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Deep Impact - EPOXI

Comet Hartley 2 Gets a Visitor (Artist Concept)

This artist's concept shows a view of NASA's EPOXI mission spacecraft during its Nov. 4, 2010 flyby of comet Hartley 2. The fluffy shell around the comet, called a coma, is made up of gas and dust that blew off the comet's core, or nucleus.
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Introducing Comet Hartley 2

Comet Hartley 2 can be seen in glorious detail in this image from NASA's EPOXI mission. It was taken as the spacecraft flew by around 6:59 a.m. PDT (9:59 a.m. EDT), from a distance of about 700 kilometers (435 miles).
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Hartley 2, Close Up

This image from the High-Resolution Instrument on NASA's EPOXI mission spacecraft shows part of the nucleus of comet Hartley 2. The sun is illuminating the nucleus from the right. A distinct cloud of individual particles is visible.
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Closing in on Comet Hartley 2

This close-up view of comet Hartley 2 was taken as NASA's EPOXI mission approached the comet at 6:58 a.m. PDT (9:58 a.m. EDT).
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Jets Galore

This enhanced image, one of the closest taken of comet Harley 2 by NASA's EPOXI mission, shows jets and where they originate from the surface. There are jets outgassing from the sunward side, the night side, and along the terminator.
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Up Close and Personal with Hartley 2

This image, one of the closest taken of comet Hartley 2 by NASA's EPOXI mission, shows many features across the comet's surface. The length of the comet is equal to the distance between the Capitol building and the Washington Monument in Washington.
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Slipping By Comet Hartley 2

This close-up view of comet Hartley 2 was taken at 7:00 a.m. PDT (10 a.m. EDT), after NASA's EPOXI mission flew by.
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Flying Under Comet Hartley 2

This image montage shows comet Hartley 2 as NASA's EPOXI mission approached and flew under the comet. The images progress in time clockwise, starting at the top left.
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Hartley 2 on the Move

This image from NASA's EPOXI mission shows Hartley 2 moving across the background field of stars. The coma, or cloud of gas and dust around the comet, expands and brightens over this time period. Animation available at the Photojournal.
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Mission Summary

The EPOXI mission recycled the Deep Impact spacecraft, which had formerly visited comet Tempel 1, to visit a second comet, Hartley 2. The Nov. 4, 2010, flyby marked only the fifth time a comet had been visited by a spacecraft.

Images snapped by the spacecraft uncovered a number of new details about the hyperactive Hartley 2, including observable variations in the strength, behavior and composition of jets on the comet's surface.

Mission Events

September 26, 2007: Commands from Earth awaken the Deep Impact spacecraft, instructing it to adjust its orbit toward comet Hartley 2.

January 22, 2008: The Deep Impact spacecraft, operating under the EPOXI mission to comet Hartley 2, aims its largest telescope toward five stars in search of alien (exosolar) planets.

November 4, 2010: EPOXI successfully flies by comet Hartley 2, marking only the fifth time a comet has been visited by a spacecraft.

Key Discoveries

November 2010: The EPOXI mission flyby reveals that comet Hartley 2's rocky ends spew out tons of golf-ball to basketball-size fluffy ice particles, while the smooth middle area is more like what was observed on comet Tempel 1 with water evaporating below the surface and percolating out through the dust.

June 2011: A science paper in the journal Science highlights some of the EPOXI mission's key findings. Including:

Strong activity in water release and carbon dioxide-powered jets does not occur equally in the different regions of Hartley 2.

Hartley 2 has an 'excited state of rotation' because it spins around one axis, but also tumbles around a different axis.

On its larger, rougher ends, the comet's surface is dotted with glittering blocks that can reach approximately 165 feet (50 meters) high and 260 feet (80 meters) wide. The block-like, shiny objects, some as big as one block long and 16 stories tall, appear to be two to three times more reflective than the surface average.

Scientific Instrument(s)

- High-Resolution Instrument (HRI)
- Medium-Resolution Instrument (MRI)

Fast Facts

Acronym:	EPOXI

Type:	Flyby

Status:	Current

Launch Date:	January 12, 2005 1:47 p.m. EST (18:45 UTC)

Launch Location:	Cape Canaveral Air Force Station, Florida

Mission End Date:	October 01, 2011

Target:	comet Hartley 2

Destination:	comet Hartley 2

Current Location:	› Click to view

Resources

› Mission Website

› NASA Mission Website

› Fact Sheet

	Science Paper Details NASA Epoxi Flyby of Hyper Comet › Read more
	NASA Spacecraft Sees Cosmic Snow Storm During Comet Encounter › Read more
	Flight of the Comet › Read more