It's Snowing in Space!

It’s snowing at Comet Hartley 2! NASA’s EPOXI spacecraft flew by the comet on November 4 and discovered that the comet is ejecting what is essentially snowballs into space.

Fluffy particles of water ice ranging in size from golf balls to basketballs are being released through the ends of the comet via carbon dioxide jets said EPOXI scientists at a NASA press conference today. Stereo images from the spacecraft show that the snowballs are behind and in front of the comet’s nucleus “making it look like a scene in one of those crystal snow globes,” said Brown University’s Pete Schultz. At least nine of the snowballs hit the spacecraft, but did not damage it.

The rocky ends of the comet where the snowballs are escaping is quite different from the mid-section, which is smooth and releases water through a different process. There water ice turns into water vapor, which is similar to what was observed at Comet Tempel 1 when it was visited by this same spacecraft in 2005. At that time it was named Deep Impact. EPOXI principal investigator Michael A’Hearn of the University of Maryland said they looked for ice particles at Tempel 1, but did not find any.

NASA and space agencies in other countries have been sending spacecraft to study comets for 25 years. Scientists believe they hold clues to understanding the formation of the solar system.

NASA’s next spacecraft encounter with a comet is only three months away. On February 14, 2011, Stardust-NExT will reach Temple 1 to study the comet five years after Deep Impact was there. It will try to image the crater created by Deep Impact and study other features both to compare with the images taken by Deep Impact and look at other areas not yet observed. Like Deep Impact, which was given a second assignment after successfully completing its primary mission, Stardust-NExT is an extended mission for the Stardust spacecraft.