Astronomers are studying data collected by the Rosetta probe. Therefore, better understanding the factors responsible for the formation of sunrise jets on Comet 67P.

The sunrise jets are unique dust and gas jets. Comets emit them. The Max Planck Institute for Solar System Research (MPS) in Germany is leading a study, also published in the journal Nature Astronomy, which identifies the rugged, duck-shaped structure of the comet as the main cause of these jets.

Far from the Sun, comets are lifeless. When they move into the inner solar system, they become active. So, strands of gas and dust extend from the comet’s surface when a comet moves into the inner solar system. Thus, becomes bathed in sunlight. Thus, causing ice to melt and water vapor to envelope the orb.

The European Space Agency’s Rosetta spacecraft orbited and observed comet 67P/Churyumov-Gerasimenko from August 2014 to September 2016. The awesome probe captured more than 70,000 images. With its scientific camera system OSIRIS, the probe revealed both sudden eruptions of gas and dust, as well as more stable, prolonged jet-like emissions.

Investigating the Phenomenon

So, researchers from the OSIRIS team have now investigated the activity that occurs regularly every morning.

“When the Sun rises over a part of the comet, the surface along the terminator almost instantaneously becomes active,” first author Dr. Xian Shi from MPS describes. “The jets of gas and dust, which we then observe within the coma, are very reliable: they are found each morning in the same places and in a similar form,” she adds.

Scientists suggested that frost is the cause of this early morning activity. Each night, tiny droplets of ice crystalize on the comet’s surface, and when the Sun’s rays touch it, it vaporizes them.

“Outbursts can often be traced back to a small area on the surface where suddenly frozen water is exposed, for example, due to a landslide,” explains Dr. Holger Sierks from the MPS, OSIRIS Principal Investigator. “In the case of cometary activity at sunrise, this is different. The frost is distributed fairly evenly over the entire surface.”

This is the first time researchers learn that the unusual shape and jagged topography of the comet cause this phenomenon. They analyzed images at different observation geometries of the Hapi region located on the “neck” of the comet. So, through computer simulations, they were able to reproduce these images thus gaining a better understanding of the driving processes.

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Thumbnail image: Left: Shortly after sunrise, scientists can see impressive jets of gas and dust above the Hapi region on comet 67P/Churyumov-Gerasimenko. Right: Computer simulations reproduce these structures. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA