Due for a cosmic whack?

Los Angeles Times

There is a small but significant chance that an asteroid will strike Earth in 2030 with a force up to 100 times the Hiroshima bomb, an international team of astronomers concluded Friday.

The International Astronomical Union and space scientists at NASA’s Jet Propulsion Laboratory said there is a 1-in-500 chance that a newly discovered asteroid-like object called 2000 SG344 could hit Earth on Sept. 21, 2030. The object could be anything from a discarded rocket booster to a sizable asteroid.

The announcement, posted on the Internet by the International Astronomical Union, is the first formal public prediction of a potential collision with a piece of the cosmic debris that litters the solar system.

The warning arises from a special astronomical review process designed to eliminate false alarms or premature predictions of celestial calamities.

On a newly devised 10-point scale for grading potential impact hazards, the object is just at the threshold of concern. It was given the lowest rating of 1, meaning it merits careful monitoring.

The object was discovered trailing in Earth’s orbit around the sun by astronomers using the 3.6-meter Canada-France-Hawaii telescope on the island of Hawaii. The high probability that it might hit Earth in 2030 was first determined earlier this week by JPL researcher Paul Chodas.

In making their concerns public Friday, the astronomers walked a delicate line between prudent secrecy and public disclosure, weighing a chance of ridicule against their demands of public responsibility.

For the time being, no one knows yet just how large the SG344 object may be, its composition, or the likelihood it would survive its fiery entry into the planet’s atmosphere.

On one hand, the object may a discarded Saturn rocket booster, lost in space since the days of the Apollo moon program and virtually certain to burn up on entry, said Brian Marsden, director of the Minor Planets Center at the Smithsonian Astrophysical Observatory in Cambridge, Mass.

But it is equally likely that the object may be an asteroid between 100 and 230 feet in diameter. If it is an asteroid — as several experts believe most likely — it could be a flying gravel pit of loosely compacted rubble that would disintegrate as it enters the atmosphere. Or it could be a lethal ball of solid stone and iron that could explode on impact with an estimated energy of two megatons, experts said.