[meteorite-list] NASA's 'Deep Impact' Team Reports First Evidence of Cometary Ice

[Ron Baalke]

Office of Media Relations
Brown University

Contact:
Wendy Lawton, 401-863-2476

February 2, 2006

NASA's 'Deep Impact' Team Reports First Evidence of Cometary Ice

Comet Tempel 1, target of last year's July 4 cosmic collision, contains 
small amounts of surface water ice. Reported in Science by members of 
NASA's Deep Impact mission, this finding marks the first evidence of 
surface ice on any comet.

PROVIDENCE, R.I. -- Comet Tempel 1, which created a flamboyant Fourth of 
July fireworks display in space last year, is covered with a small amount 
of water ice. These results, reported by members of NASA's Deep Impact 
team in an advanced online edition of Science, offer the first definitive 
evidence of surface ice on any comet.

"We have known for a long time that water ice exists in comets, but this 
is the first evidence of water ice on comets," said Jessica Sunshine, Deep 
Impact co-investigator and lead author of the Science article.

A chief scientist with Science Applications International Corporation who 
holds three Brown University degrees, Sunshine said the discovery offers 
important insight into the composition of comets -- small, Sun-orbiting 
space travelers that are believed to be leftovers from the formation of 
the solar system.

"Understanding a comet's water cycle and supply is critical to 
understanding these bodies as a system and as a possible source that 
delivered water to Earth," she said. "Add the large organic component in 
comets and you have two of the key ingredients for life."

The findings help satisfy one of the major goals of the Deep Impact 
mission: Find out what is on the inside -- and outside -- of a comet.

To that end, NASA's Jet Propulsion Laboratory teamed with the University 
of Maryland to slam a space probe into Tempel 1, then analyze materials 
from the comet's surface and interior. On July 4, 2005, mission members 
hit their mark when the copper-tipped probe collided with Tempel 1 and 
created a spectacular extraterrestrial explosion 83 million miles from 
Earth.

Since then, the Deep Impact team has reported a few key findings. These 
include an abundance of organic matter in Tempel 1's interior as well as 
its likely origins -- the region of the solar system now occupied by 
Uranus and Neptune.

According to the new research in Science, the comet's surface features 
three pockets of thin ice. The area the ice covers is small. The surface 
area of Tempel 1 is roughly 45 square miles or 1.2 billion square feet. 
The ice, however, covers roughly 300,000 square feet. And only 6 percent 
of that area consists of pure water ice. The rest is dust.

"It's like a seven-acre skating rink of snowy dirt," said Peter Schultz, 
professor of geological sciences at Brown, Deep Impact co-investigator and 
co-author on the Science paper.

Sunshine, Schultz and the rest of the team arrived at their findings by 
analyzing data captured by an infrared spectrometer, an optical instrument 
that uses light to determine the composition of matter.

Based on this spectral data, it appears that the surface ice used to be 
inside Tempel 1 but became exposed over time. The team reports that jets 
-- occasional blasts of dust and vapor -- may send this surface ice, as 
well as interior ice, to the coma, or tail, of Tempel 1.

"So we know we're looking at a geologically active body whose surface is 
changing over time," Schultz said. "Now we can begin to understand how and 
why these jets erupt."

NASA funded the work. For more information on Deep Impact, visit the JPL 
Web site:
     http://deepimpact.jpl.nasa.gov/home/index.html

IMAGE CAPTION:
[http://www.brown.edu/Administration/News_Bureau/2005-06/05-072.jpg 
(34KB)]
First evidence of water ice on a comet

The three small areas of water ice on the surface of Tempel 1 appear in 
this image, taken by an instrument aboard NASA's Deep Impact spacecraft. 
Photo: NASA