A small asteroid was discovered in late September a few hours after it passed closer to Earth than any previously known space rock
A small asteroid was discovered in late September a few hours after it passed closer to Earth than any previously known space rock. Had it struck Earth's atmosphere, it was too small to pose any serious threat, astronomers said.
The event was a common one, scientists stressed. Hundreds of similar close passes likely occur every year but the objects go undetected.
The flyby occurred, however, during an 8-day stretch when an uncommon number of space-rock reports were made around the world, from sightings of colorful explosions in the atmosphere to reported impacts on the ground. Scientists have made no connections between any of the half-dozen events.
A cosmic whisker
The asteroid is named 2003 SQ222. It came within 54,700 miles (88,000 kilometers) of Earth, or less than one-fourth the distance to the Moon, on Sept. 27, researchers said late last week. That breaks a near-miss record set in 1994.
However, in both cases, the rocks were probably no larger than a house. That is extremely small compared to other chunks of stone and iron that sometimes pass near Earth.
The discovery was made by Robert Cash, who works for Minor Planet Research, Inc. He detected the asteroid using his home computer in Fountain Hills, Arizona, while beta-testing a product for the Asteroid Discovery Station (ADS) to be installed at the Arizona Challenger Learning Center in Peoria, Arizona. The product is expected to eventually offer students a chance to find asteroids.
Cash's observations were sent to an affiliated asteroid search program at the Lowell Observatory, as well as to the Minor Planet Center in Cambridge Massachusetts, where asteroid observations worldwide are collected.
"In a good month, we find five to 10 near-Earth asteroids, but usually, the ones we discover are as big as mountains, or at least football stadiums, so this one was unique for us," said Edward Bowell, director of Lowell Observatorys Near-Earth-Object Search (LONEOS).
Further observations by the LONEOS program and other astronomers confirmed the object's rough size, path and time of close approach. It is thought to be less than 33 feet (10 meters) in diameter and to orbit the Sun every 1.85 Earth-years on an elliptical path.
Stephen Ostro, an asteroid specialist at NASA's Jet Propulsion Laboratory, told SPACE.com it was remarkable the tiny object was noticed.
No worries
Some other asteroids on the list of Top 10 close approaches to Earth are disconcerting, for their larger size suggests had they hit the planet they could have caused local or regional damage.
But 2003 SQ222 is not the sort of rock astronomers worry about too much. Had it been on target, "it would have exploded harmlessly in the upper atmosphere, with an energy comparable to that of a small atomic bomb," Bowell said.
Astronomers estimate there are about 500 million undiscovered asteroids as big or larger than 2003 SQ222 that inhabit the general space through which Earth orbits. About 3,000 of them pass closer than the Moon every year but are not detected, according to Alan Harris of the Space Science Institute in Boulder, Colorado. Perhaps 100 of them come closer than 2003 SQ222 each year, Harris estimates.
These rocks go mostly unnoticed because they are too small and too faint in the sky to be detected by the handful of telescopes devoted to asteroid hunting. They sometimes become spectacular fireballs, visible from hundreds of miles around on the ground when they vaporize in Earth's atmosphere.
"These things are completely harmless," Harris said of small asteroids like 2003 SQ222. "They are no more than interplanetary tourist attractions."
Asteroid detections have skyrocketed in recent years, meanwhile, as new electronic cameras increase sensitivity and automated telescopes scan the skies for anything that moves in relation to background stars.
On Sept. 19 this year, another small rock, named 2003 SW130, zoomed by at about 100,000 miles (160,000 kilometers) distance.
Flurry of activity
Sometimes, asteroids or pieces of them do strike the surface, as apparently occurred with two events last month during an 8-day period of unusually intense terrestrial activity generated from above. The most intriguing of these was an apparent meteor strike in India that injured three people.
2003 SQ222's record-setting close approach came within hours of the Indian meteor, but astronomers doubt any connection between the two events.
The rash of reported events did intrigue scientists, though.
"Right back in the middle of this period of stuff, about a week ago, my wife and I saw a gigantic bolide," said Clark Chapman, an asteroid expert at the Southwest Research Institute, also in Boulder. A bolide is an explosive meteor. "It was the brightest thing I've seen in years."
But Chapman said given the speed with which space objects move through space, and the number of rocks assumed to be out there, even hours of separation between events is a lot.
"It's hard to see how they could be connected, let alone things that are happening over the course of a week or two," Chapman said in a telephone interview. "But, on the other hand, I and many people have noticed there have been a lot of these reports and they don't particularly seem like they are inspired by the other ones. So who knows?"
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