- Physicists make precise replicas of asteroids and blast them with a powerful laser beam.
- It took 500 joules of energy to blast a 10-millimeter wide replica.
If Earth collides with a large asteroid, its impact would be far greater than other natural catastrophes, such as big earthquakes and eruptions of volcanos. Today humanity has reached a significant level of technological development from where it can consider the possibility of reducing or preventing the asteroid hazard in earnest.
Usually, all celestial bodies (larger than 1 meter) entering Earth atmosphere are classified as asteroids. They are mostly made of silicon, carbon, metal, and ice. Large asteroids – as big as 900 km across — traveling at 20km/s can easily wipe out the entire life on Earth.
As of now, we have two options to protect our planet from colliding with an asteroid: either deflect the asteroid or blow it into pieces so that it burns up in the atmosphere before reaching the ground.
Recently, researchers at Moscow Institute of Physics and Technology explored the second option by creating an artificial, miniature asteroid and blasting it with a laser. They modeled the shock wave emitted by a nuclear explosion on the surface of the asteroid.
In the scaled-down experiment, destroying asteroid produced catastrophic effects that matched the distributions of pressure and heat predicted for such real events.
An Accurate Replica of Asteroid
The physicists made sure the shape, rigidity, and density of artificial asteroid mimicked the real one. The structure and constituents of asteroid material correspond to that of the chondrite (non-metallic, stony) meteorites, the most common type of meteorite that accounts for approximately 86% of the total asteroid fall.
To make replicas, they used the data of chondrite meteorite that was recovered from the Lake Chebarkul, Russia, in 2013. The material of artificial asteroid was made by a sedimenting, compressing, heating, and imitating the natural formation process. They made replicas in different shapes, including cubical, spherical, ellipsoidal ones.
Reference: Journal of Experimental and Theoretical Physics | doi:10.1134/S1063776118010132 | MIPT
Energy Required To Disrupt Asteroid
They then calculated the amount of energy required to destroy these miniature replicas. Once they measured that it took 500 joules of energy to blast a 10-millimeter wide model, they evaluated how much energy would be needed to destroy a 200-meter asteroid: the laser needs to deliver an energy equivalent of 3,000 kilotons of Trinitrotoluene (TNT).
To put this into context, the most powerful bomb ever detonated — Tsar Bomba in 1961 — yielded approximately 58,600 kilotons of energy.
The lab asteroid is 15 times less massive than its space prototype and it requires twice the energy per mass unit to be fully destroyed.
Researchers used 3 laser devices (Saturn, Luch, and Iskra-5) in the experiment. Before directing the laser beam at the artificial asteroid in a vacuum chamber, they amplified its power to a predetermined level. The beam affected the replica for up to 30 nanoseconds, and the entire fragmentation dynamics were recorded for analysis.
Credit: Elena Khavina / MIPT
As per calculations, a 200-meter asteroid has to be fractured into small pieces with 10 times smaller diameter and 1,000 times less massive than its original size. These pieces would burn up in the atmosphere before making it to the ground.
The team also discovered that multiple weaker pulses didn’t have any advantage over a single beam. The explosion wasn’t much effective in both consecutive and simultaneous weaker pulses. However, targeting a cavity — intentionally made in artificial asteroids — saved a lot of energy. It saved them nearly 150 joules per gram of energy.
In near future, the team will experiment with replicas made of different constituents, such as nickel and iron. Also, they will study how exactly asteroid shape and its cavities affect disruption criterion.