Smaller asteroids could cause bigger problems
“If the stars show up on the digital camera, we can get those angles and then calibrate that image that was taken from the dash cam, and know exactly the angles to the trajectory of the fireball,” he said in the documentary. “We’ll have a very precise trajectory as it streaked through the atmosphere, so we can backtrack that to get the orbit, the pre-impact orbit.”
The program also discusses how asteroids can contain rare and valuable elements, leading researchers to seriously evaluate the benefit of harvesting them for their rare elements.
Boslough, however, also wants the research community to pay more attention to the potential risk that asteroids present.
“If something like the Tunguska event of 1908 happened now, it could kill hundreds of thousands or even a million people, if it happened right over a big city,” he said in the documentary. “An asteroid has more damage potential on the ground than a nuclear bomb of the same energy.”
The release notes that Boslough was part of a team of thirty-three researchers who completed the study featured in Nature. The study, “A 500-kiloton airburst over Chelyabinsk and an enhanced hazard from small impactors” examines the characteristics of the fireball. Boslough and his colleagues also used the simulations to help design the journal’s cover.
You also can see an animated simulation of the airburst produced by Boslough, as well as scientific animations and images by Sandia contractor and visual effect expert Brad Carvey and visual effect expert Andrea Carvey. Sandia’s Laboratory Directed Research & Development program funded the simulations.
Using data collected from his visit shortly after the asteroid struck, along with data from an international team, Boslough developed several additional simulations that he and other researchers have used to model the explosion and estimate the force of the blast.
The paper’s authors performed a global survey of airbursts of a kiloton or more and found that the number of building-sized objects may be ten times greater than estimates based on other methods.
The authors, led by Peter Brown of the University of Western Ontario, estimated the Chelyabinsk event was equivalent to an explosion of about 500 kilotons of TNT. At its peak, the airburst appeared to be thirty times brighter than the sun.
“Because the frequency of a strike of an asteroid of this size has exceeded expectations, with three such strikes in just over a century (Chelyabinsk, Tunguska and a large airburst in the South Atlantic in 1963 detected by infrasound), the number of similar-sized asteroids capable of causing damage may be greater than suspected,” Boslough said.
The authors also showed that previous models for estimating airburst damage do not match the observations.
An earlier paper by Boslough highlights the conclusion that most airbursts are more damaging than previously thought.
“We really have to rethink the risk from airbursts. Chelyabinsk was unusual due to the a low inclination at which it entered the atmosphere, but 90 percent of objects enter the atmosphere at a steeper angle and cause more damage on the surface,” Boslough said. That paper, which he wrote two years ago, was recently published online in Acta Astronautica.
The Chelyabinsk fireball is something those who saw it will never forget, and neither will Boslough.
“What’s amazing to me though, when you think about it, this is part of an asteroid that had been, floating through space, orbiting the sun for billions of years” he said for the documentary in a late February interview. “And two weeks ago, it exploded in the atmosphere, dropped to the ground, and here I am holding it in my hand! That’s amazing.”
View two airburst simulations or see photos at Sandia’s asteroid airburst Flickr set.
— Read more in P. G. Brown et al., “A 500-kiloton airburst over Chelyabinsk and an enhanced hazard from small impactors,” Nature 503 (14 November 2013): 238–41 (doi:10.1038/nature12741); and Mark Boslough, “Airburst warning and response” Acta Astronautica (1 October 2013)