There is mounting evidence that life originated off earth, traveling here from far, far away on chunks of rock and ice.
The original space travelers appear to be bacteria who, even on earth, survive against all odds in some of the most unlikely places. Research in Siberia, Alaska and Antarctic, for example, reveals live bacteria in glaciers and ice wedges. Apparently the clever microbes can simply melt a bit of ice around them and snuggle in; no need even to desiccate or sporulate.
Microbial life in ice is not a rare phenomenon, says Richard B. Hoover, at NASA’s Marshall Space Flight Center in Huntsville, Alabama who stresses that “The ability of bacteria to remain alive in ice for long periods of time is of great significance to astrobiology.” Hoover reminds us that the first validly published species of Pleistocene bacteria isolated from ice was Carnobacterium pleistocenium, an extremophile still alive on Earth today. "I found large numbers of this new species, which we named C. pleistocenium, encased in ice that had been frozen for 32,000 years in permafrost near Fox, Alaska," he says "and when the ice thawed I was astonished to discover live bacteria that immediately began swimming around."
Bacteria Travel the Universe on Metal and Ice
The ability to survive in extreme environments makes it possible for some bacteria to hitch rides around the universe in comets and be safely transferred through the Earth's atmosphere in the frozen interiors of fluffy carbonaceceous meteorites. Using scanning electron microscopy methods, Hoover and his co-worker Alexei Rozanov at the Russian Academy of Sciences in Moscow, began searching for evidence of bacterial remains in meteorites over a decade ago.
During this period, Hoover also carried out extensive field emission scanning electron microscopy studies on the shapes and chemical makeups of living and fossil cyanobacteria and other microbical extremophiles collected while on expeditions to the most hostile environments on earth. He also detected carbon-rich microfossils suggestive of cyanobacteria embedded in freshly fractured interior surfaces of both the Orgueil CI1 and Murchison CM2 carbonaceous meteorites.
This August Hoover presented additional evidence of microbial remains in meteorites at the Astrobiology XIII Conference at the Society of Photographic Instrumentation Engineers (SPIE) International Symposium held in San Diego. The new images reveal large, quintessentially cyanobacterial complex filaments, the kinds that enable bacterial mobility and reproduction, in both the Orgueil and Murchison meteorites. It also appeared that the embedded microbes, like today's cyanobacteria, were forming mats.
Notably, cyanobacterial fossils are among the easiest to recognize, according to scientist at the University of California’s Museum of Paleontology because cyanobacteria are a large ubiquituous group of aquatic microbes with an extensive fossil record and “Morphologies in the group have remained much the same for billions of years…”
“Both the Orgueil and Murchison carbonaceous meteorites are probably the remains of burned out comets,” says Hoover and “the Orgueil CI1 meteorite contains 3-5% extraterrestrial carbon and 18-22% indigenous extraterrestrial water which isn’t lost when the meteorite falls to earth. And even though the outer crusts of these meteorites become hot, they boil off and ablate during the brief flaming period when they plunge through the earth’s atmosphere which allows their interiors to remain frozen; it’s very much the same principal that protects astronauts from the fireball surrounding their re-entering space capsule.”
But Are The Fossils Recent Contaminants?
One frequently asked question is whether the cyanobacterial Hoover discovered are valid microfossils which were already inside the meteorites when they entered the earth’s atmosphere or if they were left by modern bacteria that invaded these black stones after they landed. There are a number of compelling arguments against recent contamination.
For one, cyanobacterial mats on earth form underwater and had the Orgueil meteorite been submerged after its arrival on earth it would have been destroyed because this meteorite consistes of tiny mineral grains held together by water soluble salts; thus, by implication, the bacteria had been acquired somewhere else in the universe. "Most important," says Hoover, is that the filaments in Orgueil and Murchison "don't contain detectable levels of nitrogen and nitrogen is essential for all known forms of life on earth today, it's always present in replicating cultures of modern cyanobacteria and other microbial extremophiles."
Thus, says Hoover “I am confident the filaments found in carbonaceous meteorites are undeniably biological in nature and are not the remains of modern, post-arrival bacterial contaminants and they therefore represent valid evidence for the existence of extraterrestrial life.”
Watch the video of Richard B. Hoover at work by clicking here.
A bit about Panspermia…
Panspermia literally means “seeds everywhere,” explains Brig Klyce who runs the largest panspermia blog in the world. The theory that life evolved elsewhere in the universe and seeded earth has been advocated for years; for example, in the 1900s the Swedish physicist Svante Arrhenius theorized that bacterial spores propelled through space originated life on this (and presumably other) planets.
But the concept that life originated somewhere else in the universe languished when, in the 1950s, American chemists Stanley Miller and Harold Urey demonstrated that the building blocks of life, amino acids, can be chemically produced from ammonia and methane. In the 1970s, however, British astronomers Fred Hoyle and Chandra Wickramasinghe found traces of life in stardust and proposed that comets serve as the vehicles for bacterial transport across galaxies.
In 1996 a NASA scientific team led by David S. McKay discovered evidence of fossilized bacteria in a meteorite and panspermia began to reemerge as a valid hypothesis. Since then, says Klyce, scientists to be reckoned with including E.O. Wilson, Stephen Hawking and J. Craig Venter have endorsed panspermia. Beating them all to the punch was the brilliant geneticist and neurobiologist Francis Crick who, in 1973, published a paper with the chemist Leslie Orgel suggesting that life may have arrived on Earth through a process they called “Directed Panspermia.” The “panspermia” turns out to be correct, but “directed,” not so much.
Get more information about bacteria and the origin of life on Earth here
Get more information about an important other-worldly bacterium called Deinococcus radiodurans here.
For details of this research see:
Hoover, Richard B. and Rozanov, Alexei Y.. Microfossils, Biominerals and Chemical Biomarkers in Meteorites in Perspectives in Astrobiology, Volume 366. (R.B. Hoover, R. Paepe, and A. Yu. Rozanov, eds). NATO Scence Series: Life and Behavioural Sciences, IOS Press, Amsterdam, The Netherlands, 1-18, 2005.
Hoover, Richard B. Comets, Carbonaceous Meteorites and the Origin of the Biosphere in Biosphere Origin and Evolution (N.. Dobretsov, N. Kolchanov, A. Rozanov and G. Zavarzin, Eds.) Springer, New York pp. 55-68 . 2008
Hoover, Richard B. Meteorites, Microfossils and Exobiology.Instruments Methods and Missions for the Investigation of Extraterrestrial Microorganisms, SPIE 3111, 115-136, 1997.
Hoover, Richard B. Microfossils of cyanobacteria in carbonaceous meteorites. Instruments, Methods and Missions for Astrobiology X, Proc. SPIE 6694, 669408, 2007.
Pikuta, Elena V, Hoover, Richard B., Marsic, Damien Bej et al. Carnobacterium pleistocenium sp. nov., a novel psychrotolerant, facultative anaerobe isolated from Fox Tunnel permafrost, Alaska. Int. J. Syst. Evol. Micorbiol. 55, pp. 473-478, 2005.
Marcia Stone - Almost forty years ago I walked out of a lab and into a newsroom and that was that --I knew what I wanted to do for the rest of my life ...
Join the Conversation