This still taken from an animation depicts the safe flyby of asteroid 2012 TC4 as it passes under Earth on Oct. 12, 2017. 
 
 —Dark, leisurely rotating, and traveling at about 30,000 miles per hour, asteroid 2012 TC4 is set for an Oct. 12 rendezvous with Earth. 
 
 The roughly 65-foot-wide space rock won’t hit us; astronomers calculate it will zip just 27,000 miles – one-eighth the distance to the moon – above our planet’s surface. 
 
 But the encounter highlights the threat meteors pose as well as astronomers’ urgent yet painstaking work to identify, track, and potentially deflect incoming space rocks. 
 
 “Things do hit other things, and we’re not special in that regard,” says Gareth Williams, associate director of the International Astronomical Union’s Minor Planet Center in Cambridge, Mass. “Just look up in the night sky and you can see things burning up in the atmosphere. Those are grains of sand.... Something the size of a car hits every few years.” 
 
 Astronomers have spotted most of the big ones. At the direction of Congress, the National Aeronautics and Space Administration launched a program in 1998 focused on finding 90 percent of all near-Earth objects (NEOs) larger than 1 kilometer (0.62 miles) wide. The asteroid that wiped out the dinosaurs 65 million years ago measured about 10 kilometers wide, but any impactor larger than 1 kilometer wide could trigger catastrophic climate change. 
 
 About 95 percent of those largest asteroids are now known, but in 2005 Congress directed NASA to expand its cataloging efforts to include NEOs larger than 140 meters (about 450 feet) wide. Scientists believe they have detected about a third of those so far. An impactor this size could cause local damage on land, and worse if it struck the ocean and triggered a tsunami. 
 
 “Impacts of large asteroids are extremely rare and therefore highly unlikely,” says Paul Chodas, project manager for NASA’s Center for Near Earth Object Studies in Pasadena, Calif. The odds of an asteroid 1 kilometer wide hitting Earth in any given year are 1 in about 500,000, and even an object 140 meters wide has just a 1-in-30,000 chance, he says. The larger the asteroid, the less chance of impact. 
 
 Jacob Turcotte/Staff 
 
 Asteroids do hit Earth frequently, but they’re small ones. About once every year, an asteroid 3 meters wide will strike our atmosphere, causing a spectacular fireball. Some particularly metallic rocks might make it to the ground, but they rarely cause damage. 
 
 But larger asteroids do pose a risk. The 2013 Chelyabinsk meteor, which injured nearly 1,500 people in the Russian city, was about the size of 2012 TC4. It had gone undetected before it slammed into Earth’s atmosphere, triggering a window-shattering shock wave. 
 
 What scientists need most to protect humanity from impact is time. The sooner astronomers find asteroids headed toward Earth, the better, Dr. Chodas says. “If the dinosaurs had a space program, they could have protected themselves, given enough warning,” he says. 
 
 Scientists are already working on ways to deflect potential impactors. A joint project between NASA and the European Space Agency called the Asteroid Impact & Deflection Assessment mission seeks to crash an unmanned spacecraft into the smaller body of a binary asteroid system in an effort to alter its course. 
 
 For now, astronomers are focused on finding as many asteroids as possible. 
 
 Dr. Williams says that more work needs to be done in spotting rocks like the Chelyabinsk meteor, which have struck Earth at least two or three times in the past century. 
 
 “On a human timescale, 50 years sounds like a long time,” he says. “But for mankind, 50 years hopefully is not a long projection to the future. So we really should be finding these things now so that we can ... reassure future generations that they don’t have to worry.” 
 
 “You probably want to ask me how I sleep at night,” he says. “I sleep very well, when the cats don’t disturb me.” ||||| Nasa says there will be ‘no danger’ when the asteroid 2012 TC4 shaves past Earth at just above the altitude at which most satellites operate on Thursday 
 
 House-sized asteroid will pass by Earth at just above satellite altitude 
 
 A house-size asteroid will give Earth a near-miss on Thursday, giving experts a rare chance to rehearse for a real-life strike threat as it passes inside the moon’s orbit. 
 
