Russian Federal Space Program (2006-2015)

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RSS Происхождение и эволюция атмосферыOrigin and evolution of the atmosphere

Venera-D » Science » Origin and evolution of the atmosphere

Probably, on the stage of formation, both Venus and Earth got approximately similar amount of volatile substances from the protoplanet nebula. Then several processes had an influence on planets content: degassing from the depths, dissipation, comet impacts, chemical reactions between atmosphere and surface. Their role has been studied poorly, but traces of these processes could be found in high content of inert gases and isotopes. Venus differs from Earth and Mars by extremely high content of neon and argon. Due to their relative amount it is more like meteorites and Sun. Measurements of xenon isotopes are important for exploring the early atmosphere that have not been studied so far.

Puzzle of water. There is very little quantity of water on Venus at present time: a vertical layer of condensed H2O makes up about 3 cm in comparison with 3 km on Earth. However, water could be in large amount in the past; the isotope ratio of D/H indicates it; that is 150-300 times more than on Earth. Such enrichment of deuterium can be explained by fast loss of lighter H atoms from the upper atmosphere. The ratio D/H is different above clouds and below clouds. A role of the clouds in the process of the water dissipation is to clarify.

Interaction with solar wind. Since Venus doesn’t have any magnetic field, a significant part of the exosphere is affected by solar wind flows. Venus Express detected ions Н+, Не+ and О+ being leave the atmosphere. However, the flow of neutral atoms was not estimated. Values of neutral flows are very important for investigation of climate changes on the planet. The ratio of H and O flows, and its difference from 2 (an expected coefficient of water molecule dissociation) contain significant information about role of rocks on the planet’s surface during evolution of the atmospheric oxygen content.