Spacecraft Goes AWOL, but Leaves “Deep Impact”

By David Kohn Feb 09, 2014

Eight years after Deep Impact was launched into deep space, NASA in August lost contact with the spacecraft.

But over its longer-than-expected life, the probe, conceived and managed by University of Maryland astronomers, left a long trail of discoveries about comets and other celestial bodies.

Deep Impact is most famous for its first mission in 2005, when it sent a washing machine-size “impactor” into the path of the comet 9P/Tempel. The crash left a crater on the comet the size of a football field, and gave scientists a wealth of new data about comet structure and content.

“It dramatically changed the way we look at comets,” said Maryland astronomy Professor Michael A’Hearn, who led the mission. Data from Deep Impact proved, for instance, that many comets are mostly porous, as fluffy as a bank of powdered snow.

After the first mission ended, Maryland scientists convinced NASA to keep using Deep Impact rather than let it spin off into space. Its later missions led to discoveries about comets’ chemical makeup, formation locations and surface changes.

For the UMD team, the loss of the spacecraft was an emotional blow. “When something is taken away for good, you suddenly realize how much it’s been there,” says Professor Jessica Sunshine, who along with A’Hearn helped write the 1998 proposal that led to the mission, and worked on the project to the end. “We had a helluva run."

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The inception: Deep Impact being built at Ball Aerospace & Technologies Corporation in Boulder, Colo. Image courtesy of Ball Aerospace & Technologies Corp.

An artist’s rendering of Deep Impact releasing the impactor toward the comet. Image courtesy of Ball Aerospace & Technologies Corp.; Modified By Tim Cline/UMD.

“It dramatically changed the way we look at comets,” says Maryland astronomer Michael A’Hearn, who led the mission. Data from Deep Impact proved, for instance, that many comets are mostly porous, as fluffy as a bank of powdered snow. After the first mission ended, Maryland scientists convinced NASA to keep using Deep Impact rather than let it spin off into space. Its later missions led to discoveries about comets’ chemical makeup, formation locations and surface changes. Photo by John T. Consoli/UMD

9P/Tempel, 67 seconds after it obliterated the impactor. The image was taken by the high-resolution camera; light from the collision saturated the camera’s detector, creating the bright splash seen here. The image reveals topographic features, including ridges, scalloped edges and possibly impact craters. Image courtesy of NASA / JPL-Caltech / UMD

These images show a before-and-after comparison of the area targeted by the impactor. The image on the left shows the comet surface just before the impactor hits; the arrow shows the direction of the impactor, and the spot shows the target. The image on the right shows the plume of material from the impact about 11 minutes later. Image courtesy of NASA / JPL-CALTECH / UMD

Using data from Deep Impact, NASA astronomers put together a “recipe” for a comet’s ingredients. The ingredients were excavated from 9P/Tempel when Deep Impact’s impactor hit its surface. Astronomers found evidence that the comet included clay, iron-containing compounds, carbonates (the minerals in seashells), crystallized silicates such as the green olivine minerals found on beaches, as well as polycyclic aromatic hydrocarbons, carbon-containing compounds found in car exhaust and on burnt toast. Deep Impact also found evidence of water vapor and carbon dioxide gas. The ingredients pictured here are: (back, from left to right) a cup of ice and a cup of dry ice (in measuring cups, from left to right); olivine, clay, polycyclic aromatic hydrocarbons, spinel, metallic iron; (front, from left to right) the silicate enstatite, the carbonate dolomite, and the iron sulfide marcasite. Image courtesy of George Rossman of the California Institute of Technology | Credit: NASA / JPL-Caltech

For the UMD team, the loss of the spacecraft was an emotional blow. “When something is taken away for good, you suddenly realize how much it’s been there,” says Professor Jessica Sunshine, who along with A’Hearn helped write the 1998 proposal that led to the mission. “We had a helluva run.” Photo by John T. Consoli/UMD