TY - THES
T1 - Lunar Dust Toxicity
T2 - Regolith Simulant Suitability for Biological Research
AU - Dierckx, Jenne
A2 - Baatout, Sarah
A2 - Baselet, Bjorn
N1 - Score=N/A
PY - 2022/7/1
Y1 - 2022/7/1
N2 - The return of mankind to the Moon seems inevitable. Many nations have set their sights on
reaching the lunar surface in the near future, and establishing a foothold there will hopefully
be a steppingstone to excursions further out into the solar system. While on the Moon, a
primary issue we will need to contend with is the ground up regolith covering every last bit of
surface. The constant meteoroid bombardment, harsh solar and galactic radiation and vacuum
of space has turned the lunar bedrock into a mass of peculiar particles: lunar dust. The frequent
impacts have sufficient energy to partially melt the material, causing fragments to be glassbonded together in agglutinates, can send material flying great distances, and continuously
churn and grind down material. Particle sizes vary, but many tiny grains, within the respirable
(< 2 µm) range exist. At the molecular level, the dust particles exhibit peculiar morphological
features, giving them a large surface area and conveying high reactivity. These include sharp
edges, vesicles, glass rims, nanophasic iron and dangling bonds. The changing plasma
environment on the Moon, varying with the solar wind and passage through the Earth’s
magnetotail, as well as the lunar diurnal cycle, charges the surface and regolith, and can make
particles levitate electrostatically, up to great heights.
Because of its ubiquitous and reactive nature, lunar dust has been found to impact every
human activity performed on the moon, and has managed to permeate every spacecraft that
has come into contact with it. Furthermore, it has been found to be a substance of grave
concern. It can abrade seals, scratch displays, obscure vision, coat heat-transfer surfaces and
cause respiratory discomfort. The United States National Aeronautics and Space
Administration (NASA) has listed it as a key obstacle to be overcome before the lunar surface
can be revisited for extended periods. The regolith can also be a resource, however. It could
serve as a structural building material, can be harvested for key elements like O2, metals and
water, and could be used to fabricate solar panels or soil to enable life-support systems. It is
clear that lunar dust is of key importance to our efforts in returning to moon. Studies of lunar
dust, ranging from its potential as in-situ resource utilization (ISRU) resource to its toxic
properties are therefore ongoing and increasing in number.
Performing these studies directly on lunar material is not possible due to its scarcity. Instead,
for decades, we have been making use of lunar dust simulants which mimic properties of actual
lunar regolith. Due to the very specific characteristics of lunar dust, it is not feasible to create
a cost-effective simulant that can be used for all types of investigations. Instead, the scientific
community is searching for a root simulant which could be mass produced at low cost with high
fidelity to then be amended with various additives depending on the desired experimental setups.
In this thesis we have investigated the potential of two lunar dust simulants, “LHS-1” and “LMS1”, produced by Exolith lab, to be used in biological research. There are many exposure routes
through which living organisms might come into contact with lunar dust in a lunar habitat. Of
gravest concern are the immediate effects on human astronauts, which could see first and
foremost their lungs impacted by breathing in airborne dust. Exposure through eyes, skin, or
the gastrointestinal system are also possible, however. In addition, other organisms, such as
the biological component parts of closed loop life-support systems could also be negatively
affected by contact with the regolith. Lunar dust (simulant) toxicity research has been done for
various organisms and tissue types, both in vitro and in vivo, and has so far mostly indicated
that the material behaves as terrestrial particulate pollutants.
MASTER OF SPACE STUDIES v KU LEUVEN/UGENT
In our experiments we have focused on the effects that the Exolith simulants might have on
human alveolar A549 cells. We have exposed them to various doses of LHS-1 and LMS-1, for
differing durations. Subsequently we have evaluated cytotoxicity, growth, intracellular reactive
oxygen species (ROS) and ROS sensitivity and cytokine expression. In addition, we have
performed limited SEM investigations of our simulants, to have a look at morphological
features. As a benchmark during these activities, we have included the terrestrial particulate
toxicant quartz alongside the Exolith simulants.
