Scientists Downgrade Threat of Asteroid Hitting Earth
Scientists at the Jet Propulsion Laboratory have downgraded the threat of an asteroid now speeding toward Earth and say there is no chance it will hit Earth in 2030, but a 1 in 1,000 chance it could hit Earth on Sept. 16, 2071.
Last week, scientists with NASA’s Office of Near Earth Objects and the International Astronomical Union announced there was a 1 in 500 chance that an object could hit Earth in 2030. But additional observations have improved predictions of the object’s path and suggest that it will pass no closer to Earth than 2.7 million miles on that date--11 times the distance from the Earth to the moon.
“As we noted, the most likely scenario was that we will find additional observations that would render this prediction invalid,” said Don Yeomans, manager of the NASA office. “If there are 499 chances it won’t hit and one that it will, new data will almost every time render it invalid.”
This is the second embarrassing asteroid retraction in recent years. In 1998, scientists at the Minor Planets Center in Cambridge, Mass., generated worldwide headlines when they announced that a mile-wide asteroid had a small chance of hitting Earth in 2028. The prediction was retracted a day later when more calculations were made. In that case, the corrections came from JPL.
The incident led the International Astronomical Union to create new guidelines for announcing such potential Earth-dooming events. Astronomers would only make an announcement after reaching a consensus that there was some risk to the planet and would announce their findings within 72 hours of making them.
Yeomans followed those rules--only to have the new observations come shortly after he held a news conference last Friday. The observations were made on Friday, but not given to JPL until after the announcement became public, Yeomans said.
“We followed the rules to the letter,” he said. “I have no regrets. I’d do the same thing again.”
Nevertheless, he said, astronomers may have to tweak the rules, perhaps to allow for more time to gather observations before going public.
Yeomans and his crew will continue to study the object called SG344, which is either a small asteroid about 200 feet in diameter or a spent Apollo-era rocket booster. Such a 35-foot-long piece of hardware would burn in the atmosphere and pose no threat to Earth.
Scientists determine the sizes of such objects by measuring the brightness of sunlight reflecting from them. A small, white rocket booster would be as bright as a much larger rocky asteroid.
The object looks suspiciously like a rocket booster because it has an Earthlike orbit, which natural objects rarely have. The team is tracing the path of the object backward to determine if it can be placed near Earth at the time of one of the Apollo launches, but has not yet succeeded in solving the mystery.
On a 10-point scale for grading impact hazards, Yeomans said the object had barely merited a 1 because of its small size and uncertainty over its path.
“As we noted in our first press release,” Yeomans said, “this object is much more interesting than threatening.”
