Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news about fascinating discoveries, scientific advancements and more.
The massive heart-shaped feature on Pluto’s surface has intrigued astronomers since NASA’s New Horizons spacecraft photographed it in 2015. Now researchers think they’ve solved the mystery of how the distinctive heart came to be, and it could reveal new clues about the dwarf planet’s origins.
This feature is called Tombaugh Regio in memory of astronomer Clybe Tombaugh, who discovered Pluto in 1930. However, scientists say that the heart does not consist of a single element. Details about Tombaugh Regio’s height, geological composition and distinctive shape, as well as its highly reflective surface that is brighter white than the rest of Pluto, have defied explanation for decades.
The deep basin called Sputnik Planitia, which forms the “left lobe” of the heart, hosts most of Pluto’s nitrogen ice.
The basin covers an area of 745 miles by 1,242 miles (1,200 kilometers by 2,000 kilometers), equivalent to about a quarter of the size of the United States, but it is also 1.9 to 2.5 miles (3 to 4 kilometers) lower than most of it. surface of the planet. Meanwhile, there is also a layer of nitrogen ice on the right side of the heart, but it is much thinner.
In new research on Sputnik Planitia, an international team of scientists has determined that a catastrophic event created the heart. After an analysis that included numerical simulations, the researchers concluded that a planetary body about 435 miles (700 kilometers) in diameter, or roughly twice the size of Switzerland from east to west, likely collided with Pluto early in the dwarf planet’s history.
The findings are part of a study about Pluto and its interior published Monday in the journal Nature Astronomy.
An ancient ‘warning’ is recreated on Pluto
The team had previously studied unusual features in the solar system, such as those on the far side of the moon, likely created by collisions that occurred in the early, chaotic days of the system’s formation.
The researchers created numerical simulations using smoothed particle hydrodynamics software, considered the foundation of a wide range of planetary collision studies, to model different scenarios for the potential impacts, velocities, angles and compositions of a theoretical planetary body colliding with Pluto.
The results showed that the planetary body likely hit Pluto at an oblique angle rather than head-on.
“The core of Pluto is so cold that it (the rocky body that collided with the dwarf planet) remained very hard and did not melt despite the heat of the impact, and thanks to the impact angle and low speed, the core of the impactor also melted. It did not sink into Pluto’s core, but remained intact as a warning sign on it,” the study’s lead author, Dr. Harry Ballantyne, a research fellow at the University of Bern in Switzerland, said in a statement.
So what happened to the body of Pluto after it hit it?
“Somewhere beneath Sputnik is the remnant core of another massive body that Pluto was never able to fully digest,” Erik Asphaug, a professor at the Lunar and Planetary Laboratory at the University of Arizona and one of the authors of the study, said in a statement.
The team found that Sputnik Planitia’s teardrop shape is a result of the coldness of Pluto’s core as well as the relatively low speed of the collision. Other faster and more direct types of impact would have created a more symmetrical shape.
“We’re used to thinking of planetary collisions as incredibly intense events where you can ignore details other than things like energy, momentum and density. But in the distant Solar System, speeds are much slower and solid ice is stronger, so you have to be much more precise in your calculations,” Asphaug said. “That’s where the fun begins.”
Pluto’s dark origins
While studying the heart feature, the team also focused on Pluto’s internal structure. A collision early in Pluto’s history may have created a mass deficit, causing Sputnik Planitia to slowly migrate toward the dwarf planet’s north pole over time while the planet was still forming. Researchers explained in the study that this is because, according to the laws of physics, the basin has less mass than its surroundings.
However, Sputnik Planitia is close to the dwarf planet’s equator.
Previous research has suggested that Pluto may have a subsurface ocean, and if so, the icy crust above the subsurface ocean would be thinner in the Sputnik Planitia region, creating a dense bulge of liquid water and causing the mass to migrate toward the equator. said the study authors.
But the new study offers a different explanation for the feature’s location.
“In our simulations, the entire primitive mantle of Pluto is excavated by the impact, and when the impactor’s core material splashes into Pluto’s core, it creates a local mass excess that could explain the equatorward migration without a subsurface ocean or, at most, a rock space research at the Institute of Physics at the University of Bern.” It’s very subtle,” said study co-author Dr. Martin Jutzi, a senior researcher in planetary sciences.
Kelsi Singer, principal scientist at the Southwest Research Institute in Boulder, Colorado, and deputy principal investigator for NASA’s New Horizons Mission, who was not involved in the study, said the authors did a thorough job of researching the modeling and developing their hypothesis. , but would have liked to see “a closer link to geological evidence.”
“For example, the authors suggest that the southern part of Sputnik Planitia is very deep, but most geological evidence has been interpreted to indicate that the south is shallower than the north,” Singer said.
Researchers believe a new theory about Pluto’s heart could shed more light on how the mysterious dwarf planet formed. Pluto’s origin remains unclear because it lies at the edge of the solar system and has only been studied closely by the New Horizons mission.
“Pluto is a vast wonderland filled with unique and fascinating geology, so more creative hypotheses to explain the geology are always useful,” Singer said. “What will help distinguish the different hypotheses is more information about Pluto’s surface. We can only achieve this by sending a spacecraft mission to orbit Pluto with a radar that can potentially look through the ice.”
For more CNN news and newsletters, create an account at CNN.com