<p>The 325-metre asteroid 99942 Apophis, that will safely fly by the Earth in 2029 and 2036, may strike the planet in 2068, says an article published on the NASA website.<br />The chances of it striking Earth are slim, however, with impact odds being about 2.3 in a million</p>.<p>.<br /><br />The asteroid has been the focus of considerable attention after it was discovered in December 2004 to have a significant probability of Earth impact in April 2029.<br /><br />While the 2029 potential impact was ruled out through the measurement of archival telescope images, the possibility of a potential impact in the years after 2029 continues to prove difficult to rule out.<br /><br />Based on optical and radar position measurements made in 2004-2012, the asteroid will pass the Earth in 2029 at an altitude of 31900, give or take 750 km.<br /><br />The altitude is close enough for the Earth's gravity to deflect the asteroid onto a trajectory that brings it back to an Earth impact during its next flyby.<br /><br />Such impact trajectories require Apophis to pass the Earth at a precise altitude, known as a keyhole, in 2029 en route to a subsequent impact.<br /><br />"The new report, which does not make use of the 2013 radar measurements, identifies over a dozen keyholes that fall within the range of possible 2029 encounter distances," said the article prepared by a group of scientists led by Davide Farnocchia.<br /><br />The uncertainty in predicting the asteroid's position in 2029 is completely dominated by the so-called Yarkovsky effect, a subtle non-gravitational perturbation due to thermal re-radiation of solar energy absorbed by the asteroid.<br /><br />"Only one of the potential impacts has a probability of impact greater than 1-in-a-million; there is a two-metre-wide keyhole that leads to an impact in 2068, with impact odds of about 2.3 in a million."<br /></p>
<p>The 325-metre asteroid 99942 Apophis, that will safely fly by the Earth in 2029 and 2036, may strike the planet in 2068, says an article published on the NASA website.<br />The chances of it striking Earth are slim, however, with impact odds being about 2.3 in a million</p>.<p>.<br /><br />The asteroid has been the focus of considerable attention after it was discovered in December 2004 to have a significant probability of Earth impact in April 2029.<br /><br />While the 2029 potential impact was ruled out through the measurement of archival telescope images, the possibility of a potential impact in the years after 2029 continues to prove difficult to rule out.<br /><br />Based on optical and radar position measurements made in 2004-2012, the asteroid will pass the Earth in 2029 at an altitude of 31900, give or take 750 km.<br /><br />The altitude is close enough for the Earth's gravity to deflect the asteroid onto a trajectory that brings it back to an Earth impact during its next flyby.<br /><br />Such impact trajectories require Apophis to pass the Earth at a precise altitude, known as a keyhole, in 2029 en route to a subsequent impact.<br /><br />"The new report, which does not make use of the 2013 radar measurements, identifies over a dozen keyholes that fall within the range of possible 2029 encounter distances," said the article prepared by a group of scientists led by Davide Farnocchia.<br /><br />The uncertainty in predicting the asteroid's position in 2029 is completely dominated by the so-called Yarkovsky effect, a subtle non-gravitational perturbation due to thermal re-radiation of solar energy absorbed by the asteroid.<br /><br />"Only one of the potential impacts has a probability of impact greater than 1-in-a-million; there is a two-metre-wide keyhole that leads to an impact in 2068, with impact odds of about 2.3 in a million."<br /></p>