NASA sent its probe New Horizons on a flyby in 2015. It confirmed the tiny planet harbored an ocean beneath its thick, icy shell. Pluto was always in a tough spot when it came to being a planet.

“New Horizons shattered a major paradigm of planetary science,” says Alan Stern, the mission’s principal investigator. “Pluto turns out to have as much complexity as Mars or Earth, so much so that I ...

In this series of old family photos, follow the trajectory of my father's remarkable career, which, in its way, began and ended at Pluto. Or will end, 'round about the year 2015.—Alden Tombaugh ...

Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. A huge heart-shaped ...

New Horizons Unveils Pluto’s True Face The watershed moment in Pluto’s exploration came in July 2015, when NASA’s New Horizons spacecraft flew by the dwarf planet. After a nine-year journey ...

This story appears in the July 2015 issue of National Geographic magazine. Small, cold, and absurdly far away, Pluto has always been selfish with its secrets. Since its discovery in 1930 ...

NASA's New Horizons spacecraft conducted the first and only flyby of the Pluto system, culminating at the closest approach of that distant world in July 2015. Sailing onward, the probe carried out ...

An curved arrow pointing right. NASA's New Horizons spacecraft took us to Pluto for the first time in July 2015. Scientists are astonished by the incredible features they've observed on the dwarf ...

An curved arrow pointing right. After launching off of Earth 9 years ago, NASA's New Horizons spacecraft has passed Pluto and sent back the most complex picture of its surface so far. Video ...

Pluto is too far away from Earth to be seen with ... That was until NASA's 'New Horizons' probe arrived in 2015 and transformed our understanding of this distant, enigmatic body.

This high-resolution image captured by NASA's New Horizons spacecraft combines blue, red and infrared images to show a bright expanse on Pluto known ... world in July 2015. Late last year, a ...