Interesting Science

Life on Earth may have announced its arrival billions of years ago with a whistle and a thump, according to planetary scientists.

Experiments by an international team of researchers back a controversial theory that life flourished on Earth after primitive organisms arrived aboard a meteorite, itself gouged from Mars by a giant impact.

...Charles Cockell (lab), at the Open University, who studies microbes in extreme environments, joined a team of German and Russian scientists to test whether microbes could survive the enormous shock of being blasted into space and crash landing on another planet.

...The findings support the theory of lithopanspermia*, which suggests life may be spread from one planet to another aboard lumps of rock that are knocked off the surface.

Writing in the journal Icarus, the scientists state: "These results strongly confirm the possibility of a 'direct transfer' scenario of 'lithopanspermia' for the route from Mars to Earth

Full article at "Microbe experiment suggests we could all be Martians" (The Guardian UK)

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Based on the paper:

Experimental evidence for the potential impact ejection of viable microorganisms from Mars and Mars-like planets

Dieter Stoffler, Gerda Horneck, Sieglinde Ott, Ulrich Hornemann, Charles S. Cockell, Ralf Moeller, Cornelia Meyer, Jean-Pierre de Vera, Jorg Fritz and Natalia A. Artemieva

Icarus: Volume 186, Issue 2 , February 2007, Pages 585-588
doi:10.1016/j.icarus.2006.11.007

Abstract

Bacterial spores (Bacillus subtilis), cyanobacteria (Chroococcidiopsis sp.), and lichen (Xanthoria elegans) embedded in martian analogue rock (gabbro) were exposed to shock pressures between 5 and 50 GPa which is the range of pressures observed in martian meteorites. The survival of Bacillus subtilis and Xanthoria elegans up to 45 GPa and of Chroococcidiopsis sp. up to 10 GPa supports the possibility of transfer of life inside meteoroids between Mars and Earth and it implies the potential for the transfer of life from any Mars-like planet to other habitable planets in the same stellar system.

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*See:

Impact Experiments in Support of "Lithopanspermia": The Route from Mars to Earth

D. Stoffler, C. Meyer, J. Fritz, G. Horneck, R. Moller, C. Cockell, S. Ott, J. P. de Vera, U. Hornemann, and N. A. Artemieva

37th Annual Lunar and Planetary Science Conference, March 13-17, 2006, League City, Texas, abstract no.1551

Introduction: Rather advanced knowledge on the physical and geological conditions for the transfer of solid rock fragments from Mars to Earth has been acquired recently by studying (a) the shock history of Martian meteorites, (b) numerical models for the meteorites' launch and transfer conditions, and (c) the formation and cosmic ray exposure ages of these meteorites. It is therefore safe to assume that sizeable rock fragments have been transferred from Mars to Earth at moderate p-T-conditions throughout its geological history. Shock pressures range from about 5 to 50 GPa and post-shock temperature increases are mostly in the 10 to 600 degrees C range; however, the temperature effects are limited to rather short times due to rapid cooling during ejection.

As various arguments had already lead to a revival of the 100 years old "panspermia" hypothesis, the described facts and some pioneering shock and acceleration experiments with primitive microbes prompted the view that the possibility of a transfer of "endolithic" microbes from Mars to Earth has to be taken into consideration seriously. This situation has stimulated the present co-operative project in which three types of microorganisms embedded in a gabbro host rock were subjected to high shock pressures and recovered for the study of the survival rates.

Lithopanspermia - Life in the Rocks (Full Text)

"Panspermia: Life is everywhere! Assuming that it truly is, how does it manage to get around? One answer: Lithopanspermia - life gets around inside rocks. Could it be that simple? Can living organisms actually hitchhike the galaxy embedded in rocks, frozen into stasis awaiting just the right conditions to thaw out, stretch out their proteins, and begin a process leading from microbe to mankind?"

Lithopanspermia in Star Forming Clusters

Adams FC, Spergel DN

Astrobiology. 2005 Aug;5(4):497-514

This paper considers the lithopanspermia hypothesis in star forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to the field) due to the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed and number of members in the birth aggregate. The odds of any given ejected meteroid being recaptured by another solar system are relatively low. Because the number of ejected rocks per system can be large, virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that several million rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life bearing rocks is expected to occur 10 - 16,000 times per cluster (under favorable conditions), depending on the ejection speeds. Only a small fraction of the captured rocks impact the surfaces of terrestrial planets, so that only a few lithopanspermia events are expected (per cluster).

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A recent post: "NASA Study Finds New Kind of Organics in Stardust Mission (Video)"

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