Source: The Mercury, 13 March, 1998, p.1
AN asteroid 1.5km wide is heading for Earth-and is due to arrive on October 28, 2028. Scientists say the chances of the massive chunk of space rock colliding with Earth are tiny. But uncertainties in the measurements of its orbit mean scientists cannot rule out a collision. They certainly expect it to come closer than the- Moon which is about 386,000km away. In fact, their best estimate is that the asteroid will whiz by at a mere 42,000km. Astronomer- Dan Green, of the Harvard- Smithsonian Centre for Astrophysics in Cambridge, Massachusetts, admitted: "Right now one has to say that Earth is within the error bars." This asteroid is not as large as the one scientists believe hit Earth 65 million years ago, killing two-thirds of all life, including the dinosaurs. But it is thought to be the largest object known in human history to have passed Continued Page 2
FROM PAGE 1 this close to Earth. The asteroid, designated 1997 XF11, was found in December and its newly calculated orbit was announced yesterday in the e- mail version of the International Astronomical Union Circular. There is no internationally adopted plan for what to do if an asteroid is seen on a collision course with Earth. Many astronomers and space enthusiasts have come up with detailed proposals in the past, ranging from zapping an approaching asteroid with a laser beam to blowing it up with nuclear explosives. An asteroid 1.5km across could strike Earth with enough force to wipe out a quarter of the human population say scientists. Most of the damage wouldn't come from the impact itself but from the dust that would be kicked up into the atmosphere, blocking the planet from the sun's warmth. Odds are that an impact of that size occurs about once every 300,000 years. Right now, the asteroid is moving away from Earth about 80,500km/h. Scientists already know that on October 31, 2002, the asteroid will take an early swing by Earth at a safe distance of 9.6 million km. Astronomers are now planning more observations of 1997 XF11, and are looking to see whether the asteroid shows up on older photographs of the sky. "The accuracy and precision of that orbit should improve every time we find something," said Eleanor Helin of NASA'S Jet Propulsion Laboratory in Pasadena, California. Ms Helin heads another project to locate and track near-Earth objects. Any new observations would help, but it would take some time for astronomers to calculate the precise orbit. The closest recorded asteroid- Earth encounter occurred on December 9, 1994, when a very small asteroid passed within about 105,000km. There are several groups of scientists now working to find and follow objects that could one day threaten Earth.
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