Spelunking in Space

2/24/08 – 3/1/08

by C. Zaitz

The planet Mars currently has a flotilla of spacecraft either orbiting or crawling on it. Interest has always been high when it comes to Mars, due to the strange landscape and its earth-like features, as well as the fact that it may have harbored life in its history. Recently, orbiting spacecraft have found holes the size of football fields in Mars’ landscape. After careful study, speleologists (scientists who study caves) say it is most likely that the holes are cave entrances, similar to caves on earth.

The fact that Mars has caves is interesting for a couple of reasons. First, caves can be safe havens for any life that might have taken hold on the planet. Mars is a harsh place, though it is the more earth-like than other planets. Its atmosphere is much thinner than earth’s and the weather is significantly meaner as a result. The thin atmosphere allows more killing solar radiation to reach the surface of Mars, even though it is farther away from the sun than we are. If life did form on Mars, it wouldn’t last long in the sizzle of the sun’s energy.

Caves provide protection from the more dangerous forms of radiation, and can also be shelter from raging wind and dust storms that often blast across the surface. Scientists think that caves are an excellent place to look for evidence of life on Mars. But even if life never did exist on Mars, there is another reason caves interest us. We humans have lived in caves for much of our history. They are perfect protection from fierce weather and from marauding neighbors. Though we don’t expect to have to hide from Martians, we will need protection from the elements on Mars that caves afford.

Scientists wonder how the caves formed. We know what can cause caves on earth. Falling rain water absorbs carbon dioxide. Water and carbon dioxide combine into a weak form of carbonic acid. The acid eats away rocks that are made of calcium carbonate, or limestone, and caves form as rock is dissolved and carried away in underground streams. Hollow chambers are left behind.

Caves on Mars may not be limestone, however. Mars has a very different atmosphere. It is mostly carbon dioxide, not nitrogen and oxygen. 95% of the air is poison to us, but would be very useful to plants. However, it isn’t clear that Mars has the right chemistry for the karst formations and caves we find on earth. So if the caves on Mars aren’t eroded limestone, what are they?

What Mars does have is volcanoes, like those on earth. The caves may be hollow lava tubes from ancient volcanoes. If it turns out that they are, they would provide excellent shelter for future spelunkers from earth. There might be magnificent chambers with sky lights and protected rooms for equipment and living space. These volcanic mansions might provide the right environment for exploring humans to survive on the foreign planet. Work is currently being done to design and build robots that could explore the caves on Mars, These robots could not only look for signs of past life, but could pave the way for future inhabitants to move in.

If you’d like to see Mars tonight, look to your southern sky for a bright, peach-colored light among the stars.

Until next week, my friends, enjoy the view.