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See Jupiter's Great Black Spot

H. Hammel (SSI) / NASA / ESA / Jupiter Impact Team
The Hubble Space Telescope's brand-new Wide Field Camera 3 took
this picture of the expanding black spot on Jupiter on Thursday.

Even though it's in the middle of a post-makeover checkout, the Hubble Space Telescope was turned toward Jupiter this week to capture a picture of the bruise left behind by a comet or asteroid - and it's a real beaut of a shiner.

Hubble's view, captured by its brand-new Wide Field Camera 3 on Thursday, is the sharpest visible-light image of the impact site, which was first seen by Australian amateur astronomer Anthony Wesley on Sunday and has been changing day by day. The picture also represents Hubble's first science observation since it was upgraded during May's final servicing mission by the space shuttle Atlantis' crew.

"This is just one example of what Hubble's new, state-of-the-art camera can do, thanks to the STS-125 astronauts and the entire Hubble team," Ed Weiler, associate administrator of NASA's Science Mission Directorate, said in an image advisory released today. "However, the best is yet to come!"

The team behind the observations was led by Space Science Institute astronomer Heidi Hammel. In the advisory, Hammel said the imagery "has revealed an astonishing wealth of data" about the impact site.

"By combining these images with our ground-based data at other wavelengths, our Hubble data will allow a comprehensive understanding of exactly what is happening to the impact debris," she said. Hammel was also part of a team that made mid-infrared observations of the Great Black Spot earlier in the week, using the Gemini North telescope in Hawaii.

I. de Pater (Berkeley) / H. Hammel (SSI) / T. Rector (U. of AK-Anchorage) / Gemini Obs.
This mid-infrared image of the impact site on Jupiter was captured by the Gemini
North telescope in Hawaii. The yellow arrow points to the "bruise."

Astronomers don't yet know what caused the impact, but it was almost certainly a comet or asteroid. The bruise left behind looks strikingly like the scars created 15 years earlier by Comet Shoemaker-Levy 9's famous smash-up in Jupiter's atmosphere.

Amy Simon-Miller of NASA's Goddard Space Flight Center noted that the plume of dark debris emanating from the impact area is lumpy, due to turbulence in Jupiter's atmosphere.

The Great Black Spot is currently about 6,000 miles wide, or twice as wide as the European continent. (This picture provides a length scale). Simon-Miller told me that the object causing the bruise was probably a couple of hundred meters (yards) wide - not as big as the biggest fragment from Shoemaker-Levy 9, but still pretty big. The Hubble team says the force of the explosion was thousands of times more powerful than the Tunguska impact, which devastated 500,000 acres of Siberian forest land in 1908.

One big question about the impact is: Why didn't we see this coming? What does this say about our ability to detect potential killer asteroids or comets before they hit Earth?

NASA and other agencies are spending millions of dollars to find and track thousands of near-Earth objects (including potentially hazardous asteroids). Less attention is being devoted to tracking the thousands of near-Jupiter objects (including Trojan asteroids).

Professional and amateur astronomers keep a close watch for asteroids or comets that wander into our celestial neighborhood, but they can't see everything at a distance. Some of the smaller asteroids pass right by us before they're spotted. "The reality is, if something is really dark, it's going to be hard to see," Simon-Miller said.

The good news is that Jupiter acts as something of a gravitational vacuum cleaner, sucking in deep-space impacts that might otherwise whack Earth. The bad news is that much more needs to be done to detect potentially harmful space rocks, and draw up a plan to protect our planet when (not if) we find one. In that sense, Jupiter's black eye serves as a warning that we better put up our dukes.

In addition to Hammel and Simon-Miller, the Jupiter Impact Team includes Keith Noll and Michael Wong of the Space Telescope Science Institute, John Clarke of Boston University, Imke de Pater of the University of California at Berkeley, Glenn Orton of the Jet Propulsion Laboratory and Agustin Sanchez-Lavega of the University of the Basque Country in Spain. Discretionary time for the Hubble observations was allocated by STScI director Matt Mountain.

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