Near Earth Objects Observed By NASA(1900-2021)

A near-Earth object is an asteroid or comet which passes close to the Earth's orbit. In technical terms, a NEO is considered to have a trajectory that brings it within 1.3 astronomical units of the Sun and hence within 0.3 astronomical units, or approximately 45 million kilometers, of the Earth's orbit.
NEOS represent potentially catastrophic threats to our planet. The International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG) are two entities established in 2014 as a result of United Nations-endorsed recommendations, and represent important mechanisms at the global level for strengthening coordination in the area of planetary defense.TThe scientific interest in comets and asteroids is due largely to their status as the relatively unchanged remnant debris from the solar system formation process some 4.6 billion years ago. The giant outer planets (Jupiter, Saturn, Uranus, and Neptune) formed from an agglomeration of billions of comets, and the leftover bits and pieces from this formation process are the comets we see today. Likewise, today’s asteroids are the bits and pieces left ove from the initial agglomeration of the inner planets that include Mercury, Venus, Earth, and Mars.

As the primitive, leftover building blocks of the solar system formation process, comets and asteroids offer clues to the chemical mixture from which the planets formed some 4.6 billion years ago. If we wish to know the composition of the primordial mixture from which the planets formed, then we must determine the chemical constituents of the leftover debris from this formation process - the comets and asteroids.