1
Extending the Artificial Habitability Zone to Pluto?
Payton E. Pearson III
B.S. Electrical Engineering, 1LT USAF
Offutt Air Force Base
payton.pearson.1@us.af.mil
Abstract—This paper—the second in a series of papers expanding
upon this topic—seeks to show how the habitability of various
celestial bodies throughout the universe can be engineered,
nearly regardless of distance from the host star. An atmosphere
is hypothetically engineered and shown to be theoretically viable
on the dwarf planet, Pluto. This hypothetical atmosphere is
engineered to be 280 Kelvin at the surface of Pluto, with half the
atmospheric pressure of Earth’s surface (~506 mbar). Nothing
else is significantly changed; though an explanation of possible
modification of orbital dynamics is posited, placing Pluto in a
390,000 kilometre orbit around a previously designed
hypothetical planet, PH. This paper will refer back to the
original artificial habitability paper for certain ideas. As with
the last paper, the hope in creating this series is to galvanize the
interest of prospective scientists, and stimulate discussion on the
matter of astrogeophysical engineering.
Keywords— Pluto, magnetosphere, habitability zone,
equilibrium temperature, hypsometric equation, Universal Law
of Gravitation, solar flux, atmosphere, atmospheric mass,
sputtering, orbital dynamics.
I. INTRODUCTION
So, what is it that makes a celestial body naturally habitable?
Of course, temperature is a key factor in that the surface
temperatures of a celestial body must be adequate to support
complex life in some form. Also, atmospheric pressure at the
surface is vital, because most organisms require some form of
inward pressure in order to sustain physiological equilibrium.
In addition to this, metabolism requires some form of
sustenance from an atmosphere to allow for more complex life
to eventually develop. Once more, the lowest trophic levels of
life on Earth oftentimes utilize some form of photosynthesis
for metabolic purposes as well, though some extremophiles
have been known to utilize chemical processes of Earth
instead.
Nevertheless, taking into consideration these basic
components to developing complex life on a celestial body,
the dwarf planet Pluto, which orbits the Sun at a variable
distance between 4 and 7 billion kilometres depending on
whether it is at apogee or perigee, the notion of rendering such
a distant, cold, dark celestial body habitable sounds absurd.
This paper will show that it may not be as absurd as some
think.
II. BASIC PARAMETERS OF PLUTO
The dwarf planet Pluto is an icy world that orbits the Sun at
a maximum distance of 7.311 billion kilometres and a
minimum distance of 4.437 billion kilometres. This large
variation in distance of Pluto leads to equitably large
variations in surface temperature. The surface temperature of
Pluto can be derived using the equilibrium temperature
equation, assuming that Pluto is currently in temperature
equilibrium [1].
4
𝐿 (1−𝛼)
𝑇𝑒𝑞 = √ ° 2
16𝜋𝜎𝑅
(1)
𝐴𝑈
Where Lo is solar luminosity (3.839x1026 watts), 𝛼 is the
albedo of the celestial body in question, 𝜎 is the StefanBoltzmann constant (5.670373x10-8 w/m2K4), and RAU is the
distance in meters from the Sun of the celestial body. Using
Pluto’s minimum distance from the Sun and its albedo of 0.55,
Pluto’s surface temperature reaches a maximum of:
4 (3.839𝑥1026 𝑊)(1 − 0.55)
4 𝐿° (1 − 𝛼)
𝑇𝑒𝑞 = √
=√
2
16𝜋𝜎([4.437𝑥1012 𝑚]2 )
16𝜋𝑅𝐴𝑈
= 41.8883 𝐾𝑒𝑙𝑣𝑖𝑛
The same calculation used with Pluto’s maximum
distance from the Sun reveals a minimum surface
temperature of Pluto of 32.6324 Kelvin. This implies a
temperature variation of 41.8883 – 32.6324 = 9.2559 Kelvin,
or approximately 16.66 degrees Fahrenheit. This means
that while there would be significant swings in the average
surface temperature of Pluto, these swings would not be so
drastic as to render Pluto completely uninhabitable. So far,
in Earth’s astronomers’ relatively limited understanding of
the universe, exoplanets have been discovered that have
temperature swings of several thousands of degrees
Fahrenheit, going from -150 degrees to 850 degrees
Fahrenheit over the course of 30 months [2]. Earth
experiences relatively constant temperatures, as its closest
approach to the Sun puts it just shy of 92 million miles away,
and its farthest distance puts Earth at about 95 million miles
away from the Sun. This stability is a major contributing
factor to the development of the complex ecosystems
present on Earth today.
But a 16.66 degree variation is not unacceptable,
especially considering that humanity will have the ability to
engineer the biosphere of Pluto from scratch. Seeing as how
this is the case, temperature variations will nevertheless be a
crucial component to understand in order to attain
environmental stability.
2
Another important component to the engineering of
Pluto’s atmosphere is the extremely low gravity when
compared to Earth. Pluto has a gravitational acceleration at
its surface of 0.658 m/s2. This is a mere 6.71% of the
gravitational acceleration at the surface of Earth. With such
a low gravitational acceleration, a proposed atmosphere for
Pluto of any significant mass would be exceptionally
distended compared to that of the Earth. These calculations
will be elaborated upon later in this paper. But beyond this,
there comes the issue of atmospheric sputtering due to solar
wind, a mechanism that caused the atmosphere of Mars to
dissipate from approximately the same surface pressure of
Earth to what it is today over the course of 10 million years
[3].
The design parameters that Pluto will be engineered to
have are as follows:
Atmospheric Pressure of PH = 0.506 bar
Desired Average Surface Temperature = 280 Kelvin
No other bulk parameters of Pluto will be changed for the
purposes of this design.
Fig. 1 This is an artist’s interpretation of how the surface of Pluto might look
currently. This would change drastically with the introduction of a liveable
atmosphere.
III. PRODUCING THE ATMOSPHERE FOR PLUTO
The most difficult hurdle to overcome when producing an
atmosphere for the dwarf planet is the extremely low gravity
at the surface. This would cause any atmosphere that would
be produced to be exceptionally distended and possibly
unstable, perhaps becoming several dozens of times the height
of that of Earth’s atmosphere as defined by the Karman Line.
This is evidenced through the fact that Pluto’s atmospheric
scale height is much greater than Earth. It is calculated as
follows [4]:
ℎ𝑠𝑐𝑎𝑙𝑒 =
𝑘𝑇
𝑚𝑔
(2)
Where k is the Boltzmann constant (1.38x10 -23 J/K), T is
average surface temperature in Kelvin, m is average mass of
the atmosphere in kg of atoms, and g is the gravitational
acceleration at the surface. Pluto’s atmosphere would more
than likely be composed of very similar elements to that of the
Earth. This is because the surface of Pluto is comprised in
large part of water ice as well as N 2 ice. This greatly
simplifies the equations of the atmospheric scale height, as the
same atmospheric mass per particle that is used for Earth can
be assumed for Pluto [4]. In this case, the atmospheric mass
per particle is 4.76x10-26 kg [4]. An average surface
temperature of 36 Kelvin will be used for this hypothetical
example.
