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Life From Other Planets?

BACKGROUND: A tiny cluster of bacteria that survived the fiery breakup of the space shuttle Columbia in 2003 has offered some unexpected evidence that primitive life forms could jump from one planet to another aboard meteorites, according to Bob McLean, a microbiologist at Texas State University.

ABOUT PANSPERMIA: Panspermia is the theory -- dating back to about 500 B.C. -- that the seeds of life originated elsewhere in the universe and were dispersed to Earth and other bodies as micro-organisms or other matter as stowaways on meteorites. Scientists have been skeptical of this theory, believing life could not survive passage through the earth's atmosphere. To escape Mars, for example, a rock must undergo extreme acceleration, travel through space, and then land safely on Earth, so any microbes it carries must be able to survive both extreme cold and high levels of radiation while journeying through space for thousands to millions of years, and then survive the extreme heat of entering Earth's atmosphere. The surviving bacteria from Columbia may have reached temperatures of about 385 degrees Fahrenheit as a result of atmospheric friction as the debris fell -- still four to five times less that of a meteorite, but much higher that previously expected.

WHAT ARE EXTREMOPHILES? An extremophile is any microbe that thrives in extreme conditions, such as temperature (extreme heat or cold), pressure, salinity, low oxygen environments, or high concentrations of hostile chemicals. Most extremophiles belong to a class known as archaeobacteria, but certain species of worm, crustacean and krill can also be considered extremophiles. There is growing evidence that certain extremophiles may be able to survive for very long periods of time even in deep space, traveling in a dormant state between planetary bodies, for example. Bacteria have been discovered thriving in oceanic volcanic vents, or in ice cores more than a mile beneath the Antarctic ice.

The American Society for Microbiology contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

Bob McLean, Ph.D.
Department of Biology
Texas State University
San Marcos, TX
(512) 245-3365

American Society for Microbiology
Washington, DC 20036-2904
(202) 737-3600

Under the Microscope


When Apollo 12 astronauts traveled to the moon in late 1969, they landed near an unmanned NASA spacecraft. When they returned with a piece of the craft, scientists found contaminate microbes had survived the lunar journey.


Panspermia has inspired a number of works in science fiction, most notably Jack Finney's "The Body Snatchers" and John Wyndham's "The Day of the Triffids."


Biology Department at Texas State University

NASA Astrobiology

Houston Chronicle Article

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