阿凡达

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

裸婚时代

A | 8月24日消息，辽宁喀左的百斤巨型西瓜迎来丰收，单瓜重量可以突破100斤，个头差不多抵得上成年人腰腹，京东物流连续第二年承接这批特殊西瓜的独家发货保障。 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.。

B | 当地种植户培育出的一颗163斤西瓜，曾经拍出5.1万元，拿下过拍卖会售出最贵西瓜的吉尼斯世界纪录。

C | 这种巨型西瓜培育门槛很高，一亩地只栽种56棵瓜苗，要足足长120天才成熟，还拿到了国家绿色食品A级认证，吃起来果肉脆甜。

D | 以前这种百斤大瓜发货很麻烦，不少物流看到重量直接拒收，就算愿意运，还要收取高额附加运费。今年京东物流把重货特快产品用上，依托重货揽收、航空和车队资源，核心经济圈可以做到今发明至。为了防止运输路上磕碰弄坏西瓜，包装做了专门定制。内层用加厚蜂窝纸箱搭配缓冲气泡柱，外层套带通风口的改良木箱，兼顾缓冲防护和透气。

E | 揽收之后走生鲜优先通道，当天完成中转，尽量压缩在路上耗费的时间。

F | 最有看点的是末端派送环节。一个西瓜连箱子很重，普通人搬起来很费劲。京东小哥会用上爬楼机专业设备，就算没有电梯的楼房，也可以把百斤西瓜送货上门，并且支持全国包邮。 除了辽宁喀左的巨型西瓜，京东物流也给宁夏中卫、北京庞各庄、河南开封等各大西瓜产区提供物流支持，针对河南滞销西瓜也推出过助农相关举措。