Harvesting Mars

http://science.nasa.gov/headlines/y2...riticalco2.htm

Harvesting Mars
NASA Science News
August 20, 2003

A NASA-supported scientist is learning how to use carbon dioxide--the main
gas in Mars' atmosphere--to harvest rocket fuel and water from the red
planet.

August 20, 2003: When astronauts first go to Mars, it'll be difficult for
them to bring everything they need to survive. Even the first tentative
explorations could last as long as two years--but spaceships can only carry
a limited amount.

"We might have to do what explorers have done for ages: live off the land,"
says chemical engineer Ken Debelak of Vanderbilt University.

Explorers on Earth could usually count on finding what they needed. The
animals might be strange, but they'd be there, and they'd be edible. Mars is
barren. But the challenge is the same. Astronauts will want to pull what
they need from the planet itself. And although that goal seems improbable,
Debelak believes it can be achieved. He's working on a NASA project to make
it happen. The key, he says, lies in the Martian atmosphere.

It's a meager atmosphere, compared to Earth's, and it's about 95 percent
carbon dioxide (CO2). But that turns out to be an advantage. The carbon
dioxide, says Debelak, can be used to harvest almost everything else.

Inside martian rocks and soil lies a bounty of useful elements: magnesium
and hydrogen for rocket fuel, oxygen to breath, water to drink. What's
needed is a solvent to get them out, and that's where the carbon dioxide
comes in handy.

"When CO2 is compressed to a pressure of 73 atm and heated to 31.1 degrees
Celsius, it becomes a supercritical fluid--and a marvelous solvent," says
Debelak.

A supercritical fluid is a high-pressure, high-temperature state of matter
perhaps best described as a liquid-like gas. Almost anything can become
supercritical. Water, for instance, becomes a supercritical fluid in the
high pressures and temperatures of steam turbines. Ordinary water is a good
solvent. Supercritical water is a great solvent--maybe even a little too
good. It dissolves the tips of the turbine blades.

Supercritical carbon dioxide behaves much the same. CO2 molecules flow into
solid matter, surrounding atoms, pulling them apart and away.

On Earth, supercritical CO2 is not used much to dissolve things because
there are less expensive, more effective solvents close at hand. It is,
however, used to remove the caffeine from coffee beans, and sometimes to
dry-clean clothes. On Mars, Debelak believes, supercritical CO2 will play a
much more important role.

For example: Magnesium can be dissolved quite easily by supercritical CO2,
Debelak has found. "That's an experiment that we're quite excited about at
the moment," he says. Magnesium, which is likely to be found in martian
soil, ignites easily and can be used to fuel rockets. In fact, says Debelak,
one Mars exploration scenario called for a lander to be made of
magnesium--"the legs and so on." When the astronauts were ready to go home,
"you could chop it up, pack it into a rocket engine, and then add some other
oxidizer to fire it off." Using CO2 as a solvent, magnesium could instead be
harvested directly from Mars.

Supercritical CO2 might also be used to generate water. Certain martian
rocks (like some of Earth's rocks) contain hydrogen. When these rocks are
submerged in supercritical carbon dioxide, a chemical reaction takes place.
The CO2's carbon becomes "fixed" in the rock, leaving the oxygen free to
find another partner: hydrogen. "The process kicks out water," marvels
Debelak. "You can actually use it to form water."

Pulling water from rocks will probably have the biggest payoff, at least in
the short term, says Debelak. In addition to drinking, "you can split water
into hydrogen for fuel, and oxygen for breathing--or as an oxidizer for some
sort of engine." Eventually, colonists could set up plants that use CO2 from
the martian atmosphere to process hundreds of kilograms of raw material a
day.

A supercritical fluid has some advantages over other solvents: Its
solubility changes dramatically when you alter the temperature or the
pressure. You can control it, so that sometimes it's a solvent for a
particular substance, and sometimes it's not. That makes it easy to recover
the material that has been dissolved. Let's say you have caffeine dissolved
in supercritical carbon dioxide. To recover the caffeine (caffeine recovered
from coffee beans is often put in soft drinks), you just lower the pressure
of the CO2 and the caffeine drops out.

Currently, Debelak is trying to pin down the way a variety of substances
behave in supercritical CO2. He's looking at which minerals are easily
soluble and which are not. And if they're not, he's trying to determine how
their solubility can be improved. Adding other substances to the CO2
sometimes helps, he says.

Debelak's work could be useful on Earth, too. Carbon dioxide is often
spotlighted because of its damaging role in global warming. But as a
solvent, it's benign. Many solvents common in industry are toxic. They cause
cancer, and if they get into the water system, they stay for a long time. So
there's interest, says Debelak, in learning how to use CO2 as a 'green'
alternative.

Carbon dioxide plays widely different roles on Earth and on Mars. "That's
what's intriguing," points out Debelak. "Mars is a totally foreign
environment to us. The rules are different."

