The astronauts who blasted off from Kennedy Space Center in Florida aboard the final flight of the space shuttle Endeavour this morning weren't alone—thousands of travelers are accompanying them. These passengers are a collection of microorganisms, and this morning's launch was the beginning of a trip that could show the plausibility of an even more amazing journey: Microbes traveling from Mars to Earth billions of years ago to seed our planet with life.
For the collection of five hardy species—including the radiation-resistant "water bear" and Halomonadaceae bacteria, which can survive in high-salt environments—traveling to the International Space Station and back aboard Endeavour is the first leg of a long journey. Bruce Betts, a project director at the Planetary Society, is one of the scientists planning to send a similar set of organisms, plus a few additional species, all the way to a Martian moon as part of the Living Interplanetary Flight Experiment. The society has reserved a spot on the Russian Phobos-Grunt mission ("grunt" means soil in Russian), which is set to take off for Mars' moon Phobos this November. By practicing on Endeavour, the scientists will ensure that things run as smoothly as possible as the microorganisms make their way to Mars.
This trip is intended as a test of the transpermia hypothesis: that Mars may have held life billions of years ago, and that organisms could have survived the trip to Earth and seeded this planet with life. Those organisms may have invaded the Earth by traveling inside rocks that were blasted off the Martian surface by meteorites. "Whether you can populate planets from other planets is one of the more profound questions," Betts says. "It's intriguing, and it's worth understanding whether the theory is really plausible."
Wayne Nicholson, a microbiologist at the University of Florida, says that evidence so far suggests it's possible. Mars and Earth have exchanged millions of tons rocks, and that exchange has mostly been from Mars to Earth. Earthly microbes can live inside rock, and microbes launched into space (both by accident and for research purposes) have lived to tell the tale—they survive particularly well when sheltered within soil or rock. Laboratory tests show microbes can even survive the shock of crash-landing on a planet after traveling through space.
But, Nicholson says, no experiment has ever gone this far: "There has never been an experiment where organisms have been exposed to the deep space environment, between planets, for such a long period of time." While previous studies have launched microbes into space, sometimes inadvertently, he says that most of those samples never left low-Earth orbit. By remaining within the Earth's atmosphere and magnetic fields, those organisms were partially shielded from the damaging effects of cosmic radiation. The few missions that transported microbes beyond Earth orbit did so for only a few days at a time—a far cry from the years required for interplanetary travel.
The microorganisms' trip to Phobos and back will be a bit more complicated than the shuttle flight. Samples of each organism will enjoy the flight separately from inside sealed tubes. The tubes will be wrapped in a titanium shell that's about the size of a hockey puck, with four strong seals to prevent any contamination of Mars or its moons with Earthly life.
The microbes will ride inside the Russian spacecraft in a dormant form—the excruciating conditions of interplanetary space causes the microorganisms to shut down most of their functions, as during hibernation. And although they won't be directly exposed to the space vacuum, they will suffer high levels of radiation exposure and temperature extremes on their three-year journey. According to the Planetary Society, these conditions will simulate the conditions the microorganisms would encounter if they were traveling toward Earth inside a rock that came from Mars.
The Phobos-Grunt mission's main goal is to collect soil and rock samples. Once that's done, it will blast its sample container (including the microorganisms and the rock samples) to a designated landing spot in Kazakhstan. Since the experiment will come hurtling back to Earth at 4000 g's, the titanium container is built to be nearly indestructible.
If the microbes survive their trip to Mars and back, it won't mean for sure that Earthly organisms are descended from Martians—but it does leave that possibility open. "However it turns out, it is going to be interesting," Nicholson says.
Read more: - Space Shuttle Endeavour Final Flight - Popular Mechanics http://www.popularmechanics.com/science/space/moon-mars/could-martian-life-have-seeded-the-earth
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