Simulation Of An Asteroid Impact In The Year 2880

JoeRobe writes "Researchers at UCSC have simulated a possible outcome of an impact by asteroid 1950DA when it passes near us in the year 2880. Note that there is a 0.3% chance of impact during that encounter. In the event that it impacts in the Atlantic, they predict that the '60,000 megaton blast' would create 400 foot waves along the east coast. In addition to an assessment of the danger, their studies point out the resulting geologic features that we should be looking for now, which would indicate where and when such impacts have occured in the past."

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[CowBovNeal]

Massive tsunami sweeps Atlantic Coast in asteroid impact scenario for March 16, 2880
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SANTA CRUZ, CA--If an asteroid crashes into the Earth, it is likely to splash down somewhere in the oceans that cover 70 percent of the planet's surface. Huge tsunami waves, spreading out from the impact site like the ripples from a rock tossed into a pond, would inundate heavily populated coastal areas. A computer simulation of an asteroid impact tsunami developed by scientists at the University of California, Santa Cruz, shows waves as high as 400 feet sweeping onto the Atlantic Coast of the United States.

The researchers based their simulation on a real asteroid known to be on course for a close encounter with Earth eight centuries from now. Steven Ward, a researcher at the Institute of Geophysics and Planetary Physics at UCSC, and Erik Asphaug, an associate professor of Earth sciences, report their findings in the June issue of the Geophysical Journal International.

March 16, 2880, is the day the asteroid known as 1950 DA, a huge rock two-thirds of a mile in diameter, is due to swing so close to Earth it could slam into the Atlantic Ocean at 38,000 miles per hour. The probability of a direct hit is pretty small, but over the long timescales of Earth's history, asteroids this size and larger have periodically hammered the planet, sometimes with calamitous effects. The so-called K/T impact, for example, ended the age of the dinosaurs 65 million years ago.

"From a geologic perspective, events like this have happened many times in the past. Asteroids the size of 1950 DA have probably struck the Earth about 600 times since the age of the dinosaurs," Ward said.

Ward and Asphaug's study is part of a general effort to conduct a rational assessment of asteroid impact hazards. Asphaug, who organized a NASA-sponsored scientific workshop on asteroids last year, noted that asteroid risks are interesting because the probabilities are so small while the potential consequences are enormous. Furthermore, the laws of orbital mechanics make it possible for scientists to predict an impact if they are able to detect the asteroid in advance.

"It's like knowing the exact time when Mount Shasta will erupt," Asphaug said. "The way to deal with any natural hazard is to improve our knowledge base, so we can turn the kind of human fear that gets played on in the movies into something that we have a handle on."

Although the probability of an impact from 1950 DA is only about 0.3 percent, it is the only asteroid yet detected that scientists cannot entirely dismiss as a threat. A team of scientists led by researchers at NASA's Jet Propulsion Laboratory reported on the probability of 1950 DA crossing paths with the Earth in the April 5, 2002, issue of the journal Science.

"It's a low threat, actually a bit lower than the threat of being hit by an as-yet-undiscovered asteroid in the same size range over the same period of time, but it provided a good representative scenario for us to analyze," Asphaug said.

For the simulation, the researchers chose an impact site consistent with the orientation of the Earth at the time of the predicted encounter: in the Atlantic Ocean about 360 miles from the U.S. coast. Ward summarized the results as follows:

The 60,000-megaton blast of the impact vaporizes the asteroid and blows a cavity in the ocean 11 miles across and all the way down to the seafloor, which is about 3 miles deep at that point. The blast even excavates some of the seafloor. Water then rushes back in to fill the cavity, and a ring of waves spreads out in all directions. The impact creates tsunami waves of all frequencies and wavelengths, with a peak wavelength about the same as the diameter of the cavity. Because lower-frequency waves travel faster than waves with higher frequencies, the initial impulse spreads out into a series of waves.

"In the movies they show one big wave, but you actually end up with dozens of waves. The first ones to arrive are pr