At 293K, helium atoms have a root mean square speed of about 1.35 km/s, whereas escape velocity at the Earth's surface is about 11km/s. Explain why is it nevertheless possible for helium atoms to escape from the Earth into space. Is it because near the top of the atmosphere the temperature is higher? Nitrogen does not escape from the Earth nearly as readily as helium. Refer to the Boltzmann factor in your answer. Not sure about this one. Saturn's moon Titan is similar in size to the Earth's moon; yet titan has been able to retain a significant atmosphere whereas the Moon has almost none. Refer to the Boltzmann factor in your answer. Titan is more dense than the Moon?