Make the required conditions. There are several

Make Mars
Great Again OR –  The thermodynamics of
terraforming Mars

 

Mars
is one of the smallest planets of our solar system (2nd smallest to be precise,
after mercury). This “red” planet (in lieu of its iron oxide soil) is distinctly
visible by the human eye on a clear night sky. Despite having current
conditions that make it uninhabitable for the foreseeable future (at least the
next century or so), it does fall in what’s called the “goldilocks” zone of the sun’s radius – meaning that it
does (or did) have the potential to host or sustain living organisms at one
point. However currently, due to it being far away from the sun, having only a
thin atmosphere, and no molten core (so no global magnetic field either), makes
it a very challenging planet to inhabit. The term paper looks at a few possible
solutions that look at how (theoretically) the climate of Mars can be
terraformed into something that’s bare-bones and just necessary to
sustain long-term human life. Broad (yet necessary) assumptions have been made
(they will be mentioned later), as well as several ethics-centered questions
have been ignored, mainly since that is not the focus for the paper. The
concepts covered that can theoretically aid in terraforming Mars can be broadly
divided into two main categories; The first one is tweaking conditions for
water to be stable on the surface of the planet – which can be done in ~100 years, while
the second one involves setting up an entire biosphere on the planet – which would
definitely take much longer (2 factors more to be precise) ~ 100k years.

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Terraforming
Mars became a popular topic recently when eccentric billionaire Elon Musk
proposed “Nuking the CO2 poles” of Mars to dramatically increase the
Carbon Dioxide content on the planet, as well as raise temperatures in order to
make earth-like life more sustainable on that planet. Although this wild theory
raises a host of new questions, the term paper covers a less melodramatic,
slightly more viable option of using super-greenhouse gasses and other methods
to gradually thicken the atmosphere and raise the temperature to the required
conditions.

There
are several popular methods proposed to bring about such a change, each with
their own merits and imperfections – such as large solar mirrors,
self-replicating systems (SRS), artificial greenhouse production, and kinetic
impacting. Although they will be briefly covered, the underlying point between
all these methods is that the end goal, as well as the thermodynamics remains
unchanged. Novel techniques, like changing the reflectivity of the surface can
also be used to accelerate the heating process.

The
next section covers the underlying conditions of temperature and pressure
required for the 1st phase of planet terraforming to be possible. First,
we look at existing temperature and pressure conditions on Mars and how they
compare to earth’s.

 

PICTURE

 

Although
there are several other key requirements in planetary terraforming – like
atmospheric composition, carbon/oxygen and nitrogen cycles, and magnetic
fields, we focus on the two essential ones – Surface temperature and
atmospheric pressure. The term paper covers the first phase of terraforming,
such that ideally, humans can exist on the surface while wearing an oxygen
mask. There are 3 key ways at increasing the temperature of the planet, and all
of them take advantage of the greenhouse gas phenomenon of global warming:

1.    
Importing
greenhouse gasses like ammonia and methane from volatile-rich space objects
like asteroids by colliding them with the Martian surface

2.    
Producing
“Super”
Cloroflourocarbons via factories on the martian surface

3.    
Use
orbital mirrors or similar heat sources to selectively warm parts of the
planet.

The
key similarities between these methods is that the currently existing resources
(mainly water and CO2) on Mars can be used to accelerate the process. There is
an abundance of CO2 frozen on the ice caps, and research also indicates CO2
stored in the Martian Regolith (bedrock) in the form of carbonates. Since
global warming has a built-in, self-induced positive feedback system, the
warmer the temperature gets, the thicker the atmosphere gets, and vice versa.

This indicates that although the initially required energy may be large, it
would only be a one-time thing dude to the positive feedback loop.  

Looking
at extreme conditions on Earth where humans have been surviving for a while, it
is seen that humans have been surviving in the high-altitude, mountainous Tibet
region, with an atmospheric pressure of ~55kPa. Hence the preliminary goal
would be to increase Mars’ atmospheric pressure (currently 0.6 KPa) to at least this
point.

Another
important condition for this “Phase 1” terraforming is the existence of liquid
water on the surface. There is a lot of evidence pointing towards the existence
of frozen water on Mars (NASA has evidence of liquid water flowing too). Looking
at the Phase Diagram of water (figure below), we can see the different
conditions faced by Mars (M) and Earth (E). Mars lies very close to the triple
point of water; for water to flow at the minimal 55kPa, the ambient temperature
must be above 274K.

