The moon isn't the only satellite Earth has according to astrophysicists from the University of Hawaii in Honolulu. Our planet actually gains and losses moons all the time.

Astrophysicists Mikael Granvik, Jeremie Vaubaillon, and Robert Jedicke are suggesting that the Earth has two moons at various times and that it's possible it would get another one in the future. The first moon would be the big, pockmarked Moon and the other one would be temporary satellites that fall to the Earth's gravitational pull.

"At any given time, there should be at least one natural Earth satellite of 1-meter diameter orbiting the Earth," said Granvik.

One case where Earth had two moons was back in the fall of 2006 when observers at the Catalina Survey in Arizona found a strange object orbiting the Earth. Astronomers had first considered the object as a spent rocket stage because it had a spectrum similar to the titanium white paint NASA uses on rocket stages. Closer observation revealed that the object was actually a tiny asteroid, later named 2006 RH120 that measured a few meters across and had been caught in Earth's gravity. It orbited the Earth like a natural satellite until June 2007 when it left Earth's orbit for better cosmic pastures.

According to Granvik and company 2006 RH120 wasn't an anomaly but the norm for our planet. The gravitational pull of Earth and the Moon would draw near Earth objects like comets and asteroids to join the Earth-Moon system temporarily. These objects would be in orbit for around 10 months or so and hang around for ten months, enough time to make about three revolutions of the planet. Earth could actually have a second moon right now.

Aside from the knowledge that our Moon isn't so lonely anymore, the discovery could also interest NASA. There have been proposals for manned missions to asteroids and now NASA doesn't have to go farther than our planet's orbit to get one. The space agency could send a crew out to one of these temporary moons and gather samples. Improved monitoring could tell NASA when an asteroid is orbiting Earth and plan a mission accordingly.