Me too.
Looking across the internet, it is generally held that the reason that Venus has maintained such a thick atmosphere is because CO2 is much denser than that of O2, N2 and water vapour, exerting much greater pressure on its surface, and that it has not been subject to photo-dissociation and photo-erosion, as it has been for water, O2 and N2, which all makes up Earth's atmosphere. Also, Venus is the 2nd largest rocky planet of the Solar System with greater gravity well than Mars, Moon and Mercury.
Venus does have a weak induced magnetic field produced by the solar wind interacting with the outer atoms in the atmosphere of Venus - this may play a role in reducing photo-erosion of its atmosphere.
However, Venus lack of internally generated (IG) magnetic field is a puzzle. The planet's similar size and composition to Earth should have a hot, active interior, caused by radioactive decay of isotopes in the mantle and crust, and the primordial heat left over from planetary formation. Maybe something else is keeping Earth hot and active, like the effects of the Moon tides, or Earth being a younger planet wandered into older Solar System, or even exotic causes, like Earth passing through of dark energy region, causing heating of it's core! We just don't really know. What we do know is that Venus has a very slow retrograde rotation - that may account for its lack of magnetosphere.
Venus puts a considerable constraints into what Earth-like exoplanets may be like. Many could have relatively inactive interior, lack of IG magnetic field, and atmosphere consisting of chiefly CO2. This would make Earth one of the only few very special planets in the galaxy!
Anyway, I would really love to hear what other say about this on TWO! 😊
Originally Posted by: ozone_aurora