PICT

 

The
first significant source of atmospheric pressure is Mars’ Southern Polar
Cap. It has been estimated that by sublimating the ice caps, and essentially
releasing the frozen CO2, an increase of atmospheric pressure by 9-10 kPa can
occur. Models that plot the surface temperature of the planet (Zubrin and
McKay) have been graphically represented below:

 

PICT

 

Although
polar caps do provide a significant amount of vapor pressure, it clearly falls
short by almost 45kPa from required conditions. Another significant source of
CO2 mentioned before was embedded in the Mars Regolith. Volatile solids are one
of the most efficient way of increasing pressure, while importing them from
earth is quite impractical because of sheer size and volume constraints.

Abundant deposits in the bedrock can be thus harvested to augment the CO2
content in the atmosphere. Luckily the only way to access these resources is
after the caps have been melted, so this essentially becomes a 2-step process.

Estimates for regolith contribution to vapor pressures range from 44kPa in the
conservative end, to 89.4 kPa at the other end. Both these cases can satisfy
required conditions of pressure.

The
McKay model approximates the range of temperatures on Mars using the following
set of equations:

            Tmean = S^0.25xTBB +
20(1+S)P^0.5 (Eq.1)            

            Tpole = Tmean – DT/(1 + 5P) (Eq. 2)

            Tmax = Tequator =
1.1Tmean (Eq.

3)

            T(q) = Tmax – (Tmax-Tpole)sin^1.5q (Eq.4)

Where
Tmean = blah nlah lfknlkn;lef ;lkmevklmwrfv klrelkvm;lke

This
leads to the relationship between the Vapor Pressure of CO2 and the Temperature
of the Poles – P = 1.23 x 10^7{exp(-3168/Tpole)}  (EQN 5)

Hence
the CO2 Pressure on Mars is a direct function of it’s temperature.

However if the Polar Temperature rises to a point when the Vapor pressure is
greater than Ice Cap production, then the atmospheric pressure will be
regulated by the solid volatiles in the regolith.

By
graphing polar temperature as a function of pressure, and vapor pressure as a function
of Polar Temperature, it is seen that there are two distinct points where P,T
values coincide – A and B. A represents stable equilibrium, and the current
mars condition (6mbar, 147K at poles). Whereas B represents unstable
equilibrium. According to the model, whenever the temperature curve lies above
the vapor pressure curve, the system will move to the right, i.e. towards
increased temperature and pressure; this would represent a runaway greenhouse
effect. Whenever the pressure curve lies above the temperature curve, the
system will move to the left, i.e. a temperatures and pressure will both drop
in a runaway icebox icebox effect.

 

By
increasing the temperature by even 4 K, the points A and B coincide, giving
rise to a runaway greenhouse effect that would evaporate the poles. Once these
conditions escalate to beyond point B, artificial heating wouldn’t be required at
all since the process would be self-regulated.

The
equation as estimated by McKay, that relates the regolith, atmosphere and
temperature is as follows:

P = {CMaexp(T/Td)}1/g (6)

 

This
is a modification of the Van’t Hoff equation, that relates change in
Chemical Equilibrium to temperature. Td here represents the heat required to
release volatiles from the soil. Although that value is uncertain, even
conservative (or “poor”) estimates show that a moderate increase in CO2 pressure of
around 30kPa can take place for Td= (20°-25°C). This can cause the temperature
to rise to 285K. By looking at the previous model that covers the greenhouse
effect of Martian Polar CO2, we see that the subsequent temperature increase is
beneficial to the greenhouse warming of the planet. However, if we assume the
conservative estimates to be true, it is clear that despite releasing solid
volatiles from the bedrock, the atmosphere pressure increase still falls short
by a few kPa. Furthermore, there are problems associated with completely
ridding the soil from it’s constituent volatiles; If the temperature increases beyond
a certain extent, instead of releasing volatiles, the regolith acts as a “dry sponge”, and contrastingly
absorbs the volatiles.

 

Calculating
energy needs of melting Mars’ poles:

Based
on previous data, we see that a 4K increase in temperature is favorable, as
this pushed the self-regulating warming system. Using the first and second laws
of thermodynamucss, we get:

Blah
BLha Blahodjneafljnce rg

It
is seen that the amount of energy required to completely melt the ice caps on
Mars’
poles is of the order fjnjwfn. To put this in context, it would take
approximately 5000 modern nukes to achieve such a feat. This might indicate
that although theoretically possible, we may not have the resources to send
such a large number of warheads to achieve something that the sun can do in a
somewhat longer time; The heat Mars absrorbs from the sun every year is ~ onf.

