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Dig deeper for Mars life, scientists urge

Jan. 29, 2007
Courtesy University College London
and World Science staff

Probes in search of Mar­tian life haven’t drilled deep enough to reach the liv­ing cells that sci­en­tists hope may lurk with­in the red plan­et, ac­cord­ing to new re­search.

Ra­di­a­tion would have killed off most cells near the sur­face long ago, the in­ves­ti­ga­tors said. Un­like Earth, Mars is un­pro­tect­ed by a mag­net­ic field or thick at­mos­phere; for ages it has been laid bare to ra­di­a­tion from the sun and oth­er stars. 

A sun­set on Mars, an im­age that this month was voted as fa­vor­ite in a pub­lic poll of Mars im­ages from NASA's Spir­it rov­er. (Cour­te­sy NA­SA).


The re­search, to ap­pear in the jour­nal Geo­phys­i­cal Re­search Let­ters this week, con­c­lud­ed that any less than a few me­ters (yards) deep, cells could­n’t take that beat­ing for long enough to be found alive. 

The au­thors mapped ra­di­a­tion lev­els at var­i­ous depths and con­clud­ed that the best place to search is in Ely­si­um, a new­ly dis­cov­ered fro­zen sea.

“Find­ing hints that life once ex­ist­ed—pro­teins, DNA frag­ments or fos­sil­s—would be a ma­jor dis­cov­ery in it­self. But the Ho­ly Grail for as­tro­bi­ol­ogy is find­ing a liv­ing cell that we can warm up, feed nu­tri­ents and re­a­wak­en for study­ing,” said Lew­is Dart­nell of Uni­ver­si­ty Col­lege Lon­don, the study’s lead au­thor.

Even be­fore his re­port, the over­all dry­ness of the Mars land­scape had dimmed hopes that ac­tive cells would turn up eas­i­ly. But sci­en­tists had hoped that at least some dor­mant life forms, such as spores, might be found, Dart­nell said. His con­ten­tion is that even those—while typ­i­cal­ly hardy—could­n’t have sur­vived the bil­lions of years’ worth of ra­di­a­tion that would have pelted them since wa­ter was last wide­spread.

Sci­en­tists will have to dig deeper or tar­get very spe­cif­ic, hard-to-reach ar­eas such as re­cent craters or ar­eas where wa­ter has re­cently sur­faced, he added. The team ar­gued that the choic­est hunt
­ing grounds should be the Ely­sian ices be­cause the fro­zen sea seems to have sur­faced on­ly in the last five mil­lion years, a pe­ri­od con­ceiv­a­bly sur­viv­a­ble by dor­mant life forms.

Ice al­so pro­vides a shield of hy­dro­gen to pro­tect life on Mars from de­struc­tive ra­di­a­tion par­t­i­cles, and is far eas­i­er to drill through than rock, Dart­nell’s team said. But over­all, the drill­ing is a prob­lem: even with the ice, cur­rent drills aren’t po­tent enough to reach where the liv­ing cells might be, the re­search­ers added. Oth­er ide­al sites, they said, in­clude the gul­lies re­cently dis­cov­ered in the sides of craters, as these are thought to have flowed with wa­ter in the last five years.


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Probes in search of Martian life haven’t drilled deep enough to reach the living cells that scientists hope may lurk within the red planet, according to new research. Radiation would have killed off most cells near the surface long ago, the invest igators said. Unlike Earth, Mars is unprotected by a magnetic field or thick atmosphere; for ages it has been laid bare to radiation from the sun and other stars. The research, to appear in the journal Geo physical Research Letters this week, concluded that any less than a few meters (yards) deep, cells wouldn’t survive the radiation for long enough to be found alive. The authors mapped radiation levels at various depths and concluded that the best place to search is in the ices of Elysium, a newly discovered frozen sea. “Finding hints that life once existed—proteins, DNA fragments or fossils—would be a major discovery in itself, but the Holy Grail for astrobiologists is finding a living cell that we can warm up, feed nutrients and reawaken for studying,” said Lewis Dartnell of University College London, the study’s lead author. Even before the report, the overall dryness of the Mars landscape had dimmed hopes that active cells would turn up easily. But scientists had hoped that at least some dormant life forms, such as spores, might be found, Dartnell said. His contention is that even those—while typically hardy—couldn’t have survived the billions of years’ worth of radiation that would have pelted them since water was last widespread. Scientists will have to dig deeper or target very specific, hard-to-reach areas such as recent craters or areas where water has recently surfaced, he added. The team argued the choicest searching spots should be the Elysian ice because the frozen sea seems to have surfaced only in the last five million years, a period conceivably survivable by dormant life forms. Ice also provides a shield of hydrogen to protect life on Mars from destructive radiation particles, and is far easier to drill through than rock, Dartnell’s team said. But overall, the drilling is a problem: even with the ice, current drills aren’t potent enough to reach where the living cells might be, the researchers added. Other ideal sites, they said, include the gullies recently discovered in the sides of craters, as they are thought to have flowed with water in the last five years.