The researchers believe Tempel 1's surface ice used to reside inside the comet and became exposed over time. It's also thought that occasional geyser-like blasts of dust and vapor, called jets, send the ice outward. Once ejected, the ice crystals can become incorporated into the luminous coma, a cloud of material surrounding the main body of the comet, or the ice can become part of its tail.

The same team previously reported that Tempel 1's interior also contained an abundance of organic material and suggested the comet may have originated in a region of the solar system now occupied by Uranus and Neptune.

Ice AND organic matter? I'd love to see the Discovery Institute's explanation for this one.