Dig deeper for Mars life, scientists urge
Feb 02,2007 00:00 by World-Science.net

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.

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).
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.
 
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 hunt­ing 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.