Free Astronomy Magazine January-February 2019

17 JANUARY-FEBRUARY 2019 SPACE CHRONICLES extents of any such activity.” Evi- dence strongly suggests that be- neath its thin veneer of ice, Europa has an ocean of briny water in contact with a rocky core. Europa also has a comparatively young surface, only about 20 to 180 million years old, indicating that there are as-yet-unidentified thermal or geologic processes at work. Unlike optical tele- scopes, which can only detect sunlight re- flected by planetary bodies, radio and mil- limeter-wave tele- scopes like ALMA can detect the thermal “glow” naturally emit- ted by even relatively cold object in our Solar System, including com- ets, asteroids, and moons. At its warmest, Eu- ropa’s surface tempera- ture never rises above minus 160 degrees Cel- sius (minus 260 degrees Fahrenheit). “Studying Europa’s thermal properties pro- vides a unique means of understanding its surface,” said Bryan Butler, an astronomer at the National Radio Astronomy Observa- tory in Socorro, New Mexico, and coauthor on the paper. emission,” said Samantha Trumbo, a planetary scientist at the California Institute of Technology and lead au- thor on a paper published in T he As- trophysical Journal . “Since Europa is an ocean world with potential geo- logic activity, its surface tempera- tures are of great interest because they may constrain the locations and S eries of 4 images of the surface of Europa taken with ALMA, en- abling astronomers to create the first global thermal map of Jupiter’s icy moon. [ALMA (ESO/NAOJ/NRAO), S. Trumbo et al.] !