ESA Rosetta Image: Coma surrounds comet 67P/Churyumov-Gerasimenko

The coma of comet 67P/Churyumov-Gerasimenko as seen by OSIRIS camera on board ESA Rosetta. 

The coma covers an area of 150 kilometers across. 

This image was taken on July 25th, 2014 with an exposure time of 330 seconds. 

 The hazy circular structure on the right and the center of the coma are artifacts due to overexposure of the nucleus. 

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA /UPM /DASP /IDA

Less than a week before ESA Rosetta's rendezvous with comet 67P/Churyumov-Gerasimenko, images obtained by OSIRIS, the spacecraft's onboard scientific imaging system, show clear signs of a coma surrounding the comet's nucleus.

While the OSIRIS' view of the coma covers an area of 150 kilometers across, its outskirts might reach much farther.

"Even though it sounds like a contradiction, imaging the comet's coma from nearby is more difficult than from far away", says OSIRIS Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany.

At the end of April, for example, OSIRIS had witnessed a distinct rise of cometary dust production from a distance of more than two million kilometers.

At that time, one pixel in OSIRIS' images corresponded to a region in space covering 2500 square kilometers at the nucleus.

ESA Rosetta's OSIRIS camera

The reflected light from all dust particles seen in this column worked together to create a signal.

Now, as the resolution of OSIRIS images increases, a much smaller region and thus far less dust particles contributes to one pixel.

Nevertheless, a new image dating from July 25th clearly reveals an extended coma shrouding 67P's nucleus.

"Our coma images cover an area of 150 by 150 square kilometers", says Luisa Lara from the Instituto de Astrofísica de Andalucía.

However, most likely these images show only the inner part of the coma, where particle densities are highest. Scientists expect 67P's full coma to actually reach much farther.

Another challenge for OSIRIS is the bright nucleus that outshines the surrounding coma.

While OSIRIS is designed to deal with a controlled overexposure in the region of the nucleus, the stray light from this strong source causes artifacts by the optical system.

In the current image, the hazy bright circular structure to the right of the comet's nucleus is such an artifact. The center of the image located around the position of the nucleus is obscured by overexposure.

The nucleus of comet 67P/Churyumov-Gerasimenko as seen from a distance of 1950 kilometers on July 29th, 2014. 

One pixel corresponds to approximately 37 meters. 

The bright neck region between the comet’s head and body is becoming more and more distinct. 

Credit: ESA/Rosetta/MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA /UPM /DASP /IDA

In the next weeks, the OSIRIS team will study how the comet's activity has developed so far in approach.

To this end, data obtained from different distances and with different exposure times need to be correlated.

Meanwhile, new images of the comet's nucleus confirm the collar-like appearance of the neck region which presents itself brighter than most parts of the comet's body and head.

The reason for this feature is still subject to discussion. Possible explanations range from differences in material or grain size to topological effects.

Rosetta is an ESA mission with contributions from its member states and NASA.

Rosetta's Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI.

Rosetta will be the first mission in history to rendezvous with a comet, escort it as it orbits the Sun, and deploy a lander to its surface.

ESA Rosetta Image: Comet 67P/Churymov-Gerasimenko in the constellation Ophiuchus

The OSIRIS Narrow Angle Camera aboard ESA's Rosetta probe captured this image on March 21, 2014, showing Comet 67P/Churyumov–Gerasimenko in the constellation Ophiuchus.

Credit: ESA

The ESA's Rosetta spacecraft opened its eyes in January after a 10-year voyage across the solar system and a long hibernation in deep space.

For the first time since its wakeup call, Rosetta spied its destination.

ESA released images Thursday (March 27) showing Rosetta's glimpse of its target, Comet 67P/Churyumov–Gerasimenko.

The "first light" images were captured on March 20 and 21 by the OSIRIS wide-angle camera and narrow-angle camera aboard Rosetta, from more than 3 million miles (5 million kilometers) away from the comet.



"Finally seeing our target after a 10 year journey through space is an incredible feeling," Holger Sierks, the OSIRIS principal investigator from the Max Planck Institute for Solar System Research in Germany, said in a statement.

Holger Sierks

"These first images taken from such a huge distance show us that OSIRIS is ready for the upcoming adventure."

The light from the faraway, 2.5-mile-wide (4 km) comet doesn't even fill up a single pixel.

To create the image, researchers had to obtain a series of 60–300 second exposures.

It took 37 minutes for each image to reach Earth and about an hour for each to download, ESA officials said.

ESA's Rosetta, a solar-powered probe, is on track to enter orbit around the icy body in August 2014. By then, Rosetta should have a 2-meter (6.5 feet) per pixel view of Comet 67P/Churyumov–Gerasimenko, complete with surface features.

A robotic lander called Philae, which is piggybacking on Rosetta, is scheduled to touch down on the comet in November 2014.

Securing itself with a harpoon and ice screws, Philae will drill samples and conduct experiments with its 10 science instruments, as Rosetta looks on from above.

If all goes as planned, Rosetta and Philae will continue their observations through December 2015.

ESA Rosetta Image: One of Rosetta’s 14m solar wings over Mars Mawrth Vallis region

On 25 February 2007 at 02:15 GMT, ESA Rosetta passed just 250 km from the surface of Mars. 

Rosetta’s Philae lander took this image 4 minutes before closest approach, at a distance of 1000 km. 

It captures one of Rosetta’s 14 m-long solar wings, set against the northern hemisphere of Mars, where details in the Mawrth Vallis region can be seen.

Mawrth Vallis region of Mars is of particular interest to scientists because it contains minerals formed in the presence of water – a discovery made by ESA’s Mars Express.

This image was originally published in 2007 and was taken in black-and-white.

Mawrth Vallis region of Mars

Representative colour was added to the surface of Mars and, in this version, these colours have been slightly enhanced, along with some brightening of details in the solar wing.

On Sunday 2 March, ESA Rosetta celebrates ten years since launch.

The flyby at Mars was one of four planetary gravity assists (the other three were at Earth) needed to boost the spacecraft onto the correct trajectory to meet up with its target, comet 67P/Churyumov–Gerasimenko, in August 2014.

ESA Rosetta will become the first space mission to rendezvous with a comet, the first to attempt a landing, and the first to follow a comet as it swings around the Sun.