On March 27, 1974, two days before Mariner 10 made its flyby of Mercury, instruments began registering large amounts of ultraviolet radiation in the vicinity of Mercury that, according to one astronomer, "had no right to be there".
Den 27 mars 1974, två dagar före Mariner 10 passerade planeten, började instrumenten registrera stora mängder ultraviolett strålning som enligt en astronom "inte skulle varit där".