Sky watchers say 15,000 objects have fallen to earth since 1998
More than 15,000 near-Earth objects (Neos) have been discovered by the Neo Observations programme since its inception in 1998.
The programme, sponsored by the National Aeronautics and Space Administration (Nasa) began to detect, track and characterise potentially hazardous objects, and it is responsible for issuing warnings about a possible impact with Earth.
Neos are comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that put them in the vicinity of the Earth.
Of the Neos tracked, 874 were asteroids with a diameter of 1 kilometre or larger, while 1,745 of these have been classified as potentially hazardous asteroids, a definition based on their size and how closely their orbits approach Earth.
Over billions of years, comets are thought to have created major changes to the oceans, atmosphere and climate, and may have delivered the first carbon-based molecules to our planet, triggering the process of the origins of life.
Larger asteroids occasionally crash into Earth, creating craters such as Arizona’s kilometre-wide Meteor Crater, near Flagstaff.
Another impact site, off the coast of the Yucatan Peninsula in Mexico, which is buried by ocean sediments today, is believed to be a record of the event that led to the extinction of the dinosaurs 65 million years ago.
The programme has found more than 90 per cent of Neos larger than a kilometre wide and is now focusing on finding 90 per cent of the Neo population larger than 140 metres.