Hagai Perets
Hagai Perets

Astronomers: Multiple Cosmic Collisions May Have Created Our Moon

Hagai Perets
Hagai Perets

It looks so tranquil up there. So still. But we know space is neither tranquil nor still. Our own Moon is no exception. New research suggests the Moon was the product of some very, very violent moshing: Around 4.5 billion years ago, a rowdy gang of stellar objects smashed into our young planet, creating the debris that would one day become the Moon. The astronomers published their report in the journal Nature Geoscience.

We’ve known for a while now that the Moon is made at least partially out of pieces from a banged-up Earth. But we’re still trying to sort out the details of the collision itself. At first, scientists thought Earth had been hit by one big object, like another planet. Then they thought there must have been a bunch of objects all striking around the same time. As we learned more, the single-impactor theory returned to prominence and stayed there for decades.

One 2016 study named the object—the planet Theia—and even the angle of impact. The researchers theorized that the extremely similar molecular makeup of Earth and the Moon could only have resulted from a head-on collision.

Other astronomers disagree. The authors of the new paper ran hundreds of simulations, and they argue it’s far more likely that Earth was walloped by a score of different objects called planetesimals. Each of the repeated impacts smashed up a huge amount of the young planet’s matter. That debris then drifted into orbit around Earth, where it settled into disks, which then resolved into little (gargantuan) chunks called moonlets. Over time, the baby moonlets merged into one single, spinning rock.

“Our model suggests that the ancient Earth once hosted a series of moons, each one formed from a different collision with the proto-Earth,” co-author Hagai Perets said in a statement. “It’s likely that such moonlets were later ejected, or collided with the Earth or with each other to form bigger moons.”

Perets says the moonlets could easily have crossed orbits with one another, smashed together, and been rolled up into larger bodies. “A long series of such moon-moon collisions could gradually build-up a bigger moon—the Moon we see today.”

The Moon Is Making the Days on Earth Longer

We've all complained that there aren't enough hours in the day, and apparently the Moon has always been listening. New research shows that days on Earth are getting longer, and this phenomenon can be attributed to the Moon's slow drift away from Earth, Space.com reports.

Researchers at the University of Wisconsin-Madison determined that 1.4 billion years ago, when the Moon was closer to us, a day on Earth lasted about 18 hours. Each year, the Moon moves about 1.5 inches away from our planet, mainly due to Earth's tidal forces. As the Moon grows more distant, Earth rotates more slowly around its axis "like a spinning figure skater who slows down as they stretch their arms out," Stephen Meyers, the study's co-author, explained in a statement.

However, we won't notice the difference while we're alive—and neither will our great-great-grandchildren, for that matter. A few years ago, astronomer Britt Scharringhausen estimated that in 100 years, the day will be two milliseconds longer.

The scientists at UW reached their findings, which were published in the journal Proceedings of the National Academy of Sciences, by drawing on astronomy and geology. Using a statistical method called astrochronology, they studied two rock formations in China and the Atlantic Ocean that date back 1.4 billion and 55 million years, respectively, to better understand the ancient history of the Earth.

"The geologic record is an astronomical observatory for the early solar system," Meyers explained. "We are looking at its pulsing rhythm, preserved in the rock and the history of life."

Variations in Earth's movements—known as Milankovitch cycles—are determined not just by the Moon, but also by the other planets. This ultimately determines the amount of sunlight that reaches Earth and affects our planet's climate.

[h/t space.com]

NASA, YouTube
Take an Ultra-Detailed Tour of the Moon With This NASA Video
NASA, YouTube
NASA, YouTube

A new video will give you a tour of the Moon as you've never seen it, courtesy of NASA's Lunar Reconnaissance Orbiter. The 4K-resolution visualization posted by NASA's Goddard Space Flight Center, spotted over at CBS, was created using image data collected by the spacecraft since it began orbiting the Moon in 2009.

NASA narrates a guided tour that explores features like the Moon's South Pole, the famous Tycho Crater, the Aristarchus Plateau, and the Apollo 17 landing site in the Taurus-Littrow Valley.

The high resolution of the imagery allows you to clearly see things like the mysterious 328-foot-wide boulder on top of Tycho Crater's central peak and the Apollo 17 lunar lander and rover that still sit on the surface of the Moon.

The video explains the importance of the sites pictured and what the LRO data can tell us about the Moon's structure and characteristics, like how studying shadows on the Moon's North Pole can help us scope out sites for future solar power generators. Gravity measurements from the Orientale Basin may reveal the structure of the lunar crust there, and temperature readings and reflectance could alert us to potential water ice at the South Pole.

Take your own personal tour of the Moon in the video below.

[h/t CBS]


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