The Apollo 12 lunar module in 1969
New 'moon' to leave Earth orbit
By Richard Stenger (CNN)
Monday, September 23, 2002 Posted: 1:32 PM EDT (1732 GMT)
(CNN) -- The first known object to be captured in Earth orbit probably will escape the gravitational clutches of the planet sometime next year, according to NASA scientists.
The mysterious rambler, a suspected space rock later identified as leftover junk from a manned moon mission, began orbiting Earth in April but probably will go into an orbit around the sun in June, said Paul Chodas of NASA's Near-Earth Object Program, which monitors nearby space objects.
When an amateur astronomer discovered the object two weeks ago, space enthusiasts speculated that it might be a natural Earth satellite. The reason is that it travels in an erratic orbit, which suggested that the planet had snagged a wandering space rock.
The Minor Planet Center in Massachusetts, a clearinghouse for minor planet and comet discoveries, plotted its course and determined that it most likely was a section of a Saturn 5 rocket, which took Apollo astronauts to the moon between 1969 and 1972.
Preliminary analysis suggested that it escaped Earth orbit decades ago. Moreover, there was a small chance it would hit either the moon or Earth in the coming years.
More refined orbital studies from dozens of astronomers around the world, however, indicated that the object, dubbed J002E3, likely would leave the Earth-moon neighborhood before it got a chance to strike either one in the near future.
"We are virtually certain that it originally escaped Earth orbit in March 1971, and that it will escape again next June," Chodas said. "It's only a temporary visitor."
Astronomers said they think J002E3 fell back under Earth's spell when it passed through one of numerous LaGrange points, or "portals" in space where the gravity of the sun and Earth cancel each other out.
The mechanics of its upcoming escape are much like those of the capture in reverse, according to Chodas and Steve Chesley, a colleague at the Pasadena, California-based Near-Earth Object Program office.
Last week, scientists at several academic institutions used a large optical telescope to check the spectral properties of the drifter.
"Rather than looking like a known asteroid, the colors were consistent with ... an object covered with white Titanium oxide paint," the same paint used on the third-stage of the Saturn 5, said Carl Hergentother of the University of Arizona in Tucson.
The reflective brightness and orbital path suggests that the object came from the Apollo 12 mission, which flew to the moon in November 1969.
Eventually, the debris most likely will end its journey by colliding with the moon or Earth, astronomers said.
The prediction should hardly cause alarm. Similar rocket stages from other Apollo missions burned up completely when they re-entered the Earth's atmosphere.
下图：A Saturn 5 third-stage, seen from the Apollo 8 spacecraft shortly after separation near the moon in 1968 |
|
置顶卡
变色卡
千斤顶
显身卡
