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Columbia bacteria support seed theory


www.chron.com

Experiment that survived the crash backs idea that life can drift here from space
Houston Chronicle (02/24/2006)
By MARK CARREAU

A tiny cluster of bacteria that survived the fiery breakup of the shuttle Columbia in 2003 has offered some unexpected evidence that primitive life forms could jump from one planet to another aboard meteorites, according to a Texas scientist.

The findings could support panspermia, the theory that the seeds of life originated elsewhere in the universe and were dispersed to Earth and other bodies as microorganisms or other matter.

"Our observations, which are extremely serendipitous, support the possibility of life surviving atmospheric passage," said Robert McLean, a microbiologist at Texas State University in San Marcos. "Realistically, it doesn't do any more than that, but it's an important question that has to be addressed."

The findings by McLean and two other experts are slated for May publication in Icarus, an science publication of the American Astronomical Society.

And it is all because debris from McLean's experiment aboard Columbia was recovered from a parking lot at an East Texas convenience store.

The research was a surprise outcome of the Feb. 1, 2003, breakup of the shuttle Columbia that killed its seven astronauts and created a gruesome shower of debris over Texas.

McLean sponsored one of many experiments aboard the 16-day research mission. His was designed to determine which of three common strains of bacteria, swimming together in an enclosed vial of liquid with a volume equal to that of a rain drop, would thrive in the absence of gravity.

None did. But a fourth strain, an unwanted contaminant known as Microbispora sp, survived the flight and the plummet to Earth in a vial secured inside a special holder. Columbia disintegrated at just over 200,000 feet above the Earth while traveling at nearly 14,000 mph. In essence, the samples' rugged aluminum and plastic enclosures became a surrogate meteorite.

Meteorites, particularly those blasted from other planets by the impact of asteroids and comets during the solar system's early ages, became potential modes of transport for microbes and chemical precursors of life, according to the panspermia theory.

McLean estimates his stowaway bacteria reached temperatures of about 385 degrees Fahrenheit as a result of atmospheric friction as the debris fell.

Though the heat and velocity of impact were likely four to five times less than a meteorite's, the San Marcos researcher believes the surviving bacteria offer some of the best evidence available that microbes could survive the final leg of a space journey to Earth.

Nearly a decade ago, a team of NASA researchers offered evidence of microbial fossils in heart of one of 34 meteorites from Mars that have been recovered on Earth — work that McLean cites in his article. But scientists are still debating the controversial claim.

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

At the Lunar and Planetary Institute of Houston, a NASA-funded think tank where researchers focus on the evolution of the solar system, senior scientist Allan Treiman said he regarded panspermia as a complex theory facing some daunting obstacles.

"A rock has to get off of the body where it formed, it has to travel through space, then it has to land safely on a new body, and once it get there it has to find a congenial environment," said Treiman, an expert on meteorites. "Of the three, landing is probably the easiest."

To escape from Mars as a meteorite, he said, a rock must undergo extreme acceleration, after which any microbes would have to survive extreme cold and high levels of radiation as they journey through space for thousands to millions of years.

Panspermia has been a theory since about 500 B.C., according to science histories, and was advanced by the late British astronomer Fred Hoyle.

McLean has struggled to identify the source of his microbial stowaway, a heat-tolerant bacterial strain commonly found in soil. He concluded it was mostly likely introduced unintentionally at the facilities of the commercial space company that prepared the experiment for the Columbia flight.

The experiment's hardware enclosure fell onto the parking lot in Nacogdoches. When the New York Times published a photo of the debris, an official with the East Coast company that prepared the experiment recognized the equipment.

The enclosure's two outer layers of sturdy aluminum were breached and an internal plastic container was intact.

"It basically took a hammer and a chisel to get it apart," McLean recalled.

In May 2003, McLean obtained his samples from NASA's Kennedy Space Center in Florida, where the Columbia wreckage was collected.