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There’s a planet next door that could explain the origins of life in the universe. It was probably once covered in oceans. It may have been able to support life for billions of years. No surprise, astronomers are desperate to land spacecraft there. The planet is not Mars. It’s Earth’s twin, Venus. Despite its appeal, the second planet from the sun is one of the hardest places in the solar system to get to know. That’s partly because modern Venus is famously hellish. No spacecraft have landed on the surface of Venus since 1985. A few spacecraft have visited Earth’s neighbor in the past decade. For example, the European Space Agency’s Venus Express visited Venus from 2006 to 2014. However, no NASA craft has visited Earth’s twin since 1994. That’s when the Magellan craft crashed into the atmosphere of Venus and burned up. The planet’s atmosphere is 96.5 percent carbon dioxide. That blocks scientists’ view of the surface in almost all wavelengths of light. To really understand the surface, scientists want to land a craft there. It would have to deal with the cloudy atmosphere while looking for a safe place to touch down. The best map of the planet’s surface is based on radar data from Magellan a quarter century ago. Its resolution ( 分辨率 ) is too low to show rocks or hills that might destroy a lander. James Garvin is a member of a team in NASA that is testing a computer-vision technique. Called Structure from Motion, it could help a lander map its own touch-down site. It would do this during its falling process. The system quickly analyzes many images of the ground taken from different angles. This allows it to create a 3-D picture of the surface. Garvin’s group tried it out in Maryland. It was able to identify rocks less than 19.5 inches across. That’s about the size of a pumpkin. Any lander that successfully reaches the surface of Venus faces another challenge. The first landers there were Soviet spacecraft. They landed in the 1970s and 1980s. Each lasted only an hour or two. That’s not surprising. The planet’s surface is about 460°C. But a team at NASA’s Glenn Research Center in Cleveland, Ohio is hoping to do far better. It aims to design a lander that would last months. Past landers have used their bulk ( 体积 ) to absorb heat, which can’t last long. Or they have dealt with extreme temperatures with a special cooling system. This team proposes something new. They plan to use a brand new material — silicon carbide. This material should withstand the heat and enable the craft to do a reasonable amount of work.
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同一件商品往往具有多种使用价值
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齿轮式加丶减计算器
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差分机和分析机
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机电式计算机
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