, the
remains of any star that exploded 65 million years ago would be
far across the galaxy by now, so we must look for evidence in Earth's
rocks. You might look at the patterns of extinctions--which plants
and animals died--or evidence for rare isotopes of elements that
may have come from a supernova. To help you in your search, you
might want to look up more information about supernovae, dinosaur
extinctions, radiation sickness, isotopes, cosmic rays, neutrinos,
the ozone layer, and food chains. Good luck!
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