• Introduction
    • Deep Impact


      Deep Impact

      The Deep Impact mission was the first experiment to probe beneath the surface of a comet, attempting to reveal never before seen materials that would provide clues about the internal composition and structure of a comet. The instruments onboard the spacecraft, along with ground-based telescopes and space-based observatories, observed the impact and examined the resulting debris and interior material. The mission has advanced our understanding of comets, providing a wealth of data that will take years to fully interpret.


      Mission Management

      Michael A’Hearn
      Dr. Michael A’Hearn
      Principal Investigator

      The Deep Impact mission was managed for NASA by the Jet Propulsion Laboratory, Pasadena, CA. The Principal Investigator was Dr. Michael A'Hearn of the University of Maryland. Ball Aerospace and Technologies Corporation, Boulder, CO, was responsible for all flight hardware.

  • Science Objectives
    • The primary goals of the mission were to determine the differences between the surface of a comet and its interior and to learn about the structural properties and strength of the surface layers. Additional objectives were to:

      Observe how the crater forms and measure the crater's depth and diameter

      Identify the composition of the interior of the crater and its ejecta

      Determine the changes in natural outgassing produced by the crater

      he impactor being mated to the flyby spacecraft.
      The impactor being mated to the flyby spacecraft. The High Resolution camera is at the right of the technician’s hand.
  • Details

      The Deep Impact spacecraft launched from Cape Canaveral Air Force Station, Florida, on January 12, 2005, beginning its six-month, 268-million-mile journey to comet Tempel 1.  The two-part spacecraft consisted of a larger "flyby" spacecraft carrying a smaller "impactor" that was 49% copper and about the size of a washing machine.

      The two spacecraft separated 24 hours before impact.  The battery-powered, 770-lb impactor used an autonavigation system to analyze images of the comet and target a site that would be in sunlight and visible from the flyby spacecraft.

      On the 4th of July, traveling at a speed of 23,000 miles per hour, the impactor successfully placed itself into the path of comet Tempel 1.  A camera on the impactor captured and relayed images of the comet nucleus as it approached and just before it collided with the comet.

      From 300 miles away, the flyby spacecraft observed and recorded the impact and the ejected material that blasted from the crater.  The collision sent a huge, bright cloud of debris upward and outward from the comet.  Observatories around the world and in space were part of an unprecedented coordinated campaign to observe the collision and its aftermath. 


      Deep Impact probe collided with comet Tempel 1
      This image shows the initial ejecta that resulted when the Deep Impact probe collided with comet Tempel 1. It was taken by the spacecraft's medium-resolution camera 16 seconds after impact. Credit: NASA/JPL-Caltech/UMD
  • Results
    • Deep Impact has yielded unexpected results about the structure and composition of comets.  The data show that comet nuclei are not uniform in composition, achieving one of the major objectives of the mission.  Scientists found the first definitive evidence of water ice on the surface of a comet.  The data also revealed that Tempel 1 has a very fluffy structure that is weaker than a bank of powder snow. The fine dust of the comet is held together by gravity.

      The science team was surprised to find evidence of what appear to be impact craters on the surface of the comet.  Another interesting finding is the huge increase in carbon-containing molecules detected in spectral analysis of the ejection plume, indicating that comets contain a substantial amount of organic material and thus could have brought this material to Earth early in our planet's history.

      Findings show the comet interior is well shielded from the solar heating experienced by the surface of the comet nucleus.  Data indicate the nucleus is extremely porous, allowing the surface to heat up and cool down almost instantly in response to sunlight.  This suggests heat is not easily conducted to the interior, and the ice and other material deep inside the nucleus may be pristine and unchanged from the early days of the solar system, just as many scientists had suggested.  The analyses of the vast amount of data gleaned from Comet Tempel 1 will be ongoing well into the future.

      The huge cloud created by the impact was made up of very fine, powdery material.  Due to the massive amounts of dust, the excavated crater was not visible to the spacecraft’s cameras.  However, the Stardust spacecraft was given a new assignment by NASA and is now on its way to Tempel 1 as the Stardust-NExT mission.  This unprecedented second flyby in February 2011 should reveal more about the effects of the Deep Impact experiment, and we may finally learn the crater’s size.

      Findings from the Deep Impact mission were published in a special issue of Science in October 2005, and in special issues of  Icarus in March 2007 and October 2007.  Visit the mission website Results section for more information.



      Deep Impact

      Deep Impact scientists detected the first finding of ice on the surface of a comet. This composite image shows three ice-rich regions depicted in blue.


      a young surface view from probe
      The lack of features on the smooth region at  left implies a young surface. But is it advancing toward the right and covering up rougher, older surface regions? Or is it retreating to the left, eroding and uncovering those regions? The scarp edge marked by arrows is about 10-20 m above the lower terrain.
      Credit: NASA/UM/Cornell/Peter Thomas
  • Noteworthy
    • The Planetary Society conducted the "Great Comet Crater Contest" to guess the diameter of the Deep Impact crater.  More than 7,000 people from nearly 100 countries entered the contest, but the comet didn’t co-operate.  In the 800 seconds that the flyby spacecraft had to observe the crater, the dust never cleared.  The science team estimated the diameter to be between 325 and 820 feet, so three grand prize winners were selected at random from 1,865 entries within this range. 

      Deep Impact won the Space Frontier Foundation's 2005 Vision to Reality award for the best accomplishment of the year in turning the vision of true space exploration and the gathering of scientific knowledge into reality.  Principal investigator Michael A'Hearn said, “This award is a really great tribute to the large team that put in a tremendous amount of effort to make the mission happen.  The Space Frontier Foundation is an advocate for activities in space that break the paradigm and we are proud to be put in that class."

      Impact photo
      Arrows indictate the impact location.  The great hope is to finally see the crater when Stardust-NExT takes us back to Tempel 1 in 2011.