1. Analyzing the Mechanical Properties of the JSC Mars-1A Martian Regolith Simulant
Tesla Waters
South Carolina Governor’s School for Science and Mathematics

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ABSTRACT
The first lunar landing was an enormous step in humanity’s exploration of space. Now humanity
is nearly ready to take the next step—humans landing on another planet. Scientists at NASA (National
Aeronautics and Space Administration) expect that humans will land on Mars sometime in the 2030’s.
In order to reach that goal, NASA has created a road map of technological breakthroughs that must be
accomplished prior to launch. This research project complements a recent SC NASA Space
Consortium-funded project to study the feasibility of using simulated Martian regolith (the term “soil”
refers onlyto material found on Earth) to create functional buildingblocks. The objectives of this project
are to characterize the mechanical properties of JSC-1A Martian regolith simulant, particularly its grain
size distribution and shear strength, through a series of soil mechanics experiments, and to compile,
analyze and prepare experimental data for calibrating numerical models. In order to observe the grain
size distribution, sieve and hydrometer analyses were performed on the simulant. These tests use
methods such as sifting the material and using a hydrometer to test for particle distribution in solution.
To test the shear strength and obtain the friction angle of the simulant, direct shear tests were run. These
tests apply a horizontal and vertical force to the regolith, allowing calculation of its friction angle. These
results can be used to determine whether the Martian regolith can be used to construct building blocks
on Mars. The data gathered from these tests, and others, are vital to the colonization of Mars.
INTRODUCTION
As the world focuses more research efforts on progressing the technology required for space
travel, the possibility of Mars exploration by humans is becoming a reality. Exploring the Red Planet
has been a goal in the minds of many Americans for decades, whether for resource mining, a home
beyond Earth, or simply to say that we’re the first multi-planetary nation. In advance of these
endeavors, preparations must be made on Earth to ensure survival and successful colonization light-
years away from home. Earthly supplies cannot simply be shipped to Mars, as that would be
extremely expensive in terms of both money and time. Therefore, a way must be found while still on
Earth to utilize the already existing resources on Mars. The rovers currently on Mars have analyzed
regolith samples and sent data back to Earth that allow simulation of its properties. Because capturing
all of the regolith’s properties in a single sample is impossible, many different types of simulants have
been created, each of which specializes in a few specific properties (NASA). The most commonly
studied of these simulants are the Johnson Space Center (JSC) Mars-1A simulant and the Mojave

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Martian Simulant (MMS). The following experiments were performed on the JSC Mars-1A simulant,
due to its likeness to Martian regolith particle size. Three main tests were performed, including sieve
tests, hydrometer analyses, and shear tests. The first two determine the particle size distribution of the
regolith while the latter determines the friction angle and therefore the strength of the regolith.
METHODS AND MATERIALS
A sieve analysis test was first performed to determine the grain size distribution of particles
greater than the U.S. 200 Sieve Size. To perform this test, pre-massed sieves were stacked in order of
decreasing opening sizes of U.S. 4, 10, 20, 40, 60, 100, and 200 standards, which are shown in
Table 1. A 500g JSC-1A Martian Regolith Simulant sample was selected containing regolith with
particle sizes of less than 1mm and placed into the sieve stack which was then put into a shaker for 10
minutes. The amount of regolith simulant remaining in each sieve was then massed to determine the
grain size distribution of the particles.
Table 1 - U.S. Standard Sieve Sizes
A hydrometer analysis test was then performed using the regolith finer than the U.S. 200 sieve
to determine the grain size distribution of those small particles. First a deflocculating agent (4%

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sodium hexametaphosphate) was prepared by adding 40 g of calgon to 1000 mL of distilled water.
125 mL of this deflocculating agent was then mixed into 875 mL of distilled water in a 1000-mL
graduated cylinder. The hydrometer was inserted into this mixture to obtain corrections for
temperature, meniscus, and the point that will be treated as zero on the hydrometer. A 50g regolith
simulant sample of particle size less than U.S. 200 was mixed with 125 mL of deflocculating agent
and placed into another 1000-mL graduated cylinder. Water was added to increase the volume to 1000
mL, and the contents were mixed. Immediately after mixing ceased, the hydrometer was inserted and
readings were collected every t minutes where t=0.25, 0.5, 1, 2, 4, 8, 15, 30, and 60. The hydrometer
was removed and inserted into the graduated cylinder used for corrections in between readings after
the two-minute mark to prevent particles from clinging to the sides of the hydrometer and skewing the
results. The above sieve and hydrometer analyses were then repeated with regolith simulant
containing particle diameters of up to 5mm.
Concurrently, a shear test was performed on the simulant containing particles less than 1mm
and less than 5mm. This test requires a shear ring and a specific computer program to run a DigiShear
Direct Shear test. Separate from the prior two, this test concerns the shear strength and friction angle
of the sample rather than the size of its particles. According to the lab manual, the friction angle is a
“function of the relative density of compaction of [the sample], grain size, shape, and distribution in a
given soil mass” (Das, 2002). This angle, determined by taking the inverse tangent of the slope shown
in figures 6 and 7 , demonstrates the deformity of the sample in the x and y planes when compressed
both vertically and horizontally. Three trials were performed in which vertical pressures of 2000psf,
4000psf, and 8000psf respectively were applied prior to any horizontal pressure to consolidate the
sample. Following this consolidation, the screws holding the two halves of the shear ring in place
were removed to allow horizontal displacement from the subsequently applied horizontal force. The

