ESA’s JUICE mission will help us better understand whether Jupiter’s icy moons are habitable. But we need to be open to their unexpected secrets, says principal investigator Michele Dougherty.

DECADES-LONG space missions are planned down to the second. The exact routes the craft travel through the solar system are meticulously mapped out, based on years of design and testing. If you want to deviate from these, you had better have a compelling reason.

But that is precisely what happened in 2005, during NASA’s Cassini mission to Saturn. Upon seeing something unusual, Michele Dougherty, a physicist at Imperial College London, asked for a closer look at one of Saturn’s moons, Enceladus. What the probe saw was incredible: massive plumes of water vapour erupting from cracks at the moon’s south pole.

Today, with Cassini long gone, Dougherty is looking forward to making further unusual discoveries, as the principal investigator on the Jupiter Icy Moons Explorer (JUICE) mission operated by the European Space Agency (ESA). This project, which launched in April, has a clear goal: to better understand whether Jupiter’s moons have the right ingredients to harbour life.

Jupiter has between 80 and 95 moons, but JUICE will focus on three of its four biggest. It will fly by Europa, Ganymede – the largest moon in the solar system – and Callisto, before going into orbit around Ganymede.

Dougherty tells New Scientist why we need to be open to the unexpected secrets that could lurk beneath the icy exteriors of these worlds and how she plans to reveal them.