The Moon Has No Atmosphere to Slow a Spacecraft

One major reason moon landing is difficult is that the Moon has almost no atmosphere. On Earth, spacecraft can use atmospheric drag and parachutes to slow down during descent. On the Moon, that is not possible. A lunar lander must slow itself entirely with rocket engines, which requires extremely precise control of speed, direction, and fuel use. If the engines fire too much, fuel may run out. If they fire too little, the spacecraft can crash. This makes the final landing phase very dangerous and technically challenging.