It Came from Outer Space
Posted December 8, 2000
Imagine an alien traveling through the far reaches of space in suspended animation – frozen in a block of ice for millions of years. After streaking across the cosmos
at fantastic speeds, this visitor eventually ends its journey of many light years and lands on a tiny blue planet circling a small yellow sun.
This sounds like the beginning of a new science fiction movie, but this may have happened as recently as this morning. Only the visitor was not a bug-eyed monster
from another planet. It was a microbe – a tiny bacterium that came to Earth frozen in a comet.
For many years, scientists have suggested that life on Earth did not begin in the oceans or even the atmosphere. Some scientists think that life was deposited on Earth
by comets and debris that hits our atmosphere.
Comets are mainly composed of rock and ice and are chilled to nearly absolute zero when they zip through space. According to NASA, bacteria and other microbes can
survive millions of years in a frozen state and still be alive. If particles from a comet containing microbes hit our atmosphere, the microbes could be deposited on Earth.
"Where’s the proof?" you might ask. After all, this is a fine hypothesis, but isn’t science about drawing conclusions from data?
Hundreds of tons of space debris hits our atmosphere every day. In fact, NASA has a division devoted to astrobiology - the study of life in the universe. This group
announced earlier in the month that organic molecules were found in the meteors of the Leonid meteor shower that passes over Earth each year.
Then, in November 2000, a team of international scientists discovered living bacteria floating in the atmosphere, 16 km above Earth. The scientists who discovered
this bacteria claim it is unlike any terrestrial bacteria they know. It was found on a scientific balloon, and the scientists think it was deposited there by a rogue comet.
Other scientists are skeptical. Although 16 km up is very high in the atmosphere, the scientists say that it is not too high for the microbes found to have
been terrestrial . In fact, fungi spores have been found higher than 7 km in the atmosphere.
Because the announcement of this discovery was only recently,the data is still extremely new. The group of scientists is keeping much of their findings under wraps
until they are able to study it further.
Activity
Use the Internet Web sites listed here to learn more about astrobiology and microbes in comets. Use this information to write a newspaper editorial explaining
why you agree or disagree with those that think life could have been deposited on Earth from comets.
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