MYSTERIOUS 1908 BLAST PROBABLY ASTEROID'S DEATH

                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, January 7, 1993                   TAG: 9301070007
SECTION: NATIONAL/INTERNATIONAL                    PAGE: C5   EDITION: METRO   
SOURCE: Associated Press
DATELINE: NEW YORK                                LENGTH: Short
MYSTERIOUS 1908 BLAST PROBABLY ASTEROID'S DEATH
A gigantic explosion over Siberia in 1908 probably was caused by a rocky asteroid, rather than a comet as scientists have believed, a study says.
A computer simulation found that an asteroid about 65 yards across would better fit the characteristics of the Tunguska explosion.
That blast occurred about five miles above ground and released energy equivalent to about 10 million to 20 million tons of TNT. It flattened at least 40,000 trees over 850 square miles.
The new work shows that "an absolutely typical stony asteroid will do it for you," said Christopher Chyba, a National Research Council scientist at the National Aeronautics and Space Administration's Goddard Space Flight Center in Greenbelt, Md.
Asteroids are relatively small objects, some stone and others mostly iron, that orbit the sun. Comets are chunks of dirty ice.
A stony asteroid would explode at about the presumed altitude, the simulation found. The blast would occur because at its high speed - about 9 miles per second - the asteroid would build up very high air pressure in front with a near-vacuum behind and very low pressure at the sides, Chyba said.

by Bhavesh Jinadra by CNB