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The mysterious heart-shaped feature on Pluto, first observed by NASA's New Horizons mission in 2015, has intrigued scientists for years. This feature, known as Sputnik Planitia, is part of the Tombaugh Regio and has sparked significant research due to its distinct shape and composition.

A team from the University of Bern in Switzerland and the University of Arizona employed numerical simulations to explore the origins of Sputnik Planitia. Their findings suggest that a massive collision with a planetary body about 400 miles wide formed this region. This conclusion was published in Nature Astronomy.

"The formation of Sputnik Planitia provides a critical window into the earliest periods of Pluto's history," said Adeene Denton, a planetary scientist at the UArizona Lunar and Planetary Laboratory. The study expands understanding by considering unusual formation scenarios that could apply to other Kuiper Belt objects.

Sputnik Planitia is notable for its high-albedo material, which reflects more light than surrounding areas. It spans approximately 750 by 1,250 miles and sits around 2.5 miles lower than most of Pluto's surface. "While the vast majority of Pluto's surface consists of methane ice and its derivatives covering a water-ice crust, the Planitia is predominantly filled with nitrogen ice," explained Harry Ballantyne, lead author from Bern.

The elongated shape and equatorial location of Sputnik Planitia suggest an oblique impact rather than a direct collision. Martin Jutzi from the University of Bern used Smoothed Particle Hydrodynamics simulation software to recreate such impacts. These simulations supported suspicions about an oblique angle and provided insights into the impactor's composition.

"Pluto's core is so cold that the rocks remained very hard and did not melt despite the heat of the impact," noted Ballantyne. The core strength and relatively low velocity were crucial for successful simulations: "Lower strength would result in a very symmetrical leftover surface feature."

Erik Asphaug from the Lunar and Planetary Laboratory highlighted that slower velocities in distant solar system regions require precise calculations: "That's where the fun starts."

The study also challenges previous assumptions about Pluto having a subsurface ocean. Instead, it suggests that all primordial mantle might have been excavated during impact, creating a local mass excess that explains migration toward the equator without needing a subsurface ocean.

Denton expressed optimism about this new hypothesis: "This novel and creative origin hypothesis for Pluto's heart-shaped feature may lead to a better understanding of the dwarf planet's origin."