Pluto suffered a “flip” after colliding with a planetary body

ATLANTA — A huge heart-shaped feature on Pluto’s surface has intrigued astronomers since NASA’s New Horizons spacecraft captured it in an image in 2015. Now researchers believe they have solved the mystery of how the distinctive heart appeared and could reveal new clues about the planet’s origins. troll.

This feature is called “Tombo Regio,” in honor of astronomer Clyde Tombaugh, who discovered Pluto in 1930. But scientists say the nucleus isn’t all one element. For decades, details about Tombo Reggio’s altitude, geology and distinctive shape, as well as its highly reflective surface, which is brighter white than the rest of Pluto, have eluded explanation.

A deep basin called Sputnik Planitia, which forms the “left lobe” of the core, hosts much of Pluto’s nitrogen ice.

The basin covers an area of ​​1,200 by 2,000 kilometers, about a quarter the size of the United States, but is also 3.5 to 4 kilometers lower than most of the Earth’s surface. Meanwhile, the right side of the core also contains a layer of nitrogen ice, but it is much thinner.

Through new research on Sputnik Planitia, an international team of scientists has determined that a catastrophic event created the core. After analyzing with numerical simulations, the researchers concluded that a protoplanetary body with a diameter of about 700 kilometers (about twice the size of Switzerland from east to west) had likely collided with Pluto early in the dwarf planet’s history.

These results are part of a study on Pluto and its internal structure published Monday in the journal Nature astronomy.

Recreating an old ‘hype’ about Pluto

Previously, the team studied unusual features across the solar system, such as those on the far side of the moon, which were likely created by collisions during the system’s chaotic early days.

The researchers created numerical simulations using smooth particle hydrodynamics software, which is the basis for a wide range of planetary collision studies, to model different scenarios of the possible impacts, velocities, angles and compositions of a theoretical collision of planetary bodies with Pluto.

The results showed that the planetary body would likely collide with Pluto at an oblique angle, rather than head-on.

“Pluto’s core is so cold that (the rocky body that collided with the dwarf planet) remained very solid and did not melt despite the heat of the collision, and thanks to the angle of impact and low speed, Pluto’s core is the colliding body did not melt,” says Dr. Harry Ballantyne, lead author of the study and co-researcher at the University of Bern. In Switzerland, a statement said: “It did not sink into the heart of Pluto, but remained intact like a blow.”

But what happened to the planetary body after the collision with Pluto?

“Somewhere beneath Sputnik lies the remains of the core of another massive object, one that Pluto never digested,” co-author Eric Asfaugh, a professor at the University of Arizona’s Lunar and Planetary Laboratory, said in a statement.

The team found that Sputnik Planitia’s teardrop shape is a result of Pluto’s cold core, as well as the relatively slow speed of the impact itself. Other types of faster, more direct effects would have created a more symmetrical look.

“We’re used to thinking of planetary collisions as incredibly intense events where you can ignore the details other than things like energy, momentum and density,” Asphaug said. “But in a distant solar system, speeds are much lower and solid ice is strong, so you have to be much more precise.” Your calculations.” “This is where the fun begins.”

The origin of Pluto is mysterious

While studying heart function, the team also focused on Pluto’s internal structure. An impact early in Pluto’s history would have caused a mass deficit, causing Sputnik Planitia to slowly migrate toward the dwarf planet’s north pole over time while the planet was still forming. This is because the basin is less massive than its surroundings, according to the laws of physics, the researchers explained in the study.

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

Previous research has suggested that Pluto might have a subsurface ocean, and if so, the ice crust above the subsurface ocean would be thinner in the Sputnik Planitia region, creating a dense bulge of liquid water and mass toward the equator would migrate, the research shows. authors said.

Pluto is a vast wonderland with unique and fascinating geology, so more creative hypotheses to explain that geology are always useful.

-Kelsey Singer, Chief Scientist

But the new study offers a different explanation for the location of the benefit.

“In our simulations, Pluto’s primitive mantle is completely exhumed by the impact, and because the core material from the impact is dispersed across Pluto’s core, it creates a local mass excess that could explain the migration toward the equator without a subsurface ocean. or at most an underground ocean,” he said. “It’s very thin,” says study co-author Dr. Martin Goetze, a senior researcher in space research and planetary science at the Institute of Physics of the University of Bern.

Kelsey Singer, chief scientist at the Southwest Research Institute in Boulder, Colorado and deputy co-principal investigator for NASA’s New Horizons mission, who was not involved in the study, said the authors did a thorough job examining the models and testing their hypotheses. develop, although they would have liked to. She sees a “closer connection to the geological evidence.”

“For example, the authors suggest that the southern part of Sputnik Planitia is very deep, but much of the geological evidence has been interpreted to suggest that the south is shallower than the north,” Singer said.

Researchers believe the new theory about Pluto’s core could shed more light on how the mysterious dwarf planet formed. Pluto’s origin has remained a mystery because it is located on the edge of the solar system and has only been closely studied by the New Horizons mission.

“Pluto is a vast wonderland with unique and fascinating geology, so more creative hypotheses to explain that geology are always helpful,” Singer said. “What could help distinguish between the different hypotheses is getting more information about what lies beneath Pluto’s surface. We can only achieve that by sending a spacecraft into orbit around Pluto, perhaps using a radar that can see through the ice.”