Developments in Brief : Explosion Observed on Halley’s Comet

An orbiting astronomical observatory watching Halley’s comet last March from Earth orbit saw what apparently was an explosion that blew about 100 cubic feet of ice out of the comet’s nucleus, an astrophysicist said.

Such phenomena may be what dooms some comets, and could someday destroy Comet Halley, according to Paul Feldman of Johns Hopkins University in Baltimore.

The observations were made by a small satellite called International Ultraviolet Explorer, which was making far-off observations of the comet’s tail while many other spacecraft were taking close-up pictures of Halley’s sun-facing side. Launched in 1978, the satellite is a joint project of the National Aeronautics and Space Administration, the European Space Agency and the United Kingdom’s Engineering Research Council.

Feldman, reporting in the British science journal Nature, said a camera aboard that orbiting observatory detected a flash of light on March 18 that correlated with an ultraviolet radiation sensor’s detection of an outburst of electrically charged carbon dioxide molecules. A day and a half later, ground-based observatories sighted a similar mass of carbon monoxide ions near the comet, indicating that both carbon dioxide and carbon monoxide were expelled from the comet during the same outburst, as would be expected.

Feldman calculated that the amount of material expelled from the eight-mile-long, potato-shaped nucleus of ice and dust was about 100 cubic feet.

“What this sort of tells us is that these volatile materials are located in pockets within the comet,” Feldman said. “It is possible that sometimes a comet like Halley will blow itself apart if it has a large reservoir of these more volatile materials in its interior. In fact, there are comets that come in and never get out because they are destroyed near the sun.”

Halley’s comet is due back our way in 2061.