On August 8, 2013 the Deep Impact spacecraft lost communication with NASA and was officially declared out of commission late in September. While NASA has big plans for comets on their books, this mission was one of their first forays into comet exploration. Deep Impact took nearly 500,000 images and successfully impacted comet Tempel 1 in 2005, fulfilling its primary directive.
Deep Impact’s mission was to collect data on the interior and exterior of comets in order to better understand the formation and evolution of the solar system. Comets are composed of elements, gas, ice and dust from the oldest regions of the solar system, and information collected from them gives more insight into their origins. Deep Impact consisted of two spacecrafts, one was the flyby spacecraft and the other was the impactor. The flyby spacecraft housed the impactor and released it near the comet’s nucleus, where it hit the surface facing the sun. The flyby spacecraft held two instruments for observation. The main instrument was a high resolution camera that collected data in the visible and infrared wavelengths, the other was a medium resolution camera. The instruments collected data before, during and after the impactor hit the comet.
Deep Impact completed its primary goal, impacting comet Tempel 1, on July 4th, 2005. The first surprising find was that the comet was much more porous than originally believed. We imagine a comet as a solid piece of hard rock, metal and ice in space. Instead the impact threw up very fine dust causing a flash that was much fainter than expected. It also ejected a fair amount of organic material, implying that such material could have been brought to our Earth by asteroid and meteor impacts.
With its original goal complete, NASA reenlisted the spacecraft for a flyby mission of the comet Hartley 2. The data collected from the flyby was used to study the composition of the comet, both at its nucleus and the poles of the comet. This information showed scientists that comets are not uniform, rather they have distinct regions that can be affected by seasonal changes and localized events.
Deep Impact was also used to capture images of other celestial bodies, including the moon, Earth, Mars, numerous stars and comets C/2009 P1 and ISON. The mission was brought to an end after contact with the spacecraft was severed. After numerous attempts to communicate with the spacecraft failed, it was declared lost. Deep Impact was very successful in both its original and extended missions. We can only hope that continued missions to comets and asteroids will be as successful and enrich our understanding of the solar system.