Comment by DoctorOetker

http://wordpress.mrreid.org/wp-content/uploads/2014/06/atmos...

the density is low though

observe that where Helium becomes a significant percentage, there is also Hydrogen and (monoatomic) Oxygen.

if one were driven by purism or vanity for stoichiometric exactness, then at a height of 1000 km theres 2 Hydrogens per Oxygen atom, so this could be reacted to water, and the energy used to power compression of the Helium, the water would freeze.

without this vanity, helium becomes a significant fraction at much lower heights... and thus higher densities.

The energy to compress becomes nearly insignificant at low pressures.

if humanity ever builds space elevators, this will be one of many benefits of having space elevators.