Applying high-performance computing to a scientific mystery
Red Storm simulated the airburst
and impact of a 120-meter diameter
stony asteroid, shown in this
sequence. Meteoric vapor mixes
with the atmosphere to form an
opaque fireball with a temperature
of thousands of degrees. The hot
vapor cloud expands to a diameter
of 10 km within seconds, still in
contact with the surface.
(photo by Mark Boslough)
While most natural glasses are volcanic in origin, rare exceptions are tektites, formed by shock melting associated with hypervelocity impacts of comets or asteroids. The Libyan Desert Glass falls into neither of these categories and has baffled scientists since its 1932 discovery.
Sandia physicist Mark Boslough’s study of the 1994 collision of Comet Shoemaker-Levy 9 with Jupiter provided an opportunity to model a hypervelocity atmospheric impact. Along with observation of the actual event, the model provided insights that provided a likely scenario for the formation of the Libyan Desert Glass.
Using Sandia’s Red Storm supercomputer, Boslough and his team ran a three-dimensional simulation, using huge amounts of memory and processing power. The simulation supports the hypothesis that the glass was formed by radiative heating and ablation of sandstone and alluvium near the “ground zero” of a 100- megaton or larger explosion caused by the breakup of a comet or asteroid.
Expedition camp was set up in “corridor B” in the
southern part of the Great Sand Sea, within the area
of Libyan Desert Glass. The corridors — made up
of relatively recent gravels and separated by linear
dunes — have long provided travel routes in this
remote area.
(photo by Mark Boslough)
The shock-physics simulations show a 120-meter-diameter asteroid entering the atmosphere at a speed of 20 kilometers/second and breaking apart just before hitting the ground. The fireball generated by the explosion remains in contact with the Earth’s surface at temperatures exceeding the melting temperature of quartz for more than 20 seconds. The fireball and the air speed behind the blast wave (hundreds of meters per second during the 20 seconds) are consistent with melting and rapid quenching to form the Libyan Desert Glass.
Although the risk to humans for such an impact is remote, it is not negligible, Boslough notes. The precise probability of such an event and its consequences are difficult to calculate, but research on large aerial bursts is forcing risk assessment to recognize and account for these large natural processes. Expedition camp was set up in “corridor B” in the southern part of the Great Sand Sea, within the area of Libyan Desert Glass. The corridors — made up of relatively recent gravels and separated by linear dunes — have long provided travel routes in this remote area.
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