Earth’s new ‘mini-moon’ is leaving soon - but it’ll be back

With close to 1 million known asteroids — rubble from the birth of our solar system — but hardly any spotted circling our planet, this roughly compact-car-size object is “a big deal,” tweeted Kacper Wierzchos, one of the people who made the discovery. Astronomers expect mini-moon sightings to grow far more common as a new, giant telescope going up in Chile starts scanning the sky. It’s an exciting prospect for scientists interested in someday sending a spacecraft to study one of the rocks and maybe even bring it back to Earth. “These asteroids are what built the planets,” Scott Sheppard, an astronomer at the Carnegie Institution for Science, told The Washington Post. “And if these things are in orbit of Earth, they’re very easy for us to get to.” There’s no time to plan such a visit to 2020 CD3, the mini-moon discovered this month by staffers at a NASA-funded, Arizona-based project called the Catalina Sky Survey (CSS). The object is already getting fainter, and next month it will slip away from the Earth’s gravity to join other asteroids hurtling around the sun, said Eric Christensen, who directs the CSS. Hosted in Tucson by the University of Arizona, the CSS is devoted to tracking “near-Earth objects.” Worried about asteroids that could hit the Earth and do serious damage, lawmakers have set a goal of cataloguing at least 90 percent of these near-Earth objects above a certain size. The images the project captured of the mini-moon on the night of Feb. 15 look a lot like any other asteroid streaking across the sky, he added. That new observatory will spend its first decade making an “unprecedented” survey of the visible sky, the National Science Foundation says. “I think it’s highly likely that this has been observed before but that it’s been mistaken for an artificial satellite,” said Matthew Holman, director of the Cambridge, Mass.-based Minor Planet Center. They approach the Earth at just the right velocity to find themselves pulled into a typically chaotic orbit that’s also influenced by the moon and the Sun.

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