We find that LHS-1 and LMS-1 adequately mimic the particle size and composition of true lunar
regolith, but lack certain morphological features that are unique to lunar dust. The simulants
do not contain agglutinates or nanophasic iron, for example. Despite these shortcomings, the
material still appears to elicit cell responses that are in line with those we would expect for
actual lunar dust. A549 cells were found to be less viable, grow more slowly, contain more
intracellular ROS and express more pro-inflammatory cytokines compared to controls, after
treatment with the simulants. Quartz was found to produce less effects, but this is likely due to
the fact that the used quartz sample had a particle size that was far greater than that of our
simulants.
In order to improve and refine our findings, and characterize the severity and dose-response
of the effects, more research could be done. Experimental procedures could be repeated to
increase the sample size, and some modifications could be made to further facilitate
interpretation. The simulant material could be activated by grinding or milling before the
experiments, thus producing dangling bonds that would increase reactivity by mimicking the
unsatisfied valences and ions present on lunar dust in the lunar vacuum. In addition, specific
other simulants could be included in our experiments, containing morphological features that
are lacking in LHS-1 and LMS-1, such as agglutinates or nanophasic iron, in order to improve
our understanding of whether these features are truly necessary to facilitate biological
research. Lastly, the experimental base could be expanded to other cell types or organisms to
be able to make statements about the suitability of Exolith simulants for broader biological
research. While doing so, it could be useful to pre-sieve the material to a particle size that is
relevant to the tissue being tested in order to obtain more specific results.
Overall, we can conclude that the Exolith simulants are relatively cheap and easily obtained,
mimic lunar dust to an appreciable degree, and based on our initial results, seem to produce
toxic effects in line with what would be expected from true lunar regolith. However, more work
should be done to characterize the severity and specificity of these findings
AB - The return of mankind to the Moon seems inevitable. Many nations have set their sights on
reaching the lunar surface in the near future, and establishing a foothold there will hopefully
be a steppingstone to excursions further out into the solar system. While on the Moon, a
primary issue we will need to contend with is the ground up regolith covering every last bit of
surface. The constant meteoroid bombardment, harsh solar and galactic radiation and vacuum
of space has turned the lunar bedrock into a mass of peculiar particles: lunar dust. The frequent
impacts have sufficient energy to partially melt the material, causing fragments to be glassbonded together in agglutinates, can send material flying great distances, and continuously
churn and grind down material. Particle sizes vary, but many tiny grains, within the respirable
(< 2 µm) range exist. At the molecular level, the dust particles exhibit peculiar morphological
features, giving them a large surface area and conveying high reactivity. These include sharp
edges, vesicles, glass rims, nanophasic iron and dangling bonds. The changing plasma
environment on the Moon, varying with the solar wind and passage through the Earth’s
magnetotail, as well as the lunar diurnal cycle, charges the surface and regolith, and can make
particles levitate electrostatically, up to great heights.
Because of its ubiquitous and reactive nature, lunar dust has been found to impact every
human activity performed on the moon, and has managed to permeate every spacecraft that
has come into contact with it. Furthermore, it has been found to be a substance of grave
concern. It can abrade seals, scratch displays, obscure vision, coat heat-transfer surfaces and
cause respiratory discomfort. The United States National Aeronautics and Space
Administration (NASA) has listed it as a key obstacle to be overcome before the lunar surface
can be revisited for extended periods. The regolith can also be a resource, however. It could
serve as a structural building material, can be harvested for key elements like O2, metals and
water, and could be used to fabricate solar panels or soil to enable life-support systems. It is
clear that lunar dust is of key importance to our efforts in returning to moon. Studies of lunar
dust, ranging from its potential as in-situ resource utilization (ISRU) resource to its toxic
properties are therefore ongoing and increasing in number.
