How Pluto got its heart

 The mystery of how Pluto got a giant heart-shaped feature on its surface has finally been solved by an international team of astrophysicists led by the University of Bern and members of the National Center of Competence in Research (NCCR) PlanetS. The team is the first to successfully reproduce the unusual shape with numerical simulations, attributing it to a giant and slow oblique-angle impact.

Ever since the cameras of NASA's New Horizons mission discovered a large heart-shaped structure on the surface of the dwarf planet Pluto in 2015, this "heart" has puzzled scientists because of its unique shape, geological composition, and elevation. A team of scientists from the University of Bern, including several members of the NCCR PlanetS, and the University of Arizona in Tucson have used numerical simulations to investigate the origins of Sputnik Planitia, the western teardrop-shaped part of Pluto's "heart" surface feature. According to their research, Pluto's early history was marked by a cataclysmic event that formed Sputnik Planitia: a collision with a planetary body about 700 km in diameter, roughly twice the size of Switzerland from east to west. The team's findings, which were recently published in Nature Astronomy, also suggest that the inner structure of Pluto is different from what was previously assumed, indicating that there is no subsurface ocean.

A divided heart

The "heart," also known as the Tombaugh Regio, captured the public's attention immediately upon its discovery. But it also immediately caught the interest of scientists because it is covered in a high-albedo material that reflects more light than its surroundings, creating its whiter color. However, the "heart" is not composed of a single element. Sputnik Planitia (the western part) covers an area of 1200 by 2000 kilometers, which is equivalent to a quarter of Europe or the United States. What is striking, however, is that this region is three to four kilometers lower in elevation than most of Pluto's surface. "The bright appearance of Sputnik Planitia is due to it being predominantly filled with white nitrogen ice that moves and convects to constantly smooth out the surface. This nitrogen most likely accumulated quickly after the impact due to the lower altitude," explains Dr. Harry Ballantyne from the University of Bern, lead author of the study. The eastern part of the "heart" is also covered by a similar but much thinner layer of nitrogen ice, the origin of which is still unclear to scientists, but is probably related to Sputnik Planitia.

Source: ScienceDaily