The European Space Agency's Rosetta probe has caught Comet 67P displaying poor table manners, producing a cosmic "burp" of dust and gas caused by its ongoing warming as it approaches the sun.
The comet-hunting spacecraft caught the rare instance of a dust jet at the moment of its creation, ESA scientists said.
Four months away from its closest approach to the sun the comet has produced a number of such jets from its sun-facing side, but this latest jet was seen emanating from the dark side of the comet in what scientists are calling a valuable opportunity to gather new understanding of the comet's dynamics.
"This was a chance discovery," said Holger Sierks from the Max Planck Institute for Solar System Research in Germany.
"No one has ever witnessed the wake-up of a dust jet before. It is impossible to plan such an image," said Sierks, principle investigator for Rosetta's scientific imaging system known as OSIRIS.
Captured in two sequential images of the comet, the eruption was seen coming from its shaded underside, an area the scientists have dubbed Imhotep after the ancient Egyptian god of wisdom and medicine.
"We had a very lucky shot on 12 March. We took images just two minutes apart," OSIRIS team-member Carsten Güttler told a meeting European Geosciences Union General Assembly last week in Vienna.
"In the first image, at the bottom of the nucleus, you see nothing. In the second image, within two minutes and 10 seconds, a complete jet has formed," he said.
Scientists estimated the height of the jet in the image at around 3,000 feet, suggesting that in the two minutes between the images the jet was traveling at around 25 feet per second.
A jet on the comet's "night" side was unexpected, Güttler said, but might have been coming from a small cliff standing just tall enough to catch some sunlight but not visible to Rosetta's cameras.
"If that's the case, then we just have to have normal warming activity," he said. "If that's not the case, we have to find another mechanism."
The ESA has had to move Rosetta further away from the comet over the last month, to a distance of around 60 miles, as dust from a number of the comet's jets was confusing the star trackers the spacecraft uses to orient itself.
Rosetta arrived at the comet to begin its science studies of the space rock in August of last year after a 10-year voyage. Comet 67P is moving toward perihelion on Aug. 13, the closest point it will get to the sun, on its journey through the solar system.
