As Comet 67P approaches perihelion-- its closest approach to the sun during its long 6.5-year loop around the solar system, its outgassing has been increasing, leading to its "breaking wind" in rather spectacular fashion.
The Rosetta spacecraft, keeping close company as the comet nears perihelion set for Thursday, captured dramatic images on July 29 of a jet of gas and dust spewing out dramatically from the comet's surface, warmed by its approach to the sun.
The European Space Agency (ESA) described the event snapped by its spacecraft's cameras as "one dramatic outburst event proving so powerful that it even pushed away the incoming solar wind."
Captured by Rosetta's high-resolution OSIRIS camera, the outgassing jet is by far the most dramatic yet seen, scientists say, and needed no photo enhancement as has been the case with some earlier, fainter ones.
"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 comet's nucleus and we need to stretch the contrast of the images to make them visible, but this one is brighter than the nucleus."
Three images of the comet were taken before, during and after the outburst at 18-minute intervals. "The jet of dust and gas in not seen in the first image, is at its height in the second, and has mostly faded away by the third," say the ESA scientists who estimated material in the jet was moving at least 32 feet per second, and perhaps even faster.
The jets occur as sunlight causes the comet's frozen ices, previously protected by shadows to turn to directly from solid to gas in a phenomenon known as sublimation, blowing away from the surface and carrying dust from there into space.
With perihelion close but not reached yet, there could be even more such significant jet activities as temperatures increase, ESA scientists say.
Rosetta has been orbiting the comet for the last year, arriving there after a long journey from launch in 2004. It placed a small lander, Philae, on the comet's surface and both spacecrafts have been providing astronomers with valuable information about the comet's makeup and its behavior.
After it reaches its closest point to the sun, around 115 million miles, it will begin its return trip outward to beyond the orbit of Jupiter.
