Juno spacecraft prepares for close encounter with icy moon Europa

NASA’s Juno spacecraft is about to give scientists their closest look at Jupiter’s frozen moon Europa in more than 22 years.

The mission will swoop to around 350 kilometres above Europa’s surface on 29 September, returning detailed images as well as data about the moon’s magnetic field and its icy crust.

The last time a spacecraft got similarly close to Europa was in January 2000 when NASA’s Galileo orbiter swung by at a distance of 351 kilometres.

“We’ve already completed all the preparations. We’re really excited. Everything is on target,” says Scott Bolton, the Juno mission’s principal investigator.

“Our flyby is rather unique. The part of Europa that we’re going to be able to see doesn’t have particularly high-resolution data on it from Galileo, so this’ll be the first time we’ve been able to see that [region] at very high resolution,” he says.

All of Juno’s scientific instruments will be capturing data during the rapid pass, says Bolton. Its main camera, JunoCam, will produce a handful of wide-field views while its navigation camera, known as the stellar reference unit, will be tasked with taking a single, very high-resolution picture of a small patch of Europa’s nightside, lit only by the scattered light from Jupiter’s cloud tops.

Researchers also hope to use the flyby to glean insights into Europa’s ice shell using Juno’s microwave radiometer. Bolton likens the instrument to a radar device, “except it’s passive, so we’re just looking at emission coming out [from Europa] as opposed to sending a signal in and watching it bounce off”, he says. The radiometer’s data could give scientists clues about the depth of the shell and may reveal if there are fractured regions or areas of liquid within the frozen crust.

The team will even look for signs of the water vapour plumes that studies have suggested emanate from Europa, though Bolton stresses that these features “would have to be going off at the right time in a way that we can see them”.