Moon and Mars cave exploration could be easier with ReachBot

How will future robotic explorers navigate the difficult subterranean environments of caves and lava tubes on the Moon and Mars? This is what a recent study published in Science Robotics hopes to address as a team of researchers from Stanford University investigated the use of a novel robotic explorer called ReachBot, which could potentially use its unique mechanical design to explore deep caves and lava tubes on the Moon and Mars in the future.

Here, Universe Today discusses this incredible research with Dr. Tony Chen, who is a postdoctoral research fellow in the Harvard Microrobotics Laboratory at Harvard University and lead author of the study, regarding the motivation behind developing ReachBot, significant results, what steps he thinks need to be taken for ReachBot to actually go to the Moon, and how ReachBot could contribute to the upcoming Artemis missions. Therefore, what was the motivation behind ReachBot?

Dr. Chen tells Universe Today, “ReachBot started as a NASA NIAC [NASA Innovative Advanced Concepts] project, where the program is focused on the development of far-reaching and long-term technologies. The main motivation behind ReachBot is to enable robotic exploration of previous inaccessible planetary environments (such as lava tubes) that could provide interesting scientific discoveries and advancements.”

What makes ReachBot unique is its ability to maneuver difficult terrain like uneven rock surfaces by using its elongated appendages with pivoting wrists and grippers guided by a series of algorithms to determine the best course of action. This allows ReachBot to contort its body in a variety of ways while traversing both tight and wide areas within a confined space like a tube or cave. The concept of ReachBot for use in Martian lava tubes was discussed in a 2021 study (Dr. Chen as co-author), followed by prototype testing in a 2022 study (Dr. Chen as lead author), prototype improvements in a 2022 study (Dr. Chen as co-author), and further improvements in a 2022 study (Dr. Chen as co-author).

For this study, the researchers conducted field tests of ReachBot and its capabilities within a lava tube in the Lavic Lake volcanic field in the Mojave Desert as an analog for Martian lava tubes while building off the previous studies. This included investigating how ReachBot could predict how it will both grip and grasp rocky surfaces, gripper design, rocky surface site identification and selection, and how ReachBot performed in a lava tube using its extended appendages that enables the robot’s extreme maneuverability. In the end, the researchers found a wide range of possible extensions for ReachBot, along with favoring convex (outward curved) rocky surfaces that could provide stronger grips, as well.

Dr. Chen tells Universe Today, “The lava tubes in the Mojave Desert were chosen because it was a close analogous cave system to what the lava tubes could potentially be like on Mars. It allowed us to bring a partial ReachBot system into this environment and investigate how the various subsystems perform in a realistic environment.”

This study comes as an international team of researchers led by the University of Trento in Italy successfully constructed a 3D map of a lava tube skylight entrance located in the Mare Tranquillitatis pit (MTP) on the Moon using radar data obtained by NASA’s Lunar Reconnaissance Orbiter (LRO). The team determined the lava tube could be tens of meters in length with the skylight itself being almost 100 meters in diameter, noting such lava caves could shield future astronauts from the harsh solar and cosmic radiation that endlessly blasts the lunar surface, thus opening the potential for long-term human exploration of the Moon.

Lava tubes have long been studied for potential future human exploration on both the Moon and Mars, with more than 200 skylights having been observed on the Moon up to this point. Shielding future astronauts from harmful space radiation prevents potentially catastrophic health consequences, including biological effects, radiation sickness, cancer, and death. Being able to send a robotic explorer ahead of time could help astronauts and scientists better determine the most ideal lava caves where astronauts could call home for long-term missions. Therefore, what steps does Dr. Chen believe need to be taken for ReachBot to actually go to the Moon?

“As it currently stands, only a partial prototype of ReachBot has been constructed and tested in a relevant environment,” Dr. Chen tells Universe Today. “There are many other technological developments needed in this project to push it forward. These include but are not limited to the further development of retractable space booms to be more suitable for ReachBot application, full system prototype, and further testing in relevant environments.”

This study also comes as NASA plans to send humans back to the Moon for the first time since 1972 with the agency’s Artemis Program, including landing the first woman and person of color on the lunar surface in history. This program started with the uncrewed Artemis I mission that took the Orion spacecraft, performing a couple flybys of the Moon while testing out the various flight hardware during the mission. This will be followed with the crewed Artemis II mission, which is currently scheduled for a September 2025 launch, will consist of a 10-day mission and four astronauts (three from NASA and one from the Canadian Space Agency) who conducts flybys of the Moon without touching down on the surface.

The first crewed landing on the lunar surface will be the Artemis III mission, which is currently scheduled for September 2026, which will occur near the lunar south pole in hopes of extracting water ice hidden within the deep and dark craters known as the permanently shadowed regions (PSRs). While lava caves and tubes are currently not part of the program, how can ReachBot contribute to the upcoming Artemis missions?

“As you noted earlier, ReachBot was originally designed as a concept to explore Martian lava tubes,” Dr. Chen tells Universe Today. “But there are also lava tubes on the Moon that ReachBot could also provide interesting capabilities to explore. These lava tubes could potentially be a habitat for future space explorers, and ReachBot can help both exploring these caves to provide crucial data and forceful manipulation capabilities for potential construction tasks.”

How will ReachBot help improve lava cave exploration on the Moon and Mars in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!