- The second moon that Earth has captured in its orbit this month is an asteroid called 2024 PT5.
- Mini-moons like this could be ideal targets for asteroid mining to send humans deeper into space.
The second moon that Earth now has for two months may seem like just a fun curiosity, but it's also a sneak peek at a future space industry that could change our global economy.
An asteroid called 2024 PT5, which normally orbits the sun as part of the Arjuna asteroid belt, was captured in Earth's orbit on Sunday, according to astronomers' projections. Astronomers expect it to spend about 57 days traveling along a horseshoe-shaped path around Earth before rejoining its asteroid belt.
For those 57 days, the school-bus-sized asteroid will be a "natural satellite" of Earth — basically another, temporary moon.
That makes it economically intriguing. "Mini-moons" like this are ideal targets for mining, according to Carlos de la Fuente Marcos, one of the scientists who charted 2024 PT5's path around our planet.
Asteroid mining could someday help humans travel further out into the cosmos and extend our presence through the solar system. That's because some asteroids contain valuable metals like iron or platinum, as well as water.
Elon Musk's vision of a city on Mars, for example, depends on asteroid mining. Temporary moons like 2024 PT5 could be a key stepping stone.
"Mini-moons are very important for the nascent global space economy," Marcos told Business Insider in an email. Because they come so close to Earth and take a sojourn in our orbit, he added, "they are among the objects easier to reach using low-cost missions."
Asteroids can be worth quintillions
Asteroid 2024 PT5 may not be worth much, since scientists think it's made of basalt.
It's basically "a giant boulder," Teddy Kareta, a planetary scientist at the Lowell Observatory, told Business Insider.
But some asteroids contain so much metal that they're worth more than our entire global economy.
Take Psyche, for example, an asteroid that NASA is sending a spacecraft to for scientific study, since the agency believes it to be the core of a long-dead planet.
Psyche's metal-rich makeup — mostly iron and nickel — makes it worth an estimated $100 quintillion if it were here on Earth.
Some asteroids even have precious metals like platinum, gold, and cobalt.
Nobody has mined an asteroid yet, though NASA punched one in 2020 to grab scientific samples from it.
Some startups are trying to figure out how to start mining space rocks, and do it in a cost-effective way. Flying to an asteroid isn't cheap.
One of them, called AstroForge, has launched a small probe with SpaceX, though the spacecraft wasn't able to conduct the testing they'd planned, according to Space.com. The company is now planning two more missions, which it hopes will culminate in its first landing on a metallic asteroid in 2025.
Pit stops on the way to Mars
Long-distance deep-space missions, especially if they're carrying humans and cargo, will have a fuel problem.
Fuel is heavy, so the less of it you have to load onto a spacecraft the better. On the long flight to Mars or other planets, asteroids could become gas stations.
That's because research suggests that many asteroids in Earth's neighborhood are rich in water, which can be mined and split into its elementary components — hydrogen and oxygen, both of which are critical for making rocket fuel.
Mini-moons are perfect places to start, some scientists think, because of their proximity to Earth but also because of how small they are.
It takes an immense amount of rocket fuel to escape Earth's powerful gravitational pull. But little asteroids don't have much gravity, making it easy to leapfrog off of them.
"It only takes a puff of fuel to leave the mini-moon and head back towards Earth," Richard Binzel, a planetary scientist at MIT, previously told Live Science.
Mini-moon missions at the ready
One problem with mini-moons is that scientists sometimes don't see them coming until a few weeks before they're captured in our planet's orbit.
Asteroid 2024 PT5, for example, was first identified as a mini-moon in early September and will only be in Earth's orbit for about 57 days.
That's a tight timeline for preparing and launching a mining mission. For any asteroid, "you need to learn enough about it to know whether it's worth sending a rocket up," Kareta said.
Asteroid-mining companies can work around that by having mining spacecraft ready in Earth's orbit, waiting for the right space rock to zoom by, Marcos said.
"Either if you are thinking about collecting mineral samples for research or starting a space mining venture, mini-moons are your best bet to get your business off the ground," he said.