Methods for determining material strengths and bulk properties of NEOs Original Research Article

There are 500 to 1,000 Near-Earth Objects (NEOs: asteroids and comets) larger than 1 km in diameter that can cause catastrophic global effects in a collision with Earth, and 10,000 to 25,000 NEOs that are larger than 200 m in diameter that can cause catastrophic regional or local effects including tidal waves if such an NEO falls into an ocean. To deflect or destroy such objects effectively, their structure and bulk material properties, particularly their material strengths, must be known. However, physical characterization of NEOs has only been carried out by remote sensing. Remote sensing is usually accomplished from the ground, from Earth-orbiting telescopes, and from flyby or rendezvous missions. It includes the determination of the mass, albedo, size, shape, spin state, and various inferences regarding composition and topography of the surface of an asteroid. It does not include determination of an NEOʹs internal structure or material strengths. We review methods for determining bulk properties and geologic structures of NEOs. A database will have to be established to record these properties.