How do Mars rovers navigate when messages from Earth take a long time to arrive?

Mars rovers navigate the Martian surface using onboard systems that allow them to operate as independent robotic units. Because of the significant communication delay between Earth and Mars, these rovers cannot be "driven" in real-time by human operators.1

Instead, engineers on Earth send sequences of commands that the rovers execute autonomously. To facilitate this, rovers like Sojourner were equipped with cameras that provided visual data, which were then transmitted back to Earth. Scientists and engineers used these images to analyze the terrain, identify obstacles, and plan safe paths for the rover to follow. Once a path was determined, the instructions were uploaded to the rover, allowing it to navigate the surface and conduct scientific investigations—such as analyzing rocks and soil—without requiring constant, instantaneous input from mission control.12

This autonomous capability is essential for planetary exploration, as it ensures the safety of the spacecraft while maximizing the scientific data gathered during its mission.21