A NASA spacecraft has found seven possible cave entrances on Mars, triggering interest in hunting for other caverns that might be hiding life on the Red Planet, the US space agency said.
While the possible caves discovered are too high in altitude to host life, scientists say caverns elsewhere on the Red Planet could be underground habitats, or even one day become shelters for astronauts.
Images from the Mars Odyssey orbiter showed seven dark, nearly circular spots between 100 metres and 250m wide on the slopes of the Arsia Mons volcano, located near the planet's highest peak.
Researchers concluded that the seven circles could be windows to underground spaces after checking their day-time and night-time temperatures by using Odyssey's infrared camera.
"They are cooler than the surrounding surface in the day and warmer at night," said Glen Cushing of the US Geological Survey's Astrogeology Team at Northern Arizona University, Flagstaff, Arizona.
"Their thermal behaviour is not as steady as large caves on Earth that often maintain a fairly constant temperature, but it is consistent with these being deep holes in the ground," he said in a news release from NASA.
The discovery was reported online in the journal Geophysical Research Letters.
The potential caves are so high that "they are poor candidates either for use as human habitation or for having microbial life," Dr Cushing said. "Even if life has ever existed on Mars, it may not have migrated to this height."
But the discovery of the holes, dubbed 'Seven Sisters', has triggered interest in hunting for caverns elsewhere on the planet, NASA said.
"Whether these are just deep vertical shafts or openings into spacious caverns, they are entries to the subsurface of Mars," said co-author Tim Titus of the US Geological Survey in Flagstaff.
"Somewhere on Mars, caves might provide a protected niche for past or current life, or shelter for humans in the future." © 2007 Australian Broadcasting Corporation
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