How to really terraform (part 2)

Last week I discussed how we would start to terraform Mars. How will
we finish?

For me, I think that completion of terraforming means that (a)
conventional agriculture is possible over a sizable part of the
surface, and (b) that people can exist unprotected outdoors as on
Earth. The second goal is harder as it requires a suitable atmospheric
pressure and O2 content.

The big obstacle to (a) that I see is establishing proper soil
conditions. This is an area I know very little about. The inorganic
nutrients required are already there, I assume. It is likely that
importing soil from Earth will be a part of this, as well as
specifically targeted microorganisms.

The temperature is a concern also. Since we are discussing the
equatorial regions, which have fairly constant solar input throughout
the year, it is likely that the average temperature must reach 50 F
for plants to be protected from freezing. This is only 25 F cooler
than Earth is seems to be a large problem. The introduction of water
vapor, even with the positive feedback it will cause, is unlikely to
raise it above 0 F. Other common greenhouse gases are impossible - we
can not have much CO2 in a terrestrial environment, and CH4 and NH3
will not survive.

I have mentioned the decomposition of nitrates in order to give N2 and
O2. The oxygen is key; if we get enough O2 we will also have enough N2
for any plant life. According to the chemical formula:

2 NaNO3 + SiO2 + heat - Na2SiO3 + N2 + 5/2 O2

the ratio is 2:5. The minimum conditions for humans to breathe would
be about 225 mb at this mixture ratio (this is about 15,000 ft
equivalent). Let's assume we want this pressure at the average height
of Mars's surface (this is a rough calculation anyway). I'll use
figures from part 1.

We have 80 million trillion (8e19) cu ft of air. At 225 mb the density
is around 0.02 lb/ft^3. This gives a requirement of 1.6e18 lb N2 + O2,
or 2.2e18 lb NaNO3.
Is this a plausible amount to find? The surface area of the planet is
1,600 trillion sq ft, so the density needed is 1,350 lb/ft^2 -
roughly, a 10 ft thick layer spread over the entire planet.

An alternative frequently mentioned is to impact comets on Mars. It
will be very problematic, though, finding a suitable comet. It must be
short-period, and have an orbit that already passes close enough to
Mars's (Has one been identified?). I can't see how to overcome the
lack of oxygen, though. Comets will use up all the O2 in the air, and
I am rather sure that there are no O2 comets!

Ultimately, we need to go to Mars and see what is available. I have
always though an appropriate timescale should be 200 years from our
first landing on the planet.

If space developement is to go forward, we must have a goal that
requires an infrastructure to be built. Asteroid mining does not
appear to be enough on its own, or we would have started already. SPS
is a good goal, but the right people aren't interested yet. I believe
that terraforming is something that can be understood be everyone,
which will drive us forward to become a truly space-faring society.

If the space program lacks tangible benefits now, the only good answer
is to propose programs with tangible benefits. I say that over the
next few centuries, we ought to have these goals is space: to develope
asteroid resources, to substitute SPS for all our terrestrial power
needs, and to terraform Mars. While the first two can proceed
incrementally, terraforming would absolutely require central planning
and, therefore, be a government project.

Andrew Usher

Let me add some further thoughts.

I suspect the presence of large amounts of nitrates on Mars because
Mars must have started with an N2 atmosphere (thicker than Earth's,
because farther from the Sun). Lower gravity meant more was blasted
off by impacts but likely not enough to reduce N2 to today's levels
(0.2 mb - about 0.01% of original.)

Nitrates are the stable form of N2 in oxidising, alkaline
environments. Mars is certainly oxidising, and is/was probably
alkaline due to weathering (CO2 can't change this). In fact, Earth
only has N2 in the air due to denitrifying bacteria; otherwise it
would exist as nitrates, probably dissolved in the ocean. Remember
'all nitrates are soluble'.

Despite my dismissals, we will surely have too much CO2 in the
atmosphere. If we can't get enough O2 from nitrates, then it becomes
necessary to impact comets, generating more CO2 and using up O2.
Biological processes are the best means we know of converting CO2 into
O2, but that requires sequestration of carbon. Is that possible in
anything less than geologic time? There must be some way we can
accelerate the process.

