1803 年 4 月，美国特使门罗与法国签订《路易斯安那购买条约》： 以1500万美元（约合今日 3.4 亿美元 ）购得从密西西比河到落基山脉的 82.8 万平方公里 土地。 一夜之间，美国的领土几乎翻倍，从“东部小国”变成横跨大陆的“潜在强国”。

NASA’s ambitious OSIRIS-APEX mission to study the asteroid Apophis has been spared from cancellation, but its future is far ...

According to a study conducted by University of Tokyo researchers, Ryugu maintained a "pristine record" of late water activity. By examining the lutetium and hafnium isotopes in their rock samples, ...