<P> Earth 's magnetic field protects it from solar winds and prevents escape of ions , except near the magnetic poles where charged particles stream towards the earth along magnetic field lines . The gravitational attraction of Earth 's mass prevents other non-thermal loss processes from appreciably depleting the atmosphere . Yet Earth 's atmosphere is two orders of magnitude less dense than that of Venus at the surface . Because of the temperature regime of Earth , CO and H O are sequestered in the hydrosphere and lithosphere . H O vapor is sequestered as liquid H O in oceans , greatly decreasing the atmospheric density . With liquid water running over the surface of Earth , CO can be drawn down from the atmosphere and sequestered in sedimentary rocks . Some estimates indicate that nearly all carbon on Earth is contained in sedimentary rocks , with the atmospheric portion being approximately 1 / 250,000 of Earth 's CO reservoir . If both of the reservoirs were released to the atmosphere , Earth 's atmosphere would be even denser than Venus 's atmosphere . Therefore , the dominant `` loss '' mechanism of Earth 's atmosphere is not escape to space , but sequestration . However , in 1 billion years ' time , the Sun will be 10 % brighter than it is now , making it hot enough for Earth to lose enough hydrogen to space to cause it to lose all of its water ( See Future of Earth # Loss of oceans ) . </P>
what keeps the earth 's atmosphere from floating away
The gravitational attraction of Earth 's mass Earth 's magnetic field