Imagine the Universe!
Imagine Home  |   Ask an Astrophysicist  |  
Ask an Astrophysicist

The Question

(Submitted May 25, 1997)

This question is about comets in space. How can ice, which is a form of water and which has a finite vapor pressure, exist in the near vacuum of space?

The Answer

Comets are usually in the outermost regions of the Solar system (the Oort cloud), where it is extremely cold. Water ice can survive billions of years in the Oort cloud.

However, the comets we observe -- those that come into the inner Solar system --- do lose a lot of volatiles. This is a part of the process that creates the tails, the signature we associate with comets. Comets that are trapped in the inner Solar system will soon (astronomically speaking) exhaust all their volatiles and become extinct (i.e., rocks with no cometary activities).

Koji Mukai for
Ask an Astrophysicist

Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html for help on other astronomy Q&A services.

Previous question
Prev
Main topic
Main
Next question
Next

If words seem to be missing from the articles, please read this.

Imagine the Universe! is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Barbara Mattson
Curator: Meredith Gibb
Responsible NASA Official: Phil Newman
All material on this site has been created and updated between 1997-2014.
This page last updated: Thursday, 01-Dec-2005 13:58:39 EST