Wednesday , April 14 2021

The size of the raindrops helps to identify habitable planets outside our solar system.


Raindrops fall on the outer planets

One day, humanity may set foot on another habitable planet. This planet may be very different from Earth, but one thing will be familiar – rain.

A recent study published in 2005 JGR PlanetsHarvard researchers have found that raindrops are very similar in different planetary environments, and that planets such as Earth and asteroids are slightly different. Jupiters. Understanding the behavior of raindrops on other planets is not the only way to discover the ancient climate of such planets. Management Mars But identifying habitable planets outside our solar system.

“Cloud life cycle is really important when looking at the habitable nature of the Earth,” said Keithlin Loftus, a graduate student in the Department of Earth and Astronomy and the lead author of this article. “But the clouds and the rain are really so complex that it is impossible to create them completely. We are looking for simple ways to understand how clouds grow. The first step is to see if the clouds evaporate into the atmosphere or fall to the surface like rain. ”

“Humble raindrops are an essential part of the planet’s rain cycle,” said Howard John A. Said Robin Wordsworth, professor of ecology and engineering at the Paulson School of Engineering and Applied Sciences (CS). . “If we understand how single raindrops behave, we can better represent rainfall in complex climatic models.”

A key element of raindrop behavior is, at least for climate designers, whether raindrops reach Earth’s surface reach. For these purposes, size is important. Water droplets are large due to insufficient surface tension regardless of whether the water, methane or liquid iron is too hot. Exoplanar It is called WASP-76b. Is very small and the droplets evaporate before hitting the surface.

Wordsworth Loftus defines only three zones of moderate raindrop size: droplet shape, fall rate, and evaporation rate.

“The insights we gain from thinking about raindrops and clouds in different environments are key to understanding extraterrestrial habitats.”
Robin Worthworth, Professor of Ecology and Engineering

The falling shapes are similar in different rainfall materials and depend mainly on the severity of the fall. While most of us can imagine a traditional teardrop-shaped drop, the raindrops are actually spherical and are large enough to form a shape similar to the top of a hamburger bun. The rate of fall depends on this shape as well as the thickness of the gravity and the circulating air.

The evaporation rate is more complex and is affected by atmospheric composition, pressure, temperature, relative humidity, and so on.

Taking all of these properties into account, Loftus and Wordsworth found that calculating a raindrop drop over a wide range of planetary conditions means that only a small fraction of the potential droplet size of the cloud can reach the surface.

“We can use this to guide us through modeling the cloud cycles in Explonet,” Loftus said.

“The insight we gain from thinking about raindrops and clouds in different environments is key to understanding extraterrestrial habitats,” Wordsworth said. “In the long run, they will also help us gain a deeper understanding of the Earth’s climate.”

Reference: Catalin Loftus and Robin D. “The Physics of Raindrops Fall into the Planetary Atmosphere of Different Planets”. Worthworth, March 15, 2021 JGR Planets.
DOI: 10.1029 / 2020JE006653

This study has been awarded AST-1847120 by the National Science Foundation.

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