Comet’s Demise Reverses ‘Dirty Snowball’ Theory

Astronomers watching the “under-performing” Comet Linear last July were astounded when it unexpectedly burst apart, offering them a direct view of its internal structure in its disintegrating heart. Icy comets are usually described as “dirty snowballs.” Linear was comprised of rocky matter with only a little ice, making it more of a “snowy dirtball.”

Its fragments, scientists reported in the May 18 issue of the journal Science, appear to be the same material that makes up planets.

The comet was relatively free of carbon-rich compounds observed in the ice of other comets, casting some doubt on the theory that comets delivered the precursor molecules necessary for life on Earth.