Scientists warn of risk to planet from orbiting asteroids

Bill Nye the Science Guy discusses asteroids during an international press conference to announce Astroid Day at California Academy of Sciences Dec. 3, 2014 in San Francisco, Calif. Bill Nye the Science Guy discusses asteroids during an international press conference to announce Astroid Day at California Academy of Sciences Dec. 3, 2014 in San Francisco, Calif. Photo: Leah Millis / The Chronicle Photo: Leah Millis / The Chronicle Image 1 of / 5 Caption Close Scientists warn of risk to planet from orbiting asteroids 1 / 5 Back to Gallery

In a new campaign to make the world aware of the threat from orbiting asteroids, American astronauts and astronomers are sponsoring a global program to be carried out by government space agencies and industries, astronomy organizations, schools and science museums on every continent.

They are proclaiming June 30 as Asteroid Day to focus on the effort.

Scientists know of two asteroids that have crashed on Earth, and they warn that someday one could wipe out all life in every country.

“The more we learn about asteroid impacts, the clearer it becomes that the human race has been living on borrowed time,” said Brian May, a noted British astrophysicist who is also the guitarist of the famed rock band Queen.

May spoke Wednesday during a televised press conference in London and America that was aired at the California Academy of Sciences, where former astronauts Rusty Schweickart, Ed Lu and Tom Jones also spoke.

“There are probably a million asteroids in orbit around the sun,” May said, “but we have tracked only 1 percent of them — about 10,000. And we now have the possibility — probably — to avert a major wipeout of the species.”

That possibility means detecting all the asteroids that threaten Earth, said Schweickart and Lu, who noted that space agencies around the world spend only $45 million a year in total to detect and track them, with NASA’s share from Congress accounting for $40 million.

Lu and Schweickart lead a foundation to build the first privately owned space telescope, called Sentinel. It is now being built with a launch expected by 2019. The cost: $250 million, Lu said.

“Detecting the nearby asteroids on their orbits that threaten Earth is critical and the most expensive,” the former astronauts agreed. But slowing their orbits to avoid disaster is much more simple, they said. It could be done by a small spacecraft programmed to intercept an asteroid’s course and nudging it to delay its speed by only a millimeter or two — “the pace of an ant crawling,” Lu put it — so it misses the Earth.

More than 100 scientists and political leaders around the world have now signed a “100x Asteroid Declaration” calling on their technology agencies to speed the pace of asteroid detection from today’s rate of 1,000 a year to at least 100,000 within 10 years.

The Asteroid Day effort and its programs now being developed can be found at www.asteroidday.org

David Perlman is the San Francisco Chronicle’s science editor. E-mail: dperlman@sfchronicle.com