Carbon Dioxide Atmospheres (Venus, Mars, and possibly Earth)!Opening Question: What are positive and negative feedbacks on Venus? How 1.is this a mechanism of sustained global warming? !Answer: This is only a hypothesis about weather on Venus. !A.Scientists have major problems discussing the climate of Earth, and even a.more when discussing the climate of other objects.!This is because scientists have been watching the climate on Earth for 1.centuries, but only have first look data on most objects in outer space. They do not know what is stable about these objects and what will change.!Astronomers' first measurement of the weather of Venus was in A.1962, and it was crude by 2013 standards. !To make up for lack of new data, astronomers create computer 2.models to simulate environments. These models always ignore or simplify turbulence and only deal with large scale movements, so they are only approximations at best. !Based on these models, astronomers cannot say for sure whether A.Venus is heating or cooling, or if parts of it are doing both. !Astronomers do know that Venus' air is hot from the greenhouse effect. !b.Green house effect: carbon dioxide in Venus' atmosphere absorbs 1.visible light and reradiates it in infrared. Venus also absorbs infrared light, and reradiates it in a way that is hard for it to escape.!Because Venus is so close to the sun, a lot of visible light gets A.turned into infrared, and its air heats up. !This is not the effect Earth's green houses employ to grow plants. !B.Astronomers do not know the long terms trends of Venus' weather. !c.Their one other data point is that 700 million years ago, the entire 1.crust of Venus solidified after being molten for an unknown amount of time. !The molten nature of Venus' crust back then destroys records of A.what it was before. !Astronomers know that Venus' surface must be a little cooler a.than it used to be. !In short, astronomers do not have enough data to say if Venus is 2.getting warmer, cooler, windier or clearer. They do not know about these negative and positive feedbacks. !The authors of this book are positivist, and published what is only a A.well-meaning extrapolation. !NOTE: There is a strong tendency throughout science to assume that the B.conditions of things when they were first observed by scientists are the base line/normal conditions of these things. This is a perfectly understandable assumption, but it is wrong. Just because the conditions we see are the way we saw them first, doesn't necessarily mean that these conditions are fair or proper. !For example, a lot of species come and go, but no one knows what is 1.right/wrong or good/bad about that: !The first time naturalists counted frogs in Panama, they found a lot A.of bright yellow frogs. 25 years later, the frog was almost entirely gone. This was regarded as a tragedy that had to be counteracted if possible, but no one really knows if these frogs were native and wiped out, or simply an exotic introduction that did not belong in that sort of environment. They just assumed the former because it was what they first observed. !There used to be a lot of passenger pigeons in North America B.(base line), but humans drove them to extinction. However, no one has seen this cause any harm to North American ecology!It is difficult to tell anything about the processes of objects in space 2.because all of them besides Jupiter, Saturn, Venus, and the Moon were inspected by spacecraft only once. From single look data you cannot tell if an object is changing temperature or color. !Astronomers cannot tell if Neptune's disappearing dark spot was A.normal or abnormal, or how long dark spots last. We know know they last at least five years. !The Atmosphere of Venus: !2.It wasn't until 1962 when the Mariner 2 probe looked at Venus in ultraviolet A.light that astronomers saw much of Venus' cloud pattern.!Through a visible light telescope, Venus appears to have very few a.features: phases, and an occasional blotch or spot.!This is because Venus is completely wrapped in clouds. !1.The astronomer Percival Lowell saw diagonal streaks, but was 2.ridiculed for suggesting they were surface features of Venus. !It turned out he was seeing slightly into ultraviolet. !A.Up close and in visible light, Venus' clouds look like clouds.!b.Mariner 2 was the first planetary probe, so it went to the planet closest c.to Earth (Venus)!Pictures from Mariner 2 and other ultraviolet cameras show that the clouds B.of Venus are a couple of vortices.!Venus spin on its axis once every 200 days, but its atmosphere spins on a.its axis once every 4 days. !The clouds of Venus move at a different rates than the surface of 1.Venus, because they are not pushed around by Venus' surface; they are pushed around by heat. !The cloud pattern of Venus is called a "Hadley Vortex": !b.In this pattern, Venus' atmosphere heats the most along the equator 1.and cools off by spinning out to the poles where it can lose heat. !This form was first hypothesized by George Hadley (1700s English 2.physicist) to describe the air circulation of the Earth. !In the 1800s, Benjamin Franklin proved that Earth's weather A.systems are much smaller than the Hadley vortex.!200 years later, scientists discovered that this model was a good B.description of how air moves on Venus. !Hadley had the right physics, but the wrong planet.!a.The Structure of Venus' atmosphere.!C.Polar ring clouds are observed on top of Venus' atmosphere, but driver a.cells are not. !Driver cells and polar ring clouds have blended boundaries.!1.The general features of each layer of Venus's atmosphere are upper b.haze, followed by broken clouds, followed by the main cloud deck, followed by lower haze, and then finally a clear atmosphere surrounding its surface. !This was directly observed by a probe going down through the 1.atmosphere of Venus and landing on its surface:!There is lightening under the main cloud deck, which no one 2.predicted.!This lightening is understood as much as Earth lightening, which is A.to say not really. !The clarity of air near the surface was also a surprise. !3.The temperature of various parts of Venus' atmosphere decreases as you D.get farther from its surface. !On the ground, it is over 700 kelvin. !a.0 kelvin is absolute zero (the lowest possible temperature measured). !1.By around 50 kilometers from the surface (above the clouds) the b.temperature of Venus' atmosphere has steadily dropped to about 300 kelvin
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