New Mexico State University civil engineering associate professor Douglas Cortes is investigating the amazing burrowing abilities of the common earthworm, found in soil the world over, to study the characteristics of soils on Mars and Earth’s moon and identify life-sustaining substances.
Cortes and his research team received funding from NASA and the New Mexico Space Grant Consortium to develop facilities from which to deploy a new generation of earthworm-inspired self-excavating subsurface characterization tools that are both light and small, so they could easily be transported to the moon and Mars.
The subsurface of Mars and the moon comprise a wealth of resources, from those that support basic human necessities, such as water, in the form of ice, to propellants such as methane, in the form of hydrates.
“Subsurface excavation on Earth is somewhat simple. However, one of the challenges of geotechnical engineering is that extracting information from the ground requires large and heavy equipment to provide the force necessary to drive probes into the ground,” explained Cortes. “NASA is not likely to put heavy equipment on the Space Shuttle.”
Earthworms, however, use the soil itself to gain the resistance force necessary to drive forward thrust, expanding and contracting as they penetrate deeper.
Cortes began his research on earthworm-inspired soil penetration as part of the National Science Foundation Center for Bio-Mediated and Bio-Inspired Geotechnics launched in 2015 to develop and implement nature-inspired sustainable solutions to geotechnical engineering and infrastructure problems. NMSU was named one of four universities in the consortium for the $18.5 million NSF award.
Cortes and his team developed a series of earthworm-inspired soil penetration devices that have provided insight into the mechanical advantages of earthworm penetration in sands. The group devised a very simple tool that emulates the earthworm: a tube connected to a balloon that can inflate and deflate as it moves through soil.
Control tests that mimicked conventional soil penetration and the bio-inspired soil penetration show promise: “We have conducted tests on dry and partially saturated loose and dense sands. In all cases, we find a significant reduction in penetration resistance when using the earthworm’s burrowing strategy. Seems logical that an animal that has lived underground for over 300 million years may have an edge over our soil penetration devices,” Cortes said.
The results of this research led Cortes to believe that an earthworm-inspired self-excavating geoprobe could be used to conduct Martian and lunar subsurface sampling and testing and to gain other information about underground resource deposits. However, testing the devices in ground that is similar to that found in extraterrestrial environments is as important as the development of the self-excavating devices themselves.
With the new NASA funding, Cortes will develop an instrumented regolith subsurface exploration testbed to monitor the performance of his earthworm-inspired devices under controlled laboratory conditions. Regolith is a layer of loose deposits covering solid rock that includes dust, soil, broken rock and other related materials.
“We have information on lunar regolith from the Apollo missions,” Cortes said. A mixture mimicking the lunar material is available commercially and will be used in a 55-gallon testbed, capable of accommodating probes up to four inches in diameter. The testbed will be equipped with acoustic sensors and other electronics, which will detect and record sound waves emitted from movement in the ground and how it responds to the activity of the probes. The probes will be equipped with a variety of sensors that will measure things like force and temperature. Further, the probes could be tethered to draw power from a rover.
Additionally, this project aims to enhance and expand the testbed capabilities. Cortes has also secured additional funds to purchase a modular loading frame for the 55-gallon testbed and to double the current testing depth range. Upon completion of this project, a new regolith subsurface exploration testbed will be available to meet the needs of researchers working toward the development of extraterrestrial subsurface exploration tools.
This research aligns with NASA’s goal to secure resources that would enable sustaining human life on both the moon and Mars. Cortes’ team plans to continue working with NASA on the development of landed subsurface exploration, production of water and methane from underground ice and hydrate deposits, and the development of basic infrastructure to support scientific and commercial capabilities on Mars and on the moon.
“It is a small grant but we have big ideas,” said Cortes. “It will be good for NMSU and for New Mexico to have a facility to support new research efforts in the field of self-excavating robots for terrestrial and extraterrestrial subsurface exploration. Our vision is to develop a platform in New Mexico from which to launch a new generation of devices that will help make the dream of an extraterrestrial human settlement a reality.”