--- title: Earth Has a Second Moon—For Another 300 Years, At Least description: Scientists have learned where Earth's 'second moon' came from—and how much longer it'll stick around. canonical: https://time.com/6116644/earth-second-moon/ author: Jeffrey Kluger article:opinion: false article:content_tier: free article:published_time: 2021-11-11T17:41:52.000Z article:modified_time: 2026-10-14T09:16:42.650Z article:section: Science og:title: Earth Has a Second Moon—For Another 300 Years, At Least og:description: And we just learned where it came from og:url: https://time.com/6116644/earth-second-moon/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltf390057273cb88b1/698a1ec28fd2ee0a933631ab/The-moon.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 5184 og:image:height: 2916 og:image:alt: Full frame of the full moon at sunset with a sky with clouds. og:type: article twitter:card: summary_large_image twitter:title: Earth Has a Second Moon—For Another 300 Years, At Least twitter:description: And we just learned where it came from twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltf390057273cb88b1/698a1ec28fd2ee0a933631ab/The-moon.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Earth Has a Second Moon—For Another 300 Years, At Least > Sponsored content. 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Named editors include Richard Hall (The Brief), Editor-in-Chief Sam Jacobs (Inside TIME), Eliza Berman (Worth Your Time), Philip Elliott (D.C. Brief), Justin Worland (Future Proof) and Harry Booth (In the Loop). Health Matters is written by TIME's health desk. #### How do I sign up for a TIME newsletter? Go to time.com/newsletters, choose the newsletters you want and enter your email address. There is no cost and no subscription requirement. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-network-2026q3/newsletters?i=fb24080d-2b56-4975-a2c9-50581c2c5070&cr=time-nl-network-2026q3-v1) ## Video: How Apollo 11 Got to the Moon [Watch (HLS stream): How Apollo 11 Got to the Moon](https://cdn.jwplayer.com/manifests/PkL4DeYm.m3u8) (3:09)  _Published 2009-07-15. When the Apollo 11 mission reached the moon, it was the successful culmination of several missions over nine years_  by [Jeffrey Kluger](https://time.com/author/jeffrey-kluger/)  ## Jeffrey Kluger Editor at Large Nov 11, 2021 5:41 PM UTC When the Apollo 11 mission reached the moon, it was the successful culmination of several missions over nine years  by [Jeffrey Kluger](https://time.com/author/jeffrey-kluger/)  ## Jeffrey Kluger Editor at Large Nov 11, 2021 5:41 PM UTC It’s easy to be brand loyal to the moon. We’ve only got the one, after all, unlike Jupiter and Saturn, where you’d have dozens to choose from. Here, it’s luna or nada. Or not. The fact is, there’s another sorta, kinda moon in a sorta, kinda orbit around Earth that was discovered only in 2016\. And according to a [new study in _Nature_](https://www.nature.com/articles/s43247-021-00303-7), we may at last know how it was formed. The quasi-moon—named Kamo’oalewa, after a Hawaiian word that refers to a moving celestial object—is not much to speak of, measuring less than 50 m (164 ft) across. It circles the Earth in a repeating corkscrew-like trajectory that brings it no closer than 40 to 100 times the 384,000 km (239,000 mi.) distance of our more familiar moon. Its odd flight path is caused by the competing gravitational pulls of the Earth and the sun, which continually bend and torque the moonlet’s motions, preventing it from achieving a more conventional orbit. “It’s primarily influenced just by the sun’s gravity, but this pattern shows up because it’s also—but not quite—on an Earth-like orbit. So it’s this sort of odd dance,” says graduate student Ben Sharkey of the Lunar and Planetary Laboratory at the University of Arizona, the lead author of the paper. None of this means that Kamo’oalewa has to have especially exotic origins. The solar system is littered with asteroids, some of which are captured by the gravity of other planets and become more conventional—if fragmentary—moons. Others don’t orbit other planets in the common way but fall into line in front of them or behind them and pace them in their orbits around the sun, like the flocks of so-called Trojan asteroids that precede and trail Jupiter. --- ### Most Popular from TIME --- Either way, Kamo’oalewa was bound to get attention because its composition posed a stubborn mystery. Asteroids tend to reflect brightly in certain infrared frequencies, but Kamo’oalewa just doesn’t. It’s dimmer somehow—clearly made of different stuff, which suggests a different origin. To investigate the mystery, Sharkey, under the guidance of his PhD adviser, planetary scientist Vishnu Reddy, first turned to a NASA-run telescope