Near-Earth Objects (NEOs) are asteroids, comets and large meteoroids whose orbits bring them close to Earth. One official classification of an NEO says that the object's orbit must come closer to Earth than a (perihelion) distance of 1.3 Astronomical Units - 195 000 000 kilometres.
Scientists have discovered that many asteroids and comets have collided with the Earth throughout its 4.5 billion year history. The impact of these NEOs with our planet could be catastrophic and still represents a natural hazard today.
There are about 20 000 Near Earth Asteroids of 140 metres diameter and larger. Millions of other asteroids are in distant orbits in the "Asteroid Belt" between Mars and Jupiter. There is also an unknown number of comets classed as NEOs whose orbits might cross that of Earth's.
It must be remembered that the risk from a collision with an NEO is extemely small! The highest known risk to Earth is from an asteroid called Apophis which will pass close to Earth on 13 April 2036. Scientists have calculated that there is less than a 0.003% chance of it hitting our planet. Put another way, the chance of Apophis avoiding the Earth is over 99.997%. These are long odds!
However, for a few years now, the issue of NEOs has been given more and more attention from space agencies, institutions and working groups at national, regional and international levels.
NEOS were given special attention in 2007. In February 2007, the Association of Space Explorers presented a paper to the Scientific and Technical Subcommittee at 42nd session of the Committee on the Peaceful Uses of Outer Space (COPUOS).
From that paper came an initiative which has set up a series of meetings of experts and other interested people which will explore the subject of NEOs and possible means of diverting these objects from Earth before they would hit.
The experts will draft a Treaty that should be presented to the UN General Assembly in 2009.
The IAF has interviewed Dr Roger Bonnet on his involvement in this initative.
Other initiatives
Meanwhile, related international bodies are also involved in this field. For instance, an "Action Team" from the United Nations Office of Outer Space Affairs (UN-OOSA) compiled a report in February 2007 upon what international space organisations are doing in the field. The OECD has also been active.
Some national initiatives are active. The Near Earth Object Information Centre is based in the United Kingdom. DLR in Germany maintains a database of all known NEOs. Harvard University allows anybody to contribute their expertise.
Further reading
If you are interested in NEOs, we have compiled some links to help you explore this subject.
Image information
Image 1: The near-Earth object known as 2004 VD17 may give Earth a close shave in the year 2102. Credit: Don Davis/NASA
Image 2: The near-Earth asteroid 25143 Itokawa as imaged by the Japanese space probe Hayabusa. Credit: JAXA.
Image 3: Comet Hale-Bopp sails across the sky in the vicinity of Pazin in Istria, Croatia. Credit: Philipp Salzgeber
