Expert: Philip Stahl - 10/29/2007

Question
Dear Mr. Stahl,
We are Mr. Sylvestre's 7th grade science class from Gallagher Middle School. We are doing research about comets and we are wondering if there is no water in space how are comets frozen and what is inside of them? Thank you in advance,
Mr. Sylvestre's science class :]  

Answer
Hello

First, it is not true that there is "no water in space". In fact, dozens of interstellar molecules have been discovered in space, including: hydrogen cyanide, water, hydrogen sulphide, ammonia, formaldehyde, methane, formic acid, and methyl alcohol.

The radio search for molecules in space, using advanced spectroscopic techniques, began in the 1960s. More than 80 molecules have now been identified by their spectral "fingerprints".

Comets, as objects that arose with the origin of the solar system (itself formed out of interstellar dust and gas clouds!) would naturally have incorporated many of these molecules.

Investigations of Halley's comet (with its recent passage in 1986) shows that most of the ions (atoms minus one or more electrons) in it are related to water. There was also a good deal of carbon found. Other ices, for comets like Halleys, include: ammonia and methane. Again- directly related to the molecules we already have known exist in interstellar space.

Thus, we can say that comets are more like "dirty snowballs"- the "dirt" coming from the carbon in them, and the "snow" actually a conglomerate of ices - water, methane and ammonia.

Hope this helps!