I'd believe it. Wikipedia has a similar one [1] but it shows a bit more hydrogen than helium at higher elevation. Awesome graph! Worth stating that the increas

I'd believe it. Wikipedia has a similar one [1] but it shows a bit more hydrogen than helium at higher elevation. Awesome graph! Worth stating that the increase in the relative fraction of He isn't so much because there's a lot of He out there as because there's a lot less of everything else. Overall density falls off roughly exponentially but lighter elements have a longer tail. So once you get out to a few earth radii quite a bit of what you see might be ionized helium but that doesn't mean you can do much with it. [1]: https://en.wikipedia.org/wiki/File:Chemical_composition_of_atmosphere_accordig_to_altitude.png https://en.wikipedia.org/wiki/File:Chemical_composition_of_a...