Instead of building a building on Mars from scratch to serve as a habitable base, taking advantage of caverns, as well as lava tubes, would be a much better option, to reduce work and the expense of construction materials, and in many cases to have extra protection. But first one would have to explore the interior of such underground cavities.
Natural underground spaces are created by various geological processes. In the case of lava tubes, these are tunnels that form when molten lava flows under a cooled lava field or crusts over a lava river, leaving a long, hollow tube. If the roof of a solidified lava tube collapses, a shaft opens up that can lead to the rest of the tunnel like a cavern. If the internal height and width of the tunnel are large enough, the space can be used to house humans and their belongings.
The most sensible way to explore these underground cavities is by robots. But exploring terrain underground is not the same as exploring terrain on the surface. Underground, the coverage of conventional communication systems is severely impaired.
Wolfgang Fink’s team, from the University of Arizona in the United States, has devised a system that would allow a group of robots to explore underground places on other worlds.
The system is based on a communications network that would link rovers, landers (dropships) and even submarines (in the case of stars like Titan, a moon of Saturn), allowing all these robots to work as a team, without depending on the human intervention.
One of the experimental robots used by Fink’s team to test hardware and software related to underground autonomous exploration. This prototype is equipped with cameras and other sensors for navigation. (Photo: Wolfgang Fink/University of Arizona)
The philosophy of the system is reminiscent of the strategy that the protagonists of the story “Hansel and Gretel” followed to find out which way to go back home: drop tiny but easily recognizable objects (for example, bread crumbs) during the outward journey, in order to be able to recognize in each section of the way back where they had come from.
In the system devised by Fink’s team, breadcrumbs or the like are miniaturized sensors that initially go aboard rovers. These are leaving them one by one on the ground, as they advance through a cave or other underground environment.
When the vehicle detects that the communication signal is weakening, it drops a communication node on the ground, regardless of the distance that has elapsed since the last node was placed.
By deploying communication nodes along the way, the rovers can stay connected to each other and the dropship via a wireless data link, knowing where they are at all times.
The robust network of communication nodes ensures that all data collected by the robotic explorers reaches the mother vehicle on the surface. Therefore, there is no need to recover the robots once they have done their job. They are designed to be expendable. Instead of wasting resources retracing the robots and getting out of the cave, it’s better to make them go as far as possible and abandon them once they’ve completed their mission, run out of power, or succumbed to a hostile environment.
Fink and his colleagues discuss the technical details of their underground exploration system in the academic journal Advances in Space Research, under the title “A Hansel & Gretel Breadcrumb-Style Dynamically Deployed Communication Network Paradigm using Mesh Topology for Planetary Subsurface Exploration Author links open overlay panel”. (Fountain: NCYT de Amazings)