ARES: THE AUTONOMOUS ROVING EXPLORATION SYSTEM FOR ACTIVE SOURCE SEISMOLOGYON THE MOON AND MARS S. W. Courville1, N. E. Putzig1, P. C. Sava2, M. R. Perry1,2, T. D. Mikesell3,1Planetary Science Institute, Lakewood, CO. 2Colorado School of Mines, Golden, CO. 3Boise State University, Boise,ID. (swcourville@psi.edu)

Introduction: The Mars Exploration ProgramAnalysis Group (MEPAG) recommends sending a re-source prospecting mission to Mars in advance of humanexploration [1]. High value subsurface martian resourcesinclude lava tubes, which provide a radiation shieldedhabitat, and buried water ice, which can be extracted toprovide for life support needs and the synthesis of fuel[2, 3]. Similarly, lunar lava tubes could protect a longterm human presence on the Moon. To enable humanexploration and habitation of the Moon and Mars, thespace exploration community needs the ability to surveythese valuable subsurface targets with high accuracy andconfidence prior to human arrival.

Concept overview: The Autonomous Roving Ex-ploration System (ARES) is a payload concept designedto conduct active source seismic imaging [4]. Activesource seismology originated early last century and isnow a standard method for terrestrial resource explo-ration and subsurface imaging. Thus instrumentationand methodology are well developed. The challengewith applying active source seismology on the Moon andMars in advance of human exploration is that the surveysystem must be autonomous.

ARES consists of multiple rovers: one large roverwould generate a seismic source, and two or more smallrovers would act as seismic receivers (geophones). Asdepicted in Figure 1, the system acquires data by gen-erating a seismic source and recording reflections froma subsurface target at various locations offset from thesource. Collecting data offset from the source is neces-sary to create images of subsurface structure and is su-perior to vertical sounding instruments like ground pen-etrating radar. A collection of autonomous source andreceiver rovers provide configurability and redundancyto collect enough reflection seismic data to create highlydetailed images of the subsurface.

We propose the development of ARES to comple-ment existing radar sounding systems. ARES would beparticularly useful for scenarios where orbital soundingradars like the Mars Reconnaissance Orbiter’s ShallowRadar sounder do not provide high enough resolution, orwhere rover based ground penetrating radar would atten-uate too quickly to reach adequate depths [5].

Receivers: Each receiver rover would have an at-tached geophone. For the receiver rover, we considerthe small and nimble 10kg Resource Prospector roverproduced by Lunar Outpost (Figure 2a). The ResourceProspector has the ability to autonomously navigate us-ing advanced path finding techniques guided by camerasand LiDAR. For the attached geophones, we consider

Figure 1: The ARES concept illustrated over a lava tube.Figure 4 shows a numerical simulation of this scenario.

Geophysical Technology Inc’s (GTI) NuSeis NRU 1Cnodal geophone (Figure 2b). These geophones would beable to collect and wirelessly transmit data to the largersource rover. Additionally, the small receiver roverswould operate on battery power and periodically ren-dezvous with the large rover to recharge. Presuming therover is adequately coupled with the surface, the geo-phone would sense seismic vibrations through the bodyof the small rover without being directly inserted into theground.

Source: The larger source rover would containcritical systems like communication and power genera-tion. To generate a seismic source, the rover would havean attached accelerated weight drop system. Acceleratedweight drop systems are simple, robust, and repeatable.However, weight drop sources require significant mass.Although there are lighter sources such as dynamite, theyare not repeatable, and thus could not complete a seismicsurvey.

Figure 2: Possible existing systems for ARES’s recieverrovers: (a) Lunar Outpost’s 10kg Resource Prospec-tor rover (https://www.lunaroutpost.com/space/),and (b) GTI’s NuSeis NRU 1C geophone(https://geophysicaltechnology.com/product/nru-1c/).

2623.pdf51st Lunar and Planetary Science Conference (2020)

We quantify the expected investigation depth of aweight drop source using theory developed by [6, 7].The investigation depth is dependent on the kinetic en-

Figure 3: Investigation depth as a function of sourcemass and velocity. These curves assume an impact seis-mic efficiency of 10−3, a subsurface interface with a re-flection coefficient of 0.2, a seismic quality factor of 200,a receiver noise floor of < 0.5 µm/s, and a regolith witha p-wave velocity of 500 m/s and a density of 1.5 g/cc.

BasaltLava tube voidSourcesReceivers

a).

b).

c).

Figure 4: (a) A simplified lava tube cross section modelwith a potential ARES 2D profile acquisition scenario.(b) synthetic seismic data shot gather for the source atx=0.1 km. (c) The subsurface image created through re-verse time migration.

ergy of the weight drop, the frequency of the resultingsource pulse, the seismic properties of the ground, andthe noise floor of the geophones. For a weight drop sys-tem, the greater the mass and/or velocity of the weight,the more energy that is transferred into a seismic source,and thus the greater depth that can be seen. Additionally,the more sensitive the geophones are, the deeper the sys-tem can investigate. Provided the weight’s accelerationis assisted, the system would be indifferent to gravity.Figure 3 demonstrates investigation depth as a functionof the weight drop’s mass. The values in Figure 3 areconsistent with values observed in terrestrial studies [8].Note that the mass of the source rover as a whole wouldneed to be several times heavier than the weight itself.

Numerical modeling: Using numerical simula-tions, we demonstrate that ARES could image high valuetargets like lava tubes. Figure 4 illustrates a reversetime migration seismic image generated from simulatedacoustic data acquired if the ARES system surveyed a2D profile over a lava tube. The wavelength of the seis-mic source pulse in the medium determines the resolu-tion of the image [9, 6].

Future work: We have submitted a Planetary Sci-ence and Technology Through Analog Research Pro-gram proposal to test the proposed ARES system overa lava tube on Earth. We will test whether geophonesneed to be pressed into the ground or if they can recordadequate data on board the receiver rovers. Addition-ally, we will autonomously collect data over the extentof the lava tube and compare the resulting image withthe known shape of the lava tube to address uncertainty.

Conclusion: We advocate for active source seis-mology to survey subsurface resources on bodies like theMoon and Mars. The ARES concept could accomplishan active source seismic survey and fill the surveying gapbetween near surface ground penetrating radar and or-bital radar sounding. ARES would provide a powerfultool for resource surveying in advance of human explo-ration of Mars or long term habitation on the Moon.Acknowledgements: This work was funded by aNASA Early Career Fellowship (80NSSC19K0807). Wethank Richard Degner, Karl Oeler, and Andrew Sedl-mayr of GTI; and Andrew Gemer, Colby Moxham, andLuke Bowersox of Lunar Outpost.References [1] MEPAG, 2015. [2] P. J. Boston et al. InAIP Conf. Proc., 2004. [3] A. Abbud-Madrid et al. Report ofthe Mars Water In-Situ Resource Utilization (ISRU)Planning (M-WIP) Study, 90, 2016. [4] S. W. Courville et al.AGU Fall Meeting, (P54D-02), 2018. [5] S. W. Courvilleet al. AGU Fall Meeting, (P44B-05), 2019. [6] K. Aki andP. G. Richards. Quantitative seismology. 2002. [7] M. A.Meschede et al. Geophys. J. Int., 187(1):529–537, 2011.[8] R. D. Miller et al. Geophysics, 51(11):2067–2092, 1986.[9] A.J. Berkhout. Seismic resolution. Geophys. Press, 1984.

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