Slow spin could explain why planets become hellish
Hundreds of Venus-like planets could soon help determine why some worlds become sweltering greenhouse hellscapes while others remain capable of supporting life. But before answering that question, scientists first need to know how fast those planets are spinning.
Understanding why some planets become inhospitably hot while others sustain life hinges on a fundamental yet often overlooked aspect: the speed at which these worlds spin. In a new study, planetary scientist Stephen Kane warns that current methods for measuring this rotation rate could be misleading.
Venus, often cited as a cautionary tale, serves as a prime example. While it takes 243 Earth days to complete a rotation, its upper atmosphere whizzes around the planet in just four days. This discrepancy can lead astronomers to believe they're measuring the planet's rotation when, in fact, they're observing atmospheric winds.
The problem lies in the fact that most planets don't have a solid surface visible from space. Instead, scientists must infer rotation rates from atmospheric changes. Kane proposes a solution: by observing the same planet at multiple wavelengths, including infrared, researchers can probe deeper atmospheric layers. Comparing measurements across these depths could provide a more accurate estimate of the planet's rotation rate.
This is particularly crucial as the PLATO mission, set to launch in 2027, is expected to discover hundreds of "Venus-like" planets. These planets orbit relatively bright stars, making them prime targets for follow-up atmospheric studies with telescopes like the James Webb Space Telescope. With a large population of Venus analogs to study, scientists will gain insights into how common such extreme climates are across the cosmos.
Comparing these exo-Venus candidates with our own planet could help unlock the mystery of why Venus became a scorching hellhole while Earth remained habitable. If most of these planets exhibit slow rotations, it might suggest that rotation rate plays a significant role in determining a planet's climate and habitability. Conversely, a wide range of rotation rates might point to other factors at play.
Ultimately, understanding the rotation of distant planets is essential for piecing together the puzzle of planetary climates. As Kane emphasizes, "To understand Venus, we need to see Venuses in other systems and see how they changed through time. Rotation is a huge piece of that puzzle, and we need to be careful that what we think we're measuring is really the rotation of the planet."
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