NASA says today’s asteroids flying between the Earth and Moon are grazing us by merely 50,000 miles. The Catalina Sky Survey discovered both objects on Sunday.
This near-miss was not detected earlier because these two asteroids are too small for today’s equipment. But smaller asteroids, say just 100 feet across, are dangerous. They’ll explode in the upper atmosphere sending an intensely hot jet of superheated gas over a large area.
One asteroid, 2010 RX30, estimated by NASA to be between 10 and 20 meters across, passed within 248,000 kilometers of Earth at 10.51 am BST today. The second, 2010 RF12, estimated to be only 6 to 14 meters across, will pass within 79,000 kilometers at 10:12 pm tonight. Both were only discovered on Sunday, just three days before their time of closest approach. That is due to their small size; smaller objects are harder for telescopes to pick up.
:::Fireball::: The center of mass of an exploding projectile is transported downward in the form of a high-temperature jet of expanding gas.
The burst first descends at subsonic velocity, coupling its kinetic energy and internal energy to the atmosphere.
Blast waves and thermal radiation pulses from the hot jet of vaporized projectile impact the Earth’s surface where it expands supersonically at temperatures well above the melting point of glass.
Devastation at Tunguska in Russia in 1908 is now thought to have been caused by an asteroid just 100 – 150 feet across! Current equipment is designed to give us early warning of asteroids 500 feet across. There’s some healthy discussion about what’s adequate.