The Earth may have survived its close encounters with an asteroid and a meteor Friday, but the episodes focused new attention on gaps in astronomers' ability to identify smaller space rocks like these capable of inflicting widespread destruction.
Efforts to better identify those threats are underway, including a new space telescope from a Silicon Valley foundation, and a coordinated telescope system in Hawaii.
"We're carrying out the most ambitious private interplanetary space mission ever. We're building a space telescope, we're going to find them and track them so we have decades of notice before another one of these hits," says Ed Lu, a former shuttle and International Space Station astronaut who heads the B612 Foundation. If it is able to raise $450 million, the scientists plan to launch a meteor-mapping satellite in 2017 or 2018.
Hits on its website increased more than 1,000% in the past two days, said spokeswoman Diane Murphy. "We have received tens of thousands of dollars in contributions from private online donors in support of this global effort." A $1,000 donation came in over the weekend from someone in Lithuania, she said.
Meanwhile, a team at the University of Hawaii is working on ATLAS: The Asteroid Terrestrial-Impact Last Alert System, with the aid of a $5 million grant from NASA. Using eight small telescopes, the asteroid detection system would scan the sky twice a night looking for objects moving through space. The plan is to have the system operational by the end of 2015. They predict their system could offer a one-week warning for a 50-yard diameter asteroid, or "city killer," and three weeks for a 150-yard-diameter "county killer."
"That's enough time to evacuate the area of people, take measures to protect buildings and other infrastructure, and be alert to a tsunami danger generated by ocean impacts," says John Tonry at the university's Institute for Astronomy.
GLOSSARY: Asteroids, meteorites and more
STORY: Fireball reported across California sky
STORY: Russian region begins recovery from meteor damage
The Russian meteor came as a surprise when it blazed across the sky Friday morning over Russia's Chelyabinsk? region, 900 miles east of Moscow. NASA scientists estimated it was about the size of a school bus, between 30and 50 feet across, traveling at 40,000 mph.
Thankfully, most of the meteor burned up as it hit the atmosphere 15 miles up, says Bill Cooke, lead for the Meteoroid Environments Office at NASA's Marshall Space Flight Center in Huntsville, Ala. Although a few small pieces might have hit the ground, the friction of hitting the atmosphere turned it into the fireball that transfixed the world and produced an aerial blast as powerful as 20 Hiroshima bombs, according to Russian estimates. The shock wave produced by the meteor blew out windows in an estimated 4,000 buildings, injuring around 1,200 people, mostly with glass cuts.
The day's second visitor was asteroid 2012 DA14, which astronomers had been tracking for over a year. It was clear the 150-foot chunk of rock would skim by Earth. At its closest it was 17,100 miles above the planet.
None of this is surprising. Earth resides in a cosmic shooting gallery and has been bombarded with meteor and asteroid impacts from its beginning 4.6 billion years ago, says Jay Melosh of Purdue Universityin West Lafayette, Ind. Craters on the moon, on Earth and on places stretching from Mercury to the moons of Saturn tell a story of intense meteor bombardment.
Even now, a small meteor typically strikes Earth daily, says Paul Chodasof NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Still, there's no need to lose sleep over worries another one may be headed straight for your town. "Events this large are rare events," says NASA's Cooke. He spent Friday tracking both. "They occur once every 50 to 100 years, so you're likely to see only one of these in your lifetime."
Another calming thought is that the Earth is mostly water. While the Russian meteor came in over land, "over two-thirds of them will cross over water and we won't know about them. So people should not run around thinking that cities are being destroyed," Cooke says.
In general, astronomers have a very poor handle on meteors and asteroids the size of 2012 DA14 or smaller, like the Russian one, says Melosh, simply because they are so small and hard to spot. A 2010 National Research Council report called for Congress to better fund a space agency effort to find asteroids bigger than a football field. Chodas says that funding for such efforts has improved since then, but Friday's events have spurred calls for improved telescope or space-based sentries to watch for impact threats. Overall, about 99% of all "Near-Earth Objects" are undiscovered, mostly smaller ones but also objects as big or bigger than 2012 DA14 and the Russian meteor.
A 2011 study using NASA's Wide-field Infrared Survey Explorer (WISE) spacecraft suggested that perhaps 20,500 asteroids and comets more than 100 yards wide orbit in Earth's neighborhood and confirmed that the space agency has spotted more than 90% of the largest ones - bigger than a half-mile wide. Just about 1,000 of those "civilization-busters" that would cause large-scale havoc if they hit Earth are thought to exist. None looks like a threat for now, and statistics suggest one hits Earth about once every 700,000 years.
Small asteroids and comets are especially difficult to spot from Earth-based telescopes. A space-based telescope would be much more efficient in finding them and that's just what the B612 Foundation in Mountain View, Calif., is building, says Gerald McKeegan, an astronomer at the Chabot Space and Science Center in Oakland. "These things just remind us that there's a lot of them out there and sooner or later they're going to hit us."
Making sure that doesn't happen is the reason behind the Sentinel Mission satellite currently under construction by the B612 Foundation. "We realized we could complain and worry about why someone else wasn't doing it or just do it ourselves," says Ed Lu, a former shuttle and International Space Station astronaut who heads the foundation. It gets its name from the asteroid home of The Little Prince, in the famous children's novel by Antoine de Saint-Exupéry. They rely entirely on private funding.
The satellite would launch in either 2017 or 2018 and go into a Venus-like orbit around the sun. For six and a half years it would plot the movements of every asteroid in the area. That will create a map "we'll give to the world" that should be good for about a century "so we won't need to do it again for 100 years," Lu says.
The project will cost $450 million. That might seem like a lot, but is actually about $150 million less than the price tag for the expansion of the San Francisco Museum of Modern Art. For the same amount of money "you can save the world. Literally," Lu says.