March 10 () –
Scientists specialized in planetary defense have spent the last three years modeling and simulating the atmospheric disintegration of the famous Chelyabinsk meteor.
On the morning of February 15, 2013, a small asteroid exploded over this Russian city, sending out a strong shock wave and a sonic boom throughout the region, damaging buildings and injuring some 1,200 people. The resulting meteorite, with a diameter of approximately 20 meters (about the size of a six-story building), was one of the largest detected disintegrating in Earth’s atmosphere in over a hundred years.
Their study underscores the important role that material strength and fracture played in the dynamics of rupture.
Although several research organizations have studied the Chelyabinsk event, scientists at LLNL (Lawrence Livermore National Laboratory) were the first to simulate the Chelyabinsk meteor in full 3D with a materials model based on research data from meteorites recovered from the event. Unlike historical meteor events, the 2013 outburst was recorded with mobile phones and security cameras from multiple angles. and a 500 kg fragment was recovered in Lake Chebarkul shortly after impact.
Their simulations, which largely match observed events, suggest that the object could have been monolithic, or a single chunk of rock. If so, according to the researchers, the strength and fracture of the material played an important role in the rupture of the object and the resulting shock wave.
“This is something that can only be captured with a 3D simulation,” he explains. it’s a statement Jason Pearl, principal investigator of the project. When the LLNL’s expertise in impact physics and hydrocoding is combined with the lab’s high-performance computing capabilities, we are uniquely positioned to model and simulate the meteor in 3D.”
“Our research underscores the importance of using these kinds of high-fidelity models to understand asteroid explosions,” says Pearl. “Many of the smaller asteroids are debris piles, or collections of loose space gravel, so the possibility of a monolith is really interesting“.
The research team used smoothed particle hydrodynamics (SPH), a computational method used to simulate the dynamics of solid mechanics and fluid flows, to examine the rupture mode of a Chelyabinsk-sized monolithic asteroid.
In their simulations, the team found that the outburst occurs when major cracks under tensile stress form on the back of the asteroid. The timescale of crack propagation toward the front of the asteroid controls when the asteroid breaks up into smaller fragments as it enters Earth’s atmosphere.
Next, a family of fragments near the shock front temporarily shields a region of totally damaged material until, approximately 30 km above the Earth’s surface, the intact fragments separate and the debris is exposed to free flow. Finally, the debris cloud slows rapidly, and the remaining fragments continue to break up into smaller pieces of rock.
The decay process is rich in physics, explained Mike Owen, a physicist at LLNL. The coupling of the asteroid to the atmosphere depends on its surface. The larger the surface area, the greater the object’s exposure to heat, stress, and pressure.
“When the asteroid enters the atmosphere, a kind of catastrophic failure occurs“Owen explains. “And it tends to compress in the direction of travel. It was as if the asteroid was being compressed in the direction of travel, breaking up into separate pieces that began to separate and break apart perpendicular to the direction of travel.
“Suddenly there’s a lot more material exposed to hypersonic interaction with air, a lot more heat, a lot more stress, which causes it to break down faster and sort of a cascading process occurs.”
A better understanding of the breakup process can be used to build better statistical models of the risk posed by Chelyabinsk-sized asteroids. According to Cody Raskin of LLNL, one of the main collaborators on the project, understanding how these objects break up and transfer their energy to the atmosphere is crucial. to obtain a good estimate of the damage they can cause and can serve to better base civil defense strategies.
A long-term goal of this research would be to use these models to assess the ground-based effects of a future meteor, predicting the region that might be impacted.
