YOU are entering an alien soundscape. The first thing you notice is a chorus of curious pings – or perhaps you’d call them chirps. Underneath their bright staccato is an almost ominous roar. And faintly, in the distance, could that be the whistle of a railway train?
In a few years, sounds like these might be proclaiming good news for life on Europa, the pale moon of Jupiter that may be one of the most hospitable spots in the solar system. Although its surface is an airless landscape of cracked ice, all the evidence says that beneath that bleak shell is a liquid water ocean stretching hundreds of kilometres down to the rocky mantle below. If life can thrive on Earth’s ocean floors, feeding on the chemicals that gush from the rocks, why not on Europa too?
NASA is already putting together a mission to this intriguing world. Europa Clipper should launch in the early 2020s, and when it arrives in orbit around Jupiter it will repeatedly swoop over the moon, picking up valuable magnetic and gravitational information about its structure. And there are tentative plans for a second mission that would land on Europa’s surface. According to a report published in February, the lander’s panoply of instruments should include a small seismometer – a simple device that would give scientists an ear on Europa’s inner workings.
This could enable them to learn more about its ice crust, work out the chemistry of the ocean and the rocks beneath, and perhaps pick up the music of active geysers on the surface and volcanoes erupting on the sea …