"So that's what we're doing--trying to figure out the rules," he says. "And
then we can figure out how to play the game ... on both planets."

"Ron Baalke" wrote in message
...
http://science.nasa.gov/headlines/y2...riticalco2.htm

Harvesting Mars
NASA Science News
August 20, 2003

A NASA-supported scientist is learning how to use carbon dioxide--the main
gas in Mars' atmosphere--to harvest rocket fuel and water from the red
planet.

August 20, 2003: When astronauts first go to Mars, it'll be difficult for
them to bring everything they need to survive. Even the first tentative
explorations could last as long as two years--but spaceships can only
carry
a limited amount.

"We might have to do what explorers have done for ages: live off the
land,"
says chemical engineer Ken Debelak of Vanderbilt University.

Explorers on Earth could usually count on finding what they needed. The
animals might be strange, but they'd be there, and they'd be edible. Mars
is
barren. But the challenge is the same. Astronauts will want to pull what
they need from the planet itself. And although that goal seems improbable,
Debelak believes it can be achieved. He's working on a NASA project to
make
it happen. The key, he says, lies in the Martian atmosphere.

It's a meager atmosphere, compared to Earth's, and it's about 95 percent
carbon dioxide (CO2). But that turns out to be an advantage. The carbon
dioxide, says Debelak, can be used to harvest almost everything else.

Inside martian rocks and soil lies a bounty of useful elements: magnesium
and hydrogen for rocket fuel, oxygen to breath, water to drink. What's
needed is a solvent to get them out, and that's where the carbon dioxide
comes in handy.

"When CO2 is compressed to a pressure of 73 atm and heated to 31.1 degrees
Celsius, it becomes a supercritical fluid--and a marvelous solvent," says
Debelak.

A supercritical fluid is a high-pressure, high-temperature state of matter
perhaps best described as a liquid-like gas. Almost anything can become
supercritical. Water, for instance, becomes a supercritical fluid in the
high pressures and temperatures of steam turbines. Ordinary water is a
good
solvent. Supercritical water is a great solvent--maybe even a little too
good. It dissolves the tips of the turbine blades.

Supercritical carbon dioxide behaves much the same. CO2 molecules flow
into
solid matter, surrounding atoms, pulling them apart and away.

On Earth, supercritical CO2 is not used much to dissolve things because
there are less expensive, more effective solvents close at hand. It is,
however, used to remove the caffeine from coffee beans, and sometimes to
dry-clean clothes. On Mars, Debelak believes, supercritical CO2 will play
a
much more important role.

For example: Magnesium can be dissolved quite easily by supercritical CO2,
Debelak has found. "That's an experiment that we're quite excited about at
the moment," he says. Magnesium, which is likely to be found in martian
soil, ignites easily and can be used to fuel rockets. In fact, says
Debelak,
one Mars exploration scenario called for a lander to be made of
magnesium--"the legs and so on." When the astronauts were ready to go
home,
"you could chop it up, pack it into a rocket engine, and then add some
other
oxidizer to fire it off." Using CO2 as a solvent, magnesium could instead
be
harvested directly from Mars.

Supercritical CO2 might also be used to generate water. Certain martian
rocks (like some of Earth's rocks) contain hydrogen. When these rocks are
submerged in supercritical carbon dioxide, a chemical reaction takes
place.
The CO2's carbon becomes "fixed" in the rock, leaving the oxygen free to
find another partner: hydrogen. "The process kicks out water," marvels
Debelak. "You can actually use it to form water."

Pulling water from rocks will probably have the biggest payoff, at least
in
the short term, says Debelak. In addition to drinking, "you can split
water
into hydrogen for fuel, and oxygen for breathing--or as an oxidizer for
some
sort of engine." Eventually, colonists could set up plants that use CO2
from
the martian atmosphere to process hundreds of kilograms of raw material a
day.

A supercritical fluid has some advantages over other solvents: Its
solubility changes dramatically when you alter the temperature or the
pressure. You can control it, so that sometimes it's a solvent for a
particular substance, and sometimes it's not. That makes it easy to
recover
the material that has been dissolved. Let's say you have caffeine
dissolved
in supercritical carbon dioxide. To recover the caffeine (caffeine
recovered
from coffee beans is often put in soft drinks), you just lower the
pressure
of the CO2 and the caffeine drops out.

Currently, Debelak is trying to pin down the way a variety of substances
behave in supercritical CO2. He's looking at which minerals are easily
soluble and which are not. And if they're not, he's trying to determine
how
their solubility can be improved. Adding other substances to the CO2
sometimes helps, he says.

Debelak's work could be useful on Earth, too. Carbon dioxide is often
spotlighted because of its damaging role in global warming. But as a
solvent, it's benign. Many solvents common in industry are toxic. They
cause
cancer, and if they get into the water system, they stay for a long time.
So
there's interest, says Debelak, in learning how to use CO2 as a 'green'
alternative.

