Even though Venus and Earth are so-called sister planets, they're as different as heaven and hell. Earth is a natural paradise where life has persevered under its azure skies despite multiple mass extinctions. On the other hand, Venus is a blistering planet with clouds of sulfuric acid and atmospheric pressure strong enough to squash a human being.
But the sister thing won't go away because both worlds are about the same mass and radius and are rocky planets next to one another in the inner solar system. Why are they so different? What do the differences tell us about our search for life?
The international astronomical community recognizes that understanding planetary habitability is a critical part of space science and astrobiology. Without a stronger understanding of terrestrial planets and their atmospheres, whether habitable or not, we won't really know what we're seeing when we examine a distant exoplanet. If we find an exoplanet that exhibits some signs of life, we'll never visit it, never study it up close, and never be able to sample its atmosphere.
That shifts the scientific focus to the terrestrial planets in our own solar system. Not because they appear to be habitable but because a complete model of terrestrial planets can't be complete without including ones that are near-literal hellholes, like sister Venus.
A recent research perspective in Nature Astronomy examines how the two planets diverged and what might have driven the divergence. It's titled "Venus as an anchor point for planetary habitability."
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