Rovers on Mars rely on two main power architectures that determine their battery chemistry. Solar-powered rovers typically use nickel-based rechargeable batteries (NiCd or NiMH), while rovers powered by a radioisotope thermoelectric generator (RTG) rely on lithium-ion battery packs to store energy. This mix reflects mission design choices, environmental conditions, and the need to balance weight, reliability, and performance.
To understand how these rovers operate, it helps to look at the two primary power setups: solar-powered rovers that charge from sunlight and store energy in nickel-based batteries, and RTG-powered rovers that generate continuous power from a nuclear heat source and use lithium-ion packs for energy buffering and peak loads. The chemistry chosen affects lifespan, performance in dust storms or cold temperatures, and how often the rover needs servicing from Earth.
Two power architectures on Mars rovers
Below are the main battery chemistries associated with each power approach, along with representative rovers.
Solar-powered rovers
- Sojourner (Pathfinder mission, 1997) — nickel-cadmium (NiCd) rechargeable batteries
- Spirit (Mars Exploration Rover, 2004) — nickel-metal hydride (NiMH) rechargeable batteries
- Opportunity (Mars Exploration Rover, 2004) — nickel-metal hydride (NiMH) rechargeable batteries
The solar-powered rovers store energy collected by their solar arrays in rechargeable nickel-based batteries. Over time, design refinements moved from NiCd to NiMH to improve energy density and reduce memory effects, while dust management and temperature control remain critical factors for performance.
Rovers powered by RTGs
- Curiosity (Mars Science Laboratory, 2012) — power from a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG); uses lithium-ion (Li-ion) battery packs for energy storage
- Perseverance (Mars 2020, 2021) — power from an MMRTG; uses lithium-ion (Li-ion) battery packs for energy storage
RTG-powered rovers rely on a steady electrical supply from the MMRTG, with lithium-ion batteries providing storage for peak loads and operational bursts. Li-ion packs help manage rapid power demands during data collection, mobility, and instrument use, while the RTG handles baseline electricity production and thermal regulation in the harsh Martian environment.
Battery chemistry in context
Battery choice reflects trade-offs between weight, energy density, temperature tolerance, and longevity. NiCd batteries were robust and simple for early solar rovers but heavier and prone to memory effects. NiMH offered higher energy density and fewer memory issues, improving efficiency for later solar missions. Li-ion batteries provide high energy density and lighter weight, which is advantageous for RTG-powered rovers that must balance mass with performance in extreme temperatures and long-duration missions.
Summary
The kind of batteries Mars rovers use depends on how they are powered. Solar-powered rovers historically used nickel-based chemistries (NiCd, then NiMH) to store solar energy, while newer, RTG-powered rovers (Curiosity and Perseverance) rely on lithium-ion battery packs to buffer and manage power from the MMRTG. These choices influence mission design, endurance, and resilience against dust, cold, and other Martian conditions.