Bern, Switzerland – An international team of astrophysicists led by the University of Bern and members of the National Center of Competence in Research (NCCR) PlanetS has unraveled the mystery behind the heart-shaped feature on Pluto’s surface. Through numerical simulations, the team managed to replicate the unique shape, attributing it to a colossal oblique-angle impact.
Since NASA’s New Horizons mission discovered the heart-shaped structure on Pluto in 2015, scientists have been puzzled by its distinctive shape, geological composition, and elevation. Researchers from the University of Bern and the University of Arizona conducted numerical simulations to delve into the origins of Sputnik Planitia, the western teardrop-shaped part of Pluto’s heart surface feature.
The research unveiled that a catastrophic collision with a planetary body around 400 miles in diameter, roughly the size of Arizona, shaped Sputnik Planitia in Pluto’s early history. Published in Nature Astronomy, the team’s findings challenged preconceived notions about Pluto’s internal structure, debunking the existence of a subsurface ocean.
Lead author Harry Ballantyne, a research associate at Bern, highlighted the significance of Sputnik Planitia in shedding light on the earliest periods of Pluto’s evolution. The discovery opens up new possibilities for understanding the evolution of not just Pluto but also other objects in the Kuiper Belt.
The heart-shaped feature, also known as the Tombaugh Regio, captivated the public’s attention for its high-albedo material that reflects more light, giving it a distinctive appearance. Covering an area equivalent to a quarter of Europe or the United States, Sputnik Planitia stands out for being significantly lower in elevation compared to the rest of Pluto’s surface.
The study revealed that nitrogen ice predominantly fills Sputnik Planitia, accumulating swiftly after the impact due to its lower altitude. The eastern part of the heart also features a layer of nitrogen ice, the origins of which remain a mystery but are likely linked to Sputnik Planitia.
According to Martin Jutzi of the University of Bern, the elongated shape and equatorial location of Sputnik Planitia point to an oblique collision rather than a direct impact. The team’s simulations underscore the importance of the impactor’s composition, velocity, and angle in shaping the unique features observed on Pluto.
The study not only provides new insights into Pluto’s internal structure but also challenges previous theories about the migration of Sputnik Planitia over time. By excavating all of Pluto’s primordial mantle, the impact created a local mass excess that explains the feature’s migration toward the equator without the need for a subsurface ocean. This novel hypothesis opens up new avenues for understanding the origin and evolution of Pluto.