The Jovian moon of Europa is surrounded by plenty of mystery and lots of speculation. Slightly smaller than our own moon, it is composed largely of silicate rock with a tenuous exosphere of molecular oxygen and a possible iron core. The surface is predominantly made of ice and while it is checkered with streaks and fractures it is in fact one of the smoothest in the whole solar system. This smooth but variegated surface resembles images of sea ice as seen on Earth and has led many planetary scientists to believe that there is a vast subsurface ocean of liquid water below the frozen crust.
Tentative evidence for this ocean can be seen by looking at what has been termed ‘chaos terrain’, an area where some believe the subsurface ocean has melted through the icy exterior due to tidal up-welling. Other evidence can be found in the data that the Galileo probe obtained, showing that Europa has a weak magnetic field induced through Jupiter’s own, suggesting the presence of a conductive sub layer i.e an ocean of liquid saltwater .
If indeed there is an ocean under the frigid surface, then it is plausible to think that extraterrestrial life might exist, but what kind of life? This proposition hinges on one fact: the temperature of Europa’s ocean. While the moon may possess an internal energy source, it is insufficient to provide the necessary heat to help maintain biological processes. However, the orbital resonance between Jupiter, Io, Europa and Ganymede probably heats the interior of the moon through tidal flexing which would ensure that the ocean remained liquid. The energy from the tidal flexing could also possibly be released through hydrothermal vents much like the black and white smokers that are found on Earth’s ocean floor. Europa’s hydrothermal vents could provide the ideal conditions for a more modest ecosystem than those found around Earth’s vents but they would support a hot, nutrient rich environment in which micro organisms like anaerobes and archaea could potentially thrive.
The only way that we will know for sure what lies beneath Europa’s mysterious surface is by going there, and it looks like we’re going to get our chance. NASA and ESA announced near the end of last month that they were going to undertake a joint mission to launch two probes by the end of the next decade to study Jupiter and it’s four moons. Just what discoveries will be made about Europa is anyone’s guess, but they’re sure to be extremely exciting and very compelling.
