Researchers have developed biomimetic wheels for future Mars rovers inspired by the foot structure of lizards to improve traction on sandy terrain. This design reduces slippage and prevents vehicles from sinking into Martian regolith, potentially increasing the range and efficiency of planetary exploration missions.
The development addresses a persistent failure point in planetary exploration: the tendency of wheeled vehicles to become trapped in soft, granular soil. By mimicking the directional friction and scale-like structures found in lizard feet, the new wheel design allows rovers to maintain forward momentum without the excessive spinning that often leads to “digging in” and immobilization.
Current Mars rovers, such as NASA’s Perseverance, utilize rigid aluminum wheels with cleats called grousers. While effective on hard rock, these wheels can struggle in deep sand, a challenge that nearly ended the mission of the Spirit rover in 2009 when it became permanently stuck in a sandy patch of the Martian surface.
How do lizard-inspired wheels improve Mars navigation?
The biomimetic design focuses on the way certain lizard species distribute their weight and interact with loose particles. According to research from the Korea Advanced Institute of Science and Technology (KAIST), the wheels employ a specific geometry that mimics the “scales” of a lizard’s foot, creating an asymmetric surface that provides high grip in the direction of travel while reducing resistance when moving forward.
Traditional wheels rely on friction and the physical displacement of soil. When a wheel spins in soft sand, it pushes the material backward and downward, creating a hole that eventually bottoms out the chassis of the rover. The lizard-inspired wheels utilize a series of adaptive fins or scale-like protrusions that lock into the granular media more effectively, converting more of the motor’s torque into forward motion rather than soil displacement.
This mechanism functions similarly to how a lizard’s toe scales provide grip on uneven or shifting surfaces. By optimizing the angle and stiffness of these protrusions, the wheels can maintain a higher “traction coefficient,” which refers to the ratio of the drawing force to the normal force acting on the wheel.
Why is Martian regolith a challenge for current rovers?
Martian regolith is not uniform sand; it is a complex mixture of volcanic basalt, oxidized iron, and fine dust. The particles are often jagged and lack the cohesive properties of Earth’s beach sand, making them prone to shifting under the weight of a heavy rover.
NASA has documented significant wheel wear on the Curiosity rover, where sharp rocks caused punctures and tears in the aluminum wheels. While the “sand trap” is a different problem than mechanical wear, both issues limit the “safe” areas a rover can explore. If a rover cannot traverse sandy plains or craters—where some of the most scientifically valuable sedimentary deposits are found—the mission’s scientific return is diminished.
The lizard-inspired design mitigates this by spreading the load across a larger, more adaptive surface area. This reduces the ground pressure, meaning the rover is less likely to sink into the regolith. By reducing the “slip ratio”—the difference between the theoretical distance the wheel should travel and the actual distance moved—the rover consumes less energy and reduces the risk of catastrophic immobilization.
What makes biomimetic design effective for space exploration?
Biomimicry, the practice of emulating nature’s patterns and strategies, provides solutions to engineering problems that have been “field-tested” by evolution over millions of years. In the context of space robotics, nature offers blueprints for mobility in extreme environments that traditional human engineering often overlooks.
Beyond the lizard-inspired wheel, space agencies are exploring other biological models for planetary mobility:
- Gecko-inspired adhesives: Used for robotic grippers that can adhere to smooth surfaces in a vacuum without using chemical glues.
- Insect-like legged robots: Designed to navigate rocky terrain where wheels cannot go, using multi-jointed limbs to maintain balance.
- Snake-like locomotion: Being researched for exploring narrow crevices or lava tubes on the Moon and Mars.
The shift toward biomimetic wheels represents a move away from the “brute force” approach of larger wheels and more powerful motors toward a “smart geometry” approach. By changing the shape of the wheel’s interface with the ground, engineers can achieve better results without adding significant weight to the spacecraft, which is critical given the high cost of launching mass into orbit.
Comparing biomimetic wheels to traditional rover wheels
The primary difference between traditional and lizard-inspired wheels lies in their interaction with granular media. Traditional wheels treat the soil as a surface to be pushed against; biomimetic wheels treat the soil as a medium to be engaged with.
| Feature | Traditional Aluminum Wheels | Lizard-Inspired Biomimetic Wheels |
|---|---|---|
| Surface Design | Rigid with grousers (cleats) | Adaptive scale-like protrusions |
| Sand Interaction | Pushes soil backward (high slip) | Locks into granular media (low slip) |
| Risk Factor | High risk of “digging in” and sinking | Reduced sinkage due to load distribution |
| Efficiency | Lower torque efficiency in soft soil | Higher forward-motion conversion |
While traditional wheels are superior for traversing hard, rocky plateaus, they fail in the very environments—like ancient lakebeds or dunes—where water and organic signatures are most likely to be found. The integration of biomimetic wheels could allow future rovers to enter these “high-risk, high-reward” zones with greater confidence.
What happens next for planetary mobility?
The next phase for this technology involves rigorous testing in “Mars yards”—terrestrial analogs that mimic the gravity and soil composition of the Red Planet. Researchers must determine how these scale-like structures hold up against the abrasive nature of Martian dust, which is known to be chemically reactive and physically wearing.
The long-term goal is the development of “hybrid” mobility systems. Future missions may feature rovers capable of switching between different wheel modes or combining wheels with robotic legs, allowing them to adapt their footprint based on the terrain they encounter in real-time.
As NASA and other international agencies plan for human missions to Mars, the need for reliable, high-capacity transport vehicles increases. These vehicles will be significantly heavier than current rovers, making the “sinkage” problem even more acute and increasing the necessity for biomimetic traction solutions.
The next confirmed checkpoint for planetary mobility research will be the upcoming deployment of new rover prototypes in lunar analog environments, as part of the broader Artemis program’s effort to establish a sustainable human presence on the Moon before venturing to Mars.
Do you think biomimetic robotics are the key to exploring the solar system, or should we stick to traditional engineering? Share your thoughts in the comments below.