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NASA spacecraft launched to mysterious and rare metal asteroid_我的网站

一 |           　　最近，一张超高难度的色盲测试图在网上刷屏，明明视力正常却认不出图中数字，AI识别也频频翻车。不少人对着手机屏幕反复确认，怀疑自己“是不是隐性色盲”。      　　这张图到底是如何检测一个人的辨色能力的?为什么视力正常的人也会答错?驾照、职业体检的色觉标准又是什么?　　色盲图测的不是视力　　而是辨色差      　　我们平时见到的、由彩色小圆点组成、藏着数字或图案的测试图，在医学上有个正式名字——假同色图。     　　首都医科大学附属北京同仁医院眼科副主任医师田磊介绍，这类图谱的设计逻辑是把图案和背景的明暗度拉到接近水平，只依靠细微的颜色差异区分信息。人眼视网膜上有三类视锥细胞，分别对应不同波长的光敏感，构成了人眼感知红、绿、蓝三色的生理基础。

二 | 正常色觉者能捕捉到这些细微色差，把数字从背景里“分离”出来;而红绿色觉异常者分辨红绿差异的能力下降，图案就会和背景“融”在一起。    CAPE CANAVERAL, Fla. -- NASA’s Psyche spacecraft rocketed away Friday on a six-year journey to a rare metal-covered asteroid.Most asteroids tend to be rocky or icy, and this is the first exploration of a metal world. Scientists believe it may be the battered remains of an early planet's core, and could shed light on the inaccessible centers of Earth and other rocky planets.SpaceX launched the spacecraft into an overcast midmorning sky from NASA’s Kennedy Space Center. Named for the asteroid it’s chasing, Psyche should reach the huge, potato-shaped object in 2029.“It's so thrilling,” said Laurie Leshin, director of NASA’s Jet Propulsion Laboratory. Added Arizona State University's Jim Bell, part of the Psyche team: “What a great ride so far.”An hour later, the spacecraft separated successfully from the rocket's upper stage and floated away, drawing applause from ground controllers.After decades of visiting faraway worlds of rock, ice and gas, NASA is psyched to pursue one coated in metal. Of the nine or so metal-rich asteroids discovered so far, Psyche is the biggest, orbiting the sun in the outer portion of the main asteroid belt between Mars and Jupiter alongside millions of other space rocks. It was discovered in 1852 and named after Greek mythology’s captivating goddess of the soul.“It’s long been humans’ dream to go to the metal core of our Earth. I mean, ask Jules Verne,” lead scientist Lindy Elkins-Tanton of Arizona State University said ahead of the launch. “The pressure is too high. The temperature is too high. The technology is impossible,” she said. “But there’s one way in our solar system that we can look at a metal core and that is by going to this asteroid.”Astronomers know from radar and other observations that the asteroid is big — about 144 miles (232 kilometers) across at its widest and 173 miles (280 kilometers) long. They believe it’s brimming with iron, nickel and other metals, and quite possibly silicates, with a dull, predominantly gray surface likely covered with fine metal grains from cosmic impacts.Otherwise, it’s a speck of light in the night sky, full of mystery until the spacecraft reaches it after traveling more than 2 billion miles (3.6 billion kilometers).Scientists envision spiky metal craters, huge metal cliffs and metal-encrusted eroded lava flows greenish-yellow from sulfur — “almost certain to be completely wrong,” according to Elkins-Tanton. It's also possible that trace amounts of gold, silver, platinum or iridium — iron-loving elements — could be dissolved in the asteroid's iron and nickel, she said. “There's a very good chance that it’s going to be outside of our imaginings, and that is my fondest hope," she said.Believed to be a planetary building block from the solar system’s formation 4.5 billion years ago, the asteroid can help answer such fundamental questions as how did life arise on Earth and what makes our planet habitable, according to Elkins-Tanton.On Earth, the planet's iron core is responsible for the magnetic field that shields our atmosphere and enables life.Led by Arizona State University on NASA’s behalf, the $1.2 billion mission will use a roundabout route to get to the asteroid. The van-size spacecraft with solar panels big enough to fill a tennis court will swoop past Mars for a gravity boost in 2026. Three years later, it will reach the asteroid and attempt to go into orbit around it, circling as high as 440 miles (700 kilometers) and as close as 47 miles (75 kilometers) until at least 2031.The spacecraft relies on solar electric propulsion, using xenon gas-fed thrusters and their gentle blue-glowing pulses. An experimental communication system is also along for the ride, using lasers instead of radio waves in an attempt to expand the flow of data from deep space to Earth. NASA expects the test to yield more than 10 times the amount of data, enough to transmit videos from the moon or Mars one day.The spacecraft should have soared a year ago, but was held up by delays in flight software testing attributed to poor management and other issues. The revised schedule added extra travel time. So instead of arriving at the asteroid in 2026 as originally planned, the spacecraft won’t get there until 2029.That’s the same year that another NASA spacecraft — the one that just returned asteroid samples to the Utah desert — will arrive at a different space rock as it buzzes Earth.___The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.。     　　田磊强调，假同色图检查有非常严格的前提：必须在标准光照、固定观看距离、规定时长内，使用合格的纸质原版图谱完成。我们在网上看到的图，大多经过扫描、拍照、多次压缩，再经过不同亮度、色温的电子屏幕显示，颜色早已偏离了原始标准，原本的辨色题很容易变成“猜图形题”。     　　另外，标准色觉检查要看一组图，而不是一张图，单张图答错，不能诊断为色盲。因此，对着手机自测只能当娱乐，绝不能以此给自己下“色盲”的诊断。     　　针对“AI也会认错色盲图”的热议，田磊解释，人眼和AI的识别逻辑不同，人眼是通过视锥细胞感知光波，再经视网膜和大脑形成色觉，是生理性判断;而AI更多的是依靠训练中学到的轮廓、纹理、形状来识别图中内容，色盲图刻意弱化了形状信息，在传播中又损失了色差，AI就只能靠轮廓“猜答案”，出错也就不奇怪了。