ℎ𝑠𝑐𝑎𝑙𝑒 =
𝑘𝑇
(1.38𝑥10−23 𝐽/deg)(36 𝐾)
=
= 15.886 𝑘𝑚
𝑚𝑔 (4.76𝑥10−26 𝑘𝑔)(0.658 𝑚/𝑠 2 )
Compare this to a scale height for Earth’s atmosphere of
roughly 8.7 kilometres. This may not seem like a very drastic
difference, but this alone can cause the atmosphere to be
roughly 1.826 times as distended, for an atmospheric
thickness of 182.6 kilometres based upon the Karman Line of
Earth. This approaches 16% of the overall radius of Pluto.
Once more, this does not even take into consideration the fact
that this design is intended to increase the average surface
temperature of Pluto to 280 Kelvin. As such, the scale height
of such an atmosphere would be 123.6 kilometres. This
would potentially increase the thickness of a Plutonian
atmosphere to 1421 kilometres, or roughly 120% the radius of
Pluto itself.
As can be seen clearly, this would produce an atmosphere
that is utterly gigantic by comparison to the size of Pluto. But
is this truly a problem? Before this question can be answered,
a more accurate estimate of the thickness of Pluto’s
atmosphere must be found. We will use the hypsometric
equation under the engineering assumptions of temperature
and surface pressure to find the overall thickness of the
atmosphere. The hypsometric equation is as follows [4]:
ℎ𝑎𝑡𝑚 =
𝑅∙𝑇̅
𝑔
𝑃
∙ ln ( 1)
𝑃2
(3)
Where R is the specific gas constant of the atmosphere.
Assuming it is identical to the Earth, it is 287.058 J/kgK. 𝑇̅ is
the mean temperature of a specified atmospheric layer. As
was done in a previous paper [5], we will use the Earth’s
atmospheric temperature profile in order to find the
temperatures of the respective layers of Pluto’s hypothetical
atmosphere. Also, g is the gravitational acceleration of the
celestial body with respect to distance above the surface. P1
and P2 are the pressures at the top and the bottom of the layer
of atmosphere in question.
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layer in question, the temperatures of each layer of
atmosphere using the average area theorem are [6]
ℎ1 , 506 𝑡𝑜 82.552 𝑚𝑏𝑎𝑟 ∶
Fig. 2 Earth’s temperature and composition profile as a function of elevation
above sea level. As can be seen clearly, the temperature profile does not
follow a simple, linear path, but instead is a conglomeration of discrete
functions.
It is important to note that if Pluto were heated up to
terrestrial temperatures, it would likely take the form of a
giant water ball, also known as a water world. This is because
a large proportion of the overall mass of Pluto is in fact
comprised of water ice, in particular the surface and upper
mantle. Once more, a significant layer of frozen nitrogen lies
on the very topmost portion of Pluto’s icy crust. The
ramifications of the presence of this nitrogen ice will be
elaborated upon later.
280 𝐾 + 210 𝐾
= 𝑇̅1 = 245 𝐾
2
ℎ2 , 82.552 𝑡𝑜 43.933 𝑚𝑏𝑎𝑟 ∶
210 𝐾 + 210 𝐾
= 𝑇̅2 = 210 𝐾
2
ℎ3 , 43.933 𝑡𝑜 5.0412 𝑚𝑏𝑎𝑟 ∶
210 𝐾 + 216 𝐾
= 𝑇̅3 = 213 𝐾
2
ℎ4 , 5.0412 𝑡𝑜 0.3797 𝑚𝑏𝑎𝑟 ∶
216 𝐾 + 262 𝐾
= 𝑇̅4 = 239 𝐾
2
ℎ5 , 0.3797 𝑡𝑜 0.1533 𝑚𝑏𝑎𝑟 ∶
262 𝐾 + 242 𝐾
= 𝑇̅5 = 252 𝐾
2
As was done in the previous paper in this series [5], the
termination point of Pluto’s atmosphere is based upon the
pressure at Earth’s Karman Line, not upon the derived
Karman Line of Pluto itself, which would be much higher.
Other methods can easily be proposed, but this method proves
to be adequate for the endeavour, and simplest. The
atmospheric temperature profile is thus as follows:
Layer
H1
H2
H3
H4
H5
P1 (mbar)
506.000
82.552
43.933
5.0412
0.3797
P2 (mbar)
82.552
43.933
5.0412
0.3797
0.1533
Tmean (K)
245
210
213
239
252
Table 1 This is a more organized view of the mean temperatures with respect
to the pressure layers. It is important to note that with a much lower
equilibrium temperature, the drop off in temperatures past the troposphere
would likely be much more dramatic. It must be emphasized that this is
merely an engineering approximation.
To lend credibility to this
approximation however, Titan does not experience such an exponential dropoff in temperature with respect to height until far beyond the Karman Line [7].
Now that the mean temperatures of each atmospheric layer
have been found, we can find the thickness of each layer as
follows:
ℎ𝑎𝑡𝑚 =
Fig. 3 This figure shows the dwarf planet Pluto with an engineered
atmosphere around it. The distention of 1660 kilometres will be explained
shortly.
The total height of the atmosphere will be the addition of
several discrete atmospheric layers. The thickness of the
atmosphere will thus take the following form:
ℎ𝑡𝑜𝑡 = ℎ1 + ℎ2 + ℎ3 + ⋯ + ℎ𝑛
(4)
Assuming that one half the proportional pressure of the
Plutonian atmosphere corresponds to the atmospheric pressure
of the Earth’s atmosphere with respect to the atmospheric
𝑅 ∙ 𝑇̅
𝑃1
∙ ln ( ) → ℎ1
𝑔
𝑃2
𝐽
∙ 𝐾) ∙ (245𝑘)
506
𝑘𝑔
ln (
)
82.552
0.658 𝑚⁄𝑠 2
(287.058
=
= 194,191.6793 𝑚𝑒𝑡𝑟𝑒𝑠
This will be done for each respective atmospheric layer. It
is very important to note, however, that the gravitational pull
experienced upon each atmospheric layer is significantly
different. Thus, the gravitational pull will need to be
recalculated for every layer. Rather than integrating over the
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entirety of the distention of the atmosphere, a simple
recalculation of the gravitational pull at the top of each
atmospheric layer will be accomplished for simplicity
purposes.
Calculating the gravitational pull of Pluto with respect to
height above the surface is done as follows [8]:
𝐹1,2 = 𝐺
𝑀1 𝑀2
(5)
𝑟2
Where F1,2 is the force between two bodies of mass (M1 and
M2), G is the gravitational constant (6.67384x10 -11 m3/kg s2),
and r2 is the distance between the two bodies from each
respective centre of mass. In the instance of a single celestial
body, r2 is simply the radius of the planet itself plus the height
above the surface. In addition, if M2 is of small enough mass,
it can be omitted, and an approximation of the force due to
gravity of Pluto can be found using the equation:
𝐹𝐺,𝑃𝑙𝑢𝑡𝑜+ℎ = 𝐺
𝑀𝑃𝑙𝑢𝑡𝑜
(6)
(𝑟+ℎ)2
𝑃𝑙𝑢𝑡𝑜
3
= (6.67384𝑥10−11 𝑚 ⁄𝑘𝑔 ∙ 𝑠 2 )
(1.305𝑥1022 𝑘𝑔)
∙
([1.0𝑥107 𝑚] + [1.941916793𝑥103 𝑚])2
= 0.4547 𝑚⁄𝑠 2
Thickness (m)
H1
H2
H3
H4
H5
Htot
194,191.679
83,622.610
324,856.529
633,997.100
421,219.800
1,657.890 km
𝐵∝
1
Gravitational
Pull (m/s2)
0.658
0.4547
0.4075
0.2706
0.1477
N/A
Table 2 This table is an organized form of the above equation iterated over
each pressure interval using the Universal Law of Gravitation to recalculate
the gravitational pull at each height.
