Day 29: Does this post make me look controversial?

Artist's conception of an fragment as it blasts off from Mars. Boulder-sized planetary fragments could be a mechanism that carried life between Mars and Earth, UA planetary scientist Jay Melosh says. (Painting by Don Davis. Copyright SETI Institute, 1994)

This afternoon, I wrote a post for Universe Today about Jay Melosh, a planetary scientist from the University of Arizona in Tucson. Melosh has an interesting idea about how life could have developed on Earth — after being flung from the surface of Mars along with impact ejecta.

And when I went back to check the post — mostly to see if an interesting conversation had developed in the comments section — the comments had been turned off. Had the conversation gotten out of hand? Did the theory draw the ire of Creationists, or trigger dark fancies of over-zealous science fiction aficionados? I’ve written my editor to ask, but I may have to languish in suspense until business hours … 

Controversy is one of the best things that could happen to my fledgling little blog (this one, not UT, which does quite well). But I’d be surprised if people got their games on about the suggestion that we’re all Martians, when I’ve written in the past about God, Obama and global warming with no ill effects. I’ll summarize Melosh’s idea below. You decide. 

H. Jay Melosh. Credit: Maria Schuchardt/Lunar and Planetary Lab

Jay Melosh is a long-time researcher who says he’s studied “geological violence in all its forms.” He helped forge the giant impact theory of the moon’s formation and the impact that likely led to the extinction of the dinosaurs 65 million years ago.

He points out that Martian meteorites have been routinely pummeling Earth for billions of years, which would have opened the door for past Mars microbes to hitch a ride. Less regularly, Earth has undergone impacts that sent terrestrial materials flying, and some of those could have carried microbes toward the Red Planet.

When a comet or an asteroid blasts into a planet, it sends a shock wave out from the impact site faster than the speed of sound. The interaction between that wave and the planetary surface allows material to be cast off at relatively low pressure, but high speed. “Lightly damaged material at very high speeds,” Melosh says, “is the kind of environment where microorganisms can survive.”

Making it through space isn’t so much of a problem. When the Apollo 12 astronauts landed on the moon, they retrieved a camera from Surveyor 3, an unmanned lander that had touched down nearly three years prior. Earthly microbes – including those associated with the common cold — were still living inside the camera box, Melosh said. The NASA records were good enough to reveal that one of the Surveyor technicians had actually had a cold when he worked on the camera.

Scientists also have evidence that microbes can survive for thousands or even hundreds of thousands of years when frozen on Earth, but surviving that long in space would be a different matter what with the bombardment of UV light and cosmic rays. Then again, the microbe Dienococcus radiodurans is known to survive in the cores of nuclear reactors. 

Melosh will present his idea at a talk this coming Wednesday, in Tucson. While he acknowledges scientists lack proof that such an exchange has actually occurred between Mars and Earth, he points out that science is getting ever closer to being able to track it down.