Asteroid that hit Jupiter’s moon was bigger than the one that wiped out the dinosaurs

THE Jupiter’s moon Ganymede, may have changed its axis when a gigantic asteroid collided with it about 4 billion years ago, according to a new study.

It is the largest satellite in the Solar System, even larger than Mercury and the dwarf planet Pluto. Previous research has found evidence suggesting that beneath Ganymede’s thick icy crust lies a salty ocean ten times deeper than Earth’s oceans.

But many questions still remain about the moon, and scientists need more high-resolution images of its surface to solve the mysteries surrounding Ganymede’s history and evolution.

Deep fissures cover large areas of its surface, forming a pattern of concentric circles around a point, which has led some astronomers to believe that the moon underwent a major impact event in the past.

“Jupiter’s moons — Io, Europa, Ganymede and Callisto — all have interesting individual features, but what caught my attention were these fissures on Ganymede,” said Naoyuki Hirata, an assistant professor of planetology at Kobe University in Japan, in a statement. “We know that this feature was created by an asteroid impact about 4 billion years ago, but we weren’t sure how large this event was and what effect it had on the moon.”

Hirata is the author of a new study, published last Tuesday (3) in the magazine Scientific Reportswhich explores what created Ganymede’s fissure system and the aftermath of the impact — which could be investigated more closely by the European Space Agency’s (ESA) Juice (Jupiter Icy Moons Explorer) spacecraft, which is currently en route to study Jupiter and its moons.

An ancient impact

Ganymede has long intrigued Hirata, who said he believes unraveling its evolution is “significant.” The moon’s surface is marked by contrasts, with bright regions of ridges next to grooves that cut through darker areas.

The professor took a closer look at the fissure system on Ganymede, which extends from a single point on the surface, similar to the concentric cracks that form when a rock hits a car’s windshield, he said.

Hirata noted that the central location of the fissures was along the moon’s rotation axis, which suggested that something like a large impact event caused a complete reorientation of the satellite.

Previous research has shown that a large planetary body collided with Pluto early in its history, which rearranged the distribution of ice on the dwarf planet and led to the creation of a distinctive “heart”-shaped feature on the surface. Hirata said he believes a similar scenario occurred on Ganymede, with its icy crust and subsurface ocean.

A sudden change in the distribution of mass on a planet can alter the location of its axis, or the imaginary line around which planetary bodies rotate. When a large asteroid collides with a planet, it creates a gravitational anomaly that changes the celestial body’s rotation. So Hirata calculated what kind of impact could have caused Ganymede to be oriented in the current direction.

Their equations revealed that an asteroid about 300 kilometers wide initially created a crater approximately 1,400 to 1,600 kilometers in diameter.

The asteroid was 20 times larger than the one that crashed into the present-day Yucatan Peninsula in Chicxulub, Mexico, and led to the extinction of Earth’s dinosaurs 66 million years ago. The crater left on Ganymede was 25 percent the size of Jupiter’s moon, according to the study.

Up-close investigation by the Juice mission

It’s not yet clear how much Ganymede’s axis has shifted, Hirata said. However, future data collected by the Juice mission could shed more light on the history of Ganymede and the impact event.

The spacecraft, launched in April 2023, completed a historic flyby of Earth and the moon on Aug. 21, putting it on track to reach Jupiter and its moons in 2031.

It’s difficult for researchers to know whether an ancient impact created the fissures on Ganymede without more data, which the Juice mission can provide, said Adeene Denton, a postdoctoral researcher at the University of Arizona’s Lunar and Planetary Laboratory. She was not involved in Hirata’s study.

“This paper presents an interesting premise, with much to consider about the evolution of icy moons and ocean worlds,” said Denton, who co-authored a study in April on impacts on Pluto and its large basin, called Sputnik Planitia, which makes up the left lobe of the heart-shaped feature observed by astronomers.

“It’s worth noting that some skepticism may be warranted when considering ancient, degraded geological features on planetary bodies and how they affect a planet’s orientation,” Denton said. “With so little information about these large, ancient features, it’s difficult to be confident in identifying this feature as a basin, as well as a possible mass anomaly. Fortunately, unlike Pluto and Sputnik Planitia, we’re returning to Ganymede soon and will be able to obtain the additional information needed to resolve this question.”

Researchers believe the moon’s interior may be like a “layered sandwich” made up of alternating bands of ice and ocean. Understanding how the impact altered the moon could reveal insights into its intriguing internal structure, Hirata said.

“I want to understand the origin and evolution of Ganymede and the other moons of Jupiter,” he said. “The giant collision must have had a significant impact on Ganymede’s early evolution, but the thermal and structural effects of the collision on the moon’s interior have not yet been investigated. I believe that future research applying the internal evolution of icy moons could follow.”

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This content was originally published in Asteroid that hit Jupiter’s moon was bigger than the one that wiped out dinosaurs on the CNN Brasil website.

Source: CNN Brasil