Performing these studies directly on lunar material is not possible due to its scarcity. Instead,
for decades, we have been making use of lunar dust simulants which mimic properties of actual
lunar regolith. Due to the very specific characteristics of lunar dust, it is not feasible to create
a cost-effective simulant that can be used for all types of investigations. Instead, the scientific
community is searching for a root simulant which could be mass produced at low cost with high
fidelity to then be amended with various additives depending on the desired experimental setups.
In this thesis we have investigated the potential of two lunar dust simulants, “LHS-1” and “LMS1”, produced by Exolith lab, to be used in biological research. There are many exposure routes
through which living organisms might come into contact with lunar dust in a lunar habitat. Of
gravest concern are the immediate effects on human astronauts, which could see first and
foremost their lungs impacted by breathing in airborne dust. Exposure through eyes, skin, or
the gastrointestinal system are also possible, however. In addition, other organisms, such as
the biological component parts of closed loop life-support systems could also be negatively
affected by contact with the regolith. Lunar dust (simulant) toxicity research has been done for
various organisms and tissue types, both in vitro and in vivo, and has so far mostly indicated
that the material behaves as terrestrial particulate pollutants.
MASTER OF SPACE STUDIES v KU LEUVEN/UGENT
In our experiments we have focused on the effects that the Exolith simulants might have on
human alveolar A549 cells. We have exposed them to various doses of LHS-1 and LMS-1, for
differing durations. Subsequently we have evaluated cytotoxicity, growth, intracellular reactive
oxygen species (ROS) and ROS sensitivity and cytokine expression. In addition, we have
performed limited SEM investigations of our simulants, to have a look at morphological
features. As a benchmark during these activities, we have included the terrestrial particulate
toxicant quartz alongside the Exolith simulants.
We find that LHS-1 and LMS-1 adequately mimic the particle size and composition of true lunar
regolith, but lack certain morphological features that are unique to lunar dust. The simulants
do not contain agglutinates or nanophasic iron, for example. Despite these shortcomings, the
material still appears to elicit cell responses that are in line with those we would expect for
actual lunar dust. A549 cells were found to be less viable, grow more slowly, contain more
intracellular ROS and express more pro-inflammatory cytokines compared to controls, after
treatment with the simulants. Quartz was found to produce less effects, but this is likely due to
the fact that the used quartz sample had a particle size that was far greater than that of our
simulants.
In order to improve and refine our findings, and characterize the severity and dose-response
of the effects, more research could be done. Experimental procedures could be repeated to
increase the sample size, and some modifications could be made to further facilitate
interpretation. The simulant material could be activated by grinding or milling before the
experiments, thus producing dangling bonds that would increase reactivity by mimicking the
unsatisfied valences and ions present on lunar dust in the lunar vacuum. In addition, specific
other simulants could be included in our experiments, containing morphological features that
are lacking in LHS-1 and LMS-1, such as agglutinates or nanophasic iron, in order to improve
our understanding of whether these features are truly necessary to facilitate biological
research. Lastly, the experimental base could be expanded to other cell types or organisms to
be able to make statements about the suitability of Exolith simulants for broader biological
research. While doing so, it could be useful to pre-sieve the material to a particle size that is
relevant to the tissue being tested in order to obtain more specific results.
Overall, we can conclude that the Exolith simulants are relatively cheap and easily obtained,
mimic lunar dust to an appreciable degree, and based on our initial results, seem to produce
toxic effects in line with what would be expected from true lunar regolith. However, more work
should be done to characterize the severity and specificity of these findings
KW - Lunar dust toxicity
KW - Regolith simulant suitability
KW - Biological research
KW - Solar radiation
KW - Galactic radiation
KW - Vacuum of space
KW - Lunar diurnal cycle
KW - NASA
KW - A549 cells
KW - ISRU
UR - https://ecm.sckcen.be/OTCS/llisapi.dll/open/49843002
M3 - Master's thesis
ER -