XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 343
The early stages of adapting terrestrial methods to space
environments will consist largely of finding substitutes or
work-arounds for environmental conditions that our cur-
rent beneficiation, separation, and concentration methods
are based on. Gaining experience in the space environment,
however, will certainly reveal unexpected approaches made
possible by natural processes that are obscured or have
only minor effects on Earth. Recognizing such possibili-
ties at this early stage is handicapped by the fact that most
research is conducted on the Earth’s surface. Utilizing such
processes effectively once they have been identified will
require a certain amount of operational experience in the
actual space environments.
Earth’s Moon
The first mineral processing system demonstrations in space
will happen on Earth’s Moon. This environment is like the
Earth’s in that it has constant gravity and a stable surface
covered with “soil,” but other differences will require modi-
fications to accepted mineral processing methods.
Lunar gravity is widely known to be 83% lower than
Earth’s, but the inertia is the same, so flowing material and
moving equipment will behave non-intuitively. The surface
temperature ranges from –290°F to +240°F, with the lowest
temperatures occurring in permanently shadowed regions,
found mainly near the poles, where water ice is believed
to exist. The polar regions—where the Artemis Program,
for example, will create a presence—additionally are subject
to extremely irregular light-dark periods due to the high
topographic relief combined with low sun angles (Wright
2022).
The lunar surface is exposed directly to the solar wind,
cosmic rays, and solar ultraviolet radiation such that the
regolith on the sunlit side is positively charged (about 10
volts) and the dark side is negatively charged (usually –200
volts, but reaching –4500 volts during intense solar activ-
ity Calle 2017). This causes some fine regolith particles to
jump as the line between sunlight and shadow (the termi-
nator) passes. In fact, electrostatic discharges can occur as
deep as one meter into the regolith, so significant attention
must be paid to electrostatic charge control and shielding
of equipment. Intermittent energy and mass discharges
from the Sun are hazardous to humans and machines and
the heterogeneity and low strength of the lunar crust mag-
netic fields provide no practical protection (Wieczorek et
al. 2023).
The “soil” is really just regolith (average size of
the 1-cm-passing fraction is 70 microns), and gaseous
atmosphere is essentially absent. Water is extremely rare,
apparently occurring as ice deposited between grains of the
regolith (Reach et al. 2023 this has not been confirmed yet
with physical sampling, but a mission to do so will land this
year). Human monitoring of and intervention in extractive
process systems will be very limited.
Mars
Mars is the next human destination beyond Earth’s Moon.
It is a planet with enough surface area to make local opera-
tions essentially flat its gravity is twice that of the Moon
(38% of Earth’s) and its atmosphere of mostly carbon diox-
ide is thicker, though still very sparse (average pressure is
about 0.7% of Earth’s). Water and carbon dioxide ices are
available on the surface, along with minerals that contain
water and/or hydroxyl in their structures (clays and sul-
fates). The atmosphere provides enough thermal buffering
to reduce the range of surface temperatures to –225°F to
+70°F. The Mars magnetic field is complex in space and
time, leading to both under- and over-predictions of its
strength (Johnson et al. 2020 Du et al. 2023).
Like most solar system bodies, Mars’ orbit is farther
from the Sun than Earth’s. Depending on the planets’ rela-
tive positions, communications take 5–20 minutes one-
way and are vulnerable to disruption and delay (Chappell
et al. 2024). This is too long for direct human control of
machines there (it may be possible on the Moon, for some
tasks and trained operators, per Panzirsch et al. 2020). The
Mars rover controllers instead have developed various tech-
niques, including an increasing use of autonomy, for maxi-
mizing the productivity of robot time on the ground that
provide some potentially useful lessons for remote mineral
extraction (Rankin et al. 2020, Verma et al. 2023).
Small Bodies
Small bodies include asteroids and comets. Comets origi-
nate in the outer solar system when their orbits bring them
close enough to the Sun that some of their constituent ices
are sublimated. Some asteroids are comets that have lost
their volatiles. Asteroids can be grouped further into the
primitive and differentiated types as described by Britt and
Cannon (2023), early interest is focused on pieces of frag-
mented differentiated types (for metals) and on hydrated
carbonaceous chondrite asteroids (for volatiles).
