[meteorite-list] Physicist's Journey Reveals Smaller Asteroids Could Cause Bigger Problems

[Ron Baalke]

https://share.sandia.gov/news/resources/news_releases/boslough_asteriod/

Physicist's journey reveals smaller asteroids could cause bigger problems
Sandia Labs News Release
November 20, 2013
 
ALBUQUERQUE, N.M. - Once in a lifetime, a physicist may get a chance to 
test his theories and simulations in a real-life event that changes the 
course of his scientific life. But rarely does that opportunity literally 
fall from the sky.

That's the impact of the Feb. 15 asteroid that burst over the Russian 
city of Chelyabinsk on Sandia physicist Mark Boslough, subject of a TV 
documentary that airs tonight and co-author of a recent cover story in 
Nature about the asteroid fireball that injured about 1,500 people and 
damaged more than 7,000 buildings, collapsing roofs and breaking thousands 
of windows.

Boslough's journey to Russia shortly after the impact is chronicled in 
the NOVA episode "Asteroid; Doomsday or Payday," which will air on Public 
Broadcasting Service stations beginning today.

The show focuses on the destructive potential of asteroids, chronicling 
how Boslough and his colleagues learn that small asteroids can do far 
more damage than previously thought. The Nature paper also suggests that 
there may be more small asteroids than formerly thought.

The day the asteroid hit, Boslough learned of the event via Facebook from 
posts of Russian news stories and YouTube videos showing an object that 
exploded in the Russian sky.

"I saw it on Facebook long before the sound wave had even arrived in this 
part of the world," Boslough said, estimating the transglobal sound wave 
took more than seven hours to reach New Mexico. "I really didn't expect 
to experience this in my lifetime."

As one of the first scientists to visit Chelyabinsk after the asteroid 
struck, Boslough set out to discover where the object came from. Because 
it came down near a populated area, he and his colleagues were able to 
collect videos from people who caught the asteroid on film and video, 
especially the ubiquitous Russian dashboard cameras, a staple in establishing 
blame in traffic mishaps.

"This event was certainly one of the best-documented asteroid events ever," 
said Boslough.

Boslough's goal was to perform stellar calculations of the asteroid's 
trajectory by visiting - at night when the stars shone - the exact spots 
where the footage was recorded.

"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.

But Boslough 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."

Boslough was part of a team of 33 researchers who completed the study 
featured in Nature. "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 10 
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 30 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.

Dick Spalding of Sandia's Nonproliferation Technologies Research and Development 
Department also co-authored the paper.

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."

Sandia National Laboratories is a multi-program laboratory operated by 
Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., 
for the U.S. Department of Energy's National Nuclear Security Administration. 
With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia 
has major R&D responsibilities in national security, energy and environmental 
technologies and economic competitiveness.

Sandia news media contact: Stephanie Holinka, slholin at sandia.gov, (505) 
284-9227