The search for life beyond Earth is a primary goal of NASA, and in our solar system ocean worlds such as Jupiter’s moon Europa are among the most promising targets. Europa has a global outer shell of ice which is likely to be tens of km thick – but also a lower mass meaning pressures and temperatures in the upper ocean below the shell may be similar to Earth’s polar oceans.

Natural earthquakes occur on faults ranging from 0 to 700 km beneath Earth's surface in different tectonic settings, such as along major subduction zones in Japan and the arc