三 | 　　色盲≠色弱　　驾照和职业体检到底卡在哪?      　　比起“能不能认出图”，更多人关心的是色觉异常会不会影响考驾照、找工作。田磊介绍，我国现行机动车驾驶证体检对辨色力的核心要求，是无红绿色盲。原因很直观：交通信号体系里，红、绿分别承担“停止”和“通行”的核心信息，直接关系道路安全。     　　但公众普遍存在一个误区：认为色弱和色盲完全一样，觉得“只要色弱就不能开车”。田磊明确表示，色弱依然能分辨相关颜色，只是在颜色接近时分辨能力下降。

四 | 轻度色觉异常是否符合驾驶要求，需要由有资质的医疗机构按照规范判断。     　　除了驾驶，还有不少职业对色觉设置了门槛。

五 | 田磊总结，凡是“颜色本身就是安全信息”的岗位，通常都会对色觉提出更高要求，比如——      　　航空、航海、铁路交通类岗位：需要准确识别灯光、航标、铁路信号;      　　高风险工业岗位：依靠颜色判断仪表、线路、警示信号的操作岗;      　　专业辨色岗位：部分医学检验、化工、纺织、印刷、查验类岗位。     　　(注：不同岗位的限制程度不一，以对应行业的正式体检标准为准。)      　　田磊介绍，日常筛查用假同色图足够高效。

六 | 如果对结果有争议、需要明确诊断和分型，眼科还有更精细的复核手段，比如色相排列、异常三色镜等方法。     　　重要提醒，驾照体检等正式的色觉检测，一定要以有资质医疗机构的规范结果为准，不要仅凭网上一张图、一个手机App就自行下结论。如果对自测结果有疑问，前往正规医院眼科做专业复核即可。

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