PROPOSED MISSION ARCHITECTURE AND TECHNOLOGY REQUIREMENTS FOR ROBOTIC AND
HUMAN EXPLORATION OF MARTIAN CAVES. J. J. Wynne1, C. M. Phillips-Lander2, and T. N. Titus3;
1Department of Biological Sciences, Merriam-Powell Center for Environmental Research, Northern Arizona
University, Flagstaff, AZ, jut.wynne@nau.edu; 2Space Science & Engineering Division, Southwest Research
Institute, San Antonio, TX; and, 3Astrogeology Science Center, U.S. Geological Survey, Flagstaff, AZ.
Introduction: Since the identification of atypical
pit craters in 20071, the number of cave-like features
resolved on Mars has steadily increased. To date, at
least 1,035 features have been cataloged2; most of
these features occurred within regions identified, via
thermal inertia and numerical modeling, as capable of
maintaining stable water ice deposits underground3
(Fig. 1). In addition to serving as veritable laboratories
to investigate numerous questions related to planetary
geology, martian caves: (1) represent one of the best
locations to search for evidence of life, (2) may
provide access to water ice deposits for human use,
and (3) are the safest places for human habitation.
However, beyond their locations and elementary
entrance characteristics, we know little about these
potential access points to the martian subsurface. How
do we identify the most important candidates for
astrobiology research versus human use? Importantly,
how can we evaluate and rank these features?
Moreover, what are the key planning elements to
include in robotic and human missions? Here we
briefly describe a mission architecture for robotic and
human cave missions, while identifying critical lacunas
in technologies that must be addressed to make such
missions viable, as well as to help ensure mission
success.
Mission Architecture: We propose a simplified
process to advance martian speleology from a
rudimentary understanding to acquiring the data
required to evaluate and select the best candidates for
astrobiological investigations and human outposts
(Fig. 2).
I. Remote Detection. Development Status (DS):
Combining thermal and visible imagery is a useful
approach for detecting terrestrial4-6 and martian1,2,7
cave entrances, while gravimetry has been applied to
estimate the subterranean extent of lunar caves8.
Technology Requirements (TR): A multispectral
approach will be most effective to most accurately
identify and examine martian caves of interest; this
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should include the addition of LiDAR and gravimetry
data. In concert with thermal and visible imagery,
LiDAR should be assessed for initial detection
analysis, and the limitations of gravimetry need to be
evaluated. Once entrances have been confirmed using
thermal, visible and LiDAR data, gravimetry may
ultimately be applied to differentiate large passages
and rooms (conducive to human habitation) from
deeper, more expansive caves (those likely to score
highest as astrobiology targets).
II. Candidate Selection. In addition to the
techniques elucidated in ‘step I’, these criteria (i.e.,
characteristics of regolith and local terrain; landing,
power, and traversablity considerations for robotics;
and, co-location of multiple high priority candidates)
may be used to down-select the +1000 candidate sites
to a manageable number. Subsequently, either rovers
or rotorcraft drone systems could then conduct a more
detailed analysis to further pare down the number of
suitable candidates. DS: Rovers currently used in Mars
missions may be an effective tool for surveying
entrance characteristics. Importantly, the Mars 2020
rover will include a small rotorcraft scout as part of its
payload9. TR: Post-Mars 2020, NASA will have ‘flight
proven’ Mars helicopter technology, which could be
further refined and used to examine cave entrances.
III. Robotic Exploration. Given that most cave
floors are littered with breakdown (cave ceiling
material resting on the cave floor), dual-axel rovers
will be unsuitable for most cave environments. DS:
Currently, one of the best technologies to overcome
this hurdle is the Limbed Excursion Mechanical Utility
Robot (LEMUR) 3. Once fully developed, the world’s
first rock-climbing robot will be able to independently
identify the most suitable travel route through a cave’s
entire 3D interior. This platform may be used to
acquire, process, and analyze samples to search for
evidence of life, as well as assess the structural
stability of cave interiors for human habitation. TR:
Currently, LEMUR 3 is rated at a technical readiness
level (TRL) of 6. Substantial advancements (through
adequate funding) will be necessary before the
LEMUR platform can be elevated to ‘flight qualified’
status (TRL=8).
IV. Human Use. DS: Prototypes for inflatable and
hybrid inflatable-rigid10 human habitats are in the
proof-of-concept stage and have been successfully
tested in computer simulations. Current spacesuit
technology, which has been largely unchanged since
the Apollo program and is currently used for EVAs on
the International Space Station, will be unfit for use
underground – due to restricted mobility and the high
risk of suit breach. BioSuit technology11 is a svelte-
fitting alternative that offers significant improvements
to traditional spacesuits. These suits, and associated
donning and doffing technologies, are still at the proof-
of-concept stage12. To be used in caves, BioSuits must
be extremely ruggedized to become puncture and
abrasion resistant. Finally, technical climbing and
work equipment for conducting science operations in
spacesuits does not exist for underground use, nor have
there been any studies to inspect the feasibility of such
technologies for extraterrestrial cave applications. TR:
All of these technologies need to either be developed
and/or evolve from proof-of-concept to ‘flight
qualified’ status (i.e., TRL=8) before we can safely
enter, work, and live in the martian subterranean realm.
Conclusion: Through fully developing the
analytical techniques and robotic technologies to
down-select to the highest priority targets (steps I &
II), and ultimately the technologies to support
subterranean robotic and human missions (discussed in
steps III & IV), then we will be poised to embark upon
scientific exploration of the caves on Mars.
Acknowledgements: Special thanks to Melanie
Gregory, Glen Cushing, and Anna Ross who provided
comments leading to the improvement of this abstract.
References: [1] Cushing, G.E. et al. (2007) JGR,
34, L17201. [2] Cushing, G.E. & Titus, T.N. (2018)
Mars Global Cave Candidate Catalog (MGC3), PDS
Archive. [3] Williams, K. et al. (2010) Icarus 209,
358-368. [4] Titus, T.N. et al. (2011) Abstract #8024,
1st Int. Planet. Caves Conf. [5] Wynne, J.J. et al.
(2008) EPSL 272, 240–250. [6] Wynne, J.J. et al.
(2015) Abstract #9029, 2nd Int. Planet. Caves Conf. [7]
Groemer, G. et al. (2014) Astrobiology 14, 431–437.
[8] Chappaz, L. et al. (2017) GRL, 44, 105–112. [9] El-
Maarry, M.R. et al. (2018) EPSC, 12, EPSC2018-422.
[10] Daga, A. et al. (2010) 40th Int. Conf. Env. Sys.,
AIAA2010-6072. [11] Bethke, K. et al. (2004) SAE
Trans., 426–437. [12] Anderson A. et al. (2010) 40th
Int. Conf. Env. Sys., AIAA2010-6213.
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