Earthlings can breathe a sigh of relief as the chances of an asteroid hitting Earth in the next eight years has gone from 3.1 per cent to zero, according to an update from NASA that was published on Monday (Feb. 24).
The impact risk of the asteroid named 2024 YR4 has been fluctuating since it was first discovered late last year. It was predicted to collide with Earth on Dec. 22, 2032.
Over several weeks, NASA has released updates on its impact risk. Just last week it went from 2.6 per cent on Tuesday (Feb. 18) and rose to 3.1 per cent on Wednesday (Feb. 19) only to drop to 0.28 per cent on Thursday (Feb. 20).
Now, the odds of what was dubbed a 鈥榗ity-killer鈥� asteroid hitting Earth have fallen to 0.004 per cent.
In order to learn more about the size of asteroid 2024 YR4, NASA said it will continue to observe it in March. The asteroid is estimated to be 40-90 metres (130-300 feet) across in size.
If it did strike Earth, it would cause "severe blast damage" according to the International Asteroid Warning Network (IAWN), spanning as far as 50 kilometres from the impact site.
Black Press Media spoke with Jon Willis, a professor in the University of Victoria's Department of Physics and Astronomy, who discussed the potential harm the asteroid could cause based on previous impacts on Earth by asteroids of a comparable size.
"One exploded high in the atmosphere, one exploded maybe 10 kilometres up and one hit the Earth," he said.
Willis was referring to the 'Chelyabinsk meteor', the 'Tunguska event' and the "Barringer meteor' which hit Earth at different points in the atmosphere.
According to NASA, the house-sized Chelyabinsk asteroid measuring almost 20 metres entered the atmosphere over Siberia, Russia on Feb. 15, 2013 and exploded 22.5 kilometres above ground. The explosion created a shock wave that blew out windows and damaged several buildings. The blast injured over 1,600 people, the majority of whom were hit by broken glass.
In 1908, the Tunguska event, involving an approximately 30-metre-diameter asteroid exploded about 10 to 14 kilometres in the skies over Siberia causing massive forest fires. Forty-nine thousand years ago, the 30 to 50-metre-diameter iron Berringer asteroid hit Earth creating the Meteor Crater, 1.2 kilometres across and 570 feet deep, in northern Arizona, according to NASA.
Willis says if an asteroid strikes Earth and a city like Victoria, it could most likely result in any one of these three past asteroid impact events.
NASA does not have a definitive number of the 2024 YR4's density or what it's made of at the moment, but the professor says it's about density.
"It's how compact dense is the object that's hitting the atmosphere 鈥� if it's denser, it's going to punch through," the professor said. "If it's less dense, loosely held together by gravity, it's going to break apart and then all vaporize in the upper atmosphere."
He said, the really compact iron-rich ones can cause a big impact: "The one that created Meteor Crater was rich in iron."
NASA concludes Asteroid 2024 YR4 now poses no significant threat to Earth in 2032 and beyond.
"There are a lot of things that are still in the pot being mixed around with this asteroid that scientists are still trying to follow," Willis said."There is an additional factor that is even difficult to follow with the models that they've got because the models feature gravity, but to really get this at the precise level of detail, there's effects such as what the force of sunlight is, which they're trying to model."
He said if it's an asteroid rather than a comet, that could also be a factor.
"Right now the way we describe asteroids are icy rubble piles. The way we describe comets are dirty snowballs. There's just a higher proportion of ice in comets that make them more volatile subject to outgassing and that can affect their trajectory as well."
Willis believes that in seven years, we will have a better understanding of Asteroid 2024 YR4 and that from a scientific viewpoint, he says "It's good to go back and look historically at the range of closest approaches we've had in the past."
Right now, NASA says there remains a very small chance for the asteroid to hit the moon on Dec. 22, 2032. That probability is currently 1.7 per cent.
