A nuclear weapons test warning network -- the Nuclear Test Ban Treaty Organisation -- in Canada has detected 26 multi-kiloton explosions since 2001: all due to asteroid impacts. This could be just the tip of an iceberg, says the non-profit B612 Foundation.
Information released for the foundation's Earth Day press conference says new data analysed by physics and astronomy professor Peter Brown at Western University, Canada, shows a large number of asteroid impacts on Earth during the last decade. The data came from large listening stations that pick up the low-frequency infrasound pulse from the explosions. Twenty-six of them ranged in energy between one and 600 kilotons. The atomic bomb that destroyed Hiroshima in 1945 exploded with an impact of 15 kilotons. Thankfully, many of these asteroids exploded too high in the atmosphere to damage things too much on the ground. If they do make it through, they are more likely to land in water than on land, as is shown in the video.
Wired.co.uk contacted Edward Lu, former astronaut and CEO of the non-profit B612 Foundation, who said previously the likelihood of such an impact was considered to be around 30 percent in your lifetime. Professor Brown's research puts the likelihood closer to once every 100 years for a major (city killer) impact. The last city killer asteroid documented to have hit Earth was the one that fell in June 1908 in Tunguska with an explosive energy of around five megatons.
Lu said: "The visualisation shows that asteroid impacts are not rare -- but actually 3-10 times more common than we previously thought. "While most large asteroids with the potential to destroy an entire country or continent have been detected, less than 10,000 of the more than a million dangerous asteroids with the potential to destroy an entire major metropolitan area have been found by all existing space or terrestrially-operated observatories," stated Lu. "Because we don't know where or when the next major impact will occur, the only thing preventing a catastrophe from a 'city-killer' sized asteroid has been blind luck."
The asteroid that exploded over Chelyabinsk in February 2013 exploded with an energy of around 500 kilotons. Despite having a mass of around 13,000 metric tonnes and measuring 20 metres in diameter, it entered the Earth's atmosphere undetected.
The B612 Foundation's Sentinel Space Telescope Mission aims to be our first line of defence.
Sentinel, the world's first privately funded deep space mission, will create the first comprehensive dynamic map of our inner solar system, identifying the current and future locations and trajectories of Earth-crossing asteroids.
The space telescope will take about four years to build and test, with a scheduled launch in 2018, aboard a Falcon 9 rocket.
The aim is to discover and catalogue 90 percent of the asteroids larger than 140 meters in Earth's region of the solar system. The mission should also discover a significant number of smaller asteroids, down to a diameter of 30 meters.
By observing in infrared, Sentinel should be able to discover more than 20,000 asteroids in the first month of operation -- more discoveries than all other telescopes combined have managed to discover in the last 30 years. Over 6.5 years, Sentinel will locate and follow the trajectories of more than 90 percent of asteroids larger than 140 meters -- documenting 500,000 Near Earth Asteroids (NEAs) over its lifetime.
Compiling the definitive catalog of NEAs, within a few years nearly all NEAs known to humanity will have been discovered by Sentinel. The goal of the B612 Sentinel mission is to find and track asteroids decades before they hit Earth, giving us a change to come up with a way to deflect them.
How can asteroids threatening Earth be deflected? Dismissing the idea of using nuclear weapons to try and destroy or push an asteroid, Dr Lu is the co-inventor of the "gravity tractor", a practical and controllable means of deflecting asteroids by using gravitational tug to change their orbit. At the moment, it's just a theoretical defence that is yet to be built; in the interim, we'll have to make do with luck.
This article was originally published by WIRED UK
