Rosetta Watches A Rare Outburst From Comet 67P

The recently released images from the European Space Agency (ESA) show a violent torrent of gas and dust emanating from Comet 67P/Churyumov-Gerasimenko from a distance of around 35 kilometers (21 miles) away.

“By happy coincidence, we were pointing the majority of instruments at the comet at this time, and having these simultaneous measurements provides us with the most complete set of data on an outburst ever collected,” Matt Taylor, Rosetta project scientist, said in a statement.

“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,” he said.

A full breakdown of the outburst will be found in an upcoming edition of the journal Monthly Notices of the Royal Astronomical Society (MNRAS).

^{A GIF of the outburst on February 19, 2016. ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA}

Rosetta’s OSIRIS wide-angle camera picked up the “strong brightening” of the comet at 9:40am GMT on February 19, although the data has only just been released. Between 10am and 11am GMT, Rosetta recorded the ultraviolet brightness increase by six times, and the temperature of the surrounding gas rose by 30°C (54°F).

By analyzing all this information, along with data received from Rosetta’s six other instruments, the scientists back home on Earth believe they have found the source of the outburst.

“From Rosetta’s observations, we believe the outburst originated from a steep slope on the comet’s large lobe, in the Atum region,” explained Eberhard Grün of the Max Planck Institute for Nuclear Physics in Heidelberg, and lead author of the MNRAS paper.

^{Location of the outburst on Comet 67P/Churyumov-Gerasimenko. ESA/Rosetta/NavCam – CC BY-SA IGO 3.0}

“Combining the evidence from the OSIRIS images with the long duration of the GIADA [Grain Impact Analyser and Dust Accumulator] dust impact phase leads us to believe that the dust cone was very broad. As a result, we think the outburst must have been triggered by a landslide at the surface, rather than a more focused jet bringing fresh material up from within the interior, for example,” he added.

As previously mentioned, these are the final days for Rosetta. On September 30, it will end its mission by landing on the comet it's been working towards understanding for 12 years. From here, it will drift away from both Earth and the Sun, towards the orbit of Jupiter, where it will eventually “die” from a lack of solar power.

^{Evolution of a comet outburst. Hi-Res version available here. ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; all data from Grün et al (2016)}