This atmosphere is absolutely gigantic, roughly 1.4 times
the actual radius of Pluto itself. However, even with this very
large atmosphere, there is nothing preventing it from being
sustainable, as will be illustrated. In addition, the current
estimates for the upper limits of the atmosphere that Pluto
already has indicate that it is well over 1200 kilometres above
the Plutonian surface [9].
(7)
𝑑3
Using the planet Mars as a rough guide of atmospheric
sputtering, we can determine how long it would take to sputter
away an engineered atmosphere from Pluto. During the epoch
when Mars had a significant atmosphere, it is assumed that
Mars’ atmosphere was roughly equivalent to 1 bar of pressure,
or very nearly the surface pressure of the Earth [11]. Despite
this, once the dynamo of Mars dissipated, it took a mere 10
million years to dissipate the atmosphere from Mars [12].
Using the atmospheric mass equation, the rate of atmospheric
sputtering can be derived [4].
𝑚𝑎𝑡𝑚 =
As can be seen, this is significantly different from the
gravitational pull at the surface of Pluto, 30.89% less to be
more precise. This will significantly increase the overall size
of Pluto’s atmosphere. The table below shows the overall
thickness of Pluto’s atmosphere:
Layer
IV. THE EFFECTS OF SPUTTERING ON A PLUTONIAN
ATMOSPHERE
The primary issue with developing such a humongous
atmosphere around the dwarf planet Pluto has to do with the
sputtering effects generated by the Sun as well as other
celestial bodies with significant magnetic fields. However,
Pluto is roughly 39.2 times as far away from the sun as the
Earth, indicating that the magnetic field of the Sun is 60,532
times weaker because magnetic field strength is inversely
proportional to the cubed distance from a specific frame of
reference [10].
4𝜋𝑎2 𝑃𝑠
(8)
𝑔
Where a is the radius of the celestial body, Ps is the surface
pressure of the atmosphere, and g is the gravitational pull of
the celestial body at the surface. As such, the atmospheric
mass of Pluto, and that of a proto-Mars for approximation
purposes is
𝑚𝑎𝑡𝑚,𝑃𝑙𝑢𝑡𝑜 =
4𝜋(1.184𝑥106 𝑚)2 (50,600 𝑃𝑎)
(0.658 𝑚⁄𝑠 2 )
= 1.3547𝑥1018 𝑘𝑔
𝑚𝑎𝑡𝑚,𝑀𝑎𝑟𝑠 =
4𝜋(3.396𝑥106 𝑚)2 (101,300 𝑃𝑎)
(3.711 𝑚⁄𝑠 2 )
= 3.9561𝑥1018 𝑘𝑔
With Mars’ atmosphere having dissipated down to a mere
2.3432x1016 kg mass over the course of 10 million years, this
means that Mars’ atmospheric loss rate was approximately
3.9561𝑥1018 𝑘𝑔 − 2.3432𝑥1016 𝑘𝑔 =
3.9327𝑥1018 𝑘𝑔
10 𝑚𝑖𝑙𝑙𝑖𝑜𝑛 𝑦𝑟𝑠
= 12,470.41 𝑘𝑔/𝑠𝑒𝑐𝑜𝑛𝑑
Based upon this rate alone, it would take roughly 3.447
million years for the engineered Plutonian atmosphere to
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dissipate. However, as gravitational pull decreases, the effects
of sputtering are amplified. Also, as distance from the Sun
increases, sputtering effects are decreased due to a decrease in
solar magnetic field strength. As such, the gravitational pull
at the top of the hypothetical Plutonian atmosphere will be
used for the most conservative estimate of dissipation rate.
Since the dissipation rate is a three-dimensional effect, the
effect of sputtering will be cubed.
𝑅𝑠𝑝𝑢𝑡𝑡𝑒𝑟 = (
𝑅𝑠𝑝𝑢𝑡𝑡𝑒𝑟
𝑔𝑀𝑎𝑟𝑠 3
𝑔𝑃𝑙𝑢𝑡𝑜
)
(9)
3
3.147 𝑚⁄𝑠 2
=(
) = 9,672.7 𝑡𝑖𝑚𝑒𝑠 𝑡ℎ𝑒 𝑒𝑓𝑓𝑒𝑐𝑡
0.1477 𝑚⁄𝑠 2
3.147 m/s2 is the gravitational pull at the top of Mars’
theorized atmospheric sputtering layer. But taking into
consideration Pluto’s distance from the Sun in astronomical
units as opposed to Mars’ distance from the Sun, the magnetic
effect, as shown in equation (7), is drastically decreased. This
reduces the sputtering effect by a factor of
39.264 𝐴𝑈 3
𝑅𝑠,𝑚𝑎𝑔𝑛𝑒𝑡𝑖𝑐 = (
) = 13,094 𝑡𝑖𝑚𝑒𝑠 𝑙𝑒𝑠𝑠 𝑒𝑓𝑓𝑒𝑐𝑡
1.665861 𝐴𝑈
This reduces the overall rate of sputtering by 26.1%.
Though, it must be noted that this is quite a conservative
estimate of the sputtering effect. The lowest gravitational pull
of Pluto was used, as well as the three-dimensional rate of
sputtering [11]. Nevertheless, this means that such an
atmosphere on Pluto would face depletion over the course of
4.35 million years. This is within an order of magnitude of
the dissipation rate that could be expected on an engineered
Martian atmosphere, which is acceptable, though a means to
avoid this sputtering will be discussed shortly.
Fig 4 This figure shows a graphical (and exaggerated) representation of the
Sun’s sputtering effect on a familiar celestial body, Mars. This effect is what
led to Mars’ atmosphere to being siphoned off over the course of several
million years.
V. FINDING A MEANS TO INCREASE TEMPERATURE
The mean surface temperature of Pluto is approximately 36
Kelvin, yet the desired surface temperature is 280 Kelvin.
This is a difference of 244 Kelvin, inarguably a humongous
required temperature increase, but it isn’t as difficult as some
might expect.
Using the mean temperature equation
developed by Dr. Robert Zubrin and Dr. Chris McKay, the
temperature change at the surface of Pluto with respect to an
introduced atmosphere can be approximated [3].
𝑇𝑚𝑒𝑎𝑛 = 𝑇𝑒𝑞 + 20(1 + 𝑆)𝑃0.5
(10)
Where S is the average solar output as a function of the
Sun’s age (we will assume it is always 1), and P is the
atmospheric pressure of the planet in bars at the surface. I
have further altered this equation to include the difference in
atmospheric thickness as a means of absorbing more solar
energy, as I did in a previous paper [5].
𝑇𝑚𝑒𝑎𝑛 = 𝑇𝑒𝑞 + 20(1 + 𝑆)𝐻0.5 𝑃0.5
(11)
Where H is the ratio of Pluto’s atmospheric thickness to the
atmospheric thickness of Earth. For instance, if Earth’s
atmospheric thickness is 100 kilometres, and Pluto’s
atmospheric thickness is 300 kilometres, then the ratio would
be 3. As the thickness of an engineered Plutonian atmosphere
has been previously determined, the mean surface temperature
of Pluto would increase to
𝑇𝑚𝑒𝑎𝑛 = 36 𝐾 + 20(16.57890.5 )(2)(0.506𝑚𝑏𝑎𝑟 0.5 )
= 151.854 𝐾𝑒𝑙𝑣𝑖𝑛
This still makes the required temperature increase 280 –
151.854 = 128.145 Kelvin. This difference can be overcome
using super greenhouse gases.
