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".
Así, o 27 de marzo do 1974, dous días antes de que a sonda Mariner 10 sobrevoase Mercurio, instrumentos na Terra comezaron a rexistrar incrementos nas cantidades de radiación ultravioleta na veciñanza de Mercurio, o cal, de acordo cun astrónomo, "esta non debería estar aí".