7/21/2023 0 Comments Tidal locking![]() Though weathering on Earth consumes carbon dioxide, nitrogen makes up most of the atmosphere. Kite notes that, even if Earth were moved to another star and became tidally locked, it would not be in danger. Similarly, the gas that is absorbed by weathering must be the prevalent gas in the atmosphere. Land is required for the strongly temperature-dependant weathering. The substellar point, closest to the star, cannot be underwater. To narrow that down, one must first look at how frequently tidally-locked planets might exist.įor M-type stars, "We would expect that a lot of the planets in the habitable zone would be tidally locked," Abbot said.įor ESWI to occur, certain conditions must be met on these planets. ![]() How many planets could find their atmosphere destabilized by tidal locking? "Climate instabilities are not good for the life we usually think about." "It's not enough just to rain on a planet for ten thousand years and expect interesting things to happen." "It would require a long period of habitability on a planet to allow these different steps to take place," he said. Kite explained that a number of key steps were required to get life to the point as we know it today. "It has taken a very long time for life to develop complexity on Earth," Kite said. Such fluctuations could mean trouble for life trying to evolve on a planet. Or it could simply boast wide swings over its lifetime, significant shifts from cold to hot and back again. "We sometimes see catastrophic exits from the habitable zone," Kite said.įor instance, a habitable planet could find itself moving to a Venus-like situation, with clouds of gas significantly increasing the surface temperature to points where water would boil off. The same thing could happen on other planets, but if the conditions are right (or wrong) the results could be more detrimental. Abbot studies climate dynamics on Earth and on extrasolar planets. "Weathering regulates the climate on Earth on long time scales, and makes sure it doesn't get too hot or too cold," explained Dorian Abbot, of the University of Chicago. The process removes carbon dioxide from the air and controls the greenhouse effect. On Earth, carbon dioxide from the air reacts with calcium silicate, creating calcium carbonate and silicone dioxide. "What controls the weathering rate of the planet is just that patch," Kite said. ![]() Volcanism could put more material into the atmosphere than the rocks can absorb - and since volcanoes on Earth release greenhouse gases like sulfur dioxide and carbon dioxide, presumably a runaway greenhouse effect could take flight, leading to additional heating.Īll of this happens because the heat is focused on a single region that is constantly closest to its star. Less rock is available to chemically react, and the atmospheric gas builds up. Similarly, if the substellar point cools for any reason, the weathering process slows. More rain means an abundance of fresh rock to react with the atmosphere, removing more of its components. "The harder it rains, the more it erodes," said principal investigator Edwin Kite, of the University of California at Berkeley. Rainfall leads to higher rates of rock erosion. The higher temperatures can also result in stronger rainfall, which go on to affect weathering. The process, referred to as enhanced substellar weathering instability (ESWI), is based on the fact that the influx of heat would cause an increase of weathering at the substellar point. The recent paper proposes that such constant attention could affect weathering, and thus could influence the climate of the atmosphere. ![]() Known as the substellar point, this region receives more direct sunlight, and thus more heat. On tidally-locked planets, a single region is consistently close to the star. If the erosion process keeps pace with the output of fresh gas into the atmosphere - say, from volcanic eruptions - the climate remains stable. As the rocks erode, a fresh face comes into contact with the air, allowing even more gas to be converted. When rocks and minerals are exposed to the air, they react to the gases within it. An unstable climate birthed by a tidally-locked planet could create a runaway greenhouse effect that could result in an atmosphere like Venus's.
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