Great, we live on an anorexic rock.
That raises the question of what the atmospheric pressure was in ancient times. The question has eluded science until quite recently. Last October, Sanjoy M. Som, of the U of Washington, published a PhD thesis on the topic. He suggests the atmosphere was lighter way back when. From the abstract:
For Earth, I develop a new method of investigating atmospheric density and pressure using the size of raindrop imprints, and find that raindrop imprints preserved in the 2.7 billion year old Ventersdorp Supergroup of South Africa are consistent with precipitation falling in an atmosphere of near-surface density < 2 kg/m3 and probably > 0.1 kg/m3 , compared to a modern value of 1.2 kg/m3 , further suggesting a nitrogen level of at most twice present levels and perhaps well below present levels. To constrain this further, I re-evaluate a published paleobarometry technique using the vesicle size-distribution in simply emplaced lava flows and apply it to sea-level erupted lava flows from the 2.7 billion year old Fortescue group of Western Australia. Results from three flows suggest a range for atmospheric pressure 0.07 < Patm < 0.64 atm, which has profound consequences for our interpretation of the history of the nitrogen cycle by implying that the development of the nitrogenase enzyme necessary for nitrogen fixation happened very early on in the development of life.
Yeah but how much matter is the earth gaining from meteors and other space material. Maybe it balances out.
Yeah but how much matter is the earth gaining from meteors and other space material. Maybe it balances out.