(Reuters) - The chance of a city-killing asteroid striking Earth is higher than scientists previously believed, a non-profit group building an asteroid-hunting telescope said on Tuesday.
A global network that listens for nuclear weapons detonations detected 26 asteroids that exploded in Earth's atmosphere from 2000 to 2013, data collected by the Comprehensive Nuclear Test Ban Treaty Organization shows.
The explosions include the Feb. 15, 2013, impact over Chelyabinsk, Russia, which left more than 1,000 people injured by flying glass and debris.
"There is a popular misconception that asteroid impacts are extraordinarily rare ... that's incorrect," said former astronaut Ed Lu, who now heads the California-based B612 Foundation.
The foundation on Tuesday released a video visualization of the asteroid strikes in an attempt to raise public awareness of the threat.
Asteroids as small as about 131 feet (40 meters) - less than half the size of an American football field - have the potential to level a city, Lu told reporters on a conference call
"Picture a large apartment building - moving at Mach 50," Lu said.
Mach 50 is 50 times the speed of sound, or roughly 38,000 mph (61,250 kph).
NASA already has a program in place that tracks asteroids larger than 0.65 mile (1 km). An object of this size, roughly equivalent to a small mountain, would have global consequences if it struck Earth.
An asteroid about 6 miles (10 km) in diameter hit Earth some 65 million years ago, triggering climate changes that are believed to have caused the dinosaurs - and most other life on Earth at the time - to die off.
"Chelyabinsk taught us that asteroids of even 20-meter (66-foot) size can have substantial effect," Lu said.
City-killer asteroids are forecast to strike about once every 100 years, but the prediction is not based on hard evidence.
B612 intends to address that issue with a privately funded, infrared space telescope called Sentinel that will be tasked to find potentially dangerous asteroids near Earth. The telescope, which will cost about $250 million, is targeted for launch in 2018.
B612 takes its name from the fictional planet in the book "The Little Prince," by French author and aviator Antoine de Saint-Exupery.
Deadly asteroid strike may be more probable than believed
This undated handout two-picture combo of artist conceptions provided by NASA/JPL Caltech shows what NASA says are good candidates for a mission to capture an asteroid, haul it to the moon for astronauts to visit. One prime candidate swung close by Earth in 2011 so astronomers know its size, about 20 feet, mass and density, but they donât really know what it looks like. These images are two different artist conceptions of what the lightweight asteroid could look like, either a pile of small rocks flying together in formation, left, or a larger porous rock with pebbles surrounding it, right. (AP Photo/NASA/JPL Caltech)
NASA Administrator Charles Bolden, right, talks with electric propulsion engineer John Brophy during a visit to Nasa's Jet Propulsion Laboratory in Pasadena, Calif., Thursday, May 23, 2013. They are standing next to an ion engine, which NASA engineers plan to use for an asteroid capture mission later this decade. (AP Photo/Nick Ut)
NASA Administrator Charles Bolden, left to right, Firouz Naderi, Director for the Solar System Exploration, and John Brophy, Electric Propulsion Engineer, are shown during Bolden's visit to the Jet Propulsion Laboratory in Pasadena, Calif., on Thursday, May 23, 2013. NASA engineers are developing an ion engine for an asteroid capture mission later this decade. (AP Photo/Nick Ut)
FILE - In this Feb. 15, 2013 file photo provided by Chelyabinsk.ru, shows a meteorite contrail over the Ural Mountains' city of Chelyabinsk, about 930 miles east of Moscow, Russia. After a surprise meteor hit Earth at 42,000 mph and exploded over a Russian city in February, smashing windows and causing minor injuries, scientists studying the aftermath say the threat of space rocks hurtling toward our planet is bigger than they had thought. Meteors like the one that exploded over Chelyabinsk _ and those that are even bigger and more dangerous _ are probably four to five times more likely to hit Earth than scientists thought before the February mid-air explosion, according to three studies released Wednesday in the journals Nature and Science. (AP Photo/Chelyabinsk.ru, Yekaterina Pustynnikova, File)
This artist rendering released by IMCCE (Institut de Mecanique Celeste et de Calcul des Ephemerides) shows water plumes spewing from the surface of the dwarf planet Ceres. Scientists led by the European Space Agency observed the plumes and reported their findings in the Jan. 23, 2014 issue of the journal Nature. (AP Photo/ IMCCE, Paris Observatory, CNRS)
This combination of Sept. 10 and 23, 2013 photos provided by NASA shows six comet-like tails radiating from a body in the asteroid belt, designated P/2013 P5. The Hubble Space Telescope discovered it in the asteroid belt between the orbits of Mars and Jupiter. A research team led by the University of California at Los Angeles believes the asteroid is rotating so much that its surface is flying apart. Itâs believed to be a fragment of a larger asteroid damaged in a collision 200 million years ago. (AP Photo/NASA, ESA, D. Jewitt - UCLA)
Maps show how scientists will narrow the field of impact in the weeks approaching the time of impact.; 2c x 5 inches; 96.3 mm x 127 mm;
This image provided by NASA/JPL-Caltech shows a simulation of asteroid 2012 DA14 approaching from the south as it passes through the Earth-moon system on Feb. 15, 2013. The 150-foot object will pass within 17,000 miles of the Earth. NASA scientists insist there is absolutely no chance of a collision as it passes. (AP Photo/NASA/JPL-Caltech)
An undated artist rendering released by NASA shows the NASA Dawn spacecraft in orbit around the giant asteroid Vesta. After spending a year examining Vesta, Dawn is poised to depart and head to another asteroid, Ceres, where it will arrive in 2015.(AP Photo/NASA)
This computer-generated image provided by Planetary Resources, a group of high-tech tycoons that wants to mine nearby asteroids, shows a conceptual rendering of satellites prospecting a water-rich, near-Earth asteroid. The group's mega-million dollar plan is to use commercially built robotic ships to squeeze rocket fuel and valuable minerals like platinum and gold out of the lifeless rocks that routinely whiz by Earth. One of the company founders predicts they could have their version of a space-based gas station up and running by 2020. (AP Photo/Planetary Resources)
This image released Monday, Dec. 5, 2011, by NASA is a mosaic of three images taken by the Dawn spacecraft's camera showing an impact crater on the surface of the massive asteroid Vesta. Since entering orbit around Vesta in July, Dawn has been beaming back images of the asteroid surface. (AP Photo/NASA)
This July 24, 2011 image of the Asteroid Vesta, released by NASA/JPL, was captured by the Dawn spacecraft at a distance of 3,200 miles (5,200 kilometers). Dawn entered orbit around Vesta on July 15, and will spend a year orbiting the body. After that, the next stop on its itinerary will be an encounter with the dwarf planet Ceres. (AP Photo/ NASA/JPL)