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Hagai Perets

Astronomers: Multiple Cosmic Collisions May Have Created Our Moon

Original image
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.”

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photography
Video Recreates the Moon Landing Using Photos From NASA’s Archives

If the Apollo 11 mission ever gets the full Hollywood treatment, the trailer might look something like the video below. Despite its polished style, this short film from the artist Christian Stangl wasn't made using traditional CGI: Every frame you see was constructed from still photographs pulled from NASA’s Apollo archives.

According to Sploid, the film, titled Lunar, required thousands of images to create. Stangl created the video effect by splicing several pictures into single shots and animating the scenes in Adobe After Effects. Some sequences feature stills that were taken together in rapid succession.

Stangl isn’t the first person who's thought to put NASA’s public domain photos into motion. Last year, filmmaker Chris Coupland edited together a similar short dubbed Apollo. You can watch the video here to see how the two compare.

[h/t Sploid]

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science
Astronomers Propose New Donut-Shaped Celestial Object

As though there wasn't already enough cool stuff in the cosmos, scientists say space may hold enormous, spinning space donuts made of blistering-hot vaporized rock. They published their report in the Journal of Geophysical Research: Planets.

Planetary scientists Simon Lock and Sarah Stewart were trying to understand what happens when two planets collide. As we know from our own Earth, planets are not simply dead rocks or balls of gas, but active, complex bodies, with constantly shifting temperatures, orbits, shape, rotation, and gravity.

Consequently, planet-on-planet wrecks are less like a smashing of rocks and more like a figure-skating accident, a sudden, midair arresting of whirling triple axels.

The impact of these crashes is so violent, astronomers believe, that the two bodies involved are reduced to hot rubble. Over time, that rubble cools and congeals, eventually spinning and condensing into a new celestial body. It was this kind of smash-up, some scientists say, that created the Earth.

Lock and Stewart aren’t so sure about that. They think our planet’s origins may have been bigger, and substantially more donut-shaped. They hypothesize that the heat and momentum of these collisions can fling hot debris into a big, fat rotating ring they call a synestia.

From there, the process is similar: The vaporized rock cools and begins to stick together, coalescing into a rocky baby planet—and possibly a moon or two.

After centuries of study, we’re still not totally sure how our own Moon was born. Much of its composition is similar to Earth’s, which suggests, Lock and Stewart say, that the cosmic donut could have birthed them both.

The term synestia is their invention, too, a blend of the prefix syn, meaning “together,” and Hestia, the Greek goddess of home, the hearth, and architecture.

A real synestia has yet to be spotted in space, but the scientists are confident that they’ll turn up once we dig deeper into other solar systems.

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