Worlds apart

Can a newly found exoplanet help explain why Earth and Venus diverged so radically?

by David Grinspoon

IN COMPARATIVE PLANETOLOGY we can't run controlled experiments, altering factors such as initial makeup or distance from a star and then seeing what happens over billions of years. We can only study the random experiments nature has chosen to run and try to piece together the overall story. The closest we may ever get to a controlled experiment for Earth's evolution is a comparison with Venus. Our sister world seems to have started with similar ingredients and conditions as our planet — though about a third closer to the Sun — yet it evolved into such a different planet. We're still trying to work out the timing and mechanisms for this divergence, and to find evidence for or against past oceans on our sibling world. These questions are a major motivation…

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Australian Sky & Telescope (Digital) - 1 Issue, March 2023

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