Under the icy thickness of the moon Europa, scientists believe that a strange snow could be forming. This underwater snow would fall “upside down” into the ocean of this moon of Jupiter. This remains to be verified.
Europa, the sixth moon closest to the planet Jupiter, is not just a scoop of ice cream. Under its icy and smooth crust, about ten kilometers thick, scientists believe that it shelters an ocean of liquid water (never seen directly). It is at the level of this ocean that researchers now believe that there could be another fascinating phenomenon: underwater snow, which falls “upside down”, from the bottom upwards.
This amazing hypothesis was evoked by the University of Texas at Austin, August 15, 2022. The idea is developed in a study published in Astrobiology (a pre-published version of the study is available). It should be noted that here, scientists have not studied this snow directly on Europa. They analyzed how underwater snow forms under the ice sheets (large glaciers) of Antarctica. They deduce that it could also exist on Europe.
« We focus our study on land ice formed in low temperature gradient environments [ndlr, où la température varie peu avec la profondeur]which corresponds to the conditions expected at the interfaces between the ice and the ocean of Europe write the researchers in their study. This terrestrial environment is considered to have conditions comparable to those which must exist on Europe (temperature, pressure and salinity of the ocean).
Is there snow in Europe? You have to find out
If underwater snow is found on Europa, scientists think it could influence how its ice shell formed. One of the consequences would be that this layer of ice is less salty than we imagine. However, such information is essential for the future exploration of this moon. NASA is currently developing the Clipper mission, with the goal of delivering this probe to Jupiter’s moon in 2030. The spacecraft will be equipped with radar to observe below the icy crust and help determine if the ocean could support life. But, if salt is trapped in this ice, it must be known, because this salt would potentially disturb the images obtained. It is therefore necessary to know what the ice is made of, in order to correctly interpret the data.
The authors studied the two ways in which the water freezes under the Antarctic ice sheets: “freezing” ice and frazil (ice fragments floating on the surface of the water). The former forms directly under the glacier, while frazil forms in seawater and then moves uphill, much like snow falling the wrong way. Both are less salty than seawater, especially frazil. According to the authors’ calculations, frazil could be quite frequent in Europe.
However, this scenario will have to be verified directly on site, but the scientists are enthusiastic. Better understanding the properties and structure of the ice on this moon is crucial if we ever want to know if life could exist in the ocean of Europe.