[LINK] "Life-Bearing Rocks in Slow Motion"

[rfmcdonald]

Centauri Dreams' Paul Gilster reports on the latest computer simulation suggesting that panspermia--the dispersal of life through space from one world to another--is a viable hypothesis.

I’ve been fascinated with Edward Belbruno’s work on ‘chaotic orbits’ ever since meeting him at an astrodynamics conference in Princeton some years back. The idea is to develop low-energy routes for spacecraft by analyzing so-called ‘weak stability boundaries,’ regions where motion is highly sensitive and small changes can create gradual orbital change. A low-energy route was what Belbruno used in 1991 to help the Japanese spacecraft Hiten reach the Moon using almost no fuel, a proof of concept about which the physicist said “It saved the spacecraft, and it saved my career.”

That comment came from a lecture to the Mathematical Association of America in 2009 that you can listen to here. It’s fascinating in its own right, but doubly so since Belbruno is back in the news with new findings on the idea of panspermia, and specifically that version of panspermia called lithopanspermia. In this hypothesis, elemental life forms are distributed between stars in planetary fragments created by asteroid impacts, volcanic eruptions and other disruptive events. Drifting through space, the fragments are eventually caught in another solar system’s gravity, some of them conceivably falling on worlds in the habitable zone of their star.

Could something like this have caused life to begin on Earth? Belbruno’s work, with Amaya Moro-Martín (Centro de Astrobiología and Princeton University) and Renu Malhotra (University of Arizona) simulates conditions when the Sun was young and still a part of the cluster that gave it birth. Using simulations performed by Princeton graduate student Dmitry Savransky, the researchers applied the theory behind chaotic orbits and in particular the idea of ‘weak transfer,’ which they believe offers rocky fragments moving at low velocities a high probability of moving between close stars. In fact, they believe our system could have exchanged materials with its nearest planetary system neighbor 100 trillion times before the Sun left its native cluster.

[. . .]

Moro-Martin adds that the work does not prove lithopanspermia actually happened, but indicates it is an open possibility, with further study needed into the question of rocky materials landing on a terrestrial planet. Could life have arisen on Earth before the dispersal of the cluster? The authors believe that it could, assuming life arose shortly after there is evidence of liquid water on its crust. From the paper on this work:

Within this timeframe, there was a mechanism that allowed large quantities of rocks to be ejected from the Earth: the ejection of material resulting from the impacts at Earth during the heavy bombardment of the inner solar system. This bombardment period lasted from the end of the planet accretion phase until the end of the LHB 3.8 Ga, i.e. it finished when the solar system was approximately 770 Myr old (Tera et al. 1974; Mojzsis et al. 2001; Strom et al. 2005). It represents evidence that planetesimals were being cleared from the solar system several hundred million years after planet formation (Strom et al. 2005; Tsiganis et al. 2005; Chapman et al. 2007). This period of massive bombardment and planetesimal clearing encompassed completely the “window of opportunity” for the transfer of life-bearing rocks discussed above and therefore provides a viable ejection mechanism that may have led to weak transfer.

Links to the original papers are available at the original post.