Massive shifts on Jupiter's moon Europa among recent events to fracture its icy shell, study claims

The most popular of Jupiter's 79 known moons, the icy Europa, has numerous fractures on its surface. New research shows that these fractures, and other features on its surface, could have formed from dramatic shifts of its icy shell over millions of years.Some of these fractures on Europa’s ice shell – each of them hundreds of kilometres long, and 10-20 km wide – are found parallel to one another and in concentric circles around the moon's poles. These fissures also stretched far and wide, across different kinds of terrain.Adding evidence to the theory that there was once an ocean below the surface of Europa, the findings also imply that the geologic history of the moon as researchers know it, needs to be re-examined. The findings strengthen the argument for a phenomenon called 'True polar wander' on Europa, where the true location of the North and South Poles change, or "wander", due to the moon's geological activity.Scientists think this "wandering" is among the most recent geologic events that Europa is experiencing.[caption id="attachment_7685631" align="alignnone" width="1280"]

In this image captured during the Galileo mission in the 1990s, Europa's icy surface and the long fissures cutting through them are evident. Image courtesy: NASA[/caption]"Our key finding is that the fractures associated with true polar wander on Europa cross-cut all terrains. This means that the true polar wander event is very young and that the ice shell and all features formed on it have moved more than 70° of latitude from where they first formed," a statement in the research paper reads.If proven true that the shifts and fissures were recent, researchers predict that any asymmetry in craters and thickness of the ice shell measured by satellite data of the moon [particularly from the Europa Clipper mission] might be potentially inaccurate.The research team was led by Dr Paul Schenk, a senior staff scientist at the Lunar and Planetary Institute (LPI) under the Universities Space Research Association. True polar wander caused the Europa's spin axis to reorient, which led to the circular patterns in fissures, he explained. This process would only be possible if the icy shell is separated from the rocky core of the planet, similar to the tectonic plates here on Earth that are subject to shifts and earthquake fault lines.The study was published in the journal Geophysical Research Letters on 29 July.