The alleged findings came from NASA’s Messenger Spacecraft, which has been in orbit around Mercury since 2011.

Theories that Mercury – also known as the Swift Planet – could potentially contain forms of water were already being discussed back in 1992. Back then, Earth-based telescopes had picked up “bright areas” in and around the planet’s polar regions.

Alternative explanations were put forward to account for the bright areas, but Messenger provided enough evidence for water ice to exist on the planet closest to our sun.