Article image

Pluto got its ‘heart’ in a violent collision 

An international team of astrophysicists has made a significant breakthrough in understanding the iconic heart-shaped feature on Pluto’s surface.

The team was led by the University of Bern and members of the National Center of Competence in Research (NCCR) PlanetS, in collaboration with the University of Arizona

The experts attribute the formation of this unique terrain, specifically the western lobe known as Sputnik Planitia, to a colossal oblique-angle collision with a celestial body approximately 700 kilometers in diameter – roughly twice the size of Switzerland from east to west.

The heart of Pluto

This landmark study marks the first successful use of numerical simulations to replicate the unusual teardrop shape of Sputnik Planitia, providing new insights into both the surface and internal structure of Pluto. The simulations suggest that contrary to previous assumptions, there is no subsurface ocean within Pluto.

The “heart” of Pluto, officially named Tombaugh Regio, has fascinated both the public and scientists since its discovery by NASA’s New Horizons mission in 2015. Its distinct bright appearance and unique geological composition raised questions about its origin.

“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,” said lead author Harry Ballantyne, an astrophysicist at  Bern.

Slow and indirect impact

The researchers used advanced simulation techniques to delve into the dynamics of the impact that formed this feature.

“The elongated shape of Sputnik Planitia strongly suggests that the impact was not a direct head-on collision but rather an oblique one,” said senior author Martin Jutzi, an astrophysicist at Bern.

These simulations helped confirm that the impactor’s angle and velocity were crucial in creating the teardrop shape observed today.

Understanding Pluto’s internal structure 

These findings give rise to a new understanding of Pluto’s internal structure. The simulations indicate that the impact was so powerful that it excavated all of Pluto’s primordial mantle, challenging the previous theories of a subsurface ocean. 

“In our simulations, all of Pluto’s primordial mantle is excavated by the impact, and as the impactor’s core material splats onto Pluto’s core, it creates a local mass excess that can explain the migration toward the equator without a subsurface ocean, or at most a very thin one,” Jutzi explained.

Origin of the heart-shaped feature 

Furthermore, the location of Sputnik Planitia near the equator, which is paradoxical given the expected movement of such a mass deficit toward the pole, can now be understood through these findings. The absence of a subsurface ocean is a major shift in how scientists view Pluto’s geologic and climatic history.

“This novel and inventive origin for Pluto’s heart-shaped feature may lead to a better understanding of Pluto’s origin,” said co-author Adeene Denton, a geologist and planetary scientist at the University of Arizona.

The successful application of these detailed simulations opens up new possibilities for studying other mysterious features across the solar system, potentially leading to further groundbreaking discoveries in planetary science.

More about Pluto

Pluto, once considered the ninth planet of our solar system, was reclassified as a dwarf planet in 2006 by the International Astronomical Union. This demotion was due to its size and its orbit sharing with other objects in the Kuiper Belt, a region of space beyond Neptune filled with small icy bodies. 

Pluto’s orbit is highly eccentric, veering inside Neptune’s orbit at times and taking about 248 Earth years to complete a full journey around the Sun. Its surface is extremely cold, with temperatures plummeting as low as -375 degrees Fahrenheit. 

Despite its distance from Earth, NASA’s New Horizons mission provided a close-up look at Pluto in 2015, revealing a world with blue skies, spinning moons, mountains as high as the Rockies, and hints of an underground ocean.

The mission greatly expanded our understanding of this distant world, showcasing its remarkable geology and potential for harboring conditions suitable for life.

The study is published in the journal Nature Astronomy.


Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and


News coming your way
The biggest news about our planet delivered to you each day