Ex-UH scientist has plan to avert asteroid catastrophe
A former physicist at Manoa says a space tractor could change the path of an asteroid
A NASA astronaut with Hawaii ties promoted this week his notion of a space tractor to divert asteroids that threaten Earth.
A small, relatively inexpensive spacecraft could hover near an asteroid and exert enough gravitational pull over the course of about three years to change the rock's orbit to avoid a doomsday collision, said Edward Lu, a former University of Hawaii solar physicist who spent six months aboard the International Space Station in 2003.
"We're only trying to get a really tiny change in the velocity of the asteroid to prevent an impact," Lu told a packed, 300-person-capacity Art Building Auditorium at UH-Manoa on Monday night.
The tractor craft would cost $200 million to $300 million, comparable to today's planetary research probes, but could potentially save hundreds of millions of lives, Lu said in a forum sponsored by the UH Institute for Astronomy.
Lu joined three UH scientists on the panel to characterize an asteroid impact as a rare but calamitous event that demands the same level of attention as major earthquakes, tsunamis and hurricanes.
The asteroid Apophis, for instance, will pass within about 20,000 miles of Earth in the year 2029, said its discoverer, UH planetary astronomer David Tholen. That will happen on Friday the 13th of April.
"It's going to come so close to the Earth in 2029 that its orbit will change and it might change enough so that it comes back and hits us in 2036," Tholen said. That risk should be better quantified after radar surveys during the asteroid's next close pass to the sun in 2013, Tholen added.
Small space rocks, most the size of a grain of sand, hit the Earth's atmosphere every day to appear as "shooting stars." But larger impacts have been credited with the demise of the dinosaurs 65 million years ago and, in 1908, an airburst equivalent to a 10-megaton bomb that felled 80 million trees in Tunguska, Siberia.
"The atmosphere breaks up pretty much everything that is less that the size of a football field," said Robert Jedicke, a UH astronomer specializing in so-called "near-Earth objects."
A Tunguska-size explosion would have "burned or blasted" nearly the entire island of Oahu had it occurred overhead, Jedicke said.
Rocks even a half-mile in diameter, flying at 20 miles per second, qualify as "planet killers," the scientists said.
Because the devastation would be so great, the risk for any individual of dying from a major asteroid impact is about the same as dying in a plane crash -- about 1 in 10,000 or 20,000 over a 100-year lifetime, said Jedicke. Yet many millions of dollars are spent annually on airline safety while the threat of cosmic collisions is only now being addressed, he said.
Central to the warning system is a project called Pan-STARRS that, from the summit of Mauna Kea, will conduct a survey to detect asteroids that intersect the orbit of Earth.
The telescopes will catalog small asteroids by making sensitive scans of the night sky and comparing images to spot objects moving against the static background of stars, said UH cosmologist Nick Kaiser.
"They will move, but they can't hide," he said.
When completed in 10 or 15 years, the Pan-STARRS survey should provide decades of warning about an impending collision with an asteroid or comet, the scientists said.
That should be enough time to launch a tractor spacecraft to rendezvous with the object and nudge it to a safe orbit, said Lu, 43, a veteran of two flights aboard the space shuttle Atlantis.
Only a few ounces of force applied over three years would be enough to slow or speed up an asteroid to avoid an Earth collision, Lu said.
He proposed a test mission so that the physics is demonstrated well in advance of an emergency.
To do nothing would be to invite disaster, he added.
"If we are wiped out by an asteroid, that will be our own fault at this point," he said.
