The Origin of Pluto's Heart: Unveiling an Ancient Cosmic Collision

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Astronomers have been fascinated by a large heart-shaped feature on Pluto's surface ever since NASA's New Horizons spacecraft spotted it in a 2015 image. Recent research suggests that the mystery behind the unique heart shape may have been solved, offering new insights into the origins of the dwarf planet.

The feature known as Tombaugh Regio is named after astronomer Clyde Tombaugh, the discoverer of Pluto in 1930. Scientists have found that the heart is not made up of just one element. For many years, researchers have been puzzled by the elevation, geological makeup, unique shape, and highly reflective surface of Tombaugh Regio, which appears brighter white compared to the rest of Pluto.

Located in the "left lobe" of the heart is a deep basin known as Sputnik Planitia, where a significant amount of Pluto's nitrogen ice can be found.

The basin is massive, stretching across 745 miles by 1,242 miles (1,200 kilometers by 2,000 kilometers), which is about a quarter of the size of the United States. However, it sits at a lower elevation compared to most of the Earth's surface, about 1.9 to 2.5 miles (3 to 4 kilometers) lower. On the other hand, the right side of the heart also contains a layer of nitrogen ice, although it is much thinner.

The New Horizons spacecraft took an image of Pluto's heart on July 14, 2015.

The New Horizons spacecraft took an image of Pluto's heart on July 14, 2015.

Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/NASA

New research on Sputnik Planitia has revealed that the heart was created by a cataclysmic event. Scientists from around the world analyzed data through numerical simulations and determined that a planetary body approximately 435 miles (700 kilometers) in diameter collided with Pluto in its early history.

These findings are a part of a study on Pluto and its internal structure, which was recently published in the journal Nature Astronomy.

Studying unusual features across the solar system, like those on the far side of the moon, that were probably formed by collisions during the system's early days. In a recent study, the team recreated an ancient 'splat' on Pluto.

The researchers used specialized software called smoothed particle hydrodynamics to create numerical simulations. This software is commonly used in studies involving planetary collisions. They modeled various scenarios involving different impact possibilities such as velocities, angles, and compositions of a theoretical planetary body colliding with Pluto.

The findings indicated that the collision between the planetary body and Pluto most likely occurred at an angled trajectory, rather than a direct head-on impact.

"According to lead study author Dr. Harry Ballantyne from the University of Bern in Switzerland, the rocky body that collided with Pluto did not melt despite the intense heat of the impact. This was due to the extreme coldness of Pluto's core and the specific angle and low velocity of the collision. As a result, the core of the impactor did not sink into Pluto's core but instead remained intact as a splat on its surface."

So, what happened to the planetary body after it smacked into Pluto?

Perspective view of Pluto's icy volcanic region.

Perspective view of Pluto's icy volcanic region.

NASA/JHU Applied Physics Laboratory/SRI/Isaac Herrera/Kelsi Singer

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Pluto is home to huge ice volcanoes that might suggest the presence of life. According to Erik Asphaug, a professor at the University of Arizona’s Lunar and Planetary Laboratory, there is a remnant core of a large body hidden beneath Sputnik that Pluto was not able to fully absorb.

The unique teardrop shape of Sputnik Planitia on Pluto is a result of the planet's core being very cold and the impact that formed it being relatively slow, according to the team of researchers. If the impact had been faster and more direct, the shape would have been more symmetrical.

The lead researcher, Asphaug, explained that in the outer reaches of the Solar System, collisions between objects happen at much slower speeds and solid ice is able to withstand more force. This means that calculations need to be more precise when studying these types of impacts. It adds an extra level of complexity and makes the research more interesting.

Pluto’s mysterious beginnings

The team not only examined the heart feature of Pluto but also delved into its internal structure. They theorized that an early impact on Pluto led to a mass deficit, causing Sputnik Planitia to gradually shift towards the dwarf planet's north pole during its formation. This is because the basin is lighter in mass compared to its surroundings, as explained by the researchers in their study.

However, Sputnik Planitia is near the dwarf planet’s equator.

Astronomers have found the most massive stellar black hole in our galaxy, thanks to the wobbling motion it induces on a companion star. This artist’s impression shows the orbits of both the star and the black hole, dubbed Gaia BH3, around their common centre of mass. This wobbling was measured over several years with the European Space Agency’s Gaia mission. Additional data from other telescopes, including ESO’s Very Large Telescope in Chile, confirmed that the mass of this black hole is 33 times that of our Sun. The chemical composition of the companion star suggests that the black hole was formed after the collapse of a massive star with very few heavy elements, or metals, as predicted by theory.

Astronomers have recently discovered the largest stellar black hole in our galaxy by observing the wobbling motion it causes on a nearby star. This discovery was made possible by tracking the orbits of both the star and the black hole, known as Gaia BH3, around their shared center of mass. The wobbling was monitored for several years using data from the European Space Agency's Gaia mission. Additional information from various telescopes, including ESO's Very Large Telescope in Chile, confirmed that this black hole's mass is 33 times that of our Sun.

The chemical makeup of the companion star implies that the black hole was created after a massive star collapsed with very few heavy elements, also known as metals, as predicted by scientific theory.

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Previous studies have hinted that Pluto might have a hidden ocean beneath its surface. This could mean that the icy crust above the ocean is thinner in the Sputnik Planitia area, leading to a bulge of water and a shift of mass towards the equator, according to researchers.

However, a recent study presents a new theory regarding why this unique feature is located where it is on Pluto.

Dr. Martin Jutzi, a senior researcher of space research and planetary sciences at the University of Bern's Physics Institute, explained that in their simulations, the impact on Pluto excavated all of its primordial mantle. As the impactor's core material landed on Pluto's core, it caused a local mass excess. This phenomenon could clarify why Pluto migrated towards the equator, even without a subsurface ocean or with only a very thin one.

Kelsi Singer, a principal scientist at the Southwest Research Institute in Boulder, Colorado, and co-deputy principal investigator on NASA's New Horizons Mission, who was not part of the study, praised the authors for their thorough exploration of modeling and developing hypotheses. However, she wished for a closer connection to geologic evidence in the study.

Singer explained that according to the authors, the southern part of S,putnik Planitia is believed to be deep, despite some geologic evidence suggesting it may actually be shallower than the northern part.

The researchers are optimistic that the new theory about Pluto's heart could provide valuable insights into the formation of the enigmatic dwarf planet. Pluto's origins have long been a puzzle due to its location on the outskirts of the solar system and limited exploration, with only the New Horizons mission providing up-close observations.

"Pluto is a fascinating place with its unique and interesting geology, making it a vast wonderland," Singer explained. To better understand this geology, Singer believes that more creative hypotheses would be beneficial. One way to distinguish between these hypotheses is by gathering more information about the subsurface of Pluto. This can only be achieved by sending a spacecraft mission to orbit Pluto, possibly equipped with a radar that can penetrate through the ice.

Editor's P/S:

The exploration of Pluto's enigmatic heart-shaped feature has yielded new insights into the dwarf planet's origins. Scientists have determined that the heart was formed by a cataclysmic collision with a planetary body, leaving behind a remnant core beneath the surface. This discovery adds to our understanding of the role of collisions in shaping the solar system, particularly in the outer regions where impacts occur at slower speeds.

The study also highlights the importance of multidisciplinary approaches in planetary science. By combining numerical simulations with geological observations, researchers have been able to piece together a more complete picture of Pluto's formation and evolution. Future missions with advanced instruments, such as radar, could provide even more detailed information about the subsurface structure and composition of Pluto, helping us to unravel the mysteries of this distant world.