Is there life in Martian caves?
It’s a good question, but it’s still not the right question. An international collaboration of scientists led by NAU researcher Jut Wynne has dozens of questions we need to ask and answer. Once we understand how to study caves on the Moon, Mars and other planetary bodies, we can come back to this question.
Wynne, assistant research professor of cave ecology, is senior author of two related studies, both published in a special series of articles on planetary caves by the Journal of Geophysical Research Planets. The first one, “Fundamental Science and Engineering Issues in Planetary Cave Research”, was produced by an interdisciplinary team of 31 scientists, engineers and astronauts who produced a list of 198 questions which they, together with 82 other space and cave scientists and engineers, narrowed down to the 53 most important. Harnessing the insights of a considerable portion of the space science community, this work is the first study designed to identify research and engineering priorities to advance the study of planetary caves. The team hopes their work will shed light on what will ultimately be needed to support robotic and human missions to a planetary cave, namely to the Moon and/or Mars.
The second, “Planetary Caves: A Solar System View of Products and Processes,” was born from the first study. Wynne realized that there had been no effort to catalog planetary caves across the solar system, which is another important piece of the overall puzzle. He assembled another team of planetary scientists to tackle this question.
“With the necessary financial investment and institutional support, the research and technology development needed to achieve these necessary advances over the next decade is achievable,” Wynne said. “We now have what I hope will become two seminal papers that will help propel planetary cave research from a contemplative chairside exercise to robots probing the planetary subsurfaces.”
Summary by subject groupings, workflows, statistics of panelists (surveys 1 and 3) and the wider community (survey 2), and distribution of the 53 core questions in planetary cave science and engineering by subject group. Credit: Journal of Geophysical Research: Planets (2022)
What we know about alien caves
There are many. Scientists have identified at least 3,545 potential caves on 11 different moons and planets across the solar system, including the Moon, Mars, and the moons of Jupiter and Saturn. Cave-forming processes have even been identified on comets and asteroids. If the surrounding environment allows access underground, this presents an opportunity for scientific discovery that has never been available before.
The finds in these caves could be massive. The caves could one day allow scientists to “peer into the depths” of these rocky, icy bodies, which will provide insight into how they formed (but may also provide additional information about how the Earth formed). They could also, of course, hold secrets of life.
“Caves on many planetary surfaces represent one of the best environments to search for evidence of extinct or possibly extant lifeforms,” Wynne said. “For example, because Martian caves are immune to deadly surface radiation and violent windstorms, they are more likely to exhibit a more constant temperature regime relative to the surface, and some may even contain water ice This makes caves on Mars one of the most important exploration targets in the search for life.
And it’s not just finding life – those same factors make caves good locations for astronaut shelters on Mars and the Moon when crewed missions are able to explore.
“Radiation shielding will be essential for human exploration of the Moon and Mars,” said Leroy Chiao, a retired astronaut, former commander of the International Space Station and co-author of the first paper. “One possible solution is to use caves for this purpose. Requirements for astronaut habitats, EVA suits and equipment should take into account cave exploration and development, for protection against solar and galactic cosmic radiation.
Planetary bodies for which possible cave entrances have been identified with the number of features per body provided in parentheses (top). Global locations for possible cave entrances for the Moon (center) and Mars (bottom). DeWynne et al. 2022b. Photo credit: AGU and Journal of Geophysical Research-Planets. Top photo: Real-time DNA sequencing in a laboratory installed in the Corona Lava Tube (Lanzarote, Canary Islands, Spain) as part of the ESA PANGAEA-X 2017 astronaut training program. ESA astronaut Matthias Maurer is inside the lab module with co-author Ana Miller. Photo credit: ESA.
What Earth Can Tell Us About Other Planets
Wynne, whose primary research focuses on terrestrial caves, said planetary cave research has long been a research topic parallel to the terrestrial variety for nearly two decades. Caves are home to unique ecosystems that are sometimes far removed from the surface ecosystem in the same area. Who’s to say a cave on the Moon or Mars wouldn’t be similar? So many of the questions he investigated about caves on Earth, he wondered how it might apply on other planets.
He’s not the only one making the connection. Wynne has conducted several research projects with NASA to help advance detection technologies, and her modeling of cave habitats doesn’t really care whether a cave is terrestrial or extraterrestrial. There are enough similarities in the cave environment to make reasonable predictions that will be considered in selecting cave targets for exploration.
“Tellurian caves at depth are often characterized by total darkness, a stable temperature approaching the mean annual surface temperature, little or no airflow, and an atmosphere nearly saturated with water,” he said. . “Caves in other planetary bodies likely exhibit similar environmental conditions, but these will also be influenced by the surface conditions of the planetary body and the internal structure of the cave.”
Keith Cowing, editor of SpaceRef.com and NASAWatch.com, said using a planet’s existing surface and subsurface infrastructure can help humans get to other planets. sooner than if we had to bring everything necessary to survive with us.
“Humans have lived in caves for hundreds of thousands of years. Then they built their own when none were available,” he said. “As such, it is natural to assume that caves will provide similar utility as humanity expands to other worlds. While planet-wide terraforming may be an end goal, using large pre-existing structures such as caves and lava tubes may be a more practical way to bring the technology to the maturity needed to tackle the surface of an entire planet.
Spacesuit designer and co-author Pablo de Leon tests the NDX-3 planetary spacesuit in Antarctica. The development of drilling and excavation tools will be of crucial importance for search, habitation and rescue operations in planetary caves. Photo credit: Human Spaceflight Laboratory, University of North Dakota.
Where are we now?
While much of this research is looking to the future, there is also a need to look at the resources, research, and support that currently exist. Many robotic platforms and instrumentation suites are being tested, but the roadblock comes where it so often happens: lack of funding. With enough support, a robotic exploration mission to a lunar or martian cave could be possible within the next five to ten years.
This research builds on previous work to form a sort of roadmap for moving forward; Wynne sees it as a to-do list for that same process. The questions scientists and engineers answered identify the tasks needed to prepare for this robotic exploration; it also looks even further at the necessary advances in spacesuit technology, habitation modules and hardware that will allow humans to live and work safely underground on the Moon and Mars.
“This is an untapped area of research in planetary science, and its importance in the search for life should not be overlooked,” he said. “In our lifetime, it is entirely possible that we will peer into the subterranean planet Mars to answer the age-old question: ‘Does life exist beyond Earth?’
Jut Wynne (right) with JPL roboticist Brett Kennedy field testing an early prototype of the climbing robot, LEMUR, in a lava tube cave in California’s Mojave Desert. It should be noted that Wynne is the first human to insure a robot. Courtesy of NASA JPL/Caltech.
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