Scientists, looking at data from the Rosetta spacecraft, orbiting Comet 67P/Churyumov-Gerasimenko since last year, have found a region on surface of the comet where water ice comes out and vanishes in sync with day, or rotation period of the comet.

Their findings have been published in the journal Nature on September 23, 2015.

Fabrizio Capaccioni, principal investigator for a key instrument on Rosetta named the Visible, InfraRed and Thermal Imaging Spectrometer (VIRTIS), said, "We suspected such a water-ice cycle might be at play at comets, on the basis of theoretical models and previous observations of other comets. But now, thanks to Rosetta's extensive monitoring at 67P/Churyumov-Gerasimenko, we finally have observational proof".

Maria Cristina De Sanctis, lead author of the study, said that now, they know about the mechanism that replenishes the comet's surface with fresh ice at each rotation and this helps keep the comet 'alive'.

The team looked at VIRTIS data that was taken last year in September, soon following Rosetta started orbiting the comet and almost a year away from August, 2015 perihelion of 67P's. They focused on a one square-kilometer region on 'neck', which is the narrow part of the comet between the two larger lobes, of the comet.

During that time, the comet was nearly 300 million miles away from the sun, and the neck is thought to be among the most active areas of that time. Comets have a day-night cycle, just like our planet and just like all bodies in Earth's solar system.