By Lisa M. Krieger
An asteroid the size of a 15-story building will zoom past Earth next week, flying uncommonly close but posing no danger.
If its route had been different, the morning of Friday, Feb. 15, would have been the last hurrah for a swath of landscape somewhere on Earth the size of the San Francisco Bay Area, striking with a force equivalent to 2.4 million tons of TNT.
But instead, the spinning chunk of rock will continue on its long loop, averting apocalypse and thrilling scientists.
"It is a record close approach for an asteroid of this size," said Donald Yeomans, manager of the Near Earth Objects Office at NASA's Jet Propulsion Laboratory in Pasadena, in a Thursday morning press conference.
On average, an asteroid of this diameter -- estimated to be about 150 feet -- gets this close every 40 years or so, he said. A collision would be expected every 1,200 years.
It will be tough to see from the continental U.S. The best views -- not with the naked eye, but binoculars and small telescopes -- will be in Eastern Europe, Asia and Australia, with the closest view from Indonesia. These nighttime viewers will see a traveling star-like pinpoint in the night sky, said NASA experts.
By the time the earth rotates enough to give California a glimpse, at 11:45 a.m., it will be too bright to see.
If weather cooperates, the powerful telescopes at Chabot Space & Science Center hope to catch a glimpse. Chabot's observatory is one of a team of observatories around the world that regularly searches for and tracks asteroids that may come close to the Earth.
Lick Observatory has no plans to observe the asteroid because the sky will be too bright and it will be moving too fast for the Mount Hamilton telescopes, said Elinor Gates, a Lick staff astronomer.
"At its closest approach, Asteroid 2012 DA14 -- a name only an astronomer could love, based on when it was discovered -- will be 17,200 miles away, about six times the distance from California to New York City. That's about the same distance the Earth travels in just 15 minutes -- and far nearer to us than the moon.
While that's too far away to perturb most Earthlings, it's "a close shave" according to Apollo astronaut Rusty Schweickart, who is on a mission to map all the menacing asteroids.
"It's a wake-up call from our solar system," wrote Schweickart, founder of the B612 Foundation, which urges planning for the inevitable day our paths collide.
The rock will fly between us and our beloved GPS and weather satellites, which would resemble bugs on a windshield if they collided with DA14.
Fortunately, their paths are unlikely to cross. NASA has given the satellite owners the files that describe the asteroid's trajectory, so they can calculate risk. "It is extremely unlikely that any satellite would be threatened," said NASA's Yeomans. "No one has raised a red flag."
It is traveling 7.8 kilometers a second, about eight times the velocity of a bullet, said Yeomans.
With an estimated mass of 130,000 metric tons -- larger than the gross tonnage of the world's largest passenger ship, Allure of the Seas -- any impact would level trees with an "air blast," not a crater.
Upon reaching our atmosphere, it would flatten like a pancake and explode prior to striking, said Yeomans.
Just 105 years ago, a comparable asteroid struck Earth in Siberia near Tunguska, and completely flattened a forested area of about 840 square miles.
It was a much larger asteroid that struck Mexico's Yucatan and wiped out dinosaurs and three-quarters of all plant species, cooling the Earth and redirecting evolution to create the species we know today.
New asteroids are discovered every week, and they must be tracked for several days in order to verify their orbit characteristics.
We are living in a cosmic shooting gallery.
"Although astronomers have identified some 9,500 (Near Earth Objects), we estimate there may be as many as a million that have not yet been found," said Chabot's Gerald McKeegan.
More advanced tools will give scientists a chance to map its surface, learning about its craters and boulders.
NASA's asteroid researchers will use infrared-sensing telescopes to study DA14.
In addition, scientists will ping DA14 with radar from giant dishes in the Mojave Desert between Feb. 16 and 20. They also want to study its path.
"Radar provides precise estimates of an asteroid's orbit and its physical characteristics," said Amy Mainzer, principal investigator of NEOWISE Observatory at NASA's Jet Propulsion Laboratory in Pasadena.
DA14 is small, by asteroid standards. It was discovered on Feb. 23, 2012, by the La Sagra Sky Survey telescope in Spain.
It probably came from the main asteroid belt, between Mars and Jupiter. But millions of years ago, Jupiter's gravity, combined with other forces, caused the asteroid to leave the main belt and move to an orbit closer to the sun, said Chabot's McKeengan.
Its close call with Earth will alter the fate of DA14 far more than ours.
That's because it is flying so close to Earth's gravitational pull that we'll change its orbit — shortening its spin around the sun from 368 to 317 days, shaving off several months.
Never again in our lifetimes will we see it -- or need to worry.
"The Earth will put this one in an orbit that is considerably safer than the orbit it has been on," said NASA's Yeomans.
Contact Lisa M. Krieger at 650-492-4098.