NASA finds Earth’s moon didn’t need hundreds of years to form

When the universe has seemed a vast, lonely place, people have taken comfort in Earth’s steadfast companion — the moon — ever-marching through space with this planet on an odyssey around the sun.

But at one time, some 4.5 billion years ago, the moon wasn’t around. And despite its being Earth’s cosmic bestie and closest neighbor, scientists still aren’t sure how it got there.

Since the 1980s, the leading theory has been that a massive planet, perhaps the size of Mars, crashed into Earth billions of years ago, spattering a world’s worth of gas, magma, and metals that forged the moon over tens to hundreds of years. A study published Tuesday in The Astrophysical Journal Letters suggests a bold new idea: The moon could have formed in one swift exchange, with a large chunk of baby Earth and its impactor’s material blown into a wide orbit — in a matter of hours.

If true, the research, which centered on hundreds of extremely high-resolution computer simulations of such a collision, could help resolve a longstanding head-scratcher for scientists about why the lunar crust seems so darn similar to Earth. It also provides potential answers to why the moon is tilted and has a thin outer layer. Cosmologists yearn to piece together what happened not only to flesh out the moon’s origin story, but explain a defining moment in Earth’s evolution.

NASA and collaborators put together a quick two-minute animation that attempts to show how the new model would unfold. A planet, which scientists have dubbed “Theia” over the decades, whacks a primitive version of Earth like a paint ball, casting off a mixture of planetary guts. Rather than forming a thin disk of debris, though, it divides into another blob, yo-yoing material between them. The gravity of Earth hurls the smaller body onward, but it survives. The umbilical severs.

This dance of destruction is contrasted by a musical score of lullaby-like plinking on a marimba.