It's physically impossible for an asteroid to enter our atmosphere slowly—gravity accelerates them to at least 25,000 mph. Yet, some survive the fiery entry to land intact at just 200 mph.
This survival is due to the intense braking power of the atmosphere. Earth acts as a massive gravitational well. Even if an asteroid were perfectly stationary relative to the planet, gravity would pull it in continuously. By the time an object reaches the upper atmosphere, it hits the air at hypervelocity.
What happens next depends on the rock’s size. Objects larger than 50 meters across carry too much momentum for the atmosphere to slow down. They punch through the air, retain their cosmic speed, and hit the ground with such kinetic energy that they instantly vaporize, excavating massive craters. Conversely, objects smaller than a pebble burn up entirely from atmospheric friction, creating the streaks seen as shooting stars.
Rocks that survive to the ground generally fall into a middle range, typically between the size of a basketball and a small boulder. Hitting the atmosphere at 25,000 mph, they face a wall of compressed air that melts and ablates their exterior. The physical stress of this deceleration often causes the rock to fracture or explode mid-air. However, if a solid chunk survives this violent braking phase, it sheds all its cosmic momentum miles above the ground.
At this point, the burning stops. The surviving rock enters a phase known as "dark flight." It is no longer a hypervelocity projectile, but simply a heavy stone falling from the sky. Air resistance limits its speed to terminal velocity—usually between 200 and 400 mph. It then hits the ground as an intact meteorite.
The most extreme example of atmospheric braking is the Hoba meteorite in Namibia. Weighing 60 tons, it was massive enough that it should have retained its cosmic speed and blasted a crater upon impact. Instead, its unusually flat shape caused it to skip and drag through the upper atmosphere. The extreme air resistance slowed it to roughly 720 mph before impact. It landed intact, burying itself in the soil without exploding or forming a crater.