VI. HEATING UP PLUTO WITH GREENHOUSE GASES
The greenhouse effect on planets is still only scarcely
understood at this point in human history. Though, some
valuable information can be gleaned from the body of
knowledge that has been developed thus far. From examples
such as Venus, we can see that a runaway greenhouse effect
on entire planets is not an uncommon occurrence, for it has
happened once in our own solar system. If we look at the
giant moon, Titan, we can see how having an atmosphere at
all acts as a blanket upon the surface of a celestial body,
heating it significantly above the solar equilibrium
temperature. Then beyond this, we can see how a rarefied
atmosphere such as that found on the moon can cause huge
temperature swings. Even further, we have Mars, with such a
tenuous atmosphere that a human being would instantly
embolize without a pressure suit at its surface.
The
atmosphere of Pluto will be engineered in such a way as to
minimize distention above the surface, thus minimizing
possible sputtering effects, while simultaneously providing
sufficient surface pressures to adequately sustain life.
As it is, we are distinctly aware of the necessity of having a
thick atmosphere that contains healthy amounts of heattrapping molecules, such as water vapour, CO2, methane, and
6
other gases. To figure out exactly how much greenhouse gas
would need to be produced on Pluto, we must refer to the
Earth’s atmosphere, and how it has evolved over the past 110
years due to human-induced global warming. The chart below
shows the increase in CO2 in the atmosphere of Earth in parts
per million over the past 50 years, just to give an idea of this.
The up-and-down pattern in the chart is due to the seasons;
there is a greater land mass in the northern hemisphere of
Earth as opposed to the Southern. As a result, the change in
seasons sees a change in the total number of carbon-absorbing
plants in bloom. However, the chart still shows a very clear
trend upwards in CO2 levels [13].
Fig 5 This chart shows the increase in CO2 levels on Earth from 1960 to
present day.
Over the past 110 years, the global increase in temperature
has been approximately 1 degree Celsius. During that time,
we need to determine how much CO2 humans have added to
the atmosphere. The chart below shows the yearly CO 2
production by humans during this time interval.
volumetric measurement because the density of any proposed
atmosphere decreases rapidly with altitude. This would mean
that the volumetric measurement of atmosphere would yield
much larger atmospheric numbers than a mass measurement.
This is thus more conservative. However, it was merely done
as an engineering exercise and will not be reproduced in this
design.
As such, having already calculated the atmospheric mass of
a ½ bar Plutonian atmosphere as 1.3547x10 18 kg, we can
compare this to the overall mass of the Earth’s atmosphere.
Earth’s atmosphere is roughly 5.27x10 18 kg [4, 15]. This
means that the proposed atmosphere of Pluto is only 25.71%
as massive as that of the Earth. This then means that only
8.483x1012 kg of CO2 is required for the same ppm increase
on Pluto, and thus the same temperature change. It must be
noted that such a calculation is still a very inexact science at
the current level of understanding of atmospheric evolution. It
is not yet known if temperature increases are purely based
upon ppm compositions of different elements, or if it has to do
with a variety of other factors, such as atmospheric thickness,
surface area of the proposed celestial body, etc. We will
operate under this assumption, however, for this particular
engineering design.
Nevertheless, producing this much CO2 is a Herculean
effort. Let’s consider a standard 600 MW coal power plant
operating at full capacity 24/7. The amount of CO2 produced
per kilowatt hour (kWh) is as follows:
Type of Coal
Bituminous Coal
Sub Bituminous Coal
Lignite Coal
Average
CO2 Produced (lbs/kWh)
2.08
2.16
2.18
2.14
Table 3 This table shows the amounts of CO2 produced based upon the type
of coal used [16].
With an average of 2.14 lbs. of CO2 produced per kWh, a
single 600 MW power plant would produce
1,000 𝑘𝑊ℎ 2.14 𝑙𝑏𝑠. 1 𝑘𝑔
𝑘𝑔
∙
∙
= 972.7
1 𝑀𝑊𝐻
1 𝑘𝑊ℎ 2.2 𝑙𝑏𝑠.
𝑀𝑊𝐻
Fig 6 This chart shows the total production of CO2 from 1900 to present day
in teragrams [14].
Over the course of the past 110 years, approximately 30,000
teragrams of CO2 has been emitted into the atmosphere. This
equates to 3.0 x 1013 kg. Thus
13
13
3.0𝑥10 𝑘𝑔 3.3𝑥10 𝑘𝑔
=
0.9 ℃
1℃
A different method will be used in this engineering design
compared to my previous paper [5]. Rather than using
atmospheric volume to determine the total amount of CO2
required, atmospheric mass will be used to determine the
amount of CO2 required. This is much more accurate than a
972.7
𝑘𝑔
600 𝑀𝑊
24 ℎ𝑟 365 𝑑𝑎𝑦𝑠
∙
∙
∙
𝑀𝑊𝐻 1 𝑃𝑜𝑤𝑒𝑟 𝑃𝑙𝑎𝑛𝑡 1 𝑑𝑎𝑦
1 𝑦𝑟
= 5.113𝑥109
𝑘𝑔
⁄𝑝𝑜𝑤𝑒𝑟 𝑝𝑙𝑎𝑛𝑡 𝑦𝑟
As a conservative estimate, the maximum atmospheric
pressure will be used for determining ppm composition of
Pluto’s atmosphere. This is important because the current
mass of the Plutonian atmosphere, which has a pressure of
only 0.3 Pascals at the surface, is only roughly 8x10 12 kg.
This would mean it would take 1 5 MW power plant 1 year to
heat up the Plutonian atmosphere by 1 degree Celsius. Since
we do not know whether this is the case or not, and the
atmospheric pressure would increase exponentially with the
number of power plants producing gases in addition to the
7
melting of surface ices, the most conservative means of
determining greenhouse warming of Pluto is to assume its
maximum desired surface pressure at the beginning.
In addition, these power plants are not optimized to produce
the maximum amount of CO2, so it is likely that tens to
hundreds of times the amount of CO2 could potentially be
produced from the same amount of coal if such a thing were
desired.
Under these assumptions, it would take 1,659 600 MW
power plants to increase the surface temperature of Pluto by
one degree Celsius in one year. However, a temperature rise
of 128.145 Kelvin is required, which means that it would take
212,606 power plants to produce such a temperature change in
one year. Though, this is predicated under the assumption that
the same amount of solar energy is received by Pluto as that of
the Earth, which is not the case. The amount of solar energy
that Pluto receives with respect to Earth is
𝐼∝
𝐼∝
1
(12)
𝑑2
1
1
=
∙ 100 = 0.0649% 𝐸𝑎𝑟𝑡ℎ′ 𝑠 𝑒𝑛𝑒𝑟𝑔𝑦
𝑑 2 (39.264)2
Where I is the solar energy intensity, and d is the distance in
astronomical units from the Sun. This means that the Earth
receives 1542 times the solar energy of Pluto, which thus
means it would require 327,766,265 power plants to achieve
the required temperature change in one year. This number is
astronomical, but as we will find, it is astronomically reduced
by yet more factors.
