After the EPOXI spacecraft’s spectacular flyby of comet Hartley 2 on 4 November, researchers are delighted at the high-resolution images that have given them a deeper insight into the comet’s workings.
The pictures, which contain a flurry of dry ice and snow, reveal that Hartley 2 has a strange divided structure, with some parts dominated by water and others by carbon-dioxide.
The images show chunks of ice the size of golf balls and basketballs coming from the comet’s nucleus, which astounded the team, said principal investigator Michael A’Hearn during a media briefing at NASA Headquarters in Washington D.C. on 18 November. A further spray of micron-sized, fluffy globs, “akin to a dandelion puff,” drifted around the comet’s nucleus, said Jessica Sunshine, an astronomer at the University of Maryland and EPOXI team member.
“It looks like a snow globe that you’ve shaken and let fly,” said Peter Shultz of Brown University in Providence, Rhode Island.
Behind that beauty lies some important science.
The researchers discovered that jets of sublimating carbon dioxide were pulling ice and dust grains from the comet’s rough edges while Hartley’s smooth waist—the central part of the nucleus—was mainly shooting off water vapor, said Sunshine.
“We didn’t expect to see this at all,” she said.
The waist was behaving much more like comet Temple 1, which EPOXI previously visited during the 2005 Deep Impact mission, said A’Hearn. But the unique lobes prove that Hartley 2 has more carbon dioxide in its interior than any other measured comet, he said.
The team believes that the carbon dioxide will be an important clue to understand where and how Hartley 2 was born, which could yield information on how the solar system as a whole formed, A’Hearn said. He added the flyby has emphasized how different comets are from one another, which means a straightforward creation story will not be easy to achieve.
“In science, you usually want a simple explanation, but things have gotten much more complex,” he said.
Previously: Glimpsing a comet’s heart
The 3-D image at right should be seen with blue-red glasses, where the red lens is in front of the left eye