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Watch a Comet Outburst from the Rosetta Orbiter’s Perspective

“Catching an event like this was pure luck.”

by Becky Ferreira
Aug 25 2016, 6:04pm

February 19 comet outburst. Image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The Rosetta spacecraft is living out its final days at Comet 67P/Churyumov–Gerasimenko. Scheduled to crash into the comet on September 30, the orbiter will finally rejoin its longtime companion, the recently deceased Philae lander (RIP, sweet prince).

But though its days are numbered, Rosetta is still churning out spectacular imagery and data like a boss, including newly released pictures of a powerful outburst of gas and dust released by an avalanche on the comet's surface. These eruptions are extremely capricious, so it's rare for them to be observed at all, let alone from only 35 kilometers (22 miles) away.

"Over the last year, Rosetta has shown that although activity can be prolonged, when it comes to outbursts, the timing is highly unpredictable, so catching an event like this was pure luck," said Matt Taylor, ESA's Rosetta project scientist, in a statement.

The majority of Rosetta's instruments recorded the outburst. Image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; all data from Grün et al (2016)

For months, researchers led by planetary scientist Eberhard Grün of the Max Planck Institute for Nuclear Physics mined this comprehensive data set for clues about the origins, dynamics, and scale of the outburst.

The team's findings will be published in a forthcoming issue of the Monthly Notices of the Royal Astronomical Society, but the short version is that eruption was likely sparked by a landslide along the steep slopes of the comet's Atum region, caused by sudden exposure to sunlight after a long period in shadow.

Location of the outburst. Image: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0

As ice rapidly sublimated into gas, Rosetta picked up a spike in temperature of 30℃ and a sixfold increase in ultraviolet brightness over the course of several hours. This prompted outgassing that weakened surface integrity and generated the landslide and geyser-like plume of material that followed it.

Rosetta recorded the event with its cameras, dust collectors, gas analyzers, and temperature sensors. Even the orbiter's star trackers (navigational aids that help orient Rosetta in space) detected an uptick in reflected light off the scattered detritus of the outburst.

"It's great to see the instrument teams working together on the important question of how cometary outbursts are triggered," Taylor said.

Even as it faces its impending doom, Rosetta continues to be a prolific scientific dynamo. We'll miss you, old girl.

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