本文作者： 21st
DID you have a happy Christmas? American Astronauts (宇航员) celebrated Christmas in space. On Dec 24, Rick Mastracchio and Mike Hopkins took a space walk around the International Space Station (ISS, 国际空间站). They spent seven and a half hours checking the systems (系统) of the ISS. Their colleagues (同事) on the Earth said: “That is the best Christmas gift ever!”