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UROP Student Helped Process Comet Collision

By Ramy A. Arnaout
Associate News Editor

The collision of a fragmented comet with Jupiter in July was a memorable event for Jennifer R. Mills '96, who played a key role in processing images of the impact taken by the Hubble Space Telescope.

Working under Heidi B. Hammel '82, a research scientist in the Department of Earth, Atmospheric, and Planetary Sciences, Mills wrote software that cut down the processing time per image from nearly two days to about seven minutes.

First-round image processing is usually handled by the National Aeronautics and Space Administration, and takes about two days per picture. NASA then returns the data to investigators in a format their programs can understand, Mills said. However, with over 20 comet fragments hitting the giant planet in only eight days, the pace of the Jupiter event made using NASA impractical for the group, Hammel said.

"Jennifer has taken the programs and put them all together to make them more efficient than before," Hammel said. By removing scan lines and other artifacts and correcting for distortions, the programs enhance image quality, she said.

Mills enjoyed the opportunity to work on the once-in-a-lifetime project. "When I first started this year I couldn't imagine doing this," said Mills, who landed the job through the Undergraduate Research Opportunities Program. "There were a lot of all-nighters," she said. "It was a lot of work, [but] it was exciting."

Many of the over 400 images the team collected have since appeared widely in the press and are available on the Internet.

The comet first attracted attention in April 1993, when astronomers found that a close encounter with Jupiter the year before had torn it into more than 20 fragments (labeled A, B, C, and so on), according to a press release from astronomers Lucy McFadden and Michael F. A'Hearn of the University of Maryland. By May, it appeared likely that the broken-up comet would strike the planet on its next orbit, the release said. Since then, the comet, named Shoemaker-Levy 9 after its discoverers, has been the center of interest for many astronomers.

Data down, analysis to go

Hammel's team, which shared the Hubble with another group during the week of the collision, hopes to use its data to investigate the effects that the impacts of the fragments have had on Jupiter's atmosphere. Atmospheric waves and fireball plumes are among the possible results of the collisions.

Mills, together with Hammel and a few other members of the team, monitored the collision from the Space Telescope Science Institute in Baltimore.

"We got there more than a week before the first impact," Mills said. "We wanted to get set up and get used to everything so that we would be set" for the collisions, she said.

In the weeks leading up to the event, many feared that astronomers' preparations might be in vain: Simulations predicted that the fragments would strike the far side of Jupiter, and therefore would not be visible from Earth. Observers hoped that there would still be something to see when impact sites came into view as Jupiter rotated around its axis.

Hammel's group and astronomers around the world were therefore pleasantly surprised not only to see the impact sites, but in some cases to see plumes of gaseous material rising from fresh collisions. One highlight was "the first impact, when nobody expected to see anything, and you could actually see the plume," Mills said.

With the pictures processed, "we're starting to do the science," Hammel said. "We want to know about the physics of the creation of the site."

"We've just scratched the surface of the data, the cream off the top, so to speak," Hammel said. "There are literally hundreds of pictures. We'll be busy for a very long time."

Both Mills and Hammel credit UROP with making the project possible.

"I had a UROP spring semester working on Neptune," Mills said. "Heidi offered this to me because she needed more people. I said, Yeah, sure!' It was either Jupiter" - a once-in-a-lifetime event - "or home for the summer," said Mills, who will continue the UROP into this semester.

"It's great that Jennifer could get that UROP project [and] get involved in the process," said Hammel, who participated in the program as an undergraduate. "I did UROP; it put me on the track I'm on now." Hammel currently works in conjunction with EAPS Professor James L. Elliot '65, her former UROP mentor.