Preparing for subsurface planetary exploration


DEPTHX. Credit:

In October 2018, a study committee of the National Academies of Science, Engineering, and Medicine (NAS) – specifically, the Committee on the Astrobiology Science Strategy for the Search for Life in the Universe, Space Studies Board –  published a reportproviding recommendations for a NASA astrobiology strategy for the search for life in the universe. IMHO, the report is on the mark. (Whether the White House and Congress will provide needed funding to enable the implementation of these recommendations remains to be seen.)

I am a (part-time) consultant to the NASA astrobiology program and was asked to help prepare a NASA response to the NAS committee’s recommendations. Much of the content I prepared was deleted. But it’s still interesting. So I’ll provide it here.

One of the NAS study committee’s recommendations was that “NASA’s programs and missions should reflect a dedicated focus on research and exploration of subsurface habitability in light of recent advancesdemonstrating the breadth and diversity of life in Earth’s subsurface, the history and nature of subsurface fluids on Mars, and potential habitats for life on ocean worlds.”

Exploring for evidence of subsurface habitability in the solar system is a big deal in planetary science these days. Astrobiologists are itching to get beneath the surface of Mars, Europa, and Enceladus (I should note that such missions are only ideas at this point…but good ideas, IMHO).

The work on this goal that the NASA astrobiology program has funded over the past 10-15 years (and continues to fund today) is fascinating (at least to this space science geek). And it shows how slowly, but methodically, the development of planetary exploration technologies proceeds, step by step.

Over the past several years NASA has taken some steps to advance research and exploration of subsurface habitability by funding a number of projects to develop and demonstrate subsurface exploration technologies and techniques. NASA’s Planetary Science and Technology Through Analog Research (PSTAR) Program has funded the Atacama Rover Astrobiology Drilling Studies (ARADS) project, led by Brian Glass of NASA Ames Research Center. The ARADS project, intended to iteratively develop a simulated Mars rover mission, conducted its first field test in Chile’s Atacama Desert in 2016. Several instruments have been designed, developed or modified to be tested in ARADS field experiments, including the fifth generation of a series of space-prototype, one- to two-meter-class rotary-percussive drills by Honeybee Robotics; a sample-transfer robotic arm from MDA Aerospace (the developer of robotic arms for NASA’s Phoenix and InSight missions to Mars); and a new autonomous mid-sized rover concept (K- REX2) developed by NASA Ames.

NASA also has funded the Mars Analog Rio Tinto Experiment (MARTE), led by Carol Stoker of NASA Ames. The MARTE project is developing drilling, core- and sample-handling, and instrument technologies relevant to searching for life in the martian subsurface and demonstrating them in a Mars-analog site on Earth, Spain’s Rio Tinto region. The MARTE drilling system is being developed by Honeybee Robotics for future use on Mars. Honeybee Robotics has developed drilling and sample-handling systems for NASA’s last three Mars landers, including systems for the last three of NASA’s Mars landers, including the first drill ever to look inside a rock on Mars and the sample-handling system on the Mars Science Laboratory. (I visited Honeybee Robotics in New York City several years ago – those people produce amazing technology.)

NASA’sMars 2020 rover will feature a drill that can collect core samples of the most scientifically promising rocks and soils and cache them on the surface of Mars for future retrieval and return to Earth.The European Space Agency’s (ESA’s) ExoMars 2020 rover willcollect samples with a drill down to a depth of two meters and analyze them with next-generation instruments in an onboard laboratory. NASA and ESA are closely coordinating work on these two missions and will be sharing data from science operations.NASA is providing a major portion of the premier instrument for ESA’s ExoMars mission: the mass spectrometer for the Mars Organic Molecule Analyzer.  In addition, European scientists are on a number of instrument teams for NASA’s Mars 2020 mission.  In 2018,the NASA astrobiology program awarded a $7 million grant to a Georgia Institute of Technology-led Oceans Across Space and Time alliance to intensify the search for life in our solar system’s present and past oceans. This alliance is a member of the Network for Life Detection (N-FoLD), an astrobiology research coordination network (RCN) focusing on life detection strategies and methods.

The NASA astrobiology program has supported two recent “workshopswithout walls” (virtual workshops) that focused on research and exploration of subsurface habitability: “Upstairs Downstairs: Consequences of Internal Planet Evolution for the Habitability and Detectability of Life on Extrasolar Planets,” held February 17 – 19, 2016, in Tempe, Arizona, and virtually; and “Serpentinizing Systems Science,” held January 31, 2017, virtually. NASA Astrobiology is also co-hosting a conference, “Mars Extant Life: What’s Next?” January 29–February 1, 2019, at the National Cave and Karst Research Institute. This conference will focus on understanding and discussing strategies for exploring candidate target environments on Mars that may host evidence of extant life including surface, shallow subsurface, and deep subsurface niches.

