Post contributed by Dr Candice J. Hansen, Planetary Science Institute, USA

On the 29th of September 2022 the Juno spacecraft, in orbit around Jupiter, made a close pass by Jupiter’s icy moon Europa (Image 1). The spacecraft approached from Europa’s night side, passed the terminator (day-night boundary), and departed on the day side, coming within ~350 km of the surface.  Juno’s visible color imager, JunoCam, snapped 4 images of Europa as the spacecraft sped by at a speed of 23.6 km/sec on its way to its closest approach to Jupiter.  In an elliptical polar orbit, this was the only opportunity in the mission for Juno to get close to this moon of Jupiter and the first time since the Galileo mission ended in 2003 that any spacecraft has flown so close. 

Image 1.  The first image taken by JunoCam is centered on the subjovian hemisphere, extending to ~60 deg north and south.  This was the highest resolution image acquired. Image data: NASA/JPL-Caltech/SwRI/MSSS. Image processing: Brian Swift © CC BY.

Europa is categorized as an “ocean world” with a solid ice surface over a liquid water subsurface layer.  Europa is crisscrossed by numerous cracks, bands, ridges and troughs (lineaments) that record the tidal stress the moon experiences arising from the gravitational pull of Jupiter and its other moons. JunoCam’s image reveals numerous pits along the terminator.  The almost complete lack of craters tells us that geologically this icy surface is very young, resurfaced by lineament formation due to tidal flexing.  Callanish crater, one of the few imaged by JunoCam, is the circular feature visible in the lower right of Image 1.