Asked by: Adam Waller, Sheffield
This prize belongs to Enceladus, a small moon of Saturn. Recent measurements indicate that it reflects about 90 per cent of the incident light from the Sun, making it brighter than freshly fallen snow! The reason for this high reflectivity lies in the constant replenishment of the surface with ice particles vented from hydrothermal geysers.
This implies that Enceladus has a subsurface liquid ocean that is heated by gravitational forces. This, combined with the presence of nitrogen and simple organic molecules, makes Enceladus a candidate for harbouring simple life forms. Several missions have been proposed to investigate this possibility.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.