Mars is certainly oxidising, and is/was probably
alkaline due to weathering (CO2 can't change this). In fact, Earth
only has N2 in the air due to denitrifying bacteria; otherwise it
would exist as nitrates, probably dissolved in the ocean.

Hmmm... without bacterial and plant life, there would be no O2 either. So
without biological action, Earth would have no atmosphere? And then, would
there *be* an ocean?

impact comets, generating more CO2 and using up O2.
Biological processes are the best means we know of converting CO2 into
O2, but that requires sequestration of carbon.

Which is precisely what is needed to generate soil.

Is that possible in
anything less than geologic time? There must be some way we can
accelerate the process.

We might be able to go from geological to "historical" time processes, by
high-energy means (ie solar or atomic heating of surface oxides to produce
O2), but most probably not to "human time." The system is question is just too
big.

"G EddieA95" wrote in message
...

In fact, Earth
only has N2 in the air due to denitrifying bacteria; otherwise it
would exist as nitrates, probably dissolved in the ocean.

Hmmm... without bacterial and plant life, there would be no O2 either. So
without biological action, Earth would have no atmosphere?

Only an exceedingly thin CO2 atmosphere. Sound familiar?

--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"

plant life, there would be no O2 either. So
without biological action, Earth would have no atmosphere?

Only an exceedingly thin CO2 atmosphere. Sound familiar?

So what happened on Venus? (or Titan for that matter?)

Mike Combs wrote:

"G EddieA95" wrote in message
...

In fact, Earth
only has N2 in the air due to denitrifying bacteria; otherwise it
would exist as nitrates, probably dissolved in the ocean.

Hmmm... without bacterial and plant life, there would be no O2 either. So
without biological action, Earth would have no atmosphere?

Only an exceedingly thin CO2 atmosphere. Sound familiar?


Well, no. Eartyh without life would not resemble Mars, it would resemble
some form of derivative from early earth atmosphere. The mass of atmosphere
has not increased due to life, if anything, the reverse.

--
Sander

+++ Out of cheese error +++

(G EddieA95) wrote in message ...
impact comets, generating more CO2 and using up O2.
Biological processes are the best means we know of converting CO2 into
O2, but that requires sequestration of carbon.

Which is precisely what is needed to generate soil.

The C content of th emartian atmosphere is around a ton per sq ft,
that's an awful lot of soil! There must be some other reservoir of
carbon.

Is that possible in
anything less than geologic time? There must be some way we can
accelerate the process.

We might be able to go from geological to "historical" time processes, by
high-energy means (ie solar or atomic heating of surface oxides to produce
O2), but most probably not to "human time." The system is question is just too
big.

I was thinking simply of introducing C-fixing bacteria but no
decomposing bacteria. However, it's likely that we'd accidentally
introduce decomposers (contamination) anyhow.

As far as time scale, I have in mind the figure of 200 years from
start to finish.

Andrew Usher

In these threads, I and other posters have made the assumption that
comets could be impacted onto Mars that would significantly affect its
atmmosphere. This seems to be in error.

Let's calculate that size of the comet required. Using the figures I
gave before, if the comet is 10% CO2 (very high) its mass must be 16
million trillion lb. At a density of 0.8 (50 lb/ft^3), this is 320,000
trillion cu ft, or a diameter of
850,000 ft = 260 km. We don't even know any comets this size, let
alone on a proper orbit. In fact it's unlikely that the masses of all
known comets even sum up to that total.

This idea ought to be abandoned for now and brought back only if we
are absolutely sure that there are not enough nitrates and CO2 on Mars
to get a breathable atmosphere.

Sander Vesik wrote in message ...
Mike Combs wrote:

"G EddieA95" wrote in message
...

In fact, Earth
only has N2 in the air due to denitrifying bacteria; otherwise it
would exist as nitrates, probably dissolved in the ocean.

Hmmm... without bacterial and plant life, there would be no O2 either. So
without biological action, Earth would have no atmosphere?

Only an exceedingly thin CO2 atmosphere. Sound familiar?


Well, no. Eartyh without life would not resemble Mars, it would resemble
some form of derivative from early earth atmosphere. The mass of atmosphere
has not increased due to life, if anything, the reverse.

Could you provide evidence for this assertion? What would be the
composition of your atmosphere?

Andrew Usher