Re:Rosetta finds comet's water vapour to be significantly di...
by jameshart on Wednesday December 10, 2014 @06:45PM
(#8732409)
Right, that was my thinking; so does the same not apply to nitrogen, and methane (which I think both have lower molecular mass than water)?
(EDIT: actually, on second thought, N2 would have a higher molar weight than H2O...)
Re:Rosetta finds comet's water vapour to be significantly di...
by tomr_stargazer on Wednesday December 10, 2014 @06:55PM
(#8732444)
Yes on your edit. The origin of Earth's atmospheric nitrogen is thought to be in part due to outgassing (in other words, gas that was stored inside rocks in the early Earth and then released from inside), but is highly uncertain & debated. It's actually so poorly constrained that it may end up being my PhD thesis topic (astrophysics and origins of planetary systems). So not even the experts know, yet, although cometary delivery in cyanide ices from comets is a leading hypothesis (similar to the delivery of water ices).
Re:Rosetta finds comet's water vapour to be significantly di...
by efuquen on Wednesday December 10, 2014 @07:01PM
(#8732469)
Was digging around and found some good info, looks like tomr already answered the Nitrogen part of the question, which is the same info I found.
As far as methane, it seems to all mostly be biogenic[1].
[1] - http://www.astrobio.net/news-exclusive/methane-on-earth/
Temperature is just an expression of mean kinetic energy of particles. If gases (especially light gases) are hot enough, their kinetic energy can correspond to a velocity that actually exceeds the escape velocity of Earth's gravitational well. This is how hot gases can be removed completely from the Earth's atmosphere (and then solar wind & radiation take care of removing it from there). Even at today's atmospheric temperatures, helium gas (molecular weight of 4 atomic mass units, much lighter than molecular oxygen, nitrogen, etc.) can escape from Earth's atmosphere.