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Mars may have caves, scientists say
Caves were some of the earliest refuges for human beings on Earth. Could the same be true for future pioneers on Mars?
Glen Cushing, a space scientist with the U.S. Geological Survey, thinks so. He said he has found evidence of an extensive cave system among ancient volcanoes at Mars' equator.
Using images from spacecraft orbiting the Red Planet, Cushing discovered a series of "collapse depressions" in extinct lava flows from the Arsia Mons volcano, near the equator. Twelve miles high and 270 miles across, Arsia Mons is Mars' second-largest volcano.
Cushing said these depressions are consistent with lava flows on Earth that produce caves. Flowing lava cools first on the surface, creating a hard roof, while lava continues to flow underneath. When the flow stops, what's left behind is a tube, kind of like the drinking straw left when someone is finished drinking a milkshake.
Some of these Mars depressions, or grooves, are more than 60 miles long and 150 feet across, Cushing said. He added that he could only estimate the lengths of the likely tunnels, since some tubes would have collapsed over time.
Cushing presented his findings last week at the Geological Society of America's annual meeting in Portland, Ore.
Rich Zurek, chief Mars scientist at the Jet Propulsion Lab in La Cañada Flintridge, said the new findings are consistent with past images of the Martian surface showing sunken zones in the lava flows on the flanks of the big volcanoes. "We had postulated these were collapsed lava tubes," he said. "Some were tens or hundreds of meters deep."
Cushing said the structures he found by reviewing images taken by several spacecraft, including the Mars Reconnaissance Orbiter, would be more accessible to future explorers than the sinkhole-type features Zurek referred to.
On Earth, caves protected early man from dangerous beasts. On Mars, colonists would not have to worry about teeth and claws. The danger is the environment itself, from bone-chilling cold to potentially deadly cosmic rays streaming down from space. Though the Mars lander would keep out the cold, several feet of rock would do a better job of blocking cosmic rays than the thin metal skin of a spacecraft.
"Caves can protect human explorers from a range of dangerous conditions that exist on Mars' surface," Cushing said. They also could preserve evidence of any microbial life that once survived, or still might live, on Mars, he said.
Even if humans do not visit Mars any time soon, Cushing foresees the time when "robot explorers probably will visit caves like these and show us a whole new hidden world."