How Life Could Help Atmospheric Tides Slow a Planet’s Rotation

An oxygenated Earth is vital for the evolution of complex life.
Credit: NASA
Resonating oscillations of a planet’s atmosphere caused by gravitational tides and heating from its star could prevent a planet’s rotation from steadily slowing over time, according to new research by Caleb Scharf, who is the Director of Astrobiology at Columbia University. His findings suggest that the effect is enhanced for a planet with an atmosphere that has been oxygenated by life, and the resulting „atmospheric tides“ could even act as a biosignature.

By, staff

Tides can distort a planet’s mass, which in turn affects its rotation. We’re most familiar with gravitational tides, which on Earth we feel from the gravity of the Moon and the Sun. These gravitational tides create bulges as Earth spins, and the Moon and Sun tug on those bulges, slowing the spin.

By contrast, atmospheric tides, sometimes called thermal or solar tides, occur when sunlight heats the surface and air on Earth’s daytime side. That heating shifts the atmosphere’s mass from the hottest point to cooler points on the planet. As with gravitational tides, atmospheric tides cause bulges that are vulnerable to gravitational pulls. Those bulges subtly change the shape of Earth’s atmosphere, stretching it from a sphere to something slightly less symmetrical and more elliptical. Scharf suggests imagining a „handle“ on Earth, and that forces pulling on the atmospheric handle can then help speed up or slow down the planet’s rotation. [Watch Earth Spin Through a Full Year in This Spectacular Time-Lapse Video]

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