On the 5th of March, 2011CE, the United States Airforce launched a X-37 space plane. It was meant to be in orbit for 290 days, but it returned on June the 16th, 2012, some 469 days later.
What was the X-37 doing all that time? Why did it take so long to come back? Did it encounter a space-born virus which it has returned to Earth, a virus which will wipe out all humanity? Well, no; that’s vaguely the plot of the first Quatermass serial. Still, there’s a question about what it was the X-37 was up to, and when it comes to questions about what military hardware is really doing, you know there are going to be conspiracy theories abounding.
(I apologise for the continuing attacks on “Prometheus;” all I can say is that the opportunity came up to dismiss its merits and I could not resist it.)