There is a dark side to Mars. Experts studying the reddish globe in the infrared see a wonderland of nighttime surprise. Through the art of sunless science, researchers are trying to discern whether Mars is a percolating planet of still huffing volcanoes and hot shot geysers. Since nudging itself into a science orbit around the planet in February, NASA’s Mars Odyssey has been busily snapping images of martian terrain in both infrared and visible light. That job belongs to the probe’s Thermal Emission Imaging System – better known in spectral splendor shorthand as THEMIS. “It’s like wearing night vision goggles. With the nighttime infrared