Skip to Content
Uncategorized

Earth Must Have Another Moon, Say Astronomers

A study of the way our planet temporarily captures asteroids suggests that Earth should have at least one extra moon at any one time

Back in 2006, the Catalina Sky Survey in Arizona noticed that a mysterious body had begun orbiting the Earth. This object had a spectrum that was remarkably similar to the titanium white paint used on Saturn V rocket stages and, indeed, a number of rocket stages are known to orbit the Sun close to Earth.

But this was not an object of ours. Instead, 2006 RH120, as it became known, turned out to be a tiny asteroid just a few metres across–a natural satellite like the Moon. It was captured by Earth’s gravity in September 2006 and orbited us until June 2007 when it wandered off into the Solar System in search of a more interesting neighbour.

2006 RH120 was the first reliably documented example of a temporary moon.

But there should be many more examples, say Mikael Granvik and buddies at the University of Hawaii in Honolulu. Today these guys say they have modelled the way the Earth-Moon system captures these objects to understand how frequently we can expect to have additional moons and how long they should stay in orbit.

The answer is straightforward to state. “At any given time, there should be at least one natural Earth satellite of 1-meter diameter orbiting the Earth,” say Granvik and co. These objects should hang around for about 10 months and make about three revolutions of the planet. That means Earth ought to have a metre-sized moon right now.

This is of more than academic interest. NASA has repeatedly said it is interested in sending humans to a near Earth asteroid. What better than to kick off with one that is in orbit here?

Finding a suitable candidate will be tricky though. Asteroids that are likely to become temporary satellites in the near future will be small and therefore hard to see. What’s more, they will be subject to many forces pushing and pulling them so that predicting when and if they will ever be captured will be next to impossible.

But improved monitoring might help spot them when they get here, which might allow a launch to be planned in advance. Granvik and co conclude: “The scientific potential of being able to first remotely characterize a meteoroid and then visit and bring it back to Earth would be unprecedented.”

Ref: arxiv.org/abs/1112.3781: The Population Of Natural Earth Satellites

Keep Reading

Most Popular

DeepMind’s cofounder: Generative AI is just a phase. What’s next is interactive AI.

“This is a profound moment in the history of technology,” says Mustafa Suleyman.

What to know about this autumn’s covid vaccines

New variants will pose a challenge, but early signs suggest the shots will still boost antibody responses.

Human-plus-AI solutions mitigate security threats

With the right human oversight, emerging technologies like artificial intelligence can help keep business and customer data secure

Next slide, please: A brief history of the corporate presentation

From million-dollar slide shows to Steve Jobs’s introduction of the iPhone, a bit of show business never hurt plain old business.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.