 Dubbed 2012 TC4, the space rock will shave past at an altitude of less than 44,000km (27,300 miles) – just above the 36,000km altitude at which hundreds of geosynchronous satellites orbit the Earth. 
 
 That represents about an eighth of the distance between the Earth and the moon. 
 
 Nasa’s Mike Kelley, who leads the exercise to spot, track and intimately probe the transient visitor, insisted there was “no danger. Not even for satellites”. 
 
 “We’ve now been observing TC4 for two months, so we have very accurate position information on it, which in turn allows very precise calculations of its orbit,” which will not cross that of Earth nor its satellites, he told AFP. 
 
 As its name suggests, the object was first spotted five years ago when it called on Earth at about double Thursday’s projected distance, before disappearing from view. 
 
 It is 15 to 30 metres (50 to 100ft) wide – about the size of the meteoroid that exploded in the atmosphere over Chelyabinsk in central Russia in 2013, with 30 times the kinetic energy of the atomic bomb dropped on Hiroshima. 
 
 The resulting shockwave blew out the windows of nearly 5,000 buildings and injured more than 1,200 people. 
 
 While the Chelyabinsk event caught everyone unawares, TC4 is one of thousands of space rocks whose whereabouts are known. 
 
 Millions are not. 
 
 On its 609-day loop around the Sun, TC4 will return to Earth in 2050 and 2079, according to Rüdiger Jehn of the European Space Agency’s Near-Earth Object programme in the Netherlands. 
 
 “We know today that it will also not hit the Earth in the year 2050, but the close flyby in 2050 might deflect the asteroid such that it could hit the Earth in the year 2079,” he told AFP by email. 
 
 With a one-in-750 chance of hitting the planet then, TC4 is listed at number 13 on the “risk list” of objects posing even the remotest impact risk. 
 
 “We need to make very precise observations to be able to better predict the return in the year 2050,” Jehn said. 
 
 Flybys like this one are actually quite common – about three objects similar in size to TC4 graze past at a similar distance every year. 
 
 What makes TC4 special is that it has been chosen to test the global asteroid pre-warning system, fed by a network of observatories, universities and labs around the world. 
 
 Scientists unveil new detectors in race to save Earth from next asteroid Read more 
 
 The asteroid’s close approach will allow teams to evaluate how accurate they were in predicting its orbit and size, while using telescopes to learn more about its composition. 
 
 “For us this is a test case,” said Jehn’s colleague Detlef Koschny. “We are practicing for the real serious case.” 
 
 Many scientists believe the Earth will once again be hit by a space rock of the size that wiped out the dinosaurs, though nobody knows when. 
 
 And even if they become better at predicting a strike, there is very little to be done about it, for now. 
 
 Futuristic projects mooted to deflect or destroy incoming space rocks have come to nought so far, and the only strategy would be to evacuate people in zones at risk. 
 
 TC4 will make its closest approach to Earth just before 05.41 GMT on Thursday, at a point south of Australia, according to ESA and Nasa. 
 
 It will not be visible to the naked eye nor with regular binoculars, “but it can be seen in the night of 11-12 October until about 4.00am from European observatories”, Jehn said.
– The Earth will be having a close call—astronomically speaking—when a 65-foot-wide asteroid buzzes past on Thursday, the Christian Science Monitor reports. According to AFP, asteroid 2012 TC4 will come within 27,000 miles of Earth—about one-eighth the distance between the Earth and moon and about 5,000 miles above most of the satellites orbiting Earth. There's no chance the asteroid will hit the Earth, but its proximity will be used to test an asteroid warning system. 2012 TC4 will make further passes by Earth in 2050 and 2079, and there is a chance it could make impact on the latter fly-by. "Things do hit other things, and we’re not special in that regard,” the associate director of the International Astronomical Union tells the Monitor. The asteroid is at No. 13 on the "risk list" of objects that could impact Earth.