Asteroids

Radiative pressure from the sun can change the rotation rate of asteroids, speeding them up or slowing them down depending on their shape, researchers reported Thursday in the journal Nature. Measurements showed that, over the last 40 years, the rotation of the asteroid 1862 Apollo has increased by an extra rotation per orbit around the sun. At this rate, the asteroid is expected to break up sometime in the distant future.

Caltech astronomers have detected a family of rocky objects in the Kuiper Belt that were formed by something hitting an object larger than Pluto. Such groups of objects, called collisional families, are common in the asteroid belt between Mars and Jupiter, but the new family is the first to be found in the Kuiper Belt, which is beyond Neptune, more than 3 billion miles from the sun.

A game of asteroid billiards may have set in motion the chain of events that wiped out the dinosaurs 65 million years ago, a team of researchers announced this week. According to the Czech-American team, the giant rock that hit Earth was probably a fragment from a collision in the asteroid belt about 100 million years earlier.

Talk about your cosmic pileups. An asteroid similar to the one that flattened forests in Siberia in 1908 could plow into Mars next month, scientists said Thursday. Researchers attached to NASA's Near-Earth Object Program, who sometimes jokingly call themselves the Solar System Defense Team, have been tracking the asteroid since its discovery in late November. The scientists, at the Jet Propulsion Laboratory in La Canada Flintridge, put the chances that it will hit the Red Planet on Jan.

NASA's Dawn mission to visit two asteroids has been canceled, five months after the program was put on hold because of cost overruns and technical problems. The project was capped at about $371 million, project scientists had said. But scientists asked for an additional $40 million last year for the mission, managed by the Jet Propulsion Laboratory in La Canada Flintridge.

Jet Propulsion Laboratory's Dawn mission to the asteroids Ceres and Vesta, canceled earlier this month, was given a reprieve Monday when NASA officials said they would reinstate the project despite cost overruns and technical problems. The cost overruns are not unprecedented given the mission's complexity, and the technical hurdles are well on the way to being overcome, NASA Associate Administrator Rex Geveden said in a teleconference. "We have confidence the mission will succeed," he said.

A meteorite believed to have come from an asteroid belt between Mars and Jupiter sold for $93,000 at an auction of rare space sculptures. The 355-pound chunk of iron, thousands of years old and discovered in the Campo del Cielo crater field in Argentina, was one of 10 meteorites that went for high prices at a Bonhams' New York natural history auction.

The Japanese spacecraft Hayabusa has found the first example of a "rubble pile" asteroid about 180 million miles from Earth. The findings, published in the current issue of the journal Science, show that the asteroid Itokawa is a floating pile of loosely packed rock and dust shaped like a sea otter. Rubble pile asteroids -- loose accretions of dust and rock broken up by collisions with other objects in space -- are thought to be the most common type in the near-Earth environment.

A huge asteroid whizzed by Earth early this week about 269,000 miles from the surface -- slightly farther away than the moon. The asteroid, discovered in 2004, is estimated to be as wide as half a mile, one of the largest to fly so close to Earth in the last few years. Its closest approach Monday was over the West Coast. Scientists think 2004 XP14 will have 10 more close encounters with Earth this century, none expected to pose a threat.

The possibility of a collision between Mars and an approaching asteroid has been effectively ruled out, according to scientists watching the space rock. Tracking measurements of asteroid 2007 WD5 taken from four observatories have greatly reduced uncertainties about its Jan. 30 close approach to Mars. The odds of impact have dropped to 1 in 10,000, the Near-Earth Object Program at NASA's Jet Propulsion Laboratory said in a website posting Thursday. Scientists now estimate that the asteroid will pass between 16,000 and 2,480 miles from Mars' surface.