Abstract
PALAEOMAGNETIC samples show a number of polarity transitions in the Earth's dipole field, and there seem to have been marked evolutionary changes in flora and fauna near the time of several of the reversals1. Suggestions that when the magnetic dipole moment decayed during a reversal, there would be an increase in radiation producing a sudden increase in the rate of evolution2 seem to have been discarded without considering whether the atmospheric mass would be reduced1,3. Mariner V observations show that Venus now has a dipole moment of zero or very near to zero4, so that the atmosphere of Venus may show features which can be explained by erosion and modification by the solar wind. For example, Jastrow5 has stated that the expected dissociation of CO2 and H2O in the atmosphere of Venus should have produced high altitude layers of electrons and atomic oxygen which were not found.
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References
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MCCORMAC, B., EVANS, J. Consequences of Very Small Planetary Magnetic Moments. Nature 223, 1255 (1969). https://doi.org/10.1038/2231255a0
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DOI: https://doi.org/10.1038/2231255a0
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