In 1610, thinking he had discovered two moons orbiting Saturn, Galileo composed a message:

ALTISSIMUM PLANETAM TERGEMINUM OBSERVAVI (“I have observed the most distant planet to have a triple form”)

… and sent it to Kepler as an anagram:

SMAISMRMILMEPOETALEUMIBUNENUGTTAUIRAS

Remarkably, Kepler managed to “solve” this as a message about Mars, not Saturn:

SALVE UMBISTENEUM GEMINATUM MARTIA PROLES (“Hail, twin companionship, children of Mars”)

The German astronomer had predicted that the Red Planet had two moons, and imagined that Galileo was confirming his belief.

There’s a message in this, somewhere.