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Extrasolar Planet Observation and Deep Impact Extended Investigation

Phase: Past

Launch Date: January 12, 2005

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Extrasolar Planet Observation and Deep Impact Extended Investigation EPOXI is a follow-on mission to Deep Impact and is a combination of two scientific studies; Deep Impact Extended Investigation (DIXI) and Extrasolar Planet Observation and Characterization (EPOCh).

Comet Hartley 2
In November 2010, NASA's EPOXI mission successfully flew by comet Hartley 2 and began returning images.

While Deep Impact is on route to comet Hartley 2 to continue its original theme of studying comets,  the EPOCh portion of the mission will observe three nearby stars with transiting extra-solar planets, so named because the planet transits, or passes in front of its star. Using the High-Resolution Instrument (HRI), Deep Impact will be able to stare at these stars for long periods while scientists observe multiple transits and compare the timing to see if there are any hidden worlds. By observing both extra-solar systems, scientists can compare them to our own and attempt to discover what we have in common, what we don't, and perhaps why.

For the DIXI mission, Deep Impact and will fly by and observe the nucleus of comet Hartley 2 which belongs to a currently undefined class of comets. Scientists will try to determine which comet’s features are primordial and which are the result of subsequent evolutionary processes. At the nearest point of its flyby of Hartley 2, the spacecraft will be some 550 miles from the comet.

Science goals for the DIXI mission include mapping the comet’s size, shape, craters and color variations on the surface and comparing them to other comets; searching for, mapping and tracking outbursts of gas correlating them to surface features; obtaining infrared spectral maps of the distribution of gas and dust in the inner coma; searching for frozen volatiles and mapping heat transport mechanisms;

Comets and their asteroid kin are the leftover building blocks of planets, and might have contributed water and organic material to the ancient Earth, aiding the start of life. By observing comets, scientists can start to understand more about the formation and evolution of the solar system and how life came to exist on Earth.

University of Maryland astronomer Michael A'Hearn is the Principal Investigator (PI) for the EPOXI overall mission and its DIXI component.