Taking a break from extensive testing following May's shuttle repair mission, the Hubble Space Telescope was expected to point toward Jupiter Thursday to take pictures of a dark impact scar that first appeared on the giant planet last weekend.

The Hubble Space Telescope flies away from the shuttle Atlantis after May's servicing mission. Credit: NASA

Engineers programmed Hubble to spend a few hours observing Jupiter Thursday afternoon. Imagery of Jupiter could be released by late Friday, according to Ray Villard, spokesperson for the Space Telescope Science Institute.

"This impact is regarded as a target of opportunity," Villard said. "You drop everything and go look at it."

Scientists plan procedures for such quickie observations, but Hubble has never been ordered to look at a target of opportunity so soon after a servicing mission.

Villard said Hubble's Wide Field Camera 3, a powerful new instrument just installed by the Atlantis crew, would be used to take pictures of Jupiter in ultraviolet and visible wavelengths.

Jupiter's scar was first observed Sunday by an Australian amateur astronomer. Ground-based observatories immediately turned toward Jupiter, confirming a blemish the size of the Pacific Ocean in the planet's southern hemisphere.

Infrared images of Jupiter show the impact site is bright due to reflective aerosol particles thrown high into the atmosphere. Visible light pictures show a darker bruise-like feature.

This image shows a large impact shown on the bottom left on Jupiter's south polar region captured on July 20, 2009, by NASA's Infrared Telescope Facility in Mauna Kea, Hawaii. Credit: NASA/JPL/Infrared Telescope Facility

The asteroid or comet responsible for the this week's scar hit Jupiter on the 15th anniversary of the Shoemaker-Levy 9 impact events in 1994.

More than 20 fragments struck Jupiter over a six-day period in July 1994 after the gas giant's gravity tore the comet apart two years earlier.

This week's event is only the second time astronomers have studied an impact on Jupiter.

Hubble was in the midst of a nearly four-month Servicing Mission Observatory Verification period, a series of tests and calibrations designed to check new equipment astronauts installed during May's upgrades.

"There are certain kinds of images you can only get from Hubble, in terms of sharpness, quality (and) detail," Villard said.

Astronomers could not wait long to schedule observing time on Hubble. The smudge is expected to fade over the coming weeks and months.

"Because it is transient, we have to do it now," Villard said.