Carbon dioxide plays widely different roles on Earth and on Mars. "That's
what's intriguing," points out Debelak. "Mars is a totally foreign
environment to us. The rules are different."

"So that's what we're doing--trying to figure out the rules," he says.
"And
then we can figure out how to play the game ... on both planets."

Wouldn't it be easier to just 'boil' water out of the soil? AFAIK water on
Mars exists as ice crystals, right?

In article ,
Ultimate Buu wrote:
Wouldn't it be easier to just 'boil' water out of the soil? AFAIK water on
Mars exists as ice crystals, right?

Nobody knows.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

"Christopher M. Jones" wrote in message ...
Also, Henry's being a little coy. There's far too much
evidence that Mars holds a substantial quantity of water
ice on the surface near the poles and as perma frost in
the northern and southern regions (well, pretty much
anywhere but the equatorial region really) to give a shred
of credence to theories that it might be something other
than water ice.

Actually, he's not being coy. There's the "White Mars" theory, which
is that Mars never had much water. The canyons and such would be
carved out by debris flows supported by gaseous or liquid CO2 not
water. A key difference is that it would mean that the particular
erosion process still goes on at large scales rather than be an
artifact of ancient times.


Karl Hallowell

In article ,
Christopher M. Jones wrote:
Wouldn't it be easier to just 'boil' water out of the soil? AFAIK water on
Mars exists as ice crystals, right?
Nobody knows.

If it's water there are two possibilities. Hydrate minerals
and permafrost.

Two *known* possibilities; it's always conceivable that Mars is going to
throw us a curve of some kind.

Also note that all the observations are of hydrogen, not water, although
water is much the likeliest form for it to take.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

"Henry Spencer" wrote:
Christopher M. Jones wrote:
Wouldn't it be easier to just 'boil' water out of the soil? AFAIK water on
Mars exists as ice crystals, right?
Nobody knows.

If it's water there are two possibilities. Hydrate minerals
and permafrost.

Two *known* possibilities; it's always conceivable that Mars is going to
throw us a curve of some kind.

Yes, well, quite. I tend to write to a first order approximation
most of the time (as do most sane people). Hydrates and
permafrost are definitely the frontrunners by a long margin though.
I wouldn't rule out some super-bizarre thing nobody'd ever thought
of before (Mars has surprised us in the past and no doubt will
surprise us in the future) but I'm pretty comfortable that the
alternatives are very unlikely in this case.


Also note that all the observations are of hydrogen, not water, although
water is much the likeliest form for it to take.

Now this I really have to comment on, because I've noticed it
repeatedly from a lot of folks who should know better. There
is a lot of evidence for water on Mars, most of it indirect,
most of it not entirely conclusive, but there is a much larger
body of evidence than simply the Hydrogen findings from the
Mars Odyssey neutron spectrometer data. Certainly that data
is very indicative of high concentrations of Hydrogen just
below the Martian surface (or on it in some regions) spread
over a fairly large area. And that indication of the presence
of Hydrogen is in turn fairly highly indicative of the
presence of water (likely frozen) or perhaps hydrate minerals
(though the concentrations seem far too high to be completely
explainable by hydrate minerals). So we can be highly certain
of the presence of Hydrogen (the alternative in terms of
neutron scattering properties would be exceedingly strange
and is enormously less likely than Hydrogen, given what we know
of the laws of physics) and fairly confident about the presence
of water (at the concentrations detected it would be a stretch
to imagine something other than water, though for all we know
it might be methane, or hydrazine, or hydride salts, but
any of the most likely alternatives to water / hydrates are
all fairly highly unlikely). If you want to get really picky
about it, I'd say that just using the neutron data the
evidence is good enough to meet the "preponderance of the
evidence" threshold (i.e. as in most civil legal proceedings,
roughly meaning 50% certainty), but not the "reasonable doubt"
threshold (i.e. as in most criminal legal proceedings).

However, the neutron spectrometer data is not the end nor even
the beginning of the case for large quantities of H2O on Mars.
It is the best and most direct, certainly, but there is more.
There is a large body of evidence culminated from many different
observations and many different *types* of observations which
individually and collectively point toward large quantities of
Martian water (meaning, most likely, ice, most of the time, of
course). That data and those theories correspond very well with
the newest and most direct studies. Whereas, so far as I know,
most of the competing explanations are more individualistic
(of the sort like "this is how to explain this one phenomenon
without involving water"), have not been tested as thouroughly,
and do not "hang together" in the larger picture of Mars nearly as
well (as the water theories).

And that, I think, tips the scales in the case for Martian
water nearly to the level of beyond reasonable doubt. I
expect Daffy and Marvin will either tip the scales all the way
or tip them back the other way and cast doubt on previous
theories by a fair margin (I find it enormously unlikely that
they won't be able to gather enough evidence to tip the
balance one way or the other). Nevertheless, there's a lot
more to the case for Martian water than the detection of
Hydrogen.