New Asteroid Lands on List of Earth-Threatening Objects. Don’t Get Excited.

You can worry when the Torino score gets to 5

Asteroid 2005 YU55, caught by radar during a close pass in 2011.

Asteroid 2005 YU55, caught by radar during a close pass in 2011.

The newly discovered asteroid 2013 TV135 is one of those rare space objects assigned a number on the Torino scale. Discovered last month by astronomers working at the Crimean Astrophysical Observatory in Ukraine, the rock came within about 6.7 million kilometers of Earth on this pass.

The asteroid is about 400 meters in diameter, and based on what we know today, has a 1-in-63,000 chance of colliding with Earth in 2032. That’s enough to give it a value of “1” on the Torino scale, which ranks threats to Earth from asteroids. The only other object currently assigned a number other than zero is 2007 VK184, about 130 meters in diameter, which has a 1-in-1820 chance of impacting Earth in 2048, giving it a Torino score of 1. Both objects are likely to be downgraded to zero as astronomers learn more about their orbits.

The highest Torino rating in recent years went to the asteroid 99942 Apophis, which was briefly assigned a 4 when early observations indicated a 2.7 percent probability that it would collide with Earth in 2029. With a diameter of 350 meters, it would have enough energy on impact to kill millions and devastate several countries. But as usual, further observations ruled out a collision altogether.

Any Torino score of less than 5 should not concern us very much. However, the Chelyabinsk meteor that entered Earth atmosphere over Russia last February without any warning reminds us that our detection system is far from perfect. The many impact craters found on Earth — Meteor Crater in Arizona is a stark example – not to mention the far more numerous impact scars seen on the Moon, Mars, and other rocky planets, vividly show us the devastating effects asteroid impacts can have. Even a relatively small asteroid like 2013 TV135 would hit with a force 50 times greater than the biggest nuclear bomb. That’s why near-earth object observation programs like Spaceguard are so important.

Bear in mind, though, that we partly owe our existence to a past impact. Without the huge asteroid slamming into Earth at the end of the Cretaceous period about 66 million years ago, dinosaurs might still be roaming the Earth. That catastrophe drastically changed environmental conditions on the planet. While the dinosaurs were unable to adapt, our rodent-like ancestors were. And this wasn’t the only time an impact changed the trajectory of terrestrial life – another reason why, now that we’re on top, we want to keep an eye (or two) on the skies.

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