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What lies beneath? Possible Mars caves found

Oct. 7, 2007
Courtesy NASA
and World Science staff

Sci­en­tists have re­ported find­ing en­trances to sev­en pos­si­ble ca­ves on a Mar­tian vol­cano’s slopes. 

“Whether these are just deep ver­ti­cal shafts or open­ings in­to spa­cious cav­erns, they are en­tries to the sub­sur­face of Mars,” said Tim Ti­tus of the U.S. Ge­o­log­i­cal Sur­vey in Flag­staff, Ariz., one of the re­search­ers. 

The ap­par­ent holes dubbed "Seven Sis­ters." (Cred­it: NA­SA/JPL-Caltech/ASU/USGS)

“Some­where on Mars, ca­ves might pro­vide a pro­tected niche for past or cur­rent life, or shel­ter for hu­mans in the fu­ture,” he added. The find is fu­el­ing in­ter­est in searches for ca­ves that could serve such pur­pos­es—though these would­n’t do very well, Cush­ing said, as their sur­round­ings are so harsh.

“These are at such ex­treme al­ti­tude, they are poor can­di­dates ei­ther for use as hu­man hab­ita­t­ion or for hav­ing mi­cro­bi­al life,” Cush­ing said. “Even if life has ev­er ex­isted on Mars, it may not have mi­grat­ed to this height.” Cush­ing and col­leagues re­ported their find­ings in the Sept. 15 on­line is­sue of the jour­nal Geo­phys­i­cal Re­search Let­ters. 

Sev­eral dark, nearly cir­cu­lar spots on Mars, about 100 to 250 me­ters (328 to 820 feet) wide, in­i­tially puz­zled re­search­ers who found them. They ap­peared in im­ages from two NASA or­biters, Mars Od­ys­sey and Mars Glob­al Sur­veyor. 

Us­ing Od­ys­sey’s in­fra­red cam­era to mon­i­tor the cir­cles’ tem­per­a­tures, Cush­ing’s team con­clud­ed they could be cave en­trances.

The dark spots showed a stead­i­ness in tem­per­a­ture “con­sis­tent with these be­ing deep holes,” he said, “cooler than the sur­round­ing sur­face in the day and warm­er at night.” The spots, dubbed “Seven Sis­ters,” are on a vol­ca­no named Ar­sia Mons near Mars’ tallest moun­tain. 

The re­port pro­poses that holes probably formed as a re­sult of un­der­ground stresses around the vol­ca­no, which caused ground spread­ing and fault­lines. Some of the holes are in line with strings of pits where sur­face ma­te­ri­al has ap­par­ently col­lapsed to fill a gap cre­at­ed by a fault, the re­search­ers said.

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Scientists have reported finding entrances to seven possible caves on a Martian volcano’s slopes. “Whether these are just deep vertical shafts or openings into spacious caverns, they are entries to the subsurface of Mars,” said Tim Titus of the U.S. Geological Survey in Flagstaff, Ariz., one of the researchers. “Somewhere on Mars, caves might provide a protected niche for past or current life, or shelter for humans in the future,” he added. The find is fueling interest in further searches for caves that could serve such purposes—though these particular caves wouldn’t do very well, Cushing said, because their surrounding environment is so harsh. “These are at such extreme altitude, they are poor candidates either for use as human habitation or for having microbial life,” Cushing said. “Even if life has ever existed on Mars, it may not have migrated to this height.” Cushing and colleagues reported their findings in the Sept. 15 online issue of the journal Geophysical Research Letters. Several dark, nearly circular spots on Mars, about 100 to 250 meters (328 to 820 feet) wide, initially puzzled researchers who found them in images from two NASA orbiters, Mars Odyssey and Mars Global Surveyor. Using Odyssey’s infrared camera to monitor the circles’ temperatures, Cushing’s team concluded they could be cave entrances. The dark spots showed a steadiness in temperature “consistent with these being deep holes,” he said, “cooler than the surrounding surface in the day and warmer at night.” The spots, dubbed “Seven Sisters,” are on a volcano named Arsia Mons near Mars’ tallest mountain. The report proposes that holes probably formed as a result of underground stresses around the volcano, which caused ground spreading and faultlines. Some of the holes are in line with strings of pits where surface material has apparently collapsed to fill a gap created by a fault, researchers said.