Charles (“Chick”) Capen’s serendipitous role in the 1971 Mariner 9 mission is not widely known. 

Charles "Chick" Capen (1926-1986) worked with the Mariner missions at JPL's Table Mountain Observatory (1962-69) and at Lowell Observatory (1969-83)

Capen's drawing of Mars a few months before the 1971 dust storm begins

His observation early in 1971 of a brief dust storm on Mars, coupled with his dedicated study of the Martian atmosphere and past weather occurrences on the red planet, led him to speculate about a larger storm primed to form just about the time Mariner 9 would arrive and go into Martian orbit.

Capen published his prediction in an amateur astronomy newsletter, The Strolling Astronomer, nine months before the larger storm began. He even added a Lowellian touch to his article, suggesting that the Martians may engineer such storms in order to hide their existence from nosy Earthlings.

Ever the Lowell wanna-be, Capen donned a beret and had himself photographed at the historic Lowell Observatory telescope in the same pose used by Lowell himself. Click to compare. Click again to go back.

Apparently none of his colleagues at Lowell Observatory took him seriously enough to pass this information along to scientists monitoring the Mariner 9 mission at JPL – it was hindsight that proved him right. The first official acknowledgement by NASA appeared in a post-mission report:

“In retrospect, team members realized that a major dust storm should not have been totally unexpected.” 

Mariner 9 photograph of Mars made during final approach shows planet-wide dust storm in progress. The darker areas represent the tallest peaks on the planet – everything else on the surface is obscured by the storm.

Capen’s uncanny prediction is among his papers now housed at the Roper Mountain Science Center in Greenville, South Carolina.