Back in 2015, NASA’s New Horizons spacecraft zoomed past Pluto making its way towards the Oort cloud. As it passed next to the dwarf planet, it turned its cameras towards Pluto and snapped a series of stunning images of the dwarf planet’s heart-shaped geography. On its way towards the outermost parts of the solar system, the spacecraft managed to take a peek at Pluto’s “Dark Side.”

Images of the dark side of Pluto have revealed striking geological features that have not helped scientists better understand Pluto and what the dwarf planet is like in its interior. One of the images New Horizons snapped shows black ripples of rock that happen to be at the exact opposite side of Sputnik Planitia, the basin that forms the left lobe of Pluto’s heart. These ripples offer new evidence that the dwarf planet Pluto may have a 93-mile-thick ocean (150 kilometers) located between its crust and its core.

The findings, the result of analysis of data submitted by the New Horizons spacecraft after its Pluto flyby in 2015, were presented at the Lunar and Planetary Science Conference, a virtual conference that took place online, in response to the Coronavirus pandemic.

The impact that carved the Sputnik Planitia basin probably sent shock waves around Pluto that shattered the landscape on the other side, according to results that are yet to be peer-reviewed, first published in October.

Signs of a similar event on Mercury are also evident where a 1,528-kilometer-long impact crater lies exactly on the opposite side of the planet from a region of chaotic geography, Scientific American reports.

“If the impact was large enough, the planet itself can act as a lens and focus the wave energy at the exact opposite point on the planet from the impact,” Adeene Denton, a planetary scientist at Purdue University told Science News.

So how do we know there’s actually an ocean hiding within our solar system’s favorite (ex)planet? When a cosmic body–say 450 kilometers (250miles) wide–impacts a dwarf planet like Pluto, it produced a massive shock wave followed by something called a stress wave. These waves travel across the surface of the alien world, they also happen to cross through the center. However, waves travel at different speeds through different materials: They would travel faster through the dwarf planet’s dense core, slower through an icy crust, and much lower through a liquid ocean.

IN other words, Pluto may have controlled how the shock waves caused by the impact traveled through the dwarf planet. And precisely there is where experts should look for evidence for an ocean. By analyzing the cracks in the surface ice, scientists can obtain crucial data about the thickness of the proposed ocean and the core’s chemical makeup.

To understand more, Danton and her colleagues ran a series of computer simulations of an impact and looked for clues.

The model which is still in early development offers additional, growing evidence that suggests there could be water on (inside) Pluto. Another study four years ago analyzed surface fissures on Pluto, suggesting that an ocean beneath the surface may be a possible explanation. A research paper published in 2019 suggests that the impact at Sputnik Planitia may have made its way through the dwarf planet’s cruise and caused the ocean to resurface. Once there, it froze, and it caused Pluto to tip into its current orientation.

“To explain the lines seen on the dwarf planet, not only would Pluto need a large ocean, 150 kilometers or more in thickness, but the core must contain minerals, such as serpentine, that form through interactions between rock and water,” Danton revealed to Science news.