For 30 years, a large near-Earth asteroid wandered its lone, intrepid path, passing before the scrutinizing eyes of scientists while keeping something to itself: (3552) Don Quixote, whose journey stretches to the orbit of Jupiter, now appears to be a comet.
The discovery resulted from an ongoing project coordinated by researchers at Northern Arizona University using the Spitzer Space Telescope. Through a lot of focused attention and a little bit of luck, they found evidence of cometary activity that had evaded detection for three decades.
© NASAJPL Near-Earth Object database map of 3552 Don Quixote’s orbit
"Don Quixote's orbit resembles that of a comet, so people assumed it was a comet that had gotten rid of all its ice deposits thousands of years ago," said Michael Mommert, a Ph.D. student of team member Prof. Alan Harris at the German Aerospace Center (DLR) in Berlin at the time this work was carried out. Near-Earth asteroids that are former comets make up roughly 5 percent of the whole near-Earth asteroid population, as found by Mommert and colleagues in a related study. These objects are mostly "dead comets" - comets that had shed the carbon dioxide and water that give them their spectacular comae and tails long time ago.
What Mommert, now a post-doctoral researcher at NAU, and an international team of researchers discovered, though, was that Don Quixote was not actually a dead comet. In fact, the third-biggest near-Earth asteroid out there, skirting Earth with an erratic, extended orbit, is "sopping wet," said NAU associate professor David Trilling, with large deposits of carbon dioxide and presumably water ice.
Comment: Interesting that another meteor just blew over Birmingham, Alabama yesterday as well.
Baseball-sized meteor blows up over Alabama