Why did Venus lose its oceans?

[innerlight]

I watched an episode of the new Cosmos series and in it the astronomer mentioned that Venus receives 30% more solar radiation than the Earth but that was not the cause of the out of control global warming on Venus. Further he said that Venus had oceans similar to Earth but lost them early.

I wondered why Venus lost its' oceans? If the atmosphere of early Venus was as thick as that on Earth then surely this would provide some protection for light elements such as hydrogen from being stripped from Venus. I know that Venus does not have a magnetic field generated internally (although it has a magentotail). Is that the reason Venus lost its' oceans?

Further, I know that Venus does not have plate tectonics currently. I know that water is believed to be a lubricant allowing plate tectonics to exist. But is there any data to indicate whether Venus had plate tectonics formerly when it had oceans - or was the lack of plate tectonics responsible partially for the warming and volcanic activity seen on Venus currently - perhaps helping to boil away the oceans of Venus?

 

[davenn]

Further he said that Venus had oceans similar to Earth but lost them early.

With reading I have done, I don't think you can take that as a foregone conclusion
most commentaries state that Venus MAY have had oceans

eg ...
from the Nature publication...

The planet Venus, now hellishly hot and dry, may have once have been far more like Earth, with oceans and continents. That is the implication of new research claiming to see evidence for granite highlands on the planet in data almost two decades old.

In 1990, NASA's Galileo spacecraft detected nighttime infrared emissions coming from Venus' surface. Analysing these data, an international team led by planetary scientist George Hashimoto, now at Okayama University, Japan, found that Venus's highland regions emitted less infrared radiation than its lowlands.

One interpretation of this lower infrared emission from the highlands, say the authors, is that they are composed largely of 'felsic' rocks, particularly granite. Granite, which on Earth is found in continental crust, requires water for its formation. The results are published in the Journal of Geophysical Research1.

It isn't a direct indication of oceans as such, just the presence of water in the crustal rocks

Dave

 

[OmegaOm]

If there was an ocean on Venus and there most likely was, then the ocean would of boiled away from the extreme heat caused by the greenhouse effect. The greenhouse effect caused by the high concentrations of C02 in the atmosphere. The water vapor then supposedly got broken up into hydrogen and oxygen atoms by the Solar Wind and these atoms are still escaping the planet today from the energy from the solar wind.

 

[Chronos]

Agreed with davenn, the presence of past oceans on venus is merely inferred, not confirmed. The venusion atmosphere has about 0.5% as much water vapor as Earth's atmosphere, making it highly probable it once harbored liquid water. Venus, like mars, however, has a negligible magnetic field hence its atmosphere is very susceptible to sputtering loss via the solar wind, so, the amount of liquid water that may have been present say 4 billion years ago is very uncertain.

 

[berkeman]

Thread closed temporarily for Moderation...

 

[berkeman]

Misinformation posts and responses to the misinformation have been deleted. Links to peer-reviewed journal articles are required in technical threads at the PF. Thanks!

Thread re-opened.

 

[nikkkom]

I watched an episode of the new Cosmos series and in it the astronomer mentioned that Venus receives 30% more solar radiation than the Earth but that was not the cause of the out of control global warming on Venus.

Venus receives about 190% of Earth's insolation, not 130%.

 

[nikkkom]

Agreed with davenn, the presence of past oceans on venus is merely inferred, not confirmed. The venusion atmosphere has about 0.5% as much water vapor as Earth's atmosphere, making it highly probable it once harbored liquid water.

Venus' deutherium to hydrogen ratio is 150 times higher than Earth's. This is a fairly strong indication that it had at least 150 times more water than it has now, maybe even more.

 

[Loren]

If there was an ocean on Venus and there most likely was, then the ocean would of boiled away from the extreme heat caused by the greenhouse effect. The greenhouse effect caused by the high concentrations of C02 in the atmosphere. The water vapor then supposedly got broken up into hydrogen and oxygen atoms by the Solar Wind and these atoms are still escaping the planet today from the energy from the solar wind.

It's atmospheric pressure, not just CO2 that keeps Venus hot.