Astrobiology is well represented on NASA’s Europa Clipper mission team. Europa Clipper (to launch some time in the 2020s) willconduct detailed reconnaissance of Jupiter’s moon Europa to see whether the icy body might be habitable. The science definition team for the Europa Lander mission concept study included several astrobiologists, including Alison Murray as one of the co-chairs and Ken Nealson, Chris German (Woods Hole Oceanographic Institute), Britney Schmidt (Georgia Institute of Technology), and Alexis Templeton (University of Colorado) as team members. (All three of these scientists have done fascinating astrobiology research in the field.) The SDT identified three science goals for the mission: detect and characterize biosignatures and signs of life, analyze in-situ habitability, and prepare for future exploration. The mission concept team identified a model payload for this mission that includes, among other instruments, a microscope for life detection and an organic compositional analyzer.

The technological challenges of exploring subsurface environments on icy worlds are formidable. On Earth, researchers have only reached a depth of 3.5 kilometers beneath ice. Europa’s ice shell could be as much as 15 kilometers deep. Consequently, the NASA astrobiology program has supported a number of technology development and demonstration projects for in-situ exploration of subsurface environments on other planetary bodies.

For example, the program has supported the development of four Stone Aerospace autonomous underwater vehicles (AUVs) that are prototypes for subsurface exploration of Europa: DEPTHX (Deep Phreatic Thermal Explorer), ENDURANCE (Environmentally Non-Disturbing Under-ice Robotic ANtarctiC Explorer), VALKYRIE (an ice-penetrating robot), and ARTEMIS (Autonomous Rovers/airborne-radar Transects of the Environment beneath the McMurdo Ice Shelf). (Bill Stone, founder and head of Stone Aerospace, is a brilliant engineer and obsessed with Europa.)

The NASA astrobiology program also funded the development oftwo underwater autonomous vehicles (AUVs) called Jaguar and Puma, developed by the Woods Hole Oceanographic Institution (WHOI) and deployed on WHOI’s 2007 Arctic Gakkel vents expedition (AGAVE). Jaguar and Puma are prototypes of AUVs that could look for evidence of subsurface hydrothermal activity on other planetary bodies. The NASA astrobiology program also funded the Monterey BayAquarium Research Institute’s development of another subsurface planetary exploration prototype, an Environmental Sample Processor for Deep-Sea Seep and Hydrothermal Vent Applications.

The Science Mission Directorate’s Planetary Instrument Concepts for the Advancement of Solar System Observations (PICASSO), MATuration of Instruments for Solar System Exploration (MatISSE), and Planetary Science and Technology from Analog Research (PSTAR) R&A programs have also funded a number of projects aimed at aiding the exploration of subsurface planetary environments. For example, the PICASSO program has funded work on a rover-mounted dielectric (non-conducting) spectrometer for in-situ subsurface planetary exploration, which could measure subsurface material composition at radio frequencies; and a compact color “biofinder” for fast, non-contact detection of biomarkers, biomolecules and polyaromatic hydrocarbons in ocean worlds.

The MatISSE program has funded the development and testing of a prototype digital beam-forming polarimetric synthetic aperture radar (look it up) for subsurface imaging. This instrument could detect and map buried ice deposits and measure the depths of such deposits. The PSTAR program has funded the development and demonstration of a thermal high-voltage ocean-penetrator research platform, a cryobot (a robot that can operate in freezing temperatures) capable of rapid, deep subglacial access that carries an onboard science payload optimized for environmental characterization and life detection; a seismometer designed to investigate ice and ocean structure (SIIOS) on Europa and Enceladus; the SUBSEA project, which is exploring the habitability of a seamount (a mountain on the sea floor whose peak is well below the surface of the water) off the coast of the Big Island of Hawaii as an analog for icy moons, using two submarine-type remotely operated vehicles; and the DEEP project – Detecting Extraterrestrial Piezophiles in ocean-world analog environments – which is testing a high-pressure sampling system in deep hydrothermal vents in the mid-Cayman Rise that would allow sample retrieval and manipulation without decompression, enabling sample-handling protocols that optimize life detection in high-pressure environments. (A piezophile, also known as a barophile, is an organism that thrives in high-pressure environments.)

NASA’s publicity machine tends to focus on promoting missions. But those missions are made possible by projects such as those described here. It’s going to be a long, slow trip to exploring subsurface environments in the solar system. But the trip will be worth it, I think. Given NASA’s current obsession with sending people back to the Moon and on to Mars, I keep thinking that robotic planetary exploration has been what’s delivered the goods for decades.

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