Earth Impact

Want to stay on top of all the space news? Follow @universetoday on Twitter

An Earth impact is a very real possibility. As a matter of fact, an object burns up in our atmosphere every day. Most do not make it very far into the atmosphere before being vaporized, but a few each year survive to impact the surface. These meteorites rarely cause damage, occasionally hitting a house or car. The last large Earth impact is thought to have taken place in Siberia in 1908 and is referred to as the Tunguska event.

A few years back there was quite a bit of news generated about the possibility of the asteroid 99942 Apophis(2004 MN4 Apophis) impacting the planet with devastating results. The news was mainly hype from undereducated journalists. NASA’s Near Earth Object(NEO) program was on top of the situation and would have been able to give a warning of a truly impending impact.

The possibility of an impact is so real that scientists have developed a risk assessment scale. It is called the Palermo scale. This is a technical algorithmic scale used by astronomers to assess a risk of impact. This scale proved too difficult to teach to the general class of reporter and the public, so a simpler version was developed. The simplified scale, called the Torino scale, uses a score from 0 to 10 to grade the likelihood that an object will impact Earth. A zero indicates that an object has a very low chance of hitting the Earth or will burn up in the atmosphere. On the other end of the scale, a 10 indicates an impact that will cause global devastation no matter where it impacts Earth’s surface. The scores are calculated based on the likelihood of an Earth impact and and the amount of kinetic energy, in megatons, that will be released. Apophis registered a 4 on the Torino scale initially, but was downgraded to a zero as it was studied further.

The possibility of an Earth impact is very real. There are millions of tons of debris in space. Small specks of dust burn up in Earth’s atmosphere on a daily basis, but large impactors are few and far
between. NASA continues to study and catalog each NEO so as to assess and dismiss each threat. Even so, most countries around the world have a disaster plan in place in the event of an impending impact.

There is a great article on Earth impact here on Universe Today and a good related episode on Astronomy Cast.

Sources:
http://neo.jpl.nasa.gov/risk/
http://neo.jpl.nasa.gov/risk/a99942.html
http://neo.jpl.nasa.gov/neo/
http://neo.jpl.nasa.gov/risk/doc/palermo.html

Tagged as: Asteroids, Earth impact, impact craters