Close-up look at a comet

Comet Hartley 2

First views of comet Hartley 2, courtesy NASA / JPL-Caltech / UMD.

NASA’s EPOXI mission spacecraft successfully flew past Comet Hartley 2 at 1:00am Sydney time Friday. Scientists say initial images from the flyby provide new information about the comet’s volume and material spewing from its surface.

“Early observations of the comet show that, for the first time, we may be able to connect activity to individual features on the nucleus,” said EPOXI principal investigator Michael A’Hearn of the University of Maryland, College Park. “We certainly have our hands full. The images are full of great cometary data, and that’s what we hoped for.”

EPOXI is an extended mission that uses the already in-flight Deep Impact spacecraft. Its encounter phase with Hartley 2 began on November 3, when the spacecraft began to point its two imagers at the comet’s nucleus. Imaging of the nucleus began one hour later.

“The spacecraft has provided the most extensive observations of a comet in history,” said Ed Weiler, associate administrator for NASA’s Science Mission Directorate at the agency’s Headquarters in Washington. “Scientists and engineers have successfully squeezed world-class science from a re-purposed spacecraft at a fraction of the cost to taxpayers of a new science project.”

Comet Hartley 2

A view of Hartley 2 as the EPOXI mission approached the comet, courtesy NASA / JPL-Caltech / UMD

Comet Hartley 2

Hartley 2 is an unusually active comet, emitting streams of gas and dust. Courtesy NASA / JPL-Caltech / UMD.

Images from the EPOXI mission reveal Comet Hartley 2 to have 100 times less volume than comet Tempel 1, the first target of Deep Impact. More revelations about Hartley 2 are expected as analysis continues.

Initial estimates indicate the spacecraft was about 700 kilometres from the comet at the closest-approach point. That’s almost the exact distance that was calculated by engineers in advance of the flyby.

“It is a testament to our team’s skill that we nailed the flyby distance to a comet that likes to move around the sky so much,” said Tim Larson, EPOXI project manager at NASA’s Jet Propulsion Laboratory. “While it’s great to see the images coming down, there is still work to be done. We have another three weeks of imaging during our outbound journey.”

The name EPOXI is a combination of the names for the two extended mission components: the Extrasolar Planet Observations and Characterisation (EPOCh), and the flyby of Comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft has retained the name Deep Impact. In 2005, Deep Impact successfully released an impactor into the path of Comet Tempel 1.

Comet Hartley 2

Another view of comet Hartley 2, courtesy NASA / JPL-Caltech / UMD.

Comet Hartley 2

Like all comets, Hartley 2 is a mixture of various ices, dust and rocky rubble. Courtesy NASA / JPL-Caltech / UMD.

Adapted from information issued by NASA / JPL-Caltech / UMD.

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