Should Most People Worry About Asteroid Impacts? Experts Say It's Complicated!

A NASA spacecraft the size of a golf cart has been guided to collide with an asteroid in the hopes of throwing it off track somewhat. The goal of the test is to show that we are technologically prepared if an asteroid danger is recognized in the future.

The DART (Double Asteroid Redirection Test) launched from California on November 23 atop a SpaceX rocket and will arrive at the target asteroid system in September of next year.

The expedition will go to Didymos, an asteroid that belongs to the Amor group of asteroids. Didymos is orbited every 12 hours by Dimorphos, a mini-moon or "moonlet." DART will go after the smaller part of the duo.

DART will reveal how much mass and speed are required to impact an asteroid that may pose a concern in the future. It would be tough to construct a deflection mechanism for a big asteroid danger.

Didymos and Dimorphos aren't dangerous, but should most people be concerned about asteroid impacts? It's complicated, as is the case with many things.

Should People Really Worry About Asteroid Impact?

The prospect and dread of a giant asteroid colliding with Earth in the future prompted NASA's DART mission. First and foremost, the question is not whether an asteroid will collide with the Earth: it is whether an asteroid will collide with the Earth. It has not only happened previously, but it happens regularly.

Tiny asteroids collide all the time - according to NASA (via Space.com), something the size of a small car impacts Earth's atmosphere around once a year, but such things burn up and explode far before they touch the ground.

When this happens, no one notices, except possibly to believe it's a pretty amazing show, because these rocks produce meteors, the "shooting stars" that we like viewing on a dark, beautiful night. Meteoroids, which are genuine bits of the asteroid that are burning up, create meteors. The great majority of meteoroids are only a few millimeters or fractions of an inch in diameter.

Meteorites are larger objects that fall to Earth's surface. Only one person is known to have been physically hurt by a meteorite: Ann Hodges, who was struck in the leg by a 9-pound meteorite in 1954. She didn't get a life-threatening bruise.

Meteoroids big enough to penetrate far into the Earth's atmosphere and explode are known as bolides or fireballs. A bolide may live until it is close enough to the Earth's surface for spectators to hear the explosion; certain airblasts can cause damage to neighboring residences, as happened in the Russian town of Chelyabinsk in 2013.

Many more little things are orbiting the sun than huge ones, and the ratio is nearly logarithmic. For every million sand-grain-size particles, there will be only one that weighs 2 pounds (1 kilogram). For each 2,000-pound asteroid, there will be a trillion tiny meteors (1,000 kg).

Assessing the Risk

According to NASA, the Torino scale is a system for classifying the impact threat posed by a near-Earth object (NEO). It employs a scale of 0 to 10, with 0 indicating a negligibly tiny possibility of collision and ten telling that a collision is imminent, with the hitting item massive enough to cause a worldwide calamity.

The Chicxulub impact (which is thought to have wiped off non-avian dinosaurs) was a Torino scale ten event, the Planetary Society said. The impacts that formed the Barringer Crater and the 1908 Tunguska event are both Torino Scale 8 events.

As online news and people's capacity to record occurrences grows, asteroid "near-misses" tend to instill anxiety in public. At the moment, NASA is keeping a careful check on the asteroid Bennu, which has the highest "cumulative danger rating."

Bennu's 500m diameter allows it to create a 5km crater on Earth. However, NASA has said that the asteroid has a 99.943 percent probability of missing the planet.

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