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Expert: - 4/5/2007


Question
I keep on reading comments by scientists that state that the reason why the Earth hasn't had its atmosphere blasted away by the solar wind over billions of years is because of the Earth's magnetic field. The trouble with this  theory is that it doesn't explain why Venus still has an atmosphere yet has no detectable magnetic field. What's your take on this?

Thanks,
Geoff

Answer
Hello,

You are correct that it seems counter-intuitive. However, the difference is that Venus has an atmosphere far far denser than the Earth's. With the abundance of CO2, sulphuric acid etc. the ground level pressure amounts to more than 90 atmospheres. This immense density also prevents any easy escape of the gas molecules, either from the solar wind, or simple outgassing arising from the speed of a large proportion of particles exceeding the planet's escape velocity over time.

Given Venus' dense and heavily layered atmosphere, it is highly implausible that it will "evaporate" any time soon, or that a powerful solar wind will blow it away!

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Philip Stahl

Expertise

I have forty years of experience in Astronomy, specifically solar and space physics. My specialties include the physics of solar flares, sunspots, including their effects on Earth and statistics as applied to astronomical investigations.

Experience

Astronomy: more than forty years experience starting with construction of my own simple telescopes. Worked at university observatory in college, doing astrographic measurements. M.Phil. degree in Physics/Solar Physics and more than ten years as researcher.

Organizations
American Astronomical Society (Solar Physics and Dynamical Astronomy divisions), American Mathematical Society, American Geophysical Union

Publications
Solar Physics (journal), The Journal of the Royal Astronomical Society of Canada, The Proceedings of the Meudon Solar Flare Workshop (1986), The Proceedings of the Caribbean Physics Conference (1985). Books: 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level'.

Education/Credentials
B.A. Astronomy, M. Phil. Physics

Awards and Honors
American Astronomical Society Studentship Award (1984), Barbados Government Award for Solar Research

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