First of all, CO2 does not need to be the greenhouse gas of
choice.
If, instead, we choose to use SF6 (sulphur
hexafluoride) for greenhouse warming of Pluto, then the
situation changes. SF6 is 20,000 times as efficient at trapping
solar energy when compared to CO2 [12]. This means that it
would require 20,000 times less SF6 for the same temperature
change. Thus, the mass required for the same temperature
increase becomes
1.676𝑥1018 𝑘𝑔
= 8.379𝑥1013 𝑘𝑔
20,000
This reduces the number of power plants required to 16,388.
But the efficiency of SF6’s heat trapping is not based upon a
per mass basis, but a per molecule basis. This means that
𝑔
146.054 ⁄𝑚𝑜𝑙
= 3.32 𝑡𝑖𝑚𝑒𝑠 𝑡ℎ𝑒 𝑚𝑎𝑠𝑠 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑
𝑔
44.001 ⁄𝑚𝑜𝑙
= (8.379𝑥1013 𝑘𝑔)(3.32) = 2.782𝑥1014 𝑘𝑔
Increasing the number of power plants required to 54,408.
However, the temperature increase does not need to be
accomplished in a single year. Indeed, such an engineering
endeavour would be planning for the long term. Thus, the
timescale could reasonably be increased to 100, 1,000, or even
10,000 years. If the timescale is increased to 1,000 years, the
number of power plants required decreases to 54.408 or
approximately 55.
This atmospheric production would
constitute only approximately 0.021% of the overall
atmospheric mass, and thus would not significantly change the
specific gas constant, thus leaving the distention of the
atmosphere and all other figures derived from it unchanged.
In addition to using SF6, such greenhouse gas-producing
power plants would be optimized to produce said greenhouse
gases, likely increasing the amount produced per MWH by a
factor of 100. With this taken into consideration, the total
number of power plants is reduced to 0.54408, or one 330
MWH power plant.
But what about atmospheric loss due to sputtering?
Determining the amount of atmosphere lost per year due to
sputtering is as follows:
12,470.41 𝑘𝑔
∙ (9,672.7 𝑔𝑟𝑎𝑣𝑖𝑡𝑦 𝑒𝑓𝑓𝑒𝑐𝑡)
𝑠𝑒𝑐𝑜𝑛𝑑
1
∙(
)
13,094 𝑚𝑎𝑔𝑛𝑒𝑡𝑜𝑠𝑝ℎ𝑒𝑟𝑒 𝑒𝑓𝑓𝑒𝑐𝑡
= 9,212 𝑘𝑔/𝑠𝑒𝑐𝑜𝑛𝑑
A single 600 MW power plant produces 162.1 x (efficiency
factor increase=100) = 16,210 kg of atmospheric gases per
second. This means that at least 0.5683 power plants would
be required simply to overcome the sputtering effects caused
by the Sun at this distance. Thus, the grand total number of
power plants required to produce a significant atmosphere on
the surface of Pluto is slightly more than one for a 1,000-year
period (1.112). This makes for a total of 670 megawatts of
energy production on Pluto.
However, taking into
consideration the maximum gravitational pull of Pluto and the
initial rarefied atmosphere, it would take no more than one 30
MW power plant to begin the terraforming effort at first.
These figures are not so ridiculous as to be entirely
unfathomable. Human civilization has only been in existence
in an organized fashion for roughly 10,000 years.
Technological innovation has only in the past 200 years
reached true prominence. In the last 200 years alone,
humanity went from barely having invented the steam
locomotive to sending probes billions of miles into space.
With the exponential growth in technology and innovation,
attaining a 670 megawatt energy production capacity on a farflung world may seem inconsequential 1,000 years from now.
Indeed, on Earth, it already is, with global energy production
topping countless terawatts per year [17].
VII.
OTHER CRUCIAL ATMOSPHERIC EFFECTS
An important factor to take into consideration when
engineering an atmosphere on Pluto is the large amount of
frozen nitrogen on the surface of the planetoid. Based upon
the vapour pressure of N2 that constitutes Pluto’s tenuous
atmosphere, it can be assumed that there is anywhere between
several million, to several tens of millions of square
kilometres of frozen N2 on the surface [18]. N2 turns into a
8
gas at approximately 77.355 Kelvin [19], which means that a
temperature increase of only roughly 41.355 Kelvin would be
necessary to cause the entire bulk of surface N2 to boil off or
sublime.
4
4
3
𝑇𝑁2 𝑙𝑎𝑦𝑒𝑟 = 𝜋(𝑟𝑃𝑙𝑢𝑡𝑜 )3 − 𝜋(𝑟𝑃𝑙𝑢𝑡𝑜 − 𝑟𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 )
3
3
= 1.3191𝑥106 𝑘𝑚3
∴ 𝑇𝑁2 𝑙𝑎𝑦𝑒𝑟 = 1184 𝑘𝑚 − 1183.925 𝑘𝑚 = 0.07488 𝑘𝑚3
Of course, this is assuming an equal distribution of frozen
N2 over the entirety of the Plutonian surface. Current models
predict that the amount of frozen N2 on the surface of Pluto is
not equally distributed, but patchy. This is evidenced through
the unequal albedo of Pluto’s surface, as shown in the figure
below. Even so, this estimation for N2 abundance is highly
likely to be extremely conservative, with Pluto’s surface
possibly covered in patchy layers of frozen N2 several
kilometres thick [18].
Fig 7 This figure shows liquid nitrogen as it appears on Earth. While much of
the liquid boils off into gaseous nitrogen on our home world, on Pluto, N2
would not reach sublimation temperature for quite some time. However, once
it did, a massive atmosphere would likely result.
The question then becomes, how much of this N2 is there,
and how much of it would be required to cause a runaway
atmospheric genesis? If this occurred, which is highly likely
based upon the temperature increase, producing an
atmosphere on Pluto would no longer be an issue; the only
remaining issue would be increasing the temperature of said
atmosphere. This same runaway atmospheric genesis is
believed to be fundamentally possible on Mars as well, only
with different molecules constituting the Martian atmosphere
[3].
Frozen N2 has a mass of 1.027 g/cm3. The mass of
atmosphere that needs to be produced is
1.3547𝑥1018 𝑘𝑔 − 8.032𝑥1012 𝑘𝑔 = 1.3547𝑥1018 𝑘𝑔
∴ 𝑛𝑒𝑔𝑙𝑖𝑔𝑖𝑏𝑙𝑒 𝑛𝑎𝑡𝑢𝑟𝑎𝑙 𝑎𝑡𝑚𝑜𝑠𝑝ℎ𝑒𝑟𝑒
With these numbers, we can determine the volume of solid
nitrogen required in order to produce a significant atmosphere.
1,000 𝑔
1 𝑐𝑚3
1 𝑚3
)∙(
)∙(
)
1 𝑘𝑔
1.027 𝑔
1003 𝑐𝑚3
1 𝑘𝑚3
∙(
) = 1.3191𝑥106 𝑘𝑚3
1,0003 𝑚3
Fig 8 This figure shows the clearest images of Pluto’s surface to date, as
viewed through the Hubble Space Telescope.
One way or another, an average thickness of 0.07488 km3 is
more than reasonable, and even expected when more accurate
measurements of Pluto’s surface are received by the New
Horizons space probe, which will reach Pluto in mid-2015
[20].
