NASA Should Lead Asteroid Defense, Group Says

National Geographic News
February 4, 2003

Earth has a history of being struck by asteroids, sometimes with devastating effects such as tsunamis, firestorms, and even large-scale extinction of life. Yet no one knows for sure how many large asteroids are out there and if—or when—one might be headed for us. Now a group of experts has recommended a strategy to prepare a planetary defense.

The biggest obstacle towards creating a plan to defend Earth against asteroid impacts is that no national or international organization has been tasked with the job, says an international group of scientists, engineers, and military experts who gathered to assess the danger. The group recommends that NASA should get the job.

The Workshop on Scientific Requirements for Mitigation of Hazardous Comets and Asteroids gathered 77 experts from the United States, Europe, and Japan. It released its final report this week.

"NASA should be assigned to lead a new research program to better determine the population and physical diversity of near-Earth objects that may collide with our planet, down to a size of 200 meters (200 yards)," according to a statement released by the workshop.

The workshop's report also recommended that the U.S. Department of Defense (DoD) work to more rapidly communicate surveillance data on natural airbursts of smaller rocky bodies, and it concludes that governmental policy makers must "formulate a chain of responsibility" to be better prepared in the event that a threat to Earth becomes known.

"As our discussions proceeded, it became clear that the prime impediment to further advances in this field is the lack of assigned responsibility to any national or international governmental organization," said planetary scientist Michael Belton, organizer of the September 2002 workshop. "Since it is part of NASA's newly stated mission to 'understand and protect our home planet,' it seems obvious that this responsibility should reside in NASA."

Belton presented the findings of the workshop this week in Washington, D.C., to officials at NASA, the National Science Foundation, and the Office of Management and Budget, and the report was delivered to the U.S. Congress.

About 2,225 near-Earth objects (NEOs) have been detected, primarily by ground-based optical searches, in the size range between 10 meters (11 yards) and 30 kilometers (19 miles), out of a total of about one million. But some information about the physical size and composition of these NEOs is available for only about 300 objects.

The total number of objects a kilometer in diameter or larger, a size that could cause global catastrophe upon Earth impact, is now estimated to range between 900 and 1,230, according to the workshop. The NASA-led Spaceguard Survey has a congressional mandate to detect 90 percent of these kilometer-sized (thousand-yard) objects by 2008, and it is making "excellent progress" on this goal, the report said.

However, a full survey of objects that could cause significant damage on Earth should reach down to NEOs at least as small as 200 meters (220 yards), the report said, which should be within the capability of proposed ground-based facilities such as the Large Synoptic Survey Telescope and the PanStarrs telescope system.

Ground-based radar systems will remain a "critical contributor" to obtaining the most accurate possible data on the orbits of many hazardous objects, the report said.

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