On July 29, with ESA's Rosetta spacecraft in orbital tow, the 2.5-mile (4-kilometer) -long Comet 67P/Churyumov-Gerasimenko fired its brightest jet yet since Rosetta's arrival just over a full year ago, on Aug. 6, 2014.
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Most of the images of 67P showing jets and outgassing activity released over the past few months have been edited to boost jet visibility, but this recent flare-up needed no such enhancement. Rosetta's high-resolution OSIRIS camera had no problem capturing the brief show from 115 miles (186 km) away.
Sudden outbursts of material have been witnessed before by Rosetta, like this one on March 12. But this has by far been the boldest.
"This is the brightest jet we've seen so far," said Carsten Güttler, OSIRIS team member at the Max Planck Institute for Solar System Research in Göttingen, Germany. "Usually, the jets are quite faint compared to the nucleus and we need to stretch the contrast of the images to make them visible - but this one is brighter than the nucleus."
ANALYSIS: Rosetta's Comet Fires its Jets
As comets approach the sun their surfaces heat up from increasing solar radiation. This thaws frozen material trapped beneath the surface, which sublimates (turns from solid ice straight to gas) and bursts outwards, shooting icy, reflective material into space at high velocity.