Atmospheres and Oceans of Terrestrial Planets-II

Abstract

Both Venus and Mars most likely retain their proto-atmospheres which comprise more than 95% CO₂ plus a few percent of N₂.  Mercury being so small and so close to the Sun for so long has only trace amounts of O₂ and Na. This might imply that its rocky parts (crust + mantle) became thinner and thinner with time due to sublimation. The Earth’s CO₂-rich proto-atmosphere was removed by a large quantity of supercritical H₂O released from the Moon-making giant impact process. The supercritical H₂O released from this impact reacted with Earth’s CO₂-rich proto-atmosphere to form a supercritical H₂O-CO₂ mixture which yielded the hot and soda indigenous ocean when the Earth’s surface temperature cooled down to 450~300 ^oC.  The Earth, however, retains N₂ from her proto-atmosphere. The ancient Martian oceans, on the other hand, might be derived from the entrapped magma oceans via a degassing process when the Martian surface temperature cooled much below 100 ^oC.