What event provided the final, definitive refutation of the canal theory based on direct visual evidence?

Answer

Mariner 4 flyby in 1965

The Mariner 4 mission in 1965 sent back the first close-up images, which revealed a barren, heavily cratered landscape showing no evidence of civilization or engineered networks.

What event provided the final, definitive refutation of the canal theory based on direct visual evidence?
MarsastronomyvegetationCanalsLowell