Some asteroids are actually easier to get to than Earth’s
Moon (Rivkin and DeMateo 2018), but most are not. The
small size and/or non-cohesive nature of all but the largest
asteroids mean they cannot be “landed on” instead, large
The early stages of adapting terrestrial methods to space
environments will consist largely of finding substitutes or
work-arounds for environmental conditions that our cur-
rent beneficiation, separation, and concentration methods
are based on. Gaining experience in the space environment,
however, will certainly reveal unexpected approaches made
possible by natural processes that are obscured or have
only minor effects on Earth. Recognizing such possibili-
ties at this early stage is handicapped by the fact that most
research is conducted on the Earth’s surface. Utilizing such
processes effectively once they have been identified will
require a certain amount of operational experience in the
actual space environments.
Earth’s Moon
The first mineral processing system demonstrations in space
will happen on Earth’s Moon. This environment is like the
Earth’s in that it has constant gravity and a stable surface
covered with “soil,” but other differences will require modi-
fications to accepted mineral processing methods.
Lunar gravity is widely known to be 83% lower than
Earth’s, but the inertia is the same, so flowing material and
moving equipment will behave non-intuitively. The surface
temperature ranges from –290°F to +240°F, with the lowest
temperatures occurring in permanently shadowed regions,
found mainly near the poles, where water ice is believed
to exist. The polar regions—where the Artemis Program,
for example, will create a presence—additionally are subject
to extremely irregular light-dark periods due to the high
topographic relief combined with low sun angles (Wright
2022).
The lunar surface is exposed directly to the solar wind,
cosmic rays, and solar ultraviolet radiation such that the
regolith on the sunlit side is positively charged (about 10
volts) and the dark side is negatively charged (usually –200
volts, but reaching –4500 volts during intense solar activ-
ity Calle 2017). This causes some fine regolith particles to
jump as the line between sunlight and shadow (the termi-
nator) passes. In fact, electrostatic discharges can occur as
deep as one meter into the regolith, so significant attention
must be paid to electrostatic charge control and shielding
of equipment. Intermittent energy and mass discharges
from the Sun are hazardous to humans and machines and
the heterogeneity and low strength of the lunar crust mag-
netic fields provide no practical protection (Wieczorek et
al. 2023).
The “soil” is really just regolith (average size of
the 1-cm-passing fraction is 70 microns), and gaseous
atmosphere is essentially absent. Water is extremely rare,
apparently occurring as ice deposited between grains of the
regolith (Reach et al. 2023 this has not been confirmed yet
with physical sampling, but a mission to do so will land this
year). Human monitoring of and intervention in extractive
process systems will be very limited.
Mars
Mars is the next human destination beyond Earth’s Moon.
It is a planet with enough surface area to make local opera-
tions essentially flat its gravity is twice that of the Moon
(38% of Earth’s) and its atmosphere of mostly carbon diox-
ide is thicker, though still very sparse (average pressure is
about 0.7% of Earth’s). Water and carbon dioxide ices are
available on the surface, along with minerals that contain
water and/or hydroxyl in their structures (clays and sul-
fates). The atmosphere provides enough thermal buffering
to reduce the range of surface temperatures to –225°F to
+70°F. The Mars magnetic field is complex in space and
time, leading to both under- and over-predictions of its
strength (Johnson et al. 2020 Du et al. 2023).
Like most solar system bodies, Mars’ orbit is farther
from the Sun than Earth’s. Depending on the planets’ rela-
tive positions, communications take 5–20 minutes one-
way and are vulnerable to disruption and delay (Chappell
et al. 2024). This is too long for direct human control of
machines there (it may be possible on the Moon, for some
tasks and trained operators, per Panzirsch et al. 2020). The
Mars rover controllers instead have developed various tech-
niques, including an increasing use of autonomy, for maxi-
mizing the productivity of robot time on the ground that
provide some potentially useful lessons for remote mineral
extraction (Rankin et al. 2020, Verma et al. 2023).
Small Bodies
Small bodies include asteroids and comets. Comets origi-
nate in the outer solar system when their orbits bring them
close enough to the Sun that some of their constituent ices
are sublimated. Some asteroids are comets that have lost
their volatiles. Asteroids can be grouped further into the
primitive and differentiated types as described by Britt and
Cannon (2023), early interest is focused on pieces of frag-
mented differentiated types (for metals) and on hydrated
carbonaceous chondrite asteroids (for volatiles).
Some asteroids are actually easier to get to than Earth’s
Moon (Rivkin and DeMateo 2018), but most are not. The
small size and/or non-cohesive nature of all but the largest
asteroids mean they cannot be “landed on” instead, large