Inside-out study challenges theory about comet chemistry

0 Comments | AFP, July, 2007

PARIS (AFP) — A dying comet has prompted astronomers to take issue with a mainstream theory about the impact of "space weather" on these enigmatic wanderers of the Solar System.

Comets are fragile clusters of dust, ice and carbon-based molecules that are believed to be primitive material left over from the building of our star system.

A common expectation is that the outer layers of comets must undergo change as the aeons pass. They are bashed by cosmic rays from deep space, by solar particles and by huge changes in temperature as they swing around the Sun and head back into the chilly depths of the Solar System.

In theory, this "weathering" should be especially pronounced in so-called short-period comets, which return every few years, as opposed to...