Back in July 2015, NASA's New Horizons spacecraft made a flyby Pluto on it's way to the Kuiper belt. The flyby gave us that now iconic image of Pluto and its prominent heart-shaped feature which scientists believe is a vast ocean.

The farthest planet in our solar system lies 3 billion miles away from Earth. The New Horizons was launched in Cape Canaveral, Florida back in 2006 and flew by Pluto on July 14, 2015. The spacecraft spent the next 3 days gathering data from the dwarf planet.

Data from the New Horizons flyby were used for the study that appeared in the journal Nature. These data included pictures and measurements of surface features.

Scientists have reason to believe that Tombaugh Regio, the location of our famous heart, is a viscous liquid ocean hidden behind the surface. The 325,000 square mile heart-shaped basin is made up of frozen nitrogen.

One of the researchers, MIT's Prof. Richard Binzel said that the size of Sputnik Planitia can be compared proportionally to the largest basins of Mars and Mercury and is thought to be created by an impact.

NASA's Jet Propulsion Laboratory (JPL) planetary scientist Bob Pappalardo said they believe that the crater is from a comet strike that happened 4 billion years ago and that the crash site was originally 4 miles deep.

The impact has now recessed and is filled with the slushy waters of Pluto. According to Steven Vance, astrobiologist and geophysicist from NASA's JPL, these slushy waters are made up of methanol and ethanol alcohols, methane and ethane hydrocarbons and complex molecules of carbon, nitrogen, hydrogen and oxygen. These chemicals also act as an antifreezing agent that makes the ocean a slushy sub-freezing liquid.

Pluto's subterranean ocean could also explain its interaction with one of its moons, Charon. The moon is aligned and locked in that orientation opposite Sputnik Planitia. This gravitational anomaly lacked explanation except a subsurface ocean that will cause a gravitational tug-of-war between the two.