@alan fraser said:
All the water and all the air. I'm not sure whether the air is represented as-is, ie a sliding scale of density, or whether it's all been compressed to 1 atmosphere. Either way, it weighs 5140 trillion tons.
http://www.wolframalpha.com/input/?i=total+water+on+Earth
http://www.wolframalpha.com/input/?i=homosphere+volume
http://en.wikipedia.org/wiki/Atmosphere_of_Earth
The average mass of the atmosphere is about 5 quadrillion (5Γ1015) tonnes or 1/1,200,000 the mass of Earth. According to the American National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480Γ1018 kg with an annual range due to water vapor of 1.2 or 1.5Γ1015 kg depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27Γ1016 kg and the dry air mass as 5.1352 Β±0.0003Γ1018 kg."