Limits Of Life On Earth: Are They The Key To Life On Other Planets?

     "Life flourishes on the earth in an incredibly wide range ofenvironments," explains Mike Purdy, coordinator of the NSFinitiative.  "These environments may be analogous to the harshconditions that exist now, or have existed, on earth and otherplanets.  The study of microbial life forms and the extremeenvironments they inhabit can provide new insights into howthese organisms adapted to diverse environments, and shed lighton the limits within which life can exist."

     NSF's directorates of biological sciences; engineering;geosciences; mathematical and physical sciences; and office ofpolar programs are providing total funding of $6 million toexplore the relationships between organisms and the environmentsin which they exist.  A strong emphasis has been placed onenvironments that are near the extremes of conditions on earth.Funding will also support research about our solar system andbeyond, to help identify possible new sites for life beyondearth.

     Scientists are studying environments such as the earth'shydrothermal systems, sea ice and ice sheets, anoxic habitats,hypersaline lakes, high altitude or polar deserts, and humanengineered environments such as those created for industrialprocesses.  Projects involve finding techniques for isolating andculturing microbes found in extreme environments, developingmethods of studying these microbes in their natural habitats anddevising technologies for recovering non-contaminated samples.

                              -NSF-

Attachments:  Highlights of LExEn projects.              List of LExEn Awards.

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                  HIGHLIGHTS OF LExEn PROJECTS

ú    Hyper-arid deserts are among the most extreme environmentson earth.  The Atacama Desert in Chile, with its rainlessregions, is one such hyper-arid desert here on earth.  LExEngrantees Frederick Rainey and John Battista of Louisiana StateUniversity will investigate the range of microorganisms living inthis hyper-arid desert, with the goal of shedding light on thesurvival of microorganisms in similar extreme environmentselsewhere on earth.

ú    Recent investigations have identified microbial communitiesin various crustal environments down to 9,200 feet below theearth's surface.  Very few microbial samples exist from deepwithin continental crust, because coring is expensive.  But nowTullis Onstott of Princeton University has uncovered a uniqueopportunity to study microbial communities at depths more than10,000 feet below the surface:  in the gold mines of SouthAfrica.  Reconnaissance samples taken from a hole bored into auranium-rich, gold-bearing mine in South Africa have shown thepresence of intact microbial cells.  Onstott will examine therelationship between mineralogy and bacteria living in these deeprocks by conducting intensive research at one particular SouthAfrican gold mine.

ú    Microorganisms may lie, Lazarus-like, viable but entombed inice sheets and ice caps of the Tibetan plateau, the SouthAmerican Andes, and the north and south polar regions.  A projectby Lonnie Thompson and Ellen Mosely-Thompson, glaciologists atOhio State University (OSU), and their colleagues willresuscitate microorganisms from ice cores kept at OSU's ByrdPolar Research Center, and use recovered DNA from the organismsto determine relationships to other organisms, as well asabundance and age.  The scientists will assess the longevity ofthe organisms as well as the diversity of tiny life-formsdeposited at the same geographical site thousands or evenhundreds of thousands of years apart.  The researchers hope touncover extinct genes or gene fragments to compare with moderncounterparts.

  ú    What is the telltale signature of past life in extremeenvironments? The University of Rochester's Ariel Anbar andcolleagues will study whether stable isotopes of key metabolicmetals fractionate -- and leave their "John Hancock" -- when themetals are taken up and metabolized by microorganisms.  If thisis the case, the method could be used to identify traces of lifein extreme environments where other "biomarkers," or signs oflife, cannot be used.  The study will focus on copper and zincisotopes expected to be abundant when these metals are taken upby microbes in a process catalyzed by enzymes, and iron isotopesexpected when iron is reduced in reactions mediated by microbes.

  ú    Many regions of the solar system where life is postulated toexist, such as the oceans of Jupiter's moon Europa, arecharacterized by pressures far greater than those experienced atearth's surface.  Relatively little data exists on the nature ofbarophilic (high-pressure-loving) life forms, or the pressureboundaries within which life may exist.  Douglas Bartlett of theScripps Institution of Oceanography in La Jolla, California, willconduct research on genetic components associated with survivalin high-pressure conditions.  In his studies, Bartlett will useso-called hyper-barophiles recently obtained from a high-pressurelocation at the bottom of the Japan Trench, a deep-sea locationwhere pressures reach many tons per square inch.

ú    How does one study the ancient climate of Mars?  JamesKasting of Pennsylvania State University hopes to look backthrough time and see what the paleoclimate on Mars was like.Early Mars appears to have had a warm and wet climate, butexisting climate models have been unable to explain thishypothesis.  The answer may lie in methane, which, if added tothe Martian paleoatmosphere, may have brought the surfacetemperature above the freezing point of water early in theplanet's history.  But where would this methane have come from?Such a source could, in principle, have been provided by bacterialiving on the surface of early Mars.

ú    Water, water, everywhere, and how critical to the existenceof life, but is it preserved as liquid beneath the icy crust ofCharon, Pluto's moon?  Until now, researchers have believed thatwater may be maintained on planetary surfaces through radiativeheating from nearby stars.  Douglas Lin from the University ofCalifornia and coworkers will examine whether a layer of watercan persist below the surface of a planet's moon, maintained asliquid by tidal interaction between planet and moon.  They willanalyze such interaction between Pluto and Charon as well asbetween Uranus and its "satellites."