One day, humans may set foot on another habitable planet. That planet may look very different from the Earth, but one thing will make people feel familiar-rain.
Researchers at Harvard University found in a recent paper that in different planetary environments, raindrops are very similar, even planets that are completely different from Earth and Jupiter. Understanding the behavior of raindrops on other planets is not only revealing the ancient climate on planets such as Mars, but also the key to identifying potentially habitable planets outside our solar system.
The lead author of the paper, Kaitlyn Loftus, a graduate student in the Department of Earth and Planetary Sciences, said: “When we consider the habitability of planets, the life cycle of clouds is very important.”
Robin Wordsworth, associate professor of environmental science and engineering at Harvard University’s John Paulson School of Engineering and Applied Sciences (SEAS) and senior author of the paper, said: “The humble raindrops are important for all planetary precipitation cycles. component.” . “If we understand the behavior of individual raindrops, we can better represent rainfall in complex climate models.”
At least for climate modelers, an important aspect of raindrop behavior is whether raindrops will reach the surface of the earth, because atmospheric water plays an important role in planetary climate. For this reason, size is important. It is too large, and due to insufficient surface tension, the droplets will burst. Whether it is water, methane or superheated liquid iron, it is like WASP-76b exoplanet. Too small, the water droplets will evaporate before hitting the surface.
Loftus and Wordsworth used only three attributes (droplet shape, falling speed, and evaporation speed) to determine the Goldilocks zone of raindrop size.
The shape of the water droplet is the same on different rainwater materials and mainly depends on the weight of the water droplet. Although many of us may think of traditional teardrops, raindrops are actually spherical when they are small, and gradually squeeze as the raindrops grow, until they become the top of a hamburger. The rate of descent depends on this shape and the thickness of gravity and surrounding air.
The evaporation rate is more complicated and is affected by atmospheric composition, pressure, temperature, relative humidity and so on.
Taking all these characteristics into consideration, Loftus and Wordsworth found that under a wide range of planetary conditions, the mathematical calculation of raindrops means that only a small fraction of the possible droplet size in the cloud can reach the surface.
Loftus said: “When we simulate cloud cycles on exoplanets, we can use this behavior to guide us.”
Wordsworth said: “The insights we gain by thinking about raindrops and clouds in different environments are crucial to understanding the habitability of exoplanets.” “In the long run, they can also help us understand more deeply. The climate of the earth itself.”
What is the difference between rain in the alien world?
Kaitlyn Loftus and others. The physics of raindrops falling in the atmospheres of different planets, Journal of Geophysical Research: Planets (2021). DOI: 10.1029 / 2020JE006653
Courtesy of Harvard University John Paulson School of Engineering and Applied Sciences
Citation: The size of raindrops helps to identify potentially habitable planets outside the solar system (April 5, 2021) April 6, 2021 from https://phys.org/news/2021-04-size-raindrops-potentially- habitable-planets.html retrieved
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