The First Images Are In from Rosetta’s Valentine’s Day Comet Flyby

On Saturday, Feb. 14, the Rosetta spacecraft swooped low over the surface of comet 67P/C-G in the first dedicated close pass of its mission, coming within a scant 6 km (3.7 miles) at 12:41 UTC. The image above is a mosaic of four individual NavCam images acquired just shortly afterwards, when Rosetta was about 8.9 km from the comet.

The 45m "Cheops" boulder on comet 67P/C-G (ESA/Rosetta/Navcam)
The 45m “Cheops” boulder on comet 67P/C-G (ESA/Rosetta/Navcam)

The view above looks across much of the Imhotep region along the flat bottom of comet 67P’s larger lobe. (See a map of 67P’s named regions here.) At the top is the flat “plain” where the Cheops boulder cluster can be seen – the largest of which is 45 meters (148 feet) across.

Read more: Rosetta Gets a Peek at Comet 67P’s Underside

The zero phase angle of sunlight during the pass made for fairly even illumination across the comet’s surface.

The image scale on the full mosaic is 0.76 m/pixel and the entire view encompasses a 1.35 × 1.37 km-wide area.

Other NavCam images acquired before and after the pass have been assembled into mosaics – check those out below:

Four-image mosaic made from NavCam images acquired on Feb. 14, 2015 at a distance of 35 km. Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.
Four-image mosaic made from NavCam images acquired on Feb. 14, 2015 at a distance of 35 km. Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.
Four-image mosaic made from NavCam images acquired on Feb. 14, 2015 at a distance of 12.6 km. Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.
Four-image mosaic made from NavCam images acquired on Feb. 14, 2015 at a distance of 12.6 km. Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.
Four-image mosaic made from NavCam images acquired on Feb. 14, 2015 at 19:42 UTC at a distance of 31.6 km. Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.
Four-image mosaic made from NavCam images acquired on Feb. 14, 2015 at 19:42 UTC at a distance of 31.6 km. Credits: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.

In addition to NavCam images of 67P, Rosetta also acquired high-resolution OSIRIS images of the comet and gathered scientific data about its coma environment during the flyby. These data will be downlinked and processed over the next week or so.

Flybys will be regular parts of Rosetta’s operations over the course of 2015, but due to the comet’s increasing activity none will bring the spacecraft as close as this particular pass.

Rosetta is now moving out to a distance of about 250 km (155 miles) from 67P. Watch a video below of how the Feb. 14 flyby was planned and executed:

Source: ESA’s Rosetta blog

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(Also, on Feb. 9, Rosetta captured a full-frame NavCam image of 67P from 105 km. I’ve edited that image for additional contrast and added a blue tint. Enjoy!)

Comet 67P on Feb. 9, 2015 from 105 km (65 miles)
Comet 67P on Feb. 9, 2015 from 105 km (65 miles)

Rosetta Gets a Peek at Comet 67P’s “Underside”

A particularly dramatic view of comet 67P/C-G due to the angle of solar illumination, this is a mosaic made from four images acquired by Rosetta’s NavCam on January 16, 2015, from a distance of 28.4 km (17.6 miles). The assembled image shows the larger “bottom” lobe of 67P, with a flat region called Imhotep along the left side and, on the lower right, the transition area stretching up to the comet’s smaller “head” lobe. Outgassing jets can be seen as faint streaks at the upper right, and ejected dust grains show up as bright specks above its surface.

Also in this view is one of 67P’s larger boulders, a somewhat pyramid-shaped rock dubbed “Cheops.” Can you spot it?

There it is!

Position of the Cheops boulder on 67P (ESA/Rosetta/Navcam)
Position of the Cheops boulder on 67P (ESA/Rosetta/Navcam)

One in a cluster of boulders on 67P’s “underside,” Cheops is about 45 meters wide and 25 meters high (148 x 82 feet).

When it was first observed in Rosetta images Cheops and the nearby cluster reminded scientists of the pyramids at Giza in Egypt, and so it was named for the largest of those pyramids, the Great Pyramid, a tomb for the pharaoh Cheops (the Hellenized name for Khufu) built around 2,550 BCE. (See another view of the Cheops cluster here.)

OSIRIS image of Cheops acquired on Sept. 19, 2014 (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)
OSIRIS image of Cheops acquired on Sept. 19, 2014 (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)

Scientists are still working to determine the nature of 67P’s boulders. It’s not yet known what they are made of or how they came to be where they are observed today. Did they fall into their current positions? Or were they exposed upwards from below as a result of the comet’s activity? And why do they have alternating rough and smooth areas on their surfaces?

“It almost looks as if loose dust covering the surface of the comet has settled in the boulder’s cracks. But, of course, it is much too early to be sure,” said OSIRIS Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany.

Also see: A Stunning Look at the Cliffs of Comet 67P/Churyumov-Gerasimenko

As comet 67P approaches perihelion over the course of the next six months we will get to see firsthand via Rosetta what sorts of changes occur to its surface features, including office-building-sized boulders like Cheops.

Also, for a quick look at some of 67P’s “vital stats” click here. (Added 1/22)

Source: ESA Rosetta blog