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

一 |     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.。

二 |     尼安德特人是已经灭绝的人类亲属，他们一直生活到大约4万年前，在欧亚大陆的大部分地区居住，并与现代人和其他人类如丹尼索瓦人相遇和交融。关于他们作为一个物种如何生活的证据正在积累，但新的研究深入到一个个体社区。

三 | 由马克斯-普朗克进化人类学研究所领导的一个研究小组检查了一小群10到20个尼安德特人，他们生活在西伯利亚的Chagyrskaya和Okladnikov洞穴中，距今约54000年。

四 | 该小组从17具遗骸中提取了DNA，并对其基因组进行了测序。结果发现，这些遗骸来自13个尼安德特人，包括7名男性和6名女性，其中8个是成年人，5个是儿童或青少年。基因组显示，这群人关系密切，似乎在同一时期生活和死亡。该研究的第一作者Laurits Skov说：“他们在同一时间生活的事实是非常令人兴奋的。这意味着他们可能来自同一个社会社区。因此，我们第一次可以利用遗传学来研究尼安德特人社区的社会组织。

五 | ”在这群人中，研究小组确定了一个十几岁的女性尼安德特人和她的父亲，以及一个小男孩和一个成年女性，后者是他的旁系亲属，像表妹、姨妈等。研究小组还在这些个体的线粒体DNA中发现了共同的异质体--只持续几代的遗传变体，进一步表明了密切的关系。研究小组说，社区之间的遗传多样性极低，表明是一个最多20人的小群体。

六 | 耐人寻味的是，线粒体DNA的遗传多样性要比Y染色体的多样性高得多--线粒体DNA是专门从一个人的母亲那里继承的--Y染色体是由父亲传给儿子的。这表明，是女性在社区之间移动以与男性伴侣在一起。最近对尼安德特人遗传学的其他研究揭示了对杂交程度、第一代尼安德特人/丹尼索瓦人混血儿以及克罗地亚的一个群体的深入了解，该群体可能是他们灭绝前最后幸存的人群之一。这项新的研究有助于从一个更有亲和力的角度来描绘尼安德特人。这项研究的最后一位作者Benjamin Peter说：“我们的研究提供了一幅尼安德特人社区可能是什么样子的具体画面。

七 | 在我看来，它使尼安德特人看起来更像人类。”这项研究发表在《自然》杂志上。

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