NASA has set up a Planetary Defense Coordination Office -- to defend the Earth from asteroids and comets that get too close for our comfort.
The department, which includes the position of Planetary Defense Officer, is managed by the Planetary Science Division of the Science Mission Directorate at NASA Headquarters in Washington DC. And its mission includes the early detection of potentially hazardous objects (PHOs) -- asteroids and comets which get within 0.05 Astronomical Units of Earth's orbit around the sun (7.5 million kilometers) and are large enough, greater than around 30 - 50 meters (98 - 164 feet), to reach the Earth's surface.
They must also track and issue warnings on the minor planets, or even try to redirect them. If it's too late and space rubble is found hurtling towards the Earth's surface, the team will coordinate with the U.S. government to plan a response to an actual impact threat.
are debris left over from the early formation of our solar system about 4.6 billion years ago. Rocky asteroids vary in size and are mainly found orbiting the sun between Mars and Jupiter. This area, known as the asteroid belt, is estimated to contain between 1.1 and 1.9 million asteroids larger than 1 kilometer (0.6 miles) in diameter, and millions of smaller ones.
Jupiter's massive gravity and occasional close encounters with Mars or any other object change the asteroids' orbits, knocking them out of the main belt and causing them to slam into Earth and other planets in the past.
Dark comets are icy objects that exist beyond Nepture, orbiting the sun near Pluto. They are sometimes pushed by gravity into orbits that bring them closer to the sun, at which point they become what are known as short-period comets.
Astronomers detect near-Earth objects (NEOs) using ground-based telescopes around the world as well as NASA's space-based NEOWISE infrared telescope.
So how imminent is the danger of near-Earth objects?
More than 13,500 NEOs have been discovered to date and about 1,500 are detected each year.
"Asteroid detection, tracking and defense of our planet is something that NASA, its interagency partners, and the global community take very seriously," said John Grunsfeld,
associate administrator for NASA's Science Mission Directorate in Washington.
"While there are no known impact threats at this time, the 2013 Chelyabinsk
super-fireball and the recent 'Halloween Asteroid'
close approach remind us of why we need to remain vigilant and keep our eyes to the sky."
But it's not all bad news.
Asteroids that venture too close to the Earth's surface also have their benefits. In future, they can be exploited for raw materials used in developing space structure
s or generating the rocket fuel required to explore the solar system.