The Rosetta spacecraft is long gone, but we’re still getting some interesting science from the groundbreaking mission. Now, we’ve got a new look at a plume ejecting from the comet it orbited.
The burst of dust was spotted on Comet 67P/Churyumov-Gerasimenko on July 3, 2016 by the orbiting spacecraft. Above, you can see a remarkable image snapped by the spacecraft showing the event.
What’s even more amazing, though, is that Rosetta also flew through the plume. This meant it was able to use five of its instruments to study it directly. And the results show there’s still a lot about comets we don’t understand. These were published in a paper in the Monthly Notices of the Royal Astronomical Society.
“This plume was really special,” said Jessica Agarwal of the Max Planck Institute for Solar System Research in Göttingen, Germany, lead author of the paper, in a statement.
“We have great data from five different instruments on how the surface changed and on the ejected material because Rosetta was, by chance, flying through the plume and looking at the right part of the surface when it happened.”
The scientists found that the plume ejected dust at a rate of 18 kilograms (40 pounds) every second. The bright plume blew away from the comet like a fountain.
It originated from a wall 10 meters (33 feet) high around a circular dip in the surface of the comet. And it wasn’t just dust in the plume – Rosetta also detected tiny grains of water-ice, too.
While plumes have been seen before, this one was especially interesting because Rosetta was able to sample it at the same time. At first, scientists thought it was the result of ice evaporating in sunlight, but the measurements revealed something else.
Instead, scientists think an energetic process was taking place under the surface, which would explain why so much dust was thrown off. The exact cause, however, is a bit of a mystery. Some theories suggest pressurized gas bubbles rising underground may have been the cause, or even stores of ice reacting violently to sunlight.
“Energy must have been released from beneath the surface to power it,” said Agarwal. “There are evidently processes in comets that we do not yet fully understand.”
Rosetta’s mission came to an end on September 30, 2016 when the spacecraft was purposefully crashed into the comet's surface. There’s still plenty of science to sift through from the mission, though, which will hopefully tell us more about how comets work.