This frozen nitrogen layer has very important
ramifications on the ease of terraforming Pluto. If this
nitrogen layer is indeed present, it would mean that the
surface of Pluto would only need to be heated by slightly
more than 40 Kelvin before a runaway atmospheric thickening
would occur. However, this would also significantly change
the albedo of Pluto’s surface, as frozen nitrogen has different
reflective characteristics when compared to clean, frozen
water. Clean, frozen water has an albedo of approximately
0.8 [21]. With this increase in albedo, the equilibrium
temperature of Pluto would decrease from its current 36 to 44
Kelvin down to
1.3547𝑥1018 𝑘𝑔 ∙ (
With this, we can then find the required average thickness
of a nitrogen ice layer on the surface of Pluto. This is done as
follows:
4 (3.839𝑥1026 𝑊)(1 − 0.8)
4 𝐿° (1 − 𝛼)
√
𝑇𝑒𝑞 = √
=
2
16𝜋𝜎([5.874𝑥1012 𝑚]2 )
16𝜋𝑅𝐴𝑈
= 29.725 𝐾𝑒𝑙𝑣𝑖𝑛
The difficulty that arises from this decrease in temperature
is maintaining a subsequent increase in temperature of the
surface that outpaces the boiling off of frozen nitrogen and
9
thus increase in albedo of the surface of Pluto. This should be
easily overcome, as it takes several hundreds to thousands of
years for a celestial body to reach a new equilibrium
temperature with a significant change in albedo, but
nevertheless, it must be addressed in some way here. This
decrease in surface temperature of Pluto would then change
the mean surface temperature based upon Zubrin and
McKay’s equation to roughly 145.579 Kelvin.
This is still well beyond the boiling temperature of N2, and
thus should not pose any noteworthy issues. Though, it is
possible that during the early stages of Pluto terraforming, N2
ice could sublime into gas, and quickly form back into ice.
Until a certain critical point of sublimation rate is reached,
Pluto will revert back to a natural state of equilibrium with
frozen N2. This is a negative feedback system, but it can be
broken with a significant engineering effort. Such an effect is
also theorized to be expected in a terraforming effort on Mars
[3]. The figure below shows two separate equilibrium
temperatures for Mars’ surface.
This is evidenced through the giant moon, Titan, where
surface winds at peak intensity reach no higher than 5 miles
per hour [7]. This is compared to Earth, where average
surface winds are approximately 20 miles per hour. The giant
moon, Titan, orbits at a distance approximately 10 times
farther away from the Sun than the Earth. This means that a
rocky Plutonian surface would not face extreme erosion due to
winds, and thus any solid rock formations would remain for
an exceptionally long period, perhaps indefinitely.
Fig 10 This figure shows the giant moon, Titan, as viewed in false colour.
This image provides a view of the surface of Titan while at the same time
clearly showing the massive size of the moon’s atmosphere.
Fig 9 This graph shows an example of two different equilibrium temperatures
on Mars. Such a situation could also be experienced on Pluto, once sufficient
frozen nitrogen is sublimated to produce a massive and warmed atmosphere.
But a water world Pluto does not pose significant problems,
and in fact, in some ways it makes terraforming easier. Water
has a low albedo compared to other possible surface
compounds, such as silicate sand. This means that Pluto
would absorb more solar energy, and thus would require less
constant heating from greenhouse gas production. So, while
the equilibrium of Pluto would be difficult to move past the
nitrogen sublimation stage, once done, a slow evolution
towards a liquid water stage could be a much easier transition.
It must be understood that Pluto will never have a surface
truly similar to that of the Earth in that, because of Pluto’s
composition due to its distance from the Sun, its surface will
become covered in liquid water.
Pluto is comprised
approximately of equal parts water ice and silicate rock [18],
but its surface in particular has a large amount of frozen water
mixed with frozen nitrogen and methane. Indeed, warming
Pluto would likely turn it more into a mini-water world, rather
than a super-low-gravity Earth. It is possible that small
patches of solid rock land formations would be present, but
below the rock-ice mantle of Pluto lies what is believed to be
a liquid ocean. Any solid landforms would be nothing more
than mere floating islands.
Nevertheless, due to the lack of tectonic plate movement on
Pluto because of its very small size and low internal heat, such
landforms would likely not risk devolution below the liquid
layer to any large degree. This is also due to the low amount
of solar energy that Pluto receives. With such a low solar Fig 11 This figure shows an artist’s concept of a cold water world. As can be
clearly, this planet has very large polar ice caps and is shrouded in thick
energy, the wind currents in an engineered Plutonian seen
cloud layers.
atmosphere would be very subtle, perhaps almost non-existent.
10
One of the biggest barriers to having a water world is that
there is little to no surface for photosynthetic plants to take
root. Though, thankfully, water can make up for a large
portion of the oxygen issues due to its molecular structure.
Water naturally breaks down into its constituent elements over
long periods of time, albeit in rather small amounts [4]. But,
over several thousands to several millions of years, this can
produce enough atmospheric oxygen to render a water world’s
atmosphere breathable, perhaps even more so than a planet
covered in vegetation.
VIII. LUMINOSITY AND PLANT LIFE ON PH
So, we have discussed how to actually make Pluto warm
enough for humans to comfortably survive at the surface
without pressure suits or body-heating apparatuses. But how
habitable is it to the flora and fauna upon which human
society so keenly relies to thrive? At these distances, it truly
does start to become very difficult for plant life to proliferate.
Unlike PH, a previously designed hypothetical planet over 2
billion kilometres distant from the Sun where light levels were
still significant enough for some of the most shade-tolerant
plants to thrive, on Pluto, the issue becomes entirely different.
Pluto receives only 0.0649% the sunlight that the Earth
receives (0.883 watts/m2), and only 16.73% the sunlight that
PH receives (5.281 w/m2) [5]. In addition to this, while it may
be possible to genetically engineer plants to live in such low
light levels, Pluto will likely have no solid surface, as
previously stated. This means that any flora would need to be
birthed deep beneath the Plutonian surface, in the depths of an
ocean. This surface ocean could be anywhere from several
hundreds of meters to several hundreds of kilometres thick.
At the bottom of such an ocean, even in the shallowest
locations, solar luminosity would be practically zero.
Nonetheless, even in these extreme circumstances, there are
workarounds. First of all, assuming Plutonian flora would be
genetically engineered to endure the low light levels, such
photosynthetic flora could float at the surface of a Plutonian
ocean, much in the way that seaweed floats through the ocean
on Earth. This would mean that any sunlight that Pluto does
receive could be absorbed by these floating plants with
minimal oceanic diffraction. But beyond even this, intense
study of newly discovered organisms and ecosystems on Earth
that do not require photosynthesis even at their lowest trophic
levels is being carried out. In the deepest depths of the
Earth’s oceans where practically no light can reach,
ecosystems have been found that rely exclusively upon
bacteria that consume nutrients produced by tectonic activity
on the ocean floor, nutrients ejected by hydrothermal vents
[22]. These organisms are aptly named extremophiles, for
they thrive in what humans consider extreme environments.
Fig 12 This figure shows a scanning-electron image of a water bear. Water
bears (also known as tardigrades) are known to be able to survive in
environments with literally no atmosphere (i.e. outer space). They can live
without water for decades, and can be brought back to life if frozen.
Fig 13 This figure shows a bacterium that has evolved to consume toxic waste.
