2015 has been an immensely successful year for space in pop culture, with news topics ranging from the breakout hit of The Martian to the discovery of liquid water on Mars. But the event that perhaps best captured social media’s “heart” this year was New Horizons’ Pluto flyby.

The flyby was the culmination of a three-billion mile, decades-long NASA mission to explore the last planet in our solar system (and yes, Pluto still was classified as a planet when the probe was launched in 2006). For the project to be considered a success, the New Horizons probe would have to travel for almost ten years through the vastness of space, where even a single unexpected asteroid hit or computer glitch could irreversibly destroy the $720 million project. Consequently, tensions ran high in the mission control room when New Horizons was scheduled to file its report from radio silence.

On July 14, NASA’s hard work was rewarded with a quick status update from New Horizons. Not only had the probe survived, but it would also be sending back reams of data from Pluto’s surface. Pluto, once only seen as a fuzzy gray blur, would now greet Earth with a heart, revealing a richly complex world never explored before.

Upon confirmation of New Horizon’s success, cheers erupted in the Johns Hopkins University Applied Physics Laboratory, prompting a huge wave of celebration to break out over social media. Two highlights included President Obama’s tweet, which broke 21,000 retweets, and Stephen Colbert’s interview with Neil deGrasse Tyson regarding the discovery, which reached a million views on the same day.

The New Horizon’s mission isn’t over yet. Until late 2016, the probe will continue to send even higher-resolution images and data from Pluto’s surface and its moons, and potential flybys of other objects in the Kuiper Belt may still be planned.

Coincidentally, the New Horizons’ flyby also marked the 50th anniversary of the first Mars flyby by NASA’s Mariner 4 on July 14, 1965: a full-circle “capstone,” as mission project manager Glen Fountain stated, of humanity’s “initial reconnaissance of our solar system – giving us a new perspective about how we as human beings fit into the universe.”