NASA is developing the next generation of surface exploration technology with its Exploration Rover for Navigating Extreme Sloped Terrain (ERNEST), designed with advanced mobility and autonomy capabilities to enable access to previously off-limits regions on the Moon and Mars.
In Southern California’s Colorado Desert, NASA’s ERNEST prototype is traversing rough patches of terrain as the design team at the Jet Propulsion Laboratory (JPL) continues to dial in the rover’s advanced mobility technology.
The four-wheeled, four-foot-long rover can readily handle landscapes that would be impassable for its six-wheeled predecessors, such as Curiosity and Perseverance.
NASA Lunar Navigation
ERNEST features mesh wheels for physically traversing difficult ground, as well as an intelligent decision-making system that determines the best route to its destination. As plans for humanity’s return to the lunar surface grow more ambitious, a rover capable of traveling longer distances at higher speeds will become a necessity. This is what ERNEST is accomplishing for NASA, already showing improvement over the performance of earlier rovers by an order of magnitude, as demonstrated in one test by traveling 16 miles in 37 hours.
The ERNEST prototype is less than half the size that the JPL team expects the final build to be. Since the project began in 2022, this is the third ERNEST prototype, with the other two being only two feet long and built primarily to test various suspension iterations over simulated lunar regolith packed at various slopes. They completed fabrication of the current prototype in September 2024 and operated it remotely via joystick control.
“You could do a science road trip across the Moon — or Mars — with this vehicle,” said James Keane, a JPL planetary scientist working on lunar missions.
ERNEST Project
ERNEST was a project that grew from relatively humble beginnings: initially, it sought only to replace current rovers with a simple, low-cost alternative by tweaking the rocker-boogie suspension already in use. The new active suspension developed for ERNEST allows it to balance weight among the four wheels rather than distributing it equally across all six wheels, as in the rocker-boogie system.
“We started by postulating that we could do better in designing a planetary surface robotic mobility system,” said Hari Nayar, a JPL principal technologist leading the ERNEST team. “While the rocker-bogie system has been very successful over the past 30 years, there’s been a lot of research in that time on mobility and understanding terrain interaction.”
Powered joints in front of the rover allow it to switch between squirming, wheel-walking, and obstacle-climbing gaits to adapt to changing surface conditions. For less challenging terrain, a clutch allows the system to switch to a more energy-efficient passive suspension, conserving power for longer journeys. Each wheel is articulated to allow movement in any direction, allowing the vehicle to move completely sideways.
These major mobility advances will be a boon to mission planners, who have struggled to reach hard-to-access areas on Mars and the Moon that were previously inaccessible with previous technology.
NASA’s Autonomous Rover
“This testing is helping us refine the mobility hardware and autonomy software to navigate extreme distances across a wide range of terrain and lighting conditions anticipated on the Moon,” said Issa Nesnas, a principal technologist at JPL.
To move beyond operator control to autonomous decision-making, the team used an artificial intelligence technique called reinforcement learning, in which a model learns through interactions with the environment.
A virtual testing environment, running multiple simultaneous instances for months, allowed the researchers to have the rover ready to meet its environmental challenges from its first real-world test. Conducted at JPL’s Mars Yard, the initial tests featured an obstacle course of steps, slopes, ripples, and rubble. From this, and in many subsequent tests, ERNEST proved successful in navigating a range of very difficult environments.
Further improvements to the rover’s autonomy are being pursued with an eye on intelligent long-distance travel, with the rover independently switching between suspension settings.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.