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magnitude of the deformity resulting from the soil reaching its maximum horizontal pressure tolerance
is proportional to the friction angle. The ideal friction angle for construction is roughly 45 degrees, as
this provides structural stability while maintaining the flexibility necessary to withstand trauma.
RESULTS
To determine the particle size distribution of the regolith particles within a JSC MARS-
1A sample, the quantity of soil that passed through various sieve sizes by mass within a specific
quantity was measured. From this it was determined that the Martian regolith within the sample
was poorly graded, meaning that its grain sizes are unevenly distributed, as shown in the first
seven data points of figure 3 which is the average of figures 1 and 2. This is determined by the
percent finer, or percentage of particles that were able to pass through the sieve or the percentage
of particles that had not fallen at a given time interval, and simply means that there were unequal
quantities of soil remaining in each sieve or still suspended in the fluid-filled cylinder after
settling for some time, and therefore that there was not an even representation of every particle
size. If each subsequent percent finer were proportional, it would be determined a well-graded
substance. Although poorly graded materials allow for drainage, they are not optimal for
construction as we would need to do on Mars.

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Figures 1 and 2 - Sieve Analysis Grain Size Distribution Averages on 1mm and 5mm Samples
Respectively
Figure 3 – Three Trials of Grain Size Distribution of JSC 1-A 1mm and 5mm Samples Averaged
Green: Trial 1 Average
Red: Trial 2 Average
Blue: Trial 3 Average

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To determine the grain size distribution of a JSC MARS-1A sample with particle
diameters less than .075mm, we measured the position of a hydrometer in a mixture of
deflocculating agent and our sample at time intervals of 0.25, 0.5, 1, 2, 4, 8, 15, and 30 minutes
and is shown by the final seven data points of figure 3.
To determine the shear strength of a JSC Mars-1A regolith sample, the friction angle was
found by running a shear test to measure the vertical and horizontal displacement of the sample
when placed under specific pressures. Figures 4 and 5 demonstrate the horizontal pressure per
the horizontal displacement of the sample for the 1mm and 5mm samples. The peak curvature of
the graph shows the point at which the strain overcame the strength of the soil, showing us that
with a friction angle of 41.3o
, the Martian regolith sample was relatively weak but is of roughly
the same strength as many Earth soils.
Figures 4 and 5 - Direct Shear on Martian Regolith 1mm and 5mm Samples Respectively

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Figures 6 and 7 - Direct Shear Test on 1mm and 5mm Samples Respectively
DISCUSSION
In the future, the goal is ultimately to be able to have human life on Mars. Due to the inherent
challenges of transporting materials from Earth, people living on Mars will need to be able to utilize
Martian resources. Among other things, this will require in-depth knowledge about the properties of
Martian soil and how to best manipulate the soil to fit human needs. The ability to directly build on
Mars with very little transported construction materials would significantly increase our possibility of
surviving on the planet. This research focused specifically on the particle-size distribution and friction
angles of the regolith soil samples.
Concurrently, another lab was using the various soil samples with different particle sizes and
friction angles combined with various lightweight polymers to create a plastic material that could be
used to create items on Mars with enough tensile strength to be fully functional, minimizing
transportation issues. The Martian regolith tested did have advantageous qualities to provide proper
drainage, but did not contain the necessary qualities for construction. It had a poorly graded grain size
distribution, and a low shear angle, impacting the strength of the regolith and making it a weak
material to build with. Continued research will be necessary to discover a regolith with more evenly

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distributed particle sizes, find simple ways to modify the strength of the regolith, or find an alternative
option to promote strength and ease of construction with the materials on Mars.
In addition to this, other topics must be addressed and researched prior to launch. Some of
these topics include agriculture, construction, pottery and ceramics, mineral content, and varying types
of soil in different locations on Mars. As humans continue to deplete Earth’s natural resources and
Earth’s population continues to grow, the ability to sustain life on another planet becomes ever more
important. The capacity for life on another planet could ultimately determine the sustainability of the
human species. In the grand scope of things, this endeavor may turn out to be imperative and one of
the most important accomplishments achieved by humans.
ACKNOWLEDGEMENTS
I would like to thank Dr. Qiushi Chen, Zengshou Lai, and Andrew Randazza for guidance and
instruction with this project. I would also like to thank the Civil Engineering Department at Clemson
University for allowing me to use their facilities and the South Carolina Governor’s School for Science
and Mathematics for presenting me with this opportunity.

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LITERATURE CITED
Das, B. M. (2002). Direct Shear Test on Sand. In B. M. Das, Soil Mechanics Laboratory Manual (pp.
99-108). Oxford: Oxford University Press.
NASA. (n.d.). Retrieved June 07, 2016, from http://www.nasa.gov/