The Mars Rover Spirit took this sublime view of a sunset over the rim of Gusev Crater, about 80 kilometers (50 miles) away. Taken from Husband Hill, it looks much like a sunset on Earth—a reminder that other worlds can seem eerily familiar. Sunset and twilight images help scientists to determine how high into the atmosphere the Martian dust extends and to look for dust or ice clouds. (Image: NASA/JPL-Caltech/Texas A&M/Cornell)