Unveiling Earth’s Wayward Twin

Venus, the closest planet, seems like a hellish version of our own; studying how it got that way will tell us a lot about the prospects for life among the stars.

Astronomy Astrogeology

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January-February 2021

Volume 109, Number 1
Page 30

DOI: 10.1511/2021.109.1.30

When I started studying planetary geology, I hated Venus. There’s no way to see its surface directly, because the planet is wrapped in an unbroken layer of sulfuric acid clouds. Radar can penetrate the murk, but the resulting images are so limited and ambiguous that it’s almost impossible to tease apart what exactly is going on. And forget about searching for signs of habitability in that jumble. Even though Venus is nearly the same size as Earth and orbits just slightly closer to the Sun, it is nothing like our planet. Its atmosphere consists of unbreathable carbon dioxide, so dense that it practically flows like an ocean. Temperatures on the ground resemble those inside a self-cleaning oven.

QUICK TAKE
  • Venus is a planetary puzzle. It started out similar to Earth in size, composition, and distance from the Sun, yet ended up with a crushing atmosphere and a dry, lethally hot surface.
  • No spacecraft has explored the geology of Venus in more than three decades. A modern mission could investigate why Earth and Venus developed in such starkly different ways.
  • Earth-sized planets appear to be common around other stars. Venus offers clues about how many of them could actually support life, and about how a habitable planet could die.
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