Detecting signs of water on comet surfaces

The Rosetta spacecraft, currently in a trawl around comet 67P / Churyumov - Gerasimenko, has detected 120 light spots on the comet surface with an area of ​​at least 2m.

Rosetta spacecraft finds signs of water on the surface of the comet

Many speckled water patches were discovered on the surface of a comet, according to observations from a European satellite.

The Rosetta spacecraft , currently in a trawl around comet 67P / Churyumov - Gerasimenko , has detected 120 light spots on the comet surface with an area of ​​at least 2m. While the composition of these light spots is still being considered, these points tend to lie in the area illuminated by the sun. The researchers also noticed that there were no significant changes in the light spots after a month of observation.

Antoine Pommerol, a physicist at the University of Bern, said: 'Ice water is the most accurate explanation for the appearance and nature of these light spots'.

Location of 6 different ice blocks on comet surface 67P / Churyumov - Gerasimenko

'At the time of observation, the comet is at a distance sufficient to the sun at which the rate of evaporation of water will be less than 1mm per hour, ' said Pommerol, who led the study of light spots. 'On the contrary, if the amount of carbon dioxide or carbon monoxide has been exposed, it will evaporate immediately if illuminated by the same amount of sunlight. Thus, we do not expect to see such tapes stable on the surface of comets'.

These bright spots are 10 times brighter than the average surface brightness of comets , measured by the Rosetta spacecraft. Sometimes they appear at the same time, sometimes they appear at the bottom of the pool. The team conjectures that when the brink is eroded or collapsed, material will be exposed beneath the dusty surface.

In other locations, light spots are observed alone. Scientists believe that these objects are lifted off the surface of the face when the comet movement is more active. These objects, however, do not move fast enough to escape the comet's gravity .

Close up of ice blocks of comets

Comets are often known to be rich in ice, based on the traces they leave behind. When comets approach the sun, the heat of the star warms the surface of the comet, causing the ice to melt. This process also releases the dust near the ice block. But not all dust disappears, making the comet surface darker as the dust returns to the surface.

It is not clear when the ice block formed, but there are two theories. The first hypothesis was that when 67P was near the Sun , 6.5 years ago, the comet's activity pushed ice cubes into its dark areas, protecting the comet from the sun. Another hypothesis, perhaps carbon monoxide and carbon dioxide under the surface, pushed ice blocks when comets moved.

The observations were published in Astronomy and Astrophysics, based on observations from the OSIRIS camera in late September, one month after Rosetta arrived at the comet.