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Astronomers can't yet make heads or tails out of all the crazy things they've seen in close-up pictures of comet Wild-2.
Its surface is littered with odd, well-like depressions, as well as hills, cliffs and active vents that belch gas into space. Some surface features are so large they take up half the size of the entire comet.
"Other than the Sun, this is the most active planetary surface in our solar system," said Donald Brownlee, principle investigator of the comet study.
The surface of the Wild 2 (pronounced "Vilt 2") has no significant atmosphere and is rife with strange, flat-bottomed depressions with sheer walls, possibly caused craters or gas vents. At least 10 jets were active when NASA's Stardust spacecraft swung by the comet in January, collecting data for Brownlee's study. Astronomers believe that number may double after more data analysis.
Comet Wild 2 also sports crisp cliffs unlike anything seen in close-up views of the past icy bodies like the famed comet Halley and more recent, smooth-surfaced comet Borrelly, which was visited by Deep Space 1 in 2001. Surface features range from the very small on up to 1.2 miles (two kilometers) in size, almost half the entire diameter of the 3.1-mile (5-kilometers) comet.
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