Subject: Does any of the earth's atmosphere escape into space?

I've heard that Mars may have had a more dense atmosphere in the past. I assume that it dissipated off into space. A friend of mine claimed that every molecule of atmosphere was held to Earth by gravity, since it is a larger planet. One of the answers to a question in MAD Scientists said that the Earth was losing mass as the atmosphere leaked off into space (he/she didn't know how much), and the atmosphere was being increased by CO2 and other gases released by the crust of the Earth. How much of, and how fast are these gasses added and lost? Thanks!

Re: Does any of the earth's atmosphere escape into space?