NASA's Voyager 1 spacecraft, the farthest spacecraft from Earth, just turned on some of its thrusters that haven't been used since 1980.

Currently the only spacecraft we've ever sent to interstellar space, Voyager 1's attitude control thrusters – which it had used to point its antenna towards Earth – had been wearing down. When it can no longer point its antenna to Earth, we'll no longer be able to contact it.