1.8 Ice penetrators
It would be very difficult and expensive to land a spacecraft on one of the airless icy moons. The costs would escalate if the whole craft had to be sufficiently sterile to meet the most stringent planetary protection criteria. A neat solution would be to send down a ‘penetrator’, which would be a small projectile to hit the ice at a speed of about 1 km s−1. It would come to rest 1 metre or so below the surface and could be equipped with miniaturised instruments capable of surviving the extremely rapid deceleration upon impact. Because of its small size it could carry only a small battery and might operate for only a few days, but nevertheless it would offer major advances in knowledge. It would also be easier to sterilise than the whole spacecraft.
This short video (which has no audio commentary) is an animation of a ‘penetrator’ designed in the UK by the aerospace company Astrium. What measurements would you most like it to make when embedded in the ice of a moon such as Europa?