Meteor Explosion — Article Cloze

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Read the article about the meteor explosion and choose the word or phrase that best completes each sentence.

An — choose —explosiveremoteenormous event in February of 2013 shows us the dangers that can happen when space debris strikes our — choose —surfaceimpactatmosphere . A — choose —meteorimpactatmosphere 20 meters wide travelling at 68,400 km per hour exploded over central Russia near Chelyabinsk. The blast — choose —blew outlevelleddamaging windows — choose —levellingdamagingblew out more than 7,000 buildings, and sent more than 1400 people to the hospital with cuts and scrapes.

The light from the blast was 30 times brighter than then sun causing skin burns similar to sunburn. The shock wave was so strong that many early morning — choose —surfaceatmospherepedestrians were thrown to the ground.

The power from the blast was 30 times stronger than an atomic bomb. Fortunately, the blast was 40 km high above earth's — choose —pedestrianssurfaceatmosphere which allowed the earth's atmosphere to — choose —detecteddeflectabsorb most ot the shock. If the blast had — choose —absorbdetectedoccurred closer to the ground or if the giant rock was just several meters larger, the destruction would have been — choose —explosiveenormousremote --- — choose —levelleddamaginglevelling buildings and killing thousands of people.

This blast is the biggest known meteor explosion since the 1908 Tunguska meteor blast which flattened 80 million trees in a — choose —remoteexplosiveenormous area of Siberia. The Tunguska blast — choose —levellinglevelledblew out an area more than twice the size of the New York city metropolitan area.

These two events, which have taken place in just over a single person's lifespan, show us not only the danger but the — choose —devastationdestructionlikelihood of larger objects striking the earth and causing complete — choose —destructiondevastationlikelihood of cities or even complete — choose —destructionlikelihooddevastation to the whole planet.

America's national space agency, NASA, takes these threats seriously and has established a program for finding and — choose —detecteddeflecttracking near earth objects (NEOs). More than 13,500 NEOs of all sizes have been discovered — choose —impactoccurredto date . About 1,500 new NEOs are — choose —occurredtrackingdetected each year.

NASA has discovered 90 percent of NEOs larger than 1 km and are now focusing on finding objects that are slightly bigger than a football field -- 140 meters or larger. NASA's goal is to find 90 percent of this class of NEOs within a few years and has found 45 percent of these mid-sized objects to date.

NASA also has long-term planetary defense goals which include finding ways to — choose —trackingdeflectabsorb or redirect objects that are on an — choose —meteorimpactto date course with Earth.