House hunting on Mars could soon become a thing, and researchers at the University of Arizona are already in the business of scouting real estate that future astronauts could use as habitats. Researchers in the UArizona College of Engineering have developed technology that would allow a flock of robots to explore subsurface environments on other worlds.

Wolfgang Fink, Associate Professor of Electrical and Computer engineering at UArizona, believes the approach could help address one of NASA’s Space Technology Grand Challenges by helping overcome the limited ability of current technology to safely traverse environments on comets, asteroids, moons, and planetary bodies such as Mars.

In this artist’s impression of the breadcrumb scenario, autonomous rovers can be seen exploring a lava tube after being deployed by a mother rover that remains at the entrance to maintain contact with an orbiter or a blimp. (Image: John Fowler/Wikimedia Commons, Mark Tarbell, and Wolfgang Fink/University of Arizona)

Fink is lead author of a new paper in Advances in Space Research that details a communication network that would link rovers, lake landers, and even submersible vehicles through a so-called mesh topology network, allowing the machines to work together as a team, independently from human input.

The new concept dovetails with the tier-scalable reconnaissance paradigm devised by Fink and colleagues in the early 2000s. This idea envisions a team of robots operating at different command levels — for example, an orbiter controlling a blimp, which in turn controls one or more landers or rovers on the ground.

Already, space missions have embraced this concept, several with participation by UArizona researchers. For example, on Mars, the Perseverance rover is commanding Ingenuity, a robotic helicopter. The new approach takes the idea one step further by providing a robust platform allowing robotic explorers to operate underground or even submerged in liquid environments. According to Fink, such swarms of individual, autonomous robots could also aid in search and rescue efforts in the wake of natural disasters on Earth.

A hole in the surface of Mars, spotted by the HiRISE camera, reveals a cave below. Protected from the harsh surface of Mars, such pits are believed to be good candidates to contain Martian life, making them prime targets for possible future spacecraft, robots, and even human interplanetary explorers. (Image: NASA/JPL/University of Arizona)
Tech Briefs: Why do astronauts need to scout out underground habitats?

Professor Wolfgang Fink: As we all know, NASA is pushing very much for the return of humans to the Moon. At first, we will be looking at orbiting the Moon, then at some point landing on the Moon and establishing a permanent presence on the Moon. But of course, all of that with the look toward the horizon, which is Mars, where the same will be happening as well in the future. So why do we need to scout out underground habitats? Once you want to establish a permanent presence on another planetary body, you have two choices. Either you bring all your habitat material with you, which is a great amount of payload, and they are cumbersome, or you take advantage of things and materials you find on that planetary body to build your habitat. But there is a third opportunity here which is to take advantage of caves or lava tube caves which may already exist on planetary bodies such as the Moon and Mars. And you basically scout these out, go underground, seal them off if you find them, and make it real cozy for yourself. So, the home is pretty much already prebuilt.

Tech Briefs: How will the Dynamically Deployed Communication Network paradigm (DDCN) enable a flock of robots to explore subsurface environments on planets such as Mars?

Fink: Yes, especially with Mars. We’re not yet quite ready to send humans. So, the early stages will be done by robotic explorers such as rovers and of course a cave or a lava tube environment, or any kind of subsurface environment, is naturally a high-risk environment. You want to have some kind of redundancies and send in a flock of potentially expandable smaller robotic units and see how far they can proceed into the subsurface environment. What the DDCN technology will enable is to allow for the rovers to send the data, the pictures, the measurements, temperature, humidity, and so forth to send all these data back out to a rover in front of the cave in order to transmit the data back to Earth. And another way of saying this is since there’s no cell phone network established on Mars or on the Moon, there’s no communication network, you have to basically create your own communication network as you go. So, it’s on the fly. As you proceed into the cave, you deploy your communication beacons to establish your own network.

One of the experimental rovers used by Fink’s team to test hardware and software related to autonomous exploration. This prototype is outfitted with cameras and other sensors for navigation. (Image: Wolfgang Fink/ University of Arizona)
Tech Briefs: Can you explain in simple terms how the DDCN would work, for example, on Mars?

Fink: On Mars, you would have a larger rover, for example of the size of perseverance or Mars science laboratory. Piggybacking on such a rover would be few smaller rovers, which might be expandable. The large rover would drive toward the entrance of a cave or lava tube caves or perhaps a skylight leading to these caves, and deploy these small expandable units into the cave. Each expandable unit, each mini rover would have a stack of small breadcrumb beacons as we call communication beacons, which are pretty much the size of a dollar coin with a battery. And they would basically deploy these little communication beacons as they go. The deployment would not be governed based on time or distance. It would be governed based on communication signal strength. So, as you proceed into the cave, if you realize that your connection to the previous bread crumb is below a certain threshold, you deploy simply another one and then you proceed further into the cave.

Tech Briefs: What’s the Hansel and Gretel fairy tale connection here?

Fink: The Hansel and Gretel fairy tale as we recall is when Hansel and Gretel proceed into the dark forest, basically Hansel left breadcrumbs behind in order to find the way back out. In our case, it’s not so much to leave a breadcrumb trail or for the mini rovers to find their way back out because we don’t expect them to do so. Quite on the contrary, we expect them to drive as long as possible before they expire to discover and explore the caves as much as possible. But it’s actually for the data to find their way out of the cave back to the mother rover on the outside of the cave. That is the analogy. So, it’s the data finding their way out of the cave as opposed to the rovers finding their way out of the cave.

Tech Briefs: Where are you with this research and what are the next steps?

Fink: Based on the tier-scalable reconnaissance paradigm, which my lab devised over 20 years ago that talks about multi-tiered multiagent reconnaissance missions by robotics, we have currently over the years developed a set of robotic platforms such as a larger rover, not quite the size of a Perseverance for example, but more the size of the Mars exploration rovers. We have also developed a prototype of a cave-exploring rover, called the ICE or intra-cave explorer, which is equipped with obstacle-avoidance sensors and also light arrays, such as UV light, in order to evoke fluorescence if there’s any fluorescent material such as minerals or even plants or algae inside the cave. We have these devices, which are of course prototypes — it’s understood that these are not going per se to Mars — but similar devices or similar platforms will go to Mars. We have also developed the breadcrumb prototype. We are now concerned with the deployment mechanism as well as, which is always the challenge for all these endeavors, is the system’s integration to have the mother rover, to have the small intra-cave explorer, and to put it all together to have a demonstrable system that you can deploy in a cave or in a mine.

Listen to a podcast with Wolfgang Fink. For more information, visit here .