VOA常速英语:Scientists Debate, Prepare for Killer Asteroid

NEW YORK — Earthquakes,  Tsunamis,  Volcanoes.  Now, add asteroids to the list of natural disasters that can threaten humanity and all life on our planet. 
 
For decades, Hollywood films like Deep Impact and Armageddon have let  moviegoers enjoy the terror of fictional earthbound asteroids from the safety of their seats.
 
But on February 15th of this year, residents of Chelyabinsk in central Russia discovered that the threat is as real as it gets. 

That meteorite wounded more than 1,000 people - a piNPRick compared to the one that probably wiped out the dinosaurs 65 million years ago, and far more benign than the meteor that exploded over Siberia in1908, leveling more than 2,000 square kilometers of forest.

Or the meteorite that hit present day Arizona, 50,000 years ago, and made a crater large enough to swallow up the entire city of San Francisco.

But those strikes were no flukes.

There are an estimated 10,000 known asteroids orbiting our region of the inner solar system.  That’s just one percent of the million or more asteroids scientists believe to be our near neighbors in the inner Solar System.

Recently, at the American Museum of Natural History in New York, astrophysicist Neil deGrasse Tyson warned about....

" ...asteroids crashing to earth as meteorites or exploding in the atmosphere. That would be bad," he said.

He invited a group of concerned astronaut-scientists from the Association of Space Explorers, which included Thomas Jones.

“So one of these big explosions is capable of causing a global shutdown in agriculture and starving billions of people to death, as well as those who are killed by the actual explosion itself.  Now small asteroids might level a city, but we could still lose hundreds of thousands of people," said Jones.

Asteroids are chunks of dark mineral rich rock that reflect almost no sunlight, so they are hard to spot from Earth.  But infrared sensors on a space-based telescope could detect the heat they have absorbed from the sun.

That will be the job of the Sentinel Deep Space Telescope, bristling with infrared sensors, along with mapping and communications gear.  The Sentinel mission is the brainchild of former astronaut Edward Lu and his B612 Foundation, which is committed to reducing the asteroid threat.  Sentinel is scheduled to launch in 2018.

“Our telescope is sensitive enough that you actually can see a charcoal briquette against a black sky from ten times the distance from New York to Los Angeles," said Lu.

Once the asteroids are spotted and their orbits determined, an earthbound asteroid can be nudged slightly off course with a satellite deflector or a high velocity projectile, or blown up with nuclear weapons, causing it to miss its deadly rendezvous.

Much like Hollywood imagined it would in the 1957 science fiction film The Day the Sky Exploded.
 
But this time it’s the real world that would be saved.