Dr. Ed Lu, former US Shuttle and Soyuz Astronaut and co-founder and CEO of the B612 Foundation was joined by former NASA Astronaut Tom Jones, President of the Association of Space Explorers and Apollo 8 Astronaut Bill Anders, first Chairman of the Nuclear Regulatory Commission and former Chairman and CEO of General Dynamics to discuss findings recently released from the Nuclear Test Ban Treaty Organization, which operates a network of sensors that monitors Earth around the clock listening for the infrasound signature of nuclear detonations.
A list of the impacts can be found here.
Asteroid impacts are not rare. We can expect a multi-megaton asteroid impact (large enough to destroy a major city should it hit one) about every hundred years.
No, they are random. Since most of the Earth is covered by water or is unpopulated, that is where most of these impacts occurred.
No, the point is that we currently don’t know when or where the next major impact will be. And that means we are currently defenseless to stop the next impact. But the B612 Foundation is working to change that by flying the Sentinel Mission.
Our previous estimates of the impact odds for small asteroids (such as city killers) were low by about a factor of 3 to 10. This new data suggests that Earth is hit in a random location by a multi-megaton asteroid impact (large enough to destroy a major city) about every hundred years.
The asteroid that hit on June 30, 1908 in Tunguska was about 45 meters in diameter, and had an explosive energy of about 5 megatons. This was clearly large enough to destroy a city.
With the exception of the Chelyabinsk impact, the asteroids in the video are too small to cause large damage on the ground.
Asteroids have a continuum of sizes. We are able to measure the number of very large asteroids such as the ones capable of ending human civilization because we can see these out there in space with our current telescopes. We are also able to measure the number of very very small asteroids which are numerous enough so we can count these as they hit the atmosphere as shooting stars (or meteors). In the middle our data is rather sparse because we have only been able to discover a small fraction of the asteroids in this size range because our telescope can only see them when they come close to Earth. This new data allows us to help fill in the data gap between these very largest and very smallest of asteroids.
These impacts were heard using large listening stations that pick up the low frequency infrasound pulse from the explosions. The data was supplied by Peter Brown. http://www.nature.com/news/
Some of the larger impacts in the video have been reported on previously, but the locations and visualization of this entire data set is new.
Yes, this is a measure of the amount of energy released in the explosion. But location and altitude also matter. For the most part, the asteroids in this video exploded at too high an altitude to do much damage on the ground.