Observations by astronomers tracking near-Earth asteroids have raised a new object to the top of the Earth-threat list.
The asteroid could strike the Earth in 2102. However, Don Yeomans, manager of NASA's Near Earth Object Program at the Jet Propulsion Laboratory in Pasadena, California, US, told New Scientist: "The most likely situation, by far, is that additional observations will bring it back down to a zero."
He adds: "We're more likely to be hit between now and then by an object that we don't know about."
On 23 February, new observations allowed researchers to more accurately calculate the orbit of the asteroid, named 2004 VD17, which was originally detected by the Massachusetts Institute of Technology's LINEAR project. Since the improvement did not rule out a potential collision with the Earth on 4 May 2102, they increased the asteroid's rating to level 2 on the Torino Scale, a relatively rare event.
Degrees of danger
The Torino Scale, adopted in 1999, is akin to a Richter scale for asteroid impacts. The vast majority of the 4000 or so near-Earth objects (NEOs) detected so far have been assigned to level zero on the Torino scale, meaning they have "no likely consequences".
Level 1, colour-coded green, suggests a possible impact that "merits careful monitoring". Beyond that, the risk continues to rise along the scale – levels 2, 3 and 4 are yellow; 5, 6 and 7 are orange; while 8, 9 and 10 earn red.
The highest level ever reached by an asteroid was level 4 by Apophis (2004 MN4) in December 2004, but subsequent calculations downgraded that concern to a level 1. So VD17 currently claims the top spot on NASA's online list of potential asteroid impacts.
Despite the rarity of the yellow designation, Yeomans says "Torino 2 is not very alarming." He notes that the scale does not take account of how soon an impact may occur, unlike its rival, the Palermo Scale.
Based on current observations, he says the asteroid has a 1 in 1600 chance of striking the Earth in 2102 and a 1 in 500,000 chance of hitting two years later. But further observations will soon refine the orbit calculation for VD17 – and hopefully ease minds.
NEO hunter, Andrea Milani Comparetti of the University of Pisa, Italy, says VD17 "is a serious problem, but not for our generation". He also notes that VD17 is dim and distant and is not projected to pass close by the Earth before 2102. "You will need fairly powerful telescopes to see it before it arrives," he told New Scientist.
as they say "It is not what we see that is going to HIT us, it would be something we have not mapped or seen yet" :hap5:
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