Asteroids don't hit a physical wall. They "fail" to enter either by completely missing our 67,000-mph planet, or by striking at an angle under ten degrees and skipping off like a stone.
The vast majority of space rocks simply miss us entirely. Earth is an 8,000-mile-wide target moving rapidly around the Sun, while asteroids follow their own distinct solar orbits. For an asteroid to enter the atmosphere, its orbital path and Earth's orbit must intersect at the exact same fraction of a second. Even near-Earth objects that astronomers classify as "close approaches" typically fly past millions of miles away, completely untouched by Earth's gravity or atmospheric drag.
When an asteroid's trajectory does perfectly align with Earth, the angle of approach dictates whether it penetrates. If a rock strikes the outermost layers of air too shallowly, it rebounds. These "Earth-grazing" meteoroids dip into the thin thermosphere, compress enough air to briefly glow as fireballs, and then exit back into deep space with their momentum largely intact.
People often confuse "entering the atmosphere" with "hitting the ground." Asteroids enter the Earth's atmosphere every day, but almost all of them are destroyed before reaching the surface. Because space rocks hit the atmospheric friction layer at speeds between 25,000 and 160,000 mph, the air in front of them compresses violently. This compression generates thousands of degrees of heat, causing the object to vaporize or explode miles above the surface. The 2013 Chelyabinsk meteor entered the atmosphere flawlessly but detonated 18 miles high with the energy of 500 kilotons of TNT, proving the atmosphere does not stop asteroids from entering—it simply destroys them after they do.