The Transpermia Hypothesis
Could Earth's Life be the Result of a Seeding Event From Mars?
Sep 15, 2009
Did Earth’s biosphere emerge as a homegrown phenomenon, as scientists have long suspected? Or is it possible that early microorganisms, which by 3.5 billion years ago had grown to fill the oceans, sprang from a seeding by life forms from another world? The latter hypothesis, called panspermia – or, more accurately, transpermia – does not attempt to explain how life originated, but merely moves the origin to another locale. Still, it is an intriguing possibility. Data from orbital probes sent to Mars and from NASA's Mars Exploration Rovers show that water has flowed, at least intermittently, on the Martian surface in the past. And so, it is not unreasonable to hypothesize that life existed on the Red Planet long ago, and perhaps continues to this day.
The Case For Transpermia, How Scientists Know That Materials Travel From Mars To Earth
Over the past two decades, scientists have learned that 34 meteorites found on Earth actually came from the Martian crust. The Martian origin of these rocks (which are listed for the public on NASA's Jet Propulsion Laboratory's website) is not in doubt, because characteristics of gases trapped within match precisely with atmospheric measurements that NASA’s Viking landing craft took in the 1970s.
From simulations of comet impacts on Mars, researchers know that rocks can be launched into space, on trajectories which could deliver them to Earth. Usually, such interplanetary hitchhiking is slow, taking million of years, but, as this writer and his co-author, Ben Weiss, noted in the article "Did Life Come from Another World?" (Scientific American, 2005), a small fraction of Martian rocks arriving on Earth have made much swifter journeys. Following an impact event on Mars, some material can make the trip in merely a year, and approximately ten fist-size rocks weighing more than 100 grams will reach Earth within just three years. Add pebbles, dust particles, and other small debris, and the volume of Martian material traversing quickly through the interplanetary realm, with its harsh radiation environment, increases further.
Could Living Forms Survive A Journey From Mars?
By studying magnetic properties of certain Mars meteorites, Weiss, of MIT, and other investigators, such as H. Jay Melosh, of the University of Arizona, have learned that rocks can be catapulted from Mars without being heated more than a few hundred degrees Centigrade. This is important when considering the possibility of transpermia, because there are microorganisms on Earth that can survive at such temperatures, but not much higher. Scientists also have determined that a baseball-size rock entering Earth’s atmosphere following a voyage from Mars is heated by friction only about a centimeter or so into the rock. This is good news for any cells, or for suspended, dried out life packages known as spores, tucked away in the rock’s cozy interior. Good news, that is, if the life forms completing the journey from Mars have not been fried along the way by the interplanetary space radiation.
Planetary Society Will Investigate Using Russian Space Probe
While the journey part of the scenario remains untested, now, as part of an initiative of the Planetary Society, a group of investigators led by this writer have prepared a collection of life forms to be carried within a Russian probe. Once launched on a 34-month round trip through interplanetary space, either next month or two years from now, the organisms will pass through an environment where space radiation is most severe, beyond the Van Allen belts, which protect life, including humans, from the worst component of cosmic rays. While the experiment, designated by the acronym LIFE, for Living Interplanetary Flight Experiment, cannot prove whether terrestrial life actually originated on Mars, it may provide insight as to whether a transpermia scenario is possible, and whether life, once initiated, can spread with ease throughout the cosmos.
Launch Of Phobos-Grunt Probe Delay
Just after the writing of this article, the Russian Space Agency, Roscosmos, announced that the launch the probe, called Phobos-Grunt, will be delayed from October of this year, until 2011. Within the next few weeks, scientist on the LIFE team will be meeting to discuss what to do with the loaded canisters in the intervening two years.
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