Caves spotted on Mars
But where are the cave-Martians?
The Mars Odyssey orbiter has beamed back pictures of what appear to be cave entrances on the slopes of a Martian volcano.
Seven small dark craters pepper the side of the long-extinct volcano. They range from about 100 to 200 metres in size, and are very nearly circular. The NASA team turned the thermal imaging cameras on the black circles as soon as it could. The variation in temperature, or relative lack thereof, is what prompted speculation that the circles could be entrances to much bigger underground space.
As seen by NASA's Mars Orbiter, in visible light and infrared (left to right).
"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 and of Northern Arizona University. "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."
The discovery was published online by the journal Geophysical Research Letters. Co-author Tim Titus of the US Geological Survey speculates that the caves could even harbour life.
"Whether these are just deep vertical shafts or openings into spacious caverns, they are entries to the subsurface of Mars. Somewhere on Mars, caves might provide a protected niche for past or current life or shelter for humans in the future."
But Cushing says the altitude of the "cave openings" makes it unlikely that they'd be suitable for humans to use. He also pours cold water on the idea that native life could have migrated to such extreme heights. ®