One day humans will set foot on another habitable planet.
The planet may look very different from Earth, but according to scientists, one thing that will be familiar to us is… rain.
In a recent report, Harvard researchers found that raindrops look dramatically like different planetary environments, or even very different planets like Earth and Jupiter.
Understanding raindrops on other planets is essential not only for revealing ancient climates on planets like Mars, but also for identifying habitable planets outside of our solar system.
“The life cycle of clouds is really important when we think about the viability of planets,” said Kaitlyn Loftus, graduate student in the Department of Earth and Planetary Sciences and lead author of the report. Clouds and precipitation are really complicated to fully model. We are looking for simpler ways to understand how clouds change and the first step is to find out whether the droplets evaporate into the atmosphere or float to the surface as rain. “
As Robin Wordsworth, Associate Professor of Environmental Science and Engineering at Harvard John A. Paulson School of Applied Sciences & Sciences (SEAS) explains: “The raindrop is an important component of the rain cycle. . For all planets. If we understand individual raindrops, we can better represent precipitation in complex climate models. “
The size of the raindrop matters. Too large, the droplet will rupture due to insufficient surface tension, be it water, methane or liquid iron, like on an exoplanet called WASP-76b which was discovered not long ago . Too small, the droplets evaporate before touching the surface.
Raindrops are actually spherical when they are small and flatten out as they age. The sink rate depends on the shape as well as the gravity and thickness of the surrounding air. The rate of evaporation is more complex, influenced by atmospheric composition, pressure, temperature, relative humidity, etc.
“We can use this property to model the cycles of clouds on exoplanets,” Loftus said.
Meanwhile, Wordsworth pointed out, “The knowledge we gain when we study raindrops and clouds in various environments is critical to understanding the viability of exoplanets. In the long run, it can also help us better understand the Earth’s climate. “
