[FPSPACE] Scientists debunk comet ice life theory

[LARRY KLAES]

http://www.theage.com.au/news/World/Scientists-debunk-comet-ice-life-theory/2007/08/07/1186252680988.html

Scientists debunk comet ice life theory

August 7, 2007 - 12:49PM

For the first time, there is solid data to refute a popular theory that life 
came to Earth aboard a comet, Rutgers researchers say.

Deteriorated DNA from microbes, frozen for millions of years in the 
Antarctic ice, shows that organisms could not have survived the bombardment 
of cosmic radiation during deep space travel from outside the solar system, 
said Paul Falkowski, a Rutgers biologist and oceanographer.

"It's almost an impossibility for comets to seed other planets with life 
after they've been in space for millions of years," Falkowski said.

That's because genetic material is severely damaged or destroyed by exposure 
to so-called "cosmic radiation flux", he said.

Falkowski is co-director of the two-year study of frozen glacial microbes, 
conducted in conjunction with Boston University, and published in the 
Proceedings of the National Academy of Sciences.

The researchers were mainly interested in whether genetic material from the 
microbes, which they identified as different types of bacteria, could have 
mixed with that of other organisms in the Earth's ancient oceans, and 
influenced evolution, Falkowski said.

The Rutgers study refutes at least part of the "panspermia hypothesis" - a 
theory from the Greeks, and popular among many scientists since the 19th 
century - that micro-organisms and biochemicals were carried to the planet 
by comets, meteors and asteroids.

Other scientists in New Jersey said that they were intrigued by the Rutgers 
study, but suggested there might be ways some organic material could survive 
long-term rides on a comet.

"The only question I'd have is whether the radiation can penetrate into the 
interior of a comet," said Dale Gary, an astrophysicist at the New Jersey 
Institute of Technology in Newark.

Comets are called "dirty snowballs", which implies there is a certain amount 
of rocky material at their centre which could provide a shield for 
travelling DNA, Gary said.

"Certainly anything on the surface of comets would suffer radiation damage," 
he said. Gary, chairman of physics at NJIT, had not seen the study.

"Perhaps they (Rutgers) have done some calculation of the penetration of 
these cosmic rays through ice, and concluded that, for a certain radius, it 
can destroy DNA deep inside.

"However, we don't know everything there is to know about the interior of 
comets," he said. A large comet might have enough rock in its core "to keep 
DNA material rather pristine and safe", Gary said.

Radiation might be a problem for microbes, but not for very basic organic 
material, said Kevin Conod, an astronomer and manager of the Dreyfuss 
Planetarium at the Newark Museum.

"I think the theory of panspermia is not about microbes from space, but 
amino acids, the building blocks of life," Conod said. "Radiation wouldn't 
necessarily affect those enough to kill pieces of protein."

The Rutgers researchers thawed five microbial samples taken from ice between 
100,000 years and eight million years old, and were able to grow several 
organisms in liquid media, said Kay Bidle, a Rutgers marine microbiologist 
and oceanographer.

They also wanted to know how long organisms could live over extended 
geologic periods, Bidle said.

"This is of interest to whether there is life on Mars," he said, as the site 
in Antarctica resembled icy regions on the Red Planet.

Microbes might survive a trip from Mars if encased in a meteorite, Falkowski 
of Rutgers said. "So we could all be Martians," he said.