But once more, beyond even this, there may not be a
genuine need for flora to grow on Pluto at all. If sufficient
atmospheric oxygen can be produced from the hydrosphere
alone, and the ocean covering Pluto produces a significantly
large amount of warmth through its increased albedo, then the
only issues a human civilization would need to endure are (1)
procuring food, (2) procuring desalinated water, and (3)
developing an efficient and feasible method of producing
floating colonies and energy production facilities. Given the
long timescales of such an engineering endeavour, these
issues could be tackled in perpetuity as they arise.
But what about light levels for humans? The question then
becomes, are these light levels on Pluto sufficient for humans
to conduct vital day-to-day activities? Let’s put this into
perspective. We will use a typical 60-watt light bulb to give
11
us a better understanding of light levels. A 60-watt light bulb
produces 840 lumens of brightness through a soft-whitepainted glass sheath, whereas a typical candle produces 12
lumens of light. A lumen is a measure of luminous flux. On a
typical day at the equator of Earth, the sun provides 93 lumens
per watt. From the 60-watt light bulb, we get
The light level on Titan is approximately 15.4 times that
which reaches the surface of Pluto. On the surface of Pluto,
the light level is equivalent to a very bright street light, or on
average about 250 times as bright as the full moon [23].
840 𝑙𝑢𝑚𝑒𝑛𝑠
𝑙𝑢𝑚𝑒𝑛𝑠
= 14
60 𝑤𝑎𝑡𝑡𝑠
𝑤𝑎𝑡𝑡
This means that the Sun provides
93 𝑙𝑢𝑚𝑒𝑛𝑠/𝑤𝑎𝑡𝑡
= 6.6429 𝑡𝑖𝑚𝑒𝑠 𝑡ℎ𝑒 𝑙𝑖𝑔ℎ𝑡 𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦
14 𝑙𝑢𝑚𝑒𝑛𝑠/𝑤𝑎𝑡𝑡
Or, put another way, the 60-watt light bulb provides 15.05%
the luminosity of the Sun. To put this into clearer
perspective, the luminous energy per watt on the surface of
the giant moon Titan is only 1% that of the Earth. The figure
below shows the ambient light level of Titan.
Fig. 15 This picture is a good comparison for the brightness that one may
experience on the surface of Pluto at its current distance from the Sun. While
much dimmer than daytime, these light levels are more than sufficient to
conduct activities that require high levels of visual acuity.
Fig. 16 This picture is a good representation of the light levels that may be
experienced on a Pluto with an engineered atmosphere. It is unlikely that
wooded plants or large, rocky landmasses would be commonplace on Pluto,
but the light levels are quite accurate.
Fig. 14 This picture shows the typical brightness at the surface of the moon
Titan. While this light level is still some 15 times greater than what would be
experienced on the surface of Pluto, it nevertheless is quite bright.
Assuming a human being with normal vision can write in
the light of the full moon, these light levels are more than
adequate for day-to-day activities. Though it is likely that, for
instance, driving a car would require one’s headlights to be on
constantly, no matter what time of day.
Through all of this, we can determine that the light levels
on Pluto would be in a range that would start to degrade
12
human survivability, unlike PH as shown in the previous paper
in this series [5]. Even so, this analysis shows that human
survivability on Pluto would not be impossible, and in fact, in
many aspects, it would be easier to proliferate on Pluto as
opposed to PH or even Mars. In order to really push the
envelope of human ingenuity, we require daring and
imagination, something that allows you to go beyond the folds
of normality, to think outside the box. Impossibility is a
concept based in limitations that people put upon themselves.
Nothing is impossible. All that one need do is to first believe
in possibility. This endeavour is more than within the
purview of our civilization; even now, Pluto could be
terraformed, though it would likely cost several quadrillion
USD.
IX. ANOTHER MEANS TO PREVENT SPUTTERING?
As described earlier, sputtering is a serious problem for
Pluto, even at its immense distance from the Sun. Taking into
consideration all the factors mentioned in this paper thus far, it
would take approximately 4.35 million years for an
engineered Plutonian atmosphere to be stripped away back to
its current mass. But, there are other methods that can be
employed in order to minimize and even entirely eliminate the
sputtering effect on Pluto.
Let us take the hypothetical planet, PH, which was designed
in the previous paper in this series. P H has a significant
magnetic field, one which was engineered primarily to prevent
the effects of atmospheric sputtering. This atmosphere can
also be used to protect a terraformed Pluto in the same way.
This would require engineering not only on a planetary scale,
but on an intrastellar scale. That is to say, Pluto could be
moved into an orbit around PH that would allow for the dwarf
planet to be protected by the immense magnetic field that PH
generates. Not only would Pluto be protected by P H’s
magnetic field from sputtering, but less of an effort would be
required to heat the surface of Pluto due to its closer proximity
to the Sun. Once more, the prospect of photosynthetic plants
proliferating on a Plutonian surface re-emerges.
Fig. 17 This figure shows what a typical day may look like on the surface of PH, with Pluto looming high in the sky. The Sun is far smaller than Pluto in the sky
due to its extreme distance from PH. Consequently, the sky is far darker than a typical day on Earth.
It is important to note that if Pluto is put into too close of an
orbit around PH, the dwarf planet could face a variety of
potential problems. First of all, every celestial body with a
significant magnetic field which deflects large amounts of
solar wind/radiation, requires that this deflected material go
somewhere other than the surface of the body. This usually
manifests in the form of large, highly lethal radiation belts that
surround the planet. In the case of the Earth, the Van Allen
radiation belts are a key example [24].
13
Fig. 18 This figure is a representation of the Van Allen radiation belts around
the Earth. Though not to scale, it illustrates the general shape of the belts
quite well. They surround the Earth; this is a cut-out view.
These radiation belts for smaller, Earth-sized planets with
magnetic fields of moderate strength typically do not extend
beyond 10 planetary radii above the planet’s surface. In the
case of PH, this would be 100,000 kilometres above the
surface. These radiation belts pose a number of problems for
Pluto. First of all, a radiation belt would make the surface of a
non-terraformed Pluto more or less uninhabitable for humans
without great measures put in place in order to protect against
the harmful radiation. Any extended stay in such a location
would be very difficult. Second, placing Pluto in such a
radiation belt could actually amplify the atmospheric leeching
effects caused by solar wind. This is because the engineered
atmosphere of Pluto would react with the excited material in
the radiation belts, and would rapidly dissipate. What would
normally take Pluto 4.35 million years to have its atmosphere
dissipate could be reduced to as little as 10,000 years
conservatively.
Again, even with a significant atmosphere on Pluto, having
Pluto anywhere near such a radiation belt would drastically
increase the probability of getting cancer at the surface. This
is because Pluto does not have a magnetosphere itself, and
thus cannot deflect the radiation as efficiently as P H.
Additionally, the proposed atmosphere on Pluto would only
be half as dense at the surface as compared to that of Earth,
which indicates itself a vastly reduced capacity to protect
against celestial radiation. A clear example of this is the
planet Mars. On Mars, the atmosphere is a mere 6 millibars of
pressure (1/150th of Earth). In such an environment, it takes
roughly 2 years to acquire 60 REM of radiation, an amount
that would take an airline pilot on Earth an entire lifetime to
acquire [3].
