Among the thousands of images sent back by NASA's Mars Global Surveyor are bizarre scenes that look like fields of ferns, trees, and sagebrush. Some Mars enthusiasts are convinced these structures really are plants taking root at the Red Planet's south pole. Sir Arthur C. Clarke--the author of 2001: A Space Odyssey--even wrote to Discover to call attention to them.
Ah, if only. The smallest of the formations at left is huge, larger than a football field. And Hugh Kieffer, a research geophysicist with the U.S. Geological Survey in Flagstaff, Arizona, notes that they are anything but alive. A spectrometer on the Global Surveyor indicates the fernlike forms are composed of dry ice. When winter sets in on Mars' south pole, temperatures can drop to -200 degrees Fahrenheit, and carbon dioxide, which makes up 95 percent of the atmosphere, freezes onto the surface. "Something causes a small pathway, tortuous or ...
