Final answer:
The theme of the passage is that the exploration of Mars is a complex and challenging endeavor.
Step-by-step explanation:
The statement that best expresses the theme of the passage is: The exploration of Mars is a complex and challenging endeavor. The passage discusses the complex nature of the Mars project, mentioning that it is a joint effort between multiple countries and has faced numerous setbacks and obstacles. It also explores the idea that not all exploration leads to settlement and that the colonization of space is unlikely to happen in the near future. The Braille system is a method that is widely used by blind individuals to read and write, thanks to its system of raised dots which can be felt with the fingertips.