On Tuesday, March 10, 1998, Brian Marsden, Director of the International Astronomical

Union's central telegram bureau in Cambridge, Mass., announced that celestial object 1997XF, a 1 to 2 mile wide asteroid, could pass within 30,000 miles of Earth in October of the year 2028. One day later, scientists from NASA's Jet propulsion Laboratory announced that the asteroid would instead miss Earth by 500,000 to 600,000 miles.

JPL's Paul Chodas said that the chance of it impacting the Earth was "...so unlikely as not to worry about." Essentially, zero.

Not that I doubt the scientists and their calculations, but we're talking about knowing exactly where something's going to be in 1577 weeks! Do YOU know where you're going to be in 362 months? I don't. Nevertheless, it is coming. We may not know to where, exactly. But at least now you know when.

Newsday, March 12, 1998

An urgent call has gone out to the world's astronomers to watch for asteroid 1997XF, a 1-to-2 mile-wide celestial body that could pass within 30,000 miles of Earth in the year 2028.

"The chance of an actual collision is small," said astronomer Brian Marsden. "But one is clearly not out of the question."

Mardsen, director of the International Astronomical Union's central telegram bureau in Cambridge, Mass., said an analysis of the asteroid's orbit by his group and others suggests it would be the closest asteroid ever seen passing by the Earth.

The asteroid was first spied in December by the Space Watch group, an astronomical organization in Tucsan, Ariz., that regularly scans the skies for asteroids and comets.

"I'm not worried" about being hit, Marsden said, but he suggested that it was important for other astronomers to trackthe asteroid, as well, in order to better pin down it's path. "It will be observable over the next couple of months with large telescopes, and that could help define its miss distance" when it comes by the Earth.

Present data show "it's a potentially hazardous object. Our calculations indicate it will pass 30,000 miles from Earth on Oct. 26, 2028, at 1:30 p.m. (EDT) It's quite clearly going to to come closer then the Moon," which orbits 240,000 miles from Earth.

If it does pass by on an orbit closer than the Moon, "it will be visible to the naked eye," he said. It would appear as "as a good, bright star. It would be a marvelous sight in Europe, moving across the sky in a couple of hours that evening."

As for the asteroid's size, "we know it's large, as these things go. My guess is it's about 1-mile, but it could be 2-miles wide," Marsden said.

An impact by such a body would be cataclysmic, blasting a crater 10 to 20 miles wide and tossing enough debris and vapor into the air "to make global warming seem trivial," said geologist Bruce Murray, at the California Institude of Technology. "We would notice it."

Murray said the last single object of such size to hit Earth apparently arrived about 3.5 million years ago, according to debris found around Antarctica.

Recently, scientists speculated that if a similarly sized asteroid landed at sea, such as in the North Atlantic Ocean, huge tidal waves would wash across Long Island, erasing everything from their path, pouring across the landscape for tens of miles, or more, inland.

The call from Marsden seeking help on 1997XF came on a day when research in the science journal Nature reported for the first time that five large chunks of a single asteroid - similar to the so-called "string of pearls" asteroid the slammed into Jupiter four years aga as earth-bound astronomers watched - probably smashed into our planet 214 million yaers ago.

The collisions blasted a chain of craters almost 3,000 miles long. The craters ranged from 62 miles wide down to five miles wide, hitting in the areas now known as Ukraine, France, Canada and the northen United States.

Although the comet arrived in a cluster, the impact points on the ground are now widely scattered. The huge scars were gradually repositioned during the intervening 200 million years as the Earth's continents migrated around, carrying the impact craters with them.

The researchers - John Sprya, at the University of New Brunswick, Canada; Simon Kelly, at the Open University in England and David Rowley, at the University of Chicago - concluded in Nature that "the five impact structures were formed at the same time, within hours, during a multiple impact event."

"I think this is the first [multiple impact event] that has been substantiated," said Spray, an impact geologist. Their size suggests that the original body was more than 100 miles wide before it broke up and spattered the Earth.