When it comes to the general public's ignorance of space exploration, there are two drastic poles.
Swing to the opposite end of the spectrum and you have people like Lauren Hart, who think The Martian - a sci-fi story about a man left behind on a mission to Mars - is based on real events...
We commend Lauren for her honesty: she could have shied away from her moment of ignorance, putting the nasty business behind her. Instead, she sought out internet lols.
But it seems Lauren isn't alone. In fact, she belongs to a worryingly large section of society* (*that tweet) who apparently don't know if humanity has set foot on Mars.
Two things could be happening here.
The first is that people are enjoying spreading the joke of "My mate is so thick he thought The Martian was real, lolz, wot?" - a joke that's only funny once.
The other, more concerning conclusion, is that people really do only use the internet to look at cat videos, and have never bothered to poke around on Wikipedia or NASA.org for more than five minutes.
For the record: The Martian is a book by Andy Weir, recently adapted by Ridley Scott for film. It stars Matt Damon, it's really good, and it's entirely made up. They don't even have any water up there.
Also - Titanic is based on historical events, as is Apollo 13. Avatar isn't. Nor are any of the Alien series.
Glad we could help.