Near Earth Objects
Near earth objects are comets, asteroids, meteoroids that have been brought close to earth because of their orbit. Due to their close proximity to earth there is always a danger that there may be a collision between these objects and earth. Near earth objects have also been called NEOs for short. However, while there is a danger of a collision, NEOs are very important to scientists. Their close proximity to earth allows them to be easily accessible to spacecraft and therefore they can be studied, which can give us some very important or useful information.
In the United States it has been a congressional mandate that all near earth objects that are least one kilometre wide must be catalogued. At this size or larger there is a worry if a collision was to occur the damage caused to earth would be catastrophic. To date approximately eight hundred of these NEOs have been catalogued.
There are two methods used to determine the amount of threat there is from a near earth object. The first method of determining threat is through the use of the Torino Scale. This is a tool that is intended for use by astronomers. Using this scale, a combination of probability statistics and known kinetic damage potential is used to form a single threat value. This scale ranges from zero to ten; zero being a very low risk of collision and ten being an extremely high risk of collision and potential damage.
The more complex method of determining risk is the Palermo Technical Impact Hazard Scale. This is a logarithmic scale that is used by astronomers to rate the potential impact hazard. There are two types of data used in this process of determining the risk. They use probability statistics and kinetic yield to determine a single danger value. This scale is also based on a scale of zero to ten with ten being the highest level of danger.