Expert: Ed - 6/29/2007

Question
This question concerns the planet Venus. I have read several articles on the planet and understand why the atmosphere is mostly carbon dioxide (with a lesser amount of nitrogen). This is primarily because of the lack of water which has evaporated. The articles usually say that there was probably at one time (in the distant past of the solar system) a substantial amount of water. The better articles tell the reader what happened to the water: it disassociated into oxygen and hydrogen due to radiation. One article made it clear that the hydrogen eventually escaped the gravity of Venus. None of the articles say what happened to the oxygen. Since there is little or no oxygen in Venus’s atmosphere, what happened to it??? This is an important question and it amazes me that the articles I have read fail to address it. Has it recombined with other elements? Has it helped to form the sulfur dioxide in the clouds. Please satisfy my curiosity. Thank you. –Leon Weill

Answer
Leon,

What an interesting question...  I am not a chemist, but here is what I can find.  First, look at this old article (co-authored by Carl Sagan):
http://www.sciencemag.org/cgi/content/abstract/155/3762/556

It says that the oxygen has been chemically bonded to the surface materials of Venus (as well as the Venusian atmosphere, presumably).  There isn't very much free, loose oxygen on Venus, but there's lots of oxygen bonded into the CO2 molecules, and into the sulphur dioxide, etc.

Here is a NASA article, by some Cal Tech researchers, comparing the atmosphere of Venus and Mars.  The most relevant stuff for you is in the second to last paragraph.
http://astrobiology.arc.nasa.gov/workshops/1996/palebluedot/abstracts/allen_01.h...

Here is a more recent article about the topic, in which scientists have shown some progress in understanding.
http://www.aas.org/publications/baas/v30n3/dps98/426.htm

Now that you've seen articles from the past 40 years, look at this one from just a few weeks ago, from the Harvard-Smithsnian Center for Astrophysics:
http://www.cfa.harvard.edu/sao/su/2007/su200723.html

If you google the names of the astronomers mentioned, you can find more useful stuff.

This is the kind of question that I would need more of a specialized background to answer in great detail.  But I hope this helps a little.  Please get back to me if you want to discuss it more, and I'll do my best.

Keep Looking Up!
--Ed