CAPE CANAVERAL, Fla. — Come Tuesday, Clyde Tombaugh will pass within 7,800 miles of the icy world he discovered 85 years ago.

His ashes are flying on NASA’s New Horizons spacecraft on humanity’s first journey to Pluto.

Tombaugh’s widow and two children offered up an ounce of his ashes for the journey to Pluto. The ashes are in a 2-inch aluminum capsule inscribed with these words:

“Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system’s ‘third zone.’ Adelle and Muron’s boy, Patricia’s husband, Annette and Alden’s father, astronomer, teacher, punster, and friend: Clyde Tombaugh (1906-1997)”

Annette Tombaugh-Sitze and her younger brother Alden, now in their 70s, plan to be at the flight operation base at Johns Hopkins University’s Applied Physics Laboratory in Laurel, Maryland, for Tuesday’s historic encounter.

“I think my dad would be thrilled with the New Horizons. I mean, who wouldn’t be?” Annette says online. “When he looked at Pluto, it was just a speck of light.”