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.

Over two years after Japan’s Smart Lander for Investigating Moon (SLIM) mission deployed a tiny, shape-shifting rover on the Moon, the country’s space agency JAXA has finally revealed previously unreleased details about the first-of-its-kind autonomous robotic lunar exploration.

According to a statement announcing the recently published mission account, the SLIM team deployed the rover on the Moon’s surface, “after which the rover transformed from a tiny sphere into a wheeled robot that took images of the lander and its environment.” A second rover transmitted the data back to Earth, with all steps occurring autonomously.

The team behind the historic mission said their success could pave the way for swarms of small, transformable robots capable of exploring high-scientific value areas that larger spacecraft and robots cannot reach, including caves, tunnels, lava tubes, vents, and deep extraterrestrial craters.

The Benefits of Tiny Robots and Autonomous Shape-Shifting Rovers

In the published study, the JAXA team explains that robotic technologies like SLIM “are expected to drive substantial advancements in planetary exploration and resource prospecting” by performing tasks in extraterrestrial environments that are inaccessible to other platforms, including human astronauts. For example, the team noted that miniature robots offer tremendous weight savings over bulkier platforms, especially when added to missions with “strict payload limitations.”

“Miniature robots have the potential to reduce payloads and to reach cramped spaces such as small vents and craters that are inaccessible to larger, conventional robots,” they explain.

Still, the SLIM team notes that building tiny, shape-shifting rovers capable of exploring a variety of complex environments presents its own set of challenges. The most limiting constraints involve computational power and battery capacity. The team also observed that smaller robotics platforms inherently suffer from “reduced locomotion performance” due to their small size.

Now, when revealing the details of the SLIM mission, the researchers note that advancements in miniaturization and computational performance spurred by the Internet of Things “have catalyzed the emergence of smaller, lighter, and more intelligent rovers at lower costs.”

Introducing the ‘Hopping’ Lev-1 and the ‘Transforming’ Lev-2

To build a tiny, shapeshifting robot capable of exploring the lunar surface autonomously, team leader Daichi Hirano and colleagues designed the Lunar Excursion Vehicle (LEV) system, which comprises LEV-1 and LEV-2. According to the team’s statement, LEV-1 can communicate directly with mission planners back on Earth. For locomotion, the robot moves via what the team termed “a controlled hopping mechanism.”

The second robot, LEV-2, starts out as a compact sphere 8 inches in diameter. However, once on the Moon, the mission controllers said that the tiny robot can transform into a “two-wheeled rover with cameras and a tail stabilizer.”

“Here, we introduce a two-wheeled centimeter-scale rover, designated Lunar Excursion Vehicle 2 (LEV-2), also known as SORA-Q (named after the Japanese words for space and sphere), which transforms into a wheeled configuration from a compact spherical form, enabling efficient traversal of soft lunar terrains,” they write.

Transformers Make Autonomous Robotic Exploration History

According to the new mission details, the SLIM lander deployed LEV-2 “immediately before its landing on the lunar surface.” In the mission details, the team explained that upon deployment, the rover autonomously extended its wheels, tail stabilizer, and cameras, “thereby enhancing its mobility and stability on soft lunar terrain.”

After deployment, LEV-2 navigated the lunar surface in the immediate area around the lander. According to the published study, “the palm-sized rover accomplished autonomous lunar exploration by navigating around the SLIM lander, capturing images of both the SLIM lander and its environment.” Critically, the rover’s exploration was autonomous and “without reliance on ground-based teleoperation,” marking a historic first in lunar exploration.

After finishing its exploration, the tiny robot transmitted images of its adventures to LEV-1. The hopping rover then transmitted the data to Earth. The team notes that all these steps were also accomplished autonomously.

The team notes that the LEV-2 shape-shifting rover operated for “more than 100 minutes: before losing communication with LEV-1. Although determining the exact cause may require direct examination of the two robots, Hirano’s team suspects that issues caused by LEV-1’s hopping motions or battery depletion “may have contributed to connectivity issues.”

Exploring High-Risk, Scientifically Valuable Environments

When discussing the implication of an autonomous, shape-shifting rover successfully navigating the lunar surface and completing its mission directives, the team concedes that the capabilities of a single, small rover like LEV-2 “are inherently limited.” However, they also note that their mission success highlights the potential of this category of robotic platform “as independent explorers, capable of accessing environments beyond the reach of a primary large spacecraft.” 

“Swarm-controlled small robots are poised to be deployed in high-risk yet scientifically valuable environments, such as vents, caves, and steep slope craters, that are inaccessible to larger, conventional rovers,” the researchers conclude. “This approach promises to enhance both the efficiency and safety of future planetary surface exploration.”

The study “From ball to rover: Transformable palm-sized rover SORA-Q for autonomous lunar exploration” was published in Science Robotics.

Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.