NASA’s spare Mars rover could finally get its moment — on the Moon

NASA’s Jet Propulsion Laboratory built three near-identical Mars rovers: Curiosity, Perseverance, and a ground-test twin that never left Earth. While the first two explore the Red Planet, the third has spent years enduring every simulation and failure diagnosis in JPL’s labs, earning the role of engineering backup.

Now, that overlooked sibling may finally get its shot at glory—on the Moon. Speaking at a Tuesday press briefing, NASA officials said the agency is actively considering sending the spare rover to the lunar south pole, where it would be rechristened the Polar Rover for Observation, Mapping, and In-Situ Exploration (PROMISE).

Its mission: scout the rugged polar terrain, map surface and subsurface features, and prospect for resources such as water ice—critical for both scientific research and future human bases. The rover’s existing capabilities make it a strong fit: it’s roughly SUV-sized, carries a high payload capacity for science instruments, and is powered by a plutonium-based Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), allowing it to operate through the long, frigid lunar nights.

Curiosity and Perseverance, however, are locked into their Martian duties and won’t be redeployed. The catch?

JPL currently relies on the spare to test new commands and diagnose issues for the active rovers. If the Moon mission proceeds, NASA would lose that critical fallback, effectively gambling with Mars operations to prioritize lunar exploration.

The decision hasn’t been finalized, but the announcement signals a strategic shift: with the U.S. in a heated race to the Moon against China, lunar exploration is taking center stage, potentially sidelining Mars—long the darling of planetary science—as a near-term priority.