'Potentially hazardous': Largest known asteroid to fly past Earth in 2021

The largest asteroid to fly past the Earth in 2021 is set to make a close approach to the planet on March 21.

Comparable in size to the Golden Gate Bridge, asteroid 231937 or 2001 FO32, will pass within 2,016,351 km of Earth in 2021.

Based on its brightness and the way it reflects light, 2001 FO32 is approximately between 0.767 to 1.714 kilometres in diameter. At Congress's direction, NASA has supported a ground-based program to identify the NEOs larger than one kilometre in diameter.

NASA's Jet Propulsion Laboratory has classified 2001 FO32 as a "potentially hazardous asteroid" due to its predicted close pass(es) with Earth.

Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid's potential to make threatening close approaches to the Earth.

The high-altitude explosion of a body 80 meters in diameter above Tunguska, Siberia, in 1908 flattened trees over a broad area. A differently aimed impact of this scale could flatten a modern city, with deaths in the millions.

Bodies larger than about 100 metre in size cause ground-level explosions in the giga-ton, or billions of tons, range. Such impacts would devastate whole countries. There is about a 1 per cent chance that such an impact will occur in the next century.

Assessment of the Potentially Hazardous Asteroid (PHA) population down to 100-meter scales, as part of an organized inventory of the small bodies of the solar system, is recognized as a high priority for NASA's Solar System Exploration program.

Extrapolations from existing surveys suggest that the number of PHAs larger than 100 m is on the order of 10,000 to 20,000.