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Life on Earth Spawned by Dead Alien Microbes?

Did life on Earth come from extraterrestrial microbes hopping from one star system to the next? If so, they might have arrived dead, only to be resurrected.

How life appeared on Earth is one of the biggest questions hanging over modern science. For many, the idea that simple lifeforms appeared from a primordial soup of amino acids is, well, too simple to explain the genetic diversity we see today. If life didn't form here in puddles of ooze, where did it come from?

One exciting hypothesis is that life came from an interstellar origin; hitched a ride on a speck of dust, blew out of its host star system by stellar winds and then ended up on our planet. This concept is called "panspermia."

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Alas, as highlighted by a research paper published in the journal Space Science Review, assuming that life - no matter how hardy - could dodge death from space radiation, vacuum and extreme cold, is a stretch to say the least.

"Biologically, the destructive effects of ultraviolet light and cosmic rays means that the majority of organisms arrive broken and dead on a new world," Paul Wesson, a visiting researcher at the Herzberg Institute of Astrophysics in Canada, says in the abstract of Panspermia, Past and Present: Astrophysical and Biophysical Conditions for the Dissemination of Life in Space. "The likelihood of conventional forms of panspermia must therefore be considered low."

Although these comments don't necessarily rule out panspermia as a cosmic life-spreading mechanism, Wesson does raise an important point. Although we know terrestrial life can survive for long periods in space - whether it's cyanobacteria living outside the space station for 553 days or tortured mosquito larvae - we've only tested how life copes in space for months or years. Panspermia is thought to operate over much longer timescales, possibly millions of years.

Sure, one could envisage a short hop from planet-to-planet within our own solar system - remember the stir of Mars meteorite ALH84001 (pictured top) - but for longer, interstellar journeys, panspermia via stellar wind-blown dust isn't realistic.

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This is why Wesson suggests the panspermia concept may need to be modified for interstellar hops when life dies and its genetic chemical bonds degrade in transit. Although it sounds more like the title of a sci-fi horror movie, Wesson has coined the term "necropanspermia" to describe a rather macabre means of transferring life around the cosmos. Dead organisms could spawn new life.

As noted by writer Lin Edwards, Wesson doesn't actually suggest a mechanism by which these long-dead alien interlopers spawn new life, only that his research suggests life's "information" is transferred to new worlds. If the destination is hospitable, the conditions might be right for the dead microbes' genetic code to be reassembled.

"Resurrection may, however, be possible." Wesson concludes. "Certain micro-organisms possess remarkably effective enzyme systems that can repair a multitude of strand breaks."

Alas, necropanspermia - like all incarnations of the panspermia concept - will remain pure conjecture for now. But Wesson suggests that to test his hypothesis, dust grains from the outermost regions of the solar system (to avoid contamination by Earth Brand™ life) could be collected to see if they contain information that may indicate they contain long-dead interstellar microbial life.

I personally find this research fascinating, but it's a shame necropanspermia wasn't conceived before the 1997 sci-fi horror flick Alien: Resurrection was written; reanimated aliens - rather than terrible alien-human hybrids - as the central plot line would have been awesome.

Publication: Panspermia, Past and Present: Astrophysical and Biophysical Conditions for the Dissemination of Life in Space, Paul S. Wesson, Space Science Reviews, 2010. DOI: 10.1007/s11214-010-9671-x