Another important issue with which to contend is that of
tidal forces. Though Pluto is a tiny celestial body when
compared to PH, it nevertheless can exert an impressive
gravitational force upon PH. The closer Pluto is to PH, the
stronger the force, based upon Newton’s Law of Universal
Gravitation. While 100,000 kilometres from the surface
would likely produce similar effects on P H to that of what the
Moon causes on Earth’s surface, it remains an important issue
to be considered in such an engineering design. Moreover, the
closer Pluto is to PH, the faster it needs to orbit in order to
maintain its altitude. This is due to the conservation of
angular momentum. In such an engineering situation, it
would require much larger amounts of energy to place Pluto in
a shallow orbit around PH, and thus is preferable to give Pluto
a larger orbit. These tidal forces and their effects on Pluto and
PH will be elaborated upon later.
While placing Pluto into a more distant orbit from P H is
preferable, how far is this distance? Clearly, Pluto must be
placed somewhere in the vicinity of P H’s magnetic field in
order to attain any level of protection from solar wind. The
extent of PH’s magnetic field is 392,993.4 kilometres [5].
There are a few more issues with which we must contended
before the decision can be made. The first is of the magnetic
field lines. Pluto cannot be placed in an orbit that will for any
extended period of time put it in the direct path of any of PH’s
magnetic field lines, for if Pluto is in contact with P H’s
magnetic field lines for any significant amount of time, this
can create an induced magnetic field effect on Pluto, which
thus can amplify the atmospheric sputtering effect rather than
reduce it [25]. The giant moons Callisto and Io of Jupiter can
be used as a clear example of the effects of this. Both moons
have a induced magnetic fields caused by their interactions
with the magnetic field lines of Jupiter as well as potential
liquid oceans that at least Callisto may harbor below its
cratered surface. Despite Io producing several thousands of
tons of material per second due to its high degree of
volcanism, a mechanism which should produce a significant
atmosphere of some type, Io has almost no atmosphere
whatsoever. This is because Jupiter’s magnetic field leeches it
away at a faster rate than Io’s volcanism can produce it. Even
Ganymede, the only moon in the solar system known to have
its own magnetic field, is prevented from having a significant
atmosphere for the same reasons [25].
Fig. 19 This picture shows the surface of the giant moon, Io. As can clearly
be seen, Io is a highly volcanic world. Despite this, Io has almost no
atmosphere. This is because the moon is bathed in high intensity radiation of
Jupiter, and is constantly having its atmosphere stripped away by the gas
giant’s magnetic field.
14
fact, Titan’s atmosphere has 1.45 times the surface pressure of
Earth’s atmosphere. Key to this seems to be the absence of
solar wind, or any magnetic field effects at all from either
Saturn or the Sun. A similar method can be employed for
Pluto. For these reasons, an orbital radius of 390,000
kilometres will be chosen for this design. This orbital
distance does not cause excessive tidal issues, prevents
interference from any possible radiation belts, and minimizes
the risk of intercepting the magnetic field lines of P H for any
extended period of time. The magnetic field of PH at this
distance is described by
𝐵𝐸 (𝑑) =
𝐵𝑜
𝑑3
=
𝐵𝑜
𝑑1 3
( )
𝑑2
(13)
Where BE is the magnetic field strength, BO is the magnetic
field at a specific frame of reference (in this case, the surface
of PH), d1 is the orbital radius of Pluto, and d2 is the radius of
PH. Thus, the magnetic field strength is
73.44 𝑛𝑇
Fig. 20 This figure shows the magnetosphere of Ganymede as affected by
Jupiter. While Io and Callisto do not have magnetospheres of their own like
Ganymede, the induced magnetic field effects are more or less the same. This
would strip away significant atmospheres very rapidly.
As one moves farther away from P H, the magnetic field
lines become much more dispersed, so much so in fact that an
entire celestial body could orbit comfortably within the space
between two sets of magnetic field lines. A distance
sufficiently far from PH will thus be chosen that is more than
100,000 kilometres distant, but less than 393,000 kilometres.
The final issue to take into consideration is that of the
magnetopause of PH, the point where the solar wind’s strength
matches the strength of PH’s own magnetic field. This was
already shown to be approximately 393,000 kilometres distant,
however, this is an important concept to understand. The
giant moon, Titan, orbits Saturn at a distance that places it
very close to the magnetopause of Saturn, approximately
1,200,000 kilometres. Ironically, Titan is the only known
moon in the solar system to have a significant atmosphere. In
(
390,000 𝑘𝑚 3
)
10,000 𝑘𝑚
= 0.00123 𝑛𝑇
At this distance, the Sun’s magnetic field intensity is
0.00121 nT. This puts the sum of the overall intensity at
0.00002 nT. With such a weak magnetic field effect, this
would reduce atmospheric sputtering so much that it would
take a Plutonian atmosphere roughly 4.1 times as long to
dissipate, putting the longevity of the Plutonian atmosphere at
approximately 17.8 million years. This can be reduced even
further with more exact orbital placement with relation to P H’s
magnetopause. Additionally, this is not even taking into
consideration Pluto’s natural rate of atmospheric generation,
which is on the order of several thousands of kilograms of
material per second [9].
15
Fig. 21 This figure shows the relative orbit in which Pluto would be placed with respect to P H and its magnetic field. The orbital distance of 390,000 kilometres
would put Pluto very close to the magnetopause (if not within it), which would then cause Pluto to experience similar sputtering effects to that of the giant moon,
Titan. This figure is not to scale.
A very important thing to understand is that scientists,
prior to the Voyager missions which visited Saturn, originally
believed that a body with a surface gravity as low as that of
Titan could not sustain an atmosphere of any significant mass.
In truth, our science has only just begun to scratch the surface
of the possibilities. Without the effects of a magnetosphere on
a celestial body, the potential for even a naturally occurring
atmosphere on such a small body as Pluto becomes a real one.
Placing Pluto as close as possible to the magnetopause of P H
could sustain an atmosphere on the dwarf planet in perpetuity,
with no need for extensive human modification whatsoever.
X. OTHER IMPORTANT FACTORS
Placing Pluto into such an orbit would come with some
consequences. First of all, at a distance of 390,000 kilometres
from PH’s surface, the orbital velocity of Pluto is described by
𝑣𝑜 = √
𝐺(𝑚1 +𝑚2 )
𝑟
(14)
Where G is the gravitational constant, m1 is the mass of PH,
m2 is the mass of Pluto, and r is the radius of the orbit itself
plus the radius of the celestial bodies. Thus, assuming a
perfectly circular orbit with no eccentricity, the velocity works
out to be
3
(6.67384𝑥10−11 𝑚 ⁄𝑘𝑔 ∙ 𝑠 2 ) (8.80951𝑥1024 𝑘𝑔)
√
𝑣𝑜 =
(4.1184𝑥108 𝑚)
= 1.195 𝑘𝑚/𝑠𝑒𝑐𝑜𝑛𝑑
This means that, it would take Pluto 23.73 days to make
one complete orbit around PH. Assuming Pluto has no
rotational velocity itself, this would add to the difficulty of
producing photosynthetic plants.
To understand the
magnitude of this problem, it is necessary to determine the
mechanism of tidal locking on Pluto with respect to P H. The
length of time it would take Pluto to tidally lock with P H with
respect to distance and starting rotational velocity is
approximated through the following equation [26]:
𝑡𝑙𝑜𝑐𝑘𝑒𝑑 ≈
𝜔𝑎6 𝐼