A prediction of panspermia is that organic material should be abundant throughout the universe. The recovery of micrometre-sized biotic particles at altitudes of around 40 km above the Earth is a key indicator of the validity of panspermia. A common criticism of experiments to capture atmospheric particles is that the particles could have originated from the Earth. Theoretical models of the variation of temperature with altitude above the Earth show that 10 μm diameter particles can withstand rapid deceleration without significant ablation. Experimental evidence shows that small particles containing bacteria can survive the temperature regimes imposed by entry into the Earth's lower atmosphere. This is an important step in demonstrating that life on Earth did not evolve in isolation from the remainder of the universe.