Title: A Chip off the Doomsday Rock.
Subject(s): DINOSAURS; EXTINCT animals; ASTEROIDS -- Collisions with
Earth; KYTE, Frank; NATURE (Periodical)
Source: Time, 11/30/98, Vol. 152 Issue 22, p99, 1/3p, 1c
Author(s): Jaroff, Leon
Abstract: Speculates on what caused the extinction of the dinosaurs.
Theory that an object from space landed on Mexico's Yucatan peninsula
and caused a dust cloud that blocked sunlight; Piece of an asteroid
found by University of California at Los Angeles geochemist Frank
Kyte; Report by Kyte in `Nature' magazine; Evidence that it was an
asteroid.
AN: 1297511
ISSN: 0040-781X
Note: Tucson-Pima Public Library subscribes to this magazine.
Database: MasterFILE Elite

Section: Science

A CHIP OFF THE DOOMSDAY ROCK

What killed the dinosaurs? Scientists have been debating that one for
a long time. They know that 65 million years ago, a large object, five
or six miles across, blasted a 120-mile-wide crater at the tip of what
today is Mexico's Yucatan peninsula. They also know that the impact,
or more accurately, the worldwide, sunlight-blocking shroud of dust it
kicked up, wiped out some 70% of the earth's plant and animal
species--including the dinosaurs. But what, precisely, was the object
that sealed their fate?

UCLA geochemist Frank Kyte thinks he may have found not just the
answer but also a piece of the thing itself: a tiny meteorite
fragment, a tenth of an inch across, that was extracted from a
65-million-year-old geological layer under more than 50 yds. of
sediment at the bottom of the Northern Pacific. In a report in the
current issue of Nature, Kyte notes that the little chunk contains
concentrations of metals (such as iridium and nickel) and mineral
textures that clearly show that it is extraterrestrial and that it
probably was once part of a much larger asteroid.

The fact that the meteorite exists at all, says Kyte, also strongly
suggests that it came from an asteroid, not from a comet, as many
scientists still believe. He notes that comets strike the earth at
such high speeds--many of them well over 100,000 m.p.h.--that they are
usually completely melted and vaporized. But a typical asteroid hits
at less than half that speed, and some fragments often survive. So why
did this one turn up 5,400 miles away from the Yucatan impact site?
Kyte believes it was flung by the explosion high above the atmosphere
in a ballistic path that plopped it into the Pacific.

PHOTO (COLOR): DINOSAUR CLUE: Tiny meteorite may solve big riddle

~~~~~~~~

By Leon Jaroff
_________________

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Source: Time, 11/30/98, Vol. 152 Issue 22, p99, 1/3p, 1c.
Item Number: 1297511