Rovers on Mars drive across the surface under instructions delayed by many minutes.

The longer version

Radio signals need time to cross the gap between planets, and that delay ranges from several minutes to around twenty minutes each way depending on where the two worlds sit in their orbits. Mars and Earth are separated by tens of millions of kilometers at closest approach. No remote control in real time is possible.

Because of this, a rover operates largely on its own. Controllers upload a sequence of commands, the vehicle executes them while checking for hazards, and it reports back afterward. Engineers work in a cycle of planning, driving and analysis tied to the Martian day rather than to an Earth based schedule.

Where this entry sits

The night sky looks calm, yet almost everything up there is moving, burning, or slowly changing. These facts cover planets, stars, the Moon, gravity, black holes, comets, and the story of how people began exploring beyond Earth. The full list sits on the Space and Sky page, where every entry is listed in order.