Space robotics

It takes between three and twenty-two minutes for a radio signal to travel from Earth to Mars, depending on where the two planets are in their orbits. That means if you send a command to a Mars rover and something goes wrong, you cannot respond for at least six minutes — and by then the rover has already driven off a ledge, or not. Space robotics is the art of building machines that can survive and act usefully in that kind of radical remoteness.

Space robots operate in conditions that destroy ordinary electronics and mechanisms: temperature swings of several hundred degrees Celsius between shadow and sunlight, hard radiation that corrupts computer memory, vacuum that vaporises conventional lubricants, and gravitational environments that range from lunar gravity (one-sixth of Earth's) to the weightlessness of orbit. Every component must be chosen to survive these conditions without maintenance for years, sometimes decades.

Modes of operation

Space robots work in three distinct ways depending on communication delay. In Earth orbit — where signal delays are milliseconds — an astronaut can teleoperate a robotic arm in near-real time. Canadarm2, the robotic arm on the International Space Station, has been operated this way since 2001, assembling modules, capturing visiting spacecraft, and moving astronauts performing spacewalks. On the Moon (about 1.3 seconds of signal delay), semi-autonomous control is feasible. On Mars, full autonomy is essential: Perseverance rover plans and executes its own daily drives, choosing a safe path from a rough target sent by the team on Earth.

Perseverance on Mars

NASA's Perseverance rover, which landed in Jezero Crater in February 2021, carries a suite of science instruments, a rock-coring system that collects samples for eventual return to Earth, and a small helicopter called Ingenuity — the first powered aircraft to fly on another planet. Perseverance drives using a system called AutoNav, which builds a 3D map of the terrain ahead using stereo cameras and autonomously steers around obstacles the mission team never saw. By 2025, Perseverance had driven over 30 kilometres and collected dozens of rock cores.

The frontier

The next generation of space robots is pushing into more dynamic tasks. NASA's ATHLETE (All-Terrain Hex-Legged Extra-Terrestrial Explorer) was designed to haul cargo across the lunar surface. ESA and JAXA are developing robotic systems for in-orbit servicing — refuelling or repairing satellites already in space, extending their lives by decades. Perhaps most ambitiously, researchers are exploring self-assembling robotic systems that could construct large structures — antennas, solar arrays, habitats — in orbit without human hands ever touching a bolt.

Somewhere on Mars right now, a robot is deciding, entirely on its own, whether the rock in front of it is interesting enough to drill.