The Astrobiological Significance of Impacts on the Moon
Dirk Schulze-Makuch
Center for Astronomy and Astrophysics, Technical University Berlin, Germany
Introduction
Water on the Moon
An Early Lunar Hydrosphere?
Water seems to be more abundant in lunar rocks than previously
thought (6) and some of the rocks also contain phyllosilicates (7),
evidence of an early exposure to liquid water. This observation
may be linked to vapor transport during degassing of a magmatic
source region, or from a hybrid endogenic-exogenic process
when gases were released during an impacting asteroid or comet
(8). A more speculative suggestion would be the existence of an
early Moon or Earth-Moon system hydrosphere, or perhaps a
significant accumulation of water after an impact. Evidence for
larger-scale hydrological processes would be hard to find since
any resulting surface topography would be long erased by 4
billion years of pounding with solar wind and cosmic radiation.
Nevertheless, the idea should be tested as it would be beneficial
to know what happened to the water on the Moon early on, how
much water the Moon retained, and for how long.
The possibility for the formation of ice deposits or
other volatiles on the Moon has been suggested
previously, not only by degassing form the early
Moon, but also by deposition from water-rich
meteorite impacts near lunar poles (1).
Temperatures have been estimated to not exceed
40K in shadowed Moon craters allowing the
preservation of frozen water molecules over
geologic time scales. Presence of ice has been
verified based on data from various space missions
(e.g., Figure 1) and radar measurements with the
Arecibo radio telescope.
Importance of Lunar Ice
Figure 1. Map of hydrogen concentrations inferred to be water ice at the lunar north and south poles based on results from NASA's Lunar CRater
Observation and Sensing Satellite and Lunar Reconnaissance Orbiter (purple highest concentrations, green lowest concentrations) (3).
Mining Water and Separating it from the Organics
Figure 3. Device to separate clean water from organic residue. The Surfactant Modified Zeolite
(SMZ) filter was previously tested and proved extremely efficient removing organic compounds
due to its (1) cage-like porous structure, (2) hydrophobic properties, (3) and charge
characteristics (5). SMZ has a distinct advantage over activated carbon in that regeneration of
the sorbent and recovery of the organic compounds is much easier. While activated carbon has
to be heated to desorb retained volatile organics, SMZ is readily regenerated by blowing air
through the filter. No added heat source or an ice bath condenser are needed.
Removable Lid
Removable Lid
Figure 2. Set-up to mine water on the Moon.
Material is loaded into a sealed vessel and
heated by a solar furnace while the released
gasses are recovered and condensed into
water and stored in a storage tank for later
use. The source of the sunlight (solar furnace)
could be from areas of uninterrupted solar
power such as the rims of Shalkelton or the
top of Malapert Mountain (4).
Chamber 1
61 cm
Chamber 2
30 cm
Lunar water ice has the advantage that it can be
used by future explorers to be converted into
hydrogen and oxygen for rocket fuel. There have
been several mining purposes being discussed
such as ice-mining from the permanently shadowed
areas. This can be accomplished either by a
transport rover, drag line bucket, or a combination
of the two with the material being loaded into a
sealed vessel and heated by a solar furnace, while
the released gasses are recovered and condensed
into water (Figure 2). A better option would be to
first separate the water from any organic
endowment and any other particles that the ice
might harbor, which could be done using surfactant
modified zeolite (Figure 3) or nanofilters (2). That
way the water could also be used for human
consumption, plus the organic endowment may
harbor a treasure trove of organic material. Not only
would we be able to recover organic material from
comets crashed on the Moon long ago, but these
lunar ice-filled craters are the only location where
we might find evidence of very early life on Earth.
By discovering a rock fragment that was dislodged
from Earth during a meteorite impact and landed on
the Moon, we might unravel the origin of life riddle,
possibly even detecting macromolecules before the
first life form originated on Earth.
Task 1:
Breathable
Diaphragm
Task 2: SMZ Filter
Vapors
ICE
20 cm
Collected Water
20 cm
Vacuum
Treatment of natural zeolites
with
large
cationic
surfactants
(quaternary
amines) dramatically alters
their surface chemistries.
These large organic cations
exchange selectively with
native inorganic cations to
form a stable, organic-rich
coating on the external
surfaces of the zeolite.
Surfactant
modification
allows the zeolites to sorb
nonpolar organic solutes
and anions, for which
untreated zeolites have little
affinity.
Figure 4. A very young lunar crater on the side of the Moon that faces
away from Earth, as viewed by Chandrayaan-1's Moon Mineralogy
Mapper
References
(1) Lowman, P.D. (2000) An Astrobiology Reconnaissance of the South Polar
Region of the Moon, Goddard Space Flight Center.
(2) Schulze-Makuch, D. (2013) Organic molecules in lunar ice: a window to the
early evolution of life on Earth. In Cellular Origins, Life in Extreme Habitats and
Astrobiology 28, 115-125.
(3) Feldman, W.C. et al. (1998) Fluxes of Fast and Epithermal Neutrons from
Lunar Prospector: Evidence for Water Ice at the Lunar Poles. Science 281,
1496
(4) Lowman, P.D. (2005) International Lunar Observatory: Suggested Instrument
Complement, Goddard Space Flight Center (Code 698).
(5) Schulze-Makuch, D., et al. (2003) Removal of viruses and bacteria from ground
water by surfactant modified zeolite: field applications. Ground Water
Monitoring and Remediation 24: 68-75.
(6) Lin, Y. et al. (2017) Evidence for an early wet Moon from experimental
crystallization of the lunar magma ocean. Nature Geosciences, DOI:
10.1038/NGEO2845
(7) Drever, J.I. et al. (1970) Proceedings of the Apollo 11 Lunar Science
Conference, 1, 341-345.
(8) Joy, K.H. et al. (2015) Identification of magnetite in lunar regolith breccia
60016: Evidence for oxidized conditions at the lunar surface. Meteoritics &
Planetary Science, 50, 1157-1172.
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