<P> One mechanism for sequestration is chemical; for example, most of the carbon dioxide of the Earth's original atmosphere has been chemically sequestered into carbonate rock . Very likely a similar process has occurred on Mars . Oxygen can be sequestered by oxidation of rocks; for example, by increasing the oxidation states of ferric rocks from Fe to Fe . Gases can also be sequestered by adsorption, where fine particles in the regolith capture gas which adheres to the surface particles . </P> <P> Earth is too large to lose a significant proportion of its atmosphere through Jeans escape . The current rate of loss is about three kilograms (3 kg) of hydrogen and 50 grams (50 g) of helium per second . The exosphere is the high - altitude region where atmospheric density is sparse and Jeans escape occurs . Jeans escape calculations assuming an exosphere temperature of 1,800 K show that to deplete O ions by a factor of e (2.718 ...) would take nearly a billion years . 1,800 K is higher than the actual observed exosphere temperature; at the actual average exosphere temperature, depletion of O ions would not occur even over a trillion years . Furthermore, most oxygen on Earth is bound as O, which is too massive to escape Earth by Jeans escape . </P> <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