Jupiter’s Moon, Europa, Hides A Chilly Secret

Europa's frozen surface harbors one region that is colder than all the rest.

Jupiter's moon Europa
Brady Barrineau / Shutterstock

Europa's frozen surface harbors one region that is colder than all the rest.

A new study on Europa, the smallest of Jupiter’s four Galilean moons, revealed that the icy world has strange variations in temperature. In fact, it turns out that one particular spot on Europa’s frozen surface is actually a lot colder than the rest of its ice-coated crust, reports Space.

Europa’s chilly secret was uncovered after a small team of researchers, led by Samantha Trumbo of the California Institute of Technology in Pasadena, scoured the Galilean moon with the help of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.

Looking at Europa from Earth, the scientists captured four daytime thermal images of the icy moon. The team then used the ALMA data to map out the temperature of Europa’s entire surface, with an accuracy down to 125 miles (200 kilometers).

“Together, these images comprise the first spatially resolved thermal dataset with complete coverage of Europa’s surface,” the authors wrote in their paper, available on the preprint server arXiv.

In order to further investigate the thermal properties of Europa’s surface, the scientists compared their findings with a global thermal model of the moon — based on observations made by NASA’s Voyager 2 spacecraft, which orbited Jupiter’s system in 1979.

Their efforts led to the discovery of an “anomalously cold” spot in the moon’s northern hemisphere, visible in two of the ALMA images, the team shows in the study.

“From these maps, we identify a region of either particularly high thermal inertia or low emissivity near 90 degrees West and 23 degrees North,” reads the paper, which has been accepted for publication by the Astronomical Journal.

While the researchers came across other variations in temperature as well, those discrepancies could be explained by the way the sunlight was reflected on the moon’s surface, at different angles and across all the wavelengths of the spectrum — a phenomenon known as bolometric albedo.

Europa has one of the most reflective surfaces in the solar system, thanks to its ice coating, notes Space.

But the cold spot discovered in Europa’s northern hemisphere was something else altogether.

This “weird” cold spot on Europa’s icy surface, as Space describes it, remained visible at different times of the day and didn’t seem to be connected to any notable geological features that could be causing this “local coldness.”

In a remarkable twist of events, Trumbo’s team uncovered a second region with an odd temperature discrepancy, spotted all the way on the other side of the moon. Located inside the Pwyll crater, a 28-mile wide (45 kilometers) impact crater thought to be Europa’s youngest feature, this area was “unusually warm,” states Space.

However, while the nature of the cold spot remained unexplained, the scientists deemed the warm spot at Pwyll crater less puzzling, considering that craters on other moons, such as that of Earth, have been shown to retain more heat than the crust around them.

“Curiously, with the exception of Pwyll crater, our analysis has not identified any clear correlations between the potential thermal inertia values and geologic or compositional units,” the authors concluded in their paper.