This indicates that the sun will have a major role in sustaining the greenhouse
heating process. This also questions the legitimacy of Elon Musk’s dramatic
statements about fast-forwarding the  

 

However,
in terms of solid volatiles required to increase the pressure, the story is
still unfinished. If conservative estimates are correct, then there is a need
to import volatiles from outside. Approximately 15kPa of pressure is still
required. Transporting volatiles from earth is highly impractical because of
volume constraints. Hence the best remaining option is finding a large mass
body in space containing several volatiles and trying to collide it with the
Red Planet. According to Mckaay and Zubrin, something like that is possible
even using technology available today. By directing a nuclear warhead to a deep
space asteroid, one can (via using gravity assists and the explosion exlenfl
efnlwkfnc ) gradually change the orbit of said asteroid to crash on Mars. If
the mass is sufficient enough, not only will the asteroid add the required number
of volatiles for regulating surface pressure, but the resultant collision would
also increase ambient temperature by several degrees. The uncertainty involved
in this process is twofold; One must find a potential candidate that is close
enough (<12 AU) that is also small enough to be manipulated using orbital mechanics, while at the same time must be possessing enough volatiles/mass to raise pressure to the required levels. Assuming something like an ammonia asteroid with a large enough mass (calculated Sourceoijtonfevlkn to be at least 2.6 kms in diameter) is available in the vicinity of our solar system, one can theoretically use a couple of 5000 MW nuclear powered rockets to coerce it into a collisionary orbit. The resultant collision could be strong enough to raise ambient temperatures by 3K, and the resultant release of ammonia would provide a protective atmospheric layer against UV radiation. The upsides of this process are that multiple collisions can highly accelerate the process of raising temperatures and pressures. The composition of the colliding object can also be chosen, and made to collide with specific sections of bedrock to increase the nitrogen content of the atmosphere; it is equally important to have a large amount of "neutral" gas in the atmosphere to keep the toxicity in check, as well as have the potential to make the air breathable (also too much oxygen in the environment is harmful too). However key issues with this process is the sheer uncertainty of finding objects in space that might satisfy the criteria for a viable object of collision. Furthermore, the frequency of several asteroid collisions will be detrimental to the planet. There's also the off chence of dissociation of NH# into lighter molecules like N2 and H2 which may simply escape to space. However theoretical this model may be, it serves as a benchmark for other, slightly more practical methods.

Another
viable technique involves setting up factories on the martian surface that
produce Super greenhouse gasses – like CFCs, that are nearly an order of
magnitude more efficient than CO2 at trapping heat (and hence only small
quantities are required). Studies have shown (also illustrated in the table)
that in order to have a 5K increase in temperature, a factory having the power
capacity of 1315MWe needs to be set up on the surface. For reference, a typical
nuclear power plant has a capacity of 1000MWe; implying that technology for
such a scale of production exists. The challenges faced with this method
include finding compatible gasses that aren’t toxic, nor do they eat at the ozone/UV
protection layer. Hence Chlorine and Bromine (destroy ozone) aren’t to be used.

Potential candidates include PFC’s and SF6

Another
planetary factor that can help with initial settlement is the pressure exerted
by the coulmn of atmosphere above a low elevation region. The equation shows
that pressure scales with height, and hence valleys, basins and depressions
would be the ideal places to inhabit at first.

 

Phase
1 of planetarly terraforming has several approaches to take, ranging from
shining large mirrors on the ice caps for them to melt, to asteroid collisions,
to setting up in-situ CFC factories on the surface to increase the pressure and
temperature beyond the “tipping point”/unstable equilibrium of the planet’s climate,
enabling the “planet” to take care of the
thermodynamics without additional energy input. The best approach so far would be
several combinations of the previous ones. At the end of phase 1, the climate
on mars should be stable enough for humans to survive on the surface with
oxygen masks and no pressure suits. In fact these conditions can be ideal for
hardy plants and vegetation to thrive.

Stage 2
involves making the biosphere of the planet sustainable for breathing. This
process is much longer in terms of time and energy expenditure. There are
several approaches to this too, including using the planet’s resoureces for
other gaseous matter – like Nitrogen, Oxygen, and water vapour, to adjust the
ambient composition to something that’s similar on modern day earth. Other
ideas include Introducing hardy plants that replenish soil with more
Nitrogen-rich nutrients,

 

The ethics of
planetary terraforming are always questionable- what this does essentially is
completely destroy the history of the planet. Carrying forward with sucha plan
may even remove evidence of possibnle prevous existing life on mars. However
thie paper is meant to focus on whether such a process is thermodynamically
viable. There are several factors