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Material ejected after planetary impact could seed life on outer planets

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Posted November 12, 2013

The idea of seeding life from one planet to another – or so-called theory of panspermia – isn’t new. Scientists even hypothesize about different potential mechanisms or classes of such distribution of life throughout the Solar System. One of these mechanisms is lithopanspermia, according to which organisms could be transferred via larger or smaller pieces of rocks. However, until now this way of space travel (suitable for microorganisms in best scenario) still has retained more of a speculative character.

However, researchers are willing to prove that lithopanspermia is possible.

The Mars meteorite ALH84001 shown here has been a source of controversy since its discovery in 1984 regarding the fact if it contained the biomarkers for life or not. Credit: NASA

The Mars meteorite ALH84001 shown here has been a source of controversy since its discovery in 1984 regarding the fact if it contained the biomarkers for life or not. Credit: NASA

This is exactly what scientists from the Pennsylvania State University attempted to do in a new study, results of which were published at arXiv.org. The scientists performed numerical simulations of solid rock ejections occurring during a cosmic impact. The goal of the study was to determine if a rock originated from Earth or Mars could reach the other planets of Solar System or their moons, and what is the likelihood of such even.

 Characterization of the transfer time distributions for each origin- destination pair. Time of first impact shows the minimum amount of time that was needed for an object to reach this destination after being ejected. Image courtesy of the researchers.

Characterization of the transfer time distributions for each origin-destination pair. Time of first impact shows the minimum amount of time that was needed for an object to reach this destination after being ejected. Image courtesy of the researchers.

There were over 53,000 meteorites found on Earth in 2012, of which 105 had been identified to be of Martian origin, according to the data from Meteoritical Society. Despite the lack of hard evidence for life existing in any of those rocks, a lot of studies related to the research of lithopanspermia emerged, especially considering many speculative – at least to some extent – theories claiming an existence of life on Mars sometime in the distant past. Actually, the idea of ancient habitable Mars is not completely unlikely, although it could have happened approximately 4.1 billion years ago.

The authors of the current study assumed a possibility that life existed on Mars, and included the Red planet in the list of potential sources of life, additionally to our Earth. Then the team simulated ejections of tens of thousands of meteoroids from both planets placed at randomly generated ejection angles. All eight planets – their positions and orbital motions – were included in the simulations. Also, ejection velocities of the meteoroids were considered. The scientists note, that the availability of modern computational power required for such complex simulations was one of the main factors that made this work possible.

Total numbers and rates of transfer observed in our simulations by origin and destination. The value is the probability for a single simulation transfer. Image courtesy of the researchers.

Total numbers and rates of transfer observed in simulations by origin and destination. The value is the probability for a single simulation transfer. Note – mass transferred does reflect only arbitrarily selected initial conditions, not real figures. Image courtesy of the researchers.

The results of numerical calculations showed, that the transfer of rocks following the planetary impact is quite possible. In fact, such transfers must have happened during the geological history of the Earth, with rocks reaching Venus as soon as in 8-9 years (that’s really fast, on the cosmic time scale), and Saturn in 8 million years or so, starting with the date of the impact which caused particular ejection of matter into orbit. You can see more detailed statistics related to lithopanspermia simulations in tables given in this text. The statistical data also includes probabilities for ejected rock to hit largest bodies of the Solar System (e.g. 0.18% probability to hit Mars, or 0.0069% probability to hit Saturn).

The authors conclude that the transfer of life using rocks as a travel medium from both Earth and Mars is possible, including relatively distantly located Saturn. The probabilities for rocks to land on moons of other planets (and, potentially, to leave seeds of life there) is significantly lower (e.g. ~0.00000075% for Titan, Saturn’s moon), but nonetheless cannot be ruled out.

And, in case we find life somewhere else in Solar System, we should keep in mind that this life could have emerged here, on Earth.

By Alius Noreika, Source: Technology.org

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