Fireworks on Jupiter (94 KB)

All telescopes pointed to Jupiter this summer as comet Shoemaker-Levy 9 crashed into the jumbo planet. While people day-by-day followed the news of Shoemaker-Levy 9's fiery death, a basic scientific question entered public consciousness: Could a similar large comet or asteroid someday come hurtling toward Earth? The short answer is yes. It apparently happened 65 million years ago, with disastrous consequences for the dinosaurs, and the odds are, say astronomers, it will happen again within the next 100 million years. What are the chances human life could survive such a calamity? This summer's event gave scientists an unprecedented chance to observe doomsday from a safe distance and learn from it.

"It was a unique event," says astrophysicist Mordecai-Mark Mac Low. "It's the first time we've been able to predict a large planetary impact and then observe it, and it will probably be the only time in our lifetimes that an impact this large occurs." In preparation for the comet crash, Mac Low, a postdoctoral researcher at the University of Chicago, used the CRAY C90 at Pittsburgh Supercomputing Center to forecast what would happen. "Basically, I was trying to predict the results of the impact so that observers could plan for the event. I looked at things like how bright the flash of the explosion would be and how much material from beneath the Jovian clouds would be lifted above them where it can be observed."

Using the C90 and ZEUS, a program developed at the National Center for Supercomputing Applications, Mac Low ran simulations that showed the comet would penetrate less deeply and explode more violently than other models predicted. Results from analysis so far suggest that this modeling was consistent with what actually happened. Perhaps the most important result, at least in terms of forecasting the effect of Earth impacts, is that the simulations agree with a mathematical theory called "the pancake model."

ANIMATION: Entering Jupiter's Atmosphere (2,000 KB mpeg)
This animation represents Mac Low's simulation of a comet fragment one kilometer in diameter plunging into Jupiter's atmosphere at 134,000 miles per hour. Color indicates density, with initial density of the comet core (red) corresponding to solid ice. Pressure rapidly builds in front of the comet from the aerodynamic force of impact with the atmosphere, flattening the sphere and ripping it apart within seconds. The animation shows a five-second time period, one frame every 0.025 seconds.

ANIMATION: Fireball on Jupiter (450 KB mpeg)
As the comet fragment enters Jupiter's atmosphere, the tremendous heat generated incinerates it, and the resulting explosion releases energy comparable to thousands of hydrogen bombs, with a fireball hundreds of kilometers across. This animation shows initial stages of the fireball, almost two minutes, with a frame every half-second. Image-height corresponds to 1,000 kilometers. Color represents temperature, ranging from tens of thousands of degrees Kelvin (red), several times the temperature of the sun, to hundreds of degrees Kelvin (blue).

Researcher: Mordecai-Mark Mac Low, University of Chicago.
Hardware: CRAY Y-MP C90
Software: ZEUS-3D
Keywords: Jupiter, comet, planet, space, Shoemaker-Levy 9, explosion, astrophysics, astronomy, gas dynamics, aerodynamics, ZEUS, doomsday, asteroid, stellar, fireball.

Related Material on the Web:
Home Page of the Laboratory for Computational Astrophysics at NCSA.
Collected images and news about Comet Shoemaker-Levy 9.
PSC News Release about this research.
Projects in Scientific Computing, PSC's annual research report.

References, Acknowledgements & Credits