Elon Musk's SpaceX aims to send an unmanned aircraft to Mars by 2018.
2018年6月四級真題（第一套）聽力 Section A
But they can attain more distant orbits; NASA plans for most of its future Earth-escaping payloads to the moon and Mars especially to carry CubeSats.
2019年6月六級真題（第三套）閱讀 Section B
Nasa is worried about two things: recovery time once astronauts return home, and, more importantly, how to maintain strength and fitness for the two and a half years or more that it would take to make a round-trip to mars.