Future manned missions to the moon or
Mars could use plants
as bio-harvesters to extract valuable elements from the alien soils,
researchers say.
Now they hope to launch new
experiments to follow up on
tests done with plants and lunar regolith during NASA's Apollo program
that
landed men on the moon.
Lunar regolith is a loose mixture of
dust, soil, broken rock
and other related materials that lie on top of solid bedrock. The
Apollo-era
research showed that returned lunar samples of the regolith did not
have toxins
or contain alien life-form contaminants that could threaten plants,
animals or
humans on Earth. [Plans
to grow flowers on the moon.]
Yet limited use of the precious lunar
regolith meant that
scientists could not study how well plants fared when grown in regolith.
"In spite of the fact that we
absolutely admire the
innovative science done in the Apollo era, the question of whether a
plant
could grow if you plop a seed in lunar regolith hasn't been answered,"
said Robert Ferl, a geneticist at the University of Florida in
Gainesville.
Ferl and Anna-Lisa Paul, another
geneticist at the University of Florida, hope to pick up where the
Apollo-era experiments left off. Renewed
research could take advantage of the powerful tools developed in the
past
several decades for studying molecular biology and genetics, and see
how plants
react on a molecular level by turning on or off their genes in response
to
regolith.
New studies could also push the
potential shown in how
plants apparently derived some nutrients from lunar regolith. That
could go
beyond the dreams of lunar agriculture to transform plants into planetary
harvesters, and ultimately help sustain human bases on alien
soil.
"It's not just about using lunar and
Mars regolith to
grow plants," Paul explained. "It's about capturing nutrients that
might otherwise be lost to us."
The review study of Apollo-era plant
experiments was
detailed in the April issue of the journal Astrobiology.
Safety first
NASA took great precautions with
samples returned during the
first manned missions to the Moon by building the Lunar Receiving Lab
(LRL) at
the Johnson Space Center in Houston. The LRL facility's design intended
to
ensure that no dangerous contaminants or unknown alien life forms
escaped to
threaten Earth's biosphere, even as researchers began carrying out
biological
experiments with the lunar regolith.
Any planetary
protection fears faded quickly as the first studies showed
that plants did
not wither and die from contact with lunar samples.
About 35 plant species
remained in good health after lunar
samples from the Apollo 11 and 12 missions had been rubbed onto the
leaves and
placed at their base. Similarly, animals did not suffer from any ill
effects
during exposure to lunar samples.
In fact, one study found that
germinated seedlings and plant
cultures seemed to enjoy nutritional benefits from the lunar samples.
The lunar
dust and regolith contained certain elements useful for plant growth,
such as
iron, magnesium and manganese, even if it mostly lacked necessary
elements such
as nitrogen, phosphorus, sulfur and potassium.
That pointed to the possibility of
using plants to biologically
harvest nutrients or minerals from the Moon, and suggested that lunar
farms
could contribute to life-support beyond just feeding astronauts.
"In one interesting model put out a
few years ago,
plants would live in low-pressure pods on the surface," Ferl said.
"Astronauts or lunar colonists would go out in pressure suits to
capture
them."
Taking the next step
The plants may have survived and even
thrived a small
sprinkling or rubbing of lunar material, but researchers say many
unknowns
remain after the last lunar soil experiments that took place 30 years
ago.
For instance, none of the Apollo-era
experiments examined
how lunar material affected the microorganisms such as bacteria or
fungi that
normally assist plants in harvesting nutrients. Even microbes from
human
astronauts might interact with the plant roots in the region of soil
known as
the rhizosphere.
"You have the colonization of the
plant roots by a host
of organisms
that break down and transport materials," Paul said. "These things
facilitate the harvesting of molecules from the substrate in which the
plant is
growing."
New experiments don't need to wait
for a return trip to the Moon,
according to the researchers. They already have plans that would
require just a
few grams of the hundreds of kilograms of lunar regolith collected by
NASA.
Just one gram of lunar regolith could
support the growth of
several Arabidopsis plants related to cabbage and
radish, Paul pointed
out. That model organism represented the first plant to have its genome
sequenced, and so would provide a great baseline for lunar biology
experiments.
.From Earth to the Moon and
Mars
Such testing concepts could also
become part of experiments
done on the Moon itself, whenever a human base does get established.
Those experiments
would not only answer questions about basic plant biology, but also
provide the
seeds of knowledge for developing ecology
off of
Earth.
"One goal is to use plants for
life-support and find
out the best means to do that, and [figure out if] plants use lunar
resources
to do that," Ferl said. "The other question is what the limits of
terrestrial life are, and does the Moon's surface represent a place
that
terrestrial biology can inhabit."
That approach could also help tackle
problems related to
growing plants in Martian regolith. Some studies on Earth have already
tested
plant growth in Mars-simulant regolith augmented with certain
chemicals, even
if a Martian sample has yet to reach Earth.
In the end, the same need to use all
available resources and
help sustain human colonists would become even greater for a trip to
Mars.
"Going to Mars is so much more
difficult, because the
concept of taking all your resources with you for the whole trip
becomes more
difficult," Paul said. "The drivers that would point toward using
plants for life support actually become more crucial."
Planting the seeds
More Earth experiments also could
help engineers and
scientists better design future orbital or extraterrestrial farms.
"Testing on extreme environments on
Earth could be very
useful to identify critical design aspects to be fixed prior to build
and fly a
demonstration system on the [International Space Station]," said
Claudio
Finetto, an engineering consultant for Thales Alenia Space-Italia in
Torino, Italy.
Finetto and colleagues Cesare
Lobascio and Alessandro
Rapisarda calculated that a bio-regenerative life support system with
just 20
percent of food re-supplied from Earth would become more convenient for
an
18-person moon base inhabited for longer than five years, as opposed to
relying
on complete food re-supply from Earth.
Their work is detailed in the
May-June issue of the journal Acta
Astronautica. The Lunar FARM concept also grew out of a
post-graduate
course in SpacE Exploration and Development Systems (SEEDS) Second
Edition at
Politecnico di Torino, where Finetto worked with Salvatore Cusumano,
Daniele
Renzoni, Amir Sabbagh and Cosimo Sinesi.
Even if NASA has scrapped immediate
plans to return to the Moon,
Finetto agreed that a manned Mars mission could benefit from a
self-sustaining
approach. He added that a spacecraft greenhouse could support
astronauts on the
Martian surface just as easily as during the six-month journeys to and
from the
red planet.
More advanced robots could also
reduce the amount of time
human astronauts spend on cultivating their plants, according to
Finetto.
That still looks a long way off from
the Apollo-era
experiments with bits of lunar regolith sprinkled atop plants. But
someday,
robots could maintain a self-sustaining greenhouse orbiting above Mars
as human
explorers focus on science and exploration down on the surface below.
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