In what seems like a great stroke of luck, the Rosetta probe has captured data and images of a brilliant comet outburst, which astronomers think may be the aftermath of a landslide.
On February 19, as Rosetta trailed Comet 67P/Churyumov–Gerasimenko from about 22 miles, nine of the spacecraft’s instruments were pointed at the comet for coordinated monitoring. Suddenly, a cloud of gas and dust rose from the comet in an outburst. With its instruments in focus for the next few hours, Rosetta captured a series of images and data, transmitting them back to Earth within a couple days.
“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,” Matt Taylor, ESA’s Rosetta project scientist, said in a statement.
“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.”
When astronomers reviewed the data, they reconstructed a chain of events leading up to the outburst, which they now think may have been the result of a landslide. Outburst signals grew by a factor of one hundred. Ultraviolet signals from the Sun were reflected from the center of the outburst cloud. The probe was blasted by grains of dust.
“From Rosetta’s observations, we believe the outburst originated from a steep slope on the comet’s large lobe, in the Atum region,” said Eberhart Grün, lead author of a paper published accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.
“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 continued.
“We’ll continue to analyze the data, not only to dig into the details of this particular event, but also to see if it can help us better understand the many other outbursts witnessed over the course of the mission,” added Taylor. “It’s great to see the instrument teams working together on the important question of how cometary outbursts are triggered.”
This announcement comes just over a month before Rosetta is scheduled to meet its demise in a crash landing on the comet.