NASA's Spitzer and Deep Impact Build Recipe for Comet Soup
http://www.jpl.nasa.gov/news/news.cfm?release=2005-144

Composition of a Comet Poses a Puzzle for Scientists
By KENNETH CHANG
Published: September 7, 2005
"In the burst of light after the collision, Spitzer detected specific colors of infrared light that indicated that Tempel 1 contained clays and carbonates, the minerals of limestone and seashells.
"Clays and carbonates both require liquid water to form.
"How do clays and carbonates form in frozen comets where there isn't liquid water?" said Carey M. Lisse, a research scientist at the Applied Physics Laboratory at Johns Hopkins University who is presenting the Spitzer data today at a meeting of the Division for Planetary Sciences in Cambridge, England. "Nobody expected this."
http://www.nytimes.com/2005/09/07/science/07comet.html?oref=login
[may require free registration]

I'm surprised Lisse would say nobody expected the aqueous minerals to be seen. It is a well-known theory among comet researchers that radioactive heating may have allowed liquid water to form in comets early on in the Solar Systems history.
This theory was probably only controversial because it raises the possibility of life in comets, especially given the large abundance of organics, also confirmed by Deep Impact, in comets.

Bob Clark