in Hawaii routinely used for studying Earth-vicinity asteroids. But even through the usually reliable instrument, the infrared signature seemed too faint. Instead they switched to a University of Arizona-run monocular telescope that, as Sharkey says, could “squeeze every last ounce of photons out of that object.” That produced better, clearer results, but still they were incomplete. The rock was made of common silicates like other asteroids, but they were common only in their general composition, not in their infrared signature, which remained stubbornly off. At last, the answer suggested itself. If Kamo’oalewa was behaving like a sort of quasi-moon, perhaps it was an artifact of the actual moon. Earlier in Sharkey’s PhD program, one of his advisers published a paper on lunar samples brought back by the Apollo 14 mission in 1971\. When Sharkey compared the data he was getting in his telescope with what the earlier geologists came up with in the rock lab, the results matched perfectly. The kind of space-weathering lunar silicates undergo when they’re still on the surface of the moon precisely accounted for the differences in the infrared reflectivity between common asteroids and Kamo’oalewa. “Visually, what you’re seeing is weathered silicate,” says Sharkey. “The eons of exposure to space environment and the micrometeorite impacts, it’s almost like a fingerprint and it’s hard to miss.” How Kamo’oalewa shook free of our lunar companion is no mystery. The moon’s been getting bombarded by space rocks for billions of years, resulting in all manner of lunar debris getting ejected into space (nearly 500 bits of which have made it to the surface of the Earth as meteorites). Kamo’oalewa is one such piece of lunar rubble that spiraled away from the moon. But rather than landing on Earth or simply tumbling off into the void, it found itself a quasi-satellite in its own right. “We see thousands of craters on the moon, so some of this lunar ejecta has to be sticking around in space,” says Sharkey. Kamo’oalewa won’t stick around all that long, as its current trajectory is not entirely stable. According to estimates from Sharkey and others, the object will remain an earthly companion for only about 300 more years—nothing at all on the cosmic clock—after which it will break free of its current gravitational chains and twirl off into the void. Originally a part of the moon, then a companion of Earth, it will spend the rest of its long life traveling on its own. ## Transcript >> That's one small step for man, one giant leap for mankind. >> On July 20th, 1969, Neil Armstrong said these famous words, as the first person to set foot on the moon. >> Now we're getting a picture on the TV. >> Great. >> But that one day, that one moment, was actually 9 grueling years in the making. From launch pad to splash down, nearly every detail of Apollo 11's mission had been meticulously rehearsed and tested by NASA astronauts, engineers, systems people, and thousands of support workers. The rocket that pushed them into space, the Saturn V, was the biggest then and since. But it evolved from pretty humble beginnings. In 1962, NASA's Mercury- Redstone program shut Alan B. Shepard into suborbital space, atop a modified ICBM. That's a nuclear missile with a 5- foot, 11- inch man inside instead of a bomb. Missiles don't get you very far, or at least not far enough. So NASA scientists realized that to get a spaceship to escape earth's gravity all together, they were going to need something of unimaginable power. Eight years and 21- man launches later, they have their behemoth of a booster which was taller than the spires of St. Patrick's Cathedral. Apollo 11 was actually two spacecrafts. The command module had to detach from the last stage, spin around and dock with the landing module, all while traveling in space at the speed of 35, 579 feet per second. So how did they do it? NASA's Gemini program was designed to test this maneuver in 1966. At one point, Gemini astronauts Neil Armstrong and Dave Scott went into such a dangerously uncontrolled spin during the docking run. They almost died. A roundtrip to the moon was expected to last nearly 14 days, which would be comparable to spending a fortnight locked in a station wagon. NASA had no idea if people could handle such a journey either physically or mentally. So Gemini astronauts Frank Borman and Jim Lovell orbited the earth seated next to each other, shoulder to shoulder for 2 weeks, bumping up against the overhead doors only inches from their heads. >> Houston, Tranquility Base here. The Eagle has landed. >> As for the actual landing on the moon, well, how can you practice that? It was a first, and as such, an unknown to everybody. 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