Near-Earth asteroids – How dangerous are they?


They are called near-Earth asteroids, objects made of rock that travel through our solar system and come very close to the planet Earth. Scientists think that some of them may be a threat to our planet. NASA and other space agencies have started scanning the skies for potential asteroids that could collide with Earth.

The American space agency has stated that there are currently about 8,000 asteroids that cross the Earth’s orbit around the sun and may pose a threat to our planet. These lone asteroids are what is left of the formation of our solar system billions of years ago. Some of them come from the asteroid belt between Mars and Jupiter, while others originate elsewhere in the solar system


Although asteroids hit the earth almost every year, they are very small, rarely more than a few meters in diameter. Most of them burn up in our atmosphere and never hit the ground. However, they develop immense energy, sometimes equivalent to the energy that was set free when the first atomic bomb was dropped over Japan during World War II.


Collisions with large objects have happened over and over again during the Earth’s geologic history. About 65 million years ago a giant asteroid hit the Yucatan peninsula in Mexico and formed a crater of about 150 km in diameter. The impact led to climate change on earth and resulted in the extinction of dinosaurs.


In recent history an asteroid exploded over Siberia in 1908. It destroyed trees that covered an area of over 2,000 square kilometers. In the last few decades several objects hit the Earth in various locations. In 2013, over a thousand people were injured after a meteorite exploded in Chelyabinsk, Russia.       

There have also been several close approaches to our planet over the past decades. Most of these asteroids pass earth at a distance of a few thousand miles, somewhere between earth and the moon. Scientists agree that a collision causing massive damage will occur one day, but it is hard to say when.

NASA has set up a program called Safeguard, which aims at finding out where dangerous asteroids are located and tracing their orbits. A new telescope called WISE was launched into space in 2009 and discovered over a hundred asteroids and other objects that had been previously unknown. NASA confirms that there are twice as many potential hazards in space than previously thought.

Other scientists are working on ways of coping with such threats from space.  One method calls for laser beams to destroy asteroids on a collision course with Earth or to bring them off their track. Such a system however would be costly and would need to be assembled in Earth’s orbit. Other plans call for a nuclear bomb to destroy such a deadly object, similar to the way Bruce Willis destroyed an asteroid in the film Armageddon.



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  • aim = task, job
  • although = while
  • assemble = build
  • asteroid belt = many small planets that go around the sun between Mars and Jupiter
  • billion = a thousand million
  • cause = lead to
  • close approach = moving very near towards something
  • collide = crash
  • confirm = to say that something is true
  • cope = deal with
  • costly = expensive
  • cross = go across
  • currently = at the moment
  • decade = a period of ten years
  • destroy = damage completely
  • diameter = a straight line from one end to the other
  • discover = to find for the first time
  • equivalent = equal, the same as
  • extinction = when a life form dies out
  • formation = creation
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  • injure = hurt
  • laser beam = line of powerful light produced by a laser
  • launch = send to space
  • lone = single, isolated
  • massive = great
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  • orbit = to go around an object
  • originate = come from
  • peninsula = piece of land with water around it on three sides
  • pose = be, create
  • potential = possible
  • previously = before, up to that time
  • rarely = not often
  • recent = happening only a short time ago
  • result = lead to
  • scan = look for
  • scientist = person who is trained in science and works in a  laboratory
  • several = many
  • similar = like
  • space agency = organization that controls space programs in a country
  • state = to say officially
  • telescope = object that is shaped like a tube and used for making faraway objects look larger
  • threat = danger
  • trace = find, discover
  • track = path, route
  • twice = two times
  • various = different