The search for extraterrestrial life keeps getting more complicated. When NASA’s New Horizons probe passed by Pluto in 2015, it beamed back incredible images of a heart-shaped region on the dwarf planet’s surface. But more important than the heart may be what appears to lie beneath it: a vast underground ocean of slushy water, according to researchers who have been analyzing the mission data. Watch the video above to understand how exactly scientists found evidence of the giant hidden body of saltwater, and get a sense of what it could mean for the ongoing search for life beyond regions that have been the focus of our search.