Wonderful new images of Comet 67P/Churyumov-Gerasimenko from Rosetta “ESA’s comet chaser” have been released in the past week or so:

* OSIRIS catches activity in the act –

The comet’s activity has been significantly increasing over the last weeks and months. As the comet moves closer to the Sun along its orbit, its nucleus gets warmer and warmer. Frozen gases sublimate from its surface, carrying dust particles with it and enshrouding the nucleus in a dense coma. With only four months to go until perihelion – the closest point to the Sun – this process is well underway, with pronounced dust jets seen at all times on the comet’s day side.

Rosetta’s OSIRIS wide-angle camera captures the moment a jet bursts
into action. The first image was captured at 07:13 CET on 12 March
2015, the  second two minutes later.
Credits: ESA/Rosetta/MPS for OSIRIS Team 

The two images released today show the remarkable onset of such a jet for the first time. They were taken on 12 March from a distance of 75 kilometres. In the first image, obtained at 07:13 CET, several rays of dust jets frame the upper, illuminated side of the comet. The dark underside shows no such features. Two minutes later, the picture has changed: a spectacular new jet has emerged on the dark side, hurtling dust into space and displaying a clearly discernable fine structure.

“This was a chance discovery,” says OSIRIS principal investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany. “No one has ever witnessed the wake-up of a dust jet before. It is impossible to plan such an image.”

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* CometWatch 15 April  –

Today’s CometWatch entry is a single frame NAVCAM image obtained on 15 April, from a distance of 170 km from the centre of Comet 67P/Churyumov-Gerasimenko. At this distance, the resolution is 14.5 m/pixel; the image has been cropped to 11.4 km (the original frame, provided at the end of the post, measures 14.8 km across).

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* CometWatch 15 April – 4 hours later –

Today’s CometWatch entry is another single frame NAVCAM image taken on 15 April, almost four hours after the one that was published last Friday. The new picture was obtained at about 165 km from the centre of Comet 67P/Churyumov-Gerasimenko, where the resolution of NAVCAM is 14 m/pixel. The image has been cropped and measures 10.4 km (the original frame, provided at the end of the post, measures 14.4 km across).

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* “Crescent comet” – CometWatch 15 and 16 April –

The image [below] was captured on 15 April 2015 by Rosetta’s Navigation camera from a distance of 162 km from the comet centre. The resolution is 14 m/pixel and the image measures 14 km across. It has been processed to bring out the incredible detail of the comet’s activity streaming away from the nucleus.

 

The previous two CometWatch entries were also acquired on 15 April and today’s image fits into the sequence nicely, captured just before midday spacecraft time, a little over two hours after Monday’s entry.

Under the viewing conditions at this time, the comet appears largely in shadow, with the ‘underside’ of the comet’s large lobe beautifully silhouetted against the background glow of activity that surrounds the nucleus.

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* Rosetta update: Two close flybys of an increasingly active comet – The Planetary Society –  Emily Lakdawalla gives a tour of the new images.

 

In the two months since I last checked up on the Rosetta mission, the comet has heated up, displaying more and more jet activity. Perihelion is now only four months away, and the pictures are just getting more and more dramatic with time.

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