Defense against asteroids begins study
By Robert Roy Britt
SPACE.com -- A mission to smash into a space rock to deflect it and study its structure has been given priority over five other potential asteroid projects by the European Space Agency.
The slam-bang 'Don Quijote' mission would help scientists figure out how to deflect or destroy any asteroid in the future that might be found to be on a collision course with Earth. The project uses the Spanish spelling of Don Quixote, the protagonist in Cervantes' novel who has chivalrous ideas that tend toward the impractical.
The lofty modern-day Don Quijote would help solve a practical problem.
Scientists don't know enough about asteroid insides to predict how one would respond to attempts to nudge it off an Earth-impact course or turn it into harmless dust. While no asteroids are currently known to be on track to hit the planet, experts say a regional catastrophe is inevitable in the very long run-- over millennia. And run-ins with small asteroids that could incinerate a large city occur ever few thousand years.
"We want to investigate the internal structure of an asteroid, and at the same time develop and test the technology necessary, in a worst case scenario, to deflect a sizeable asteroid," says Andrea Milani, an asteroid expert at the University of Pisa who is helping to plan the mission.
The mission would involve two spacecraft -- Sancho and Hidalgo -- launched on different trajectories toward one asteroid about 550 yards (500 meters) in diameter. A rock that size would cause serious damage across a widespread area and absolute destruction at the local level.
Sancho would arrive first and orbit the asteroid for several months. It would deploy some penetrating probes to form a seismic network on the asteroid to examine its structure before and after its sister craft's smashing arrival.
Hidalgo would crash into the asteroid at about 22,370 mph (10 kilometers per second).
Sancho would observe from a safe distance, then move in for a closer look. It would study changes in the asteroid's orbit, rotation and structure caused by the impact, said Willy Benz, a member of the mission's study team from the University of Bern in Switzerland.
The mission would "provide information about how an asteroid reacts to such stresses, which is an important step in the whole impact hazard reduction business," Benz said.
A European Space Agency panel considering six asteroid protection missions recommended Don Quijote "as the highest priority for further studies," Benz said. It is still in an early planning stage, however, and would eventually need funding approval.
He said the mission could launch in five to six years.
Don Quijote is similar to NASA's Deep Impact mission, which is slated to fling a small probe at a comet on July 4, 2005.
Comets are loaded with water ice, while asteroids are generally composed of rock and metals. Scientists know little about either, and both are thought to harbor clues about the solar system's formation.
From a safe distance, the Deep Impact mothership will take pictures and record other data as its probe blows a seven-story-deep crater in the comet Tempel 1. Experts say Deep Impact's cosmic fireworks might be visible from Earth to backyard skywatchers.
Both missions will alter the courses of the objects they hit.
Deep Impact will fly past its target, limiting the time for close-up observations. The European craft, in orbit around its as-yet-unknown target, would take a more detailed approach to studying the comet before, during and after the collision.
"The important difference between Deep Impact and Don Quijote is that the target asteroid is studied six to seven months prior to impact and again three to four months after the impact," Benz said.
Shake it up
Don Quijote could create a seismic shift in the understanding of asteroid interiors.
The probes that would be embedded in the asteroid prior to the main event would monitor how the rock's structure changes in the collision by recording seismic waves created by small explosions the probes detonate. The method was used by Apollo astronauts to examine the Moon's interior, and it's used on Earth to search for oil, natural gas and other minerals.
There are currently no firm plans by NASA or any other agency to deal with any impending asteroid catastrophes. Scientists have contemplated the theory of asteroid deflection and destruction, but no tests have been performed like the one planned in the Don Quijote mission.
"Although the probability of a big impact is very small, for the first time in human history we have the means of avoiding such a catastrophic event," Jose Gonzalez, another member of the study team, has said. "But it is essential that we improve our knowledge of asteroids. We must know in detail the internal structure of asteroids, and how they respond to impacts before we can design effective mitigation methods."
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