We sometimes hear news in which [A] asteroids pass near Earth, with the possibility of a catastrophic outcome if there was a direct hit.
But most experts agree that there is little likelihood that large asteroids or other space objects will collide on Earth and cause great destruction.
Many organizations recognize the real risk of such an event. An example is NASA, the space agency of the US government. NASA and its international partners are constantly searching for what scientists call Near Earth Objects (NEOs). These objects include asteroids and comets that are within 50 million kilometers of Earth orbit.
This week, NASA is working with the US Federal Emergency Management Agency (FEMA) and international experts to investigate the possibility of a NEO on Earth. At a conference near Washington, DC, scientists will simulate a fictional asteroid to find out what could happen if a real hit is defended.
What is an asteroid?
An asteroid is a rocky, airless object. Asteroids are sometimes referred to as minor planets. They are left over from the early formation of our solar system about 4.6 million years ago. Most asteroids can orbit the sun between the planets of Mars and Jupiter. NASA reports that scientists have identified more than 795,000 asteroids in total.
A comet is a small, sometimes active object that contains ice. In sunlight, the Eisdose can evaporate to a dust and gas atmosphere.
NASA reports that an asteroid the size of an automobile passes into the Earth's atmosphere about once a year. Such objects turn into a fireball and burn before they reach the Earth's surface.
About every 2,000 years, a much larger object hits Earth and causes great damage. However, NASA experts say that an object large enough to threaten Earth's civilization occurs only every few million years.
The Assembly this week – from April 29 to May 3 – is called the Planetary Defense Conference. Participants from NASA, FEMA and other government agencies and experts from around the world will participate in a simulated test exercise.
The "Table Exercise" considered a false threat from an asteroid invented by NASA's Jet Propulsion Laboratory (JPL). Groups will investigate possible emergency and response measures to deal with man-made asteroid hazards.
Lindley Johnson is a NASA planetary defense officer. He said the exercise would be an opportunity to create better international preparation and response in the event of a real threat. "This … will help us develop more effective communication with each other and with our governments," he added.
The exercise is based on the invented discovery of a NEO that, according to conference organizers, will hit Earth 2027. The exercise estimates the 1: 100 chance that the NEO hits the planet.
NASA officials say the international community has decided that in real life, a 1 in 100 chance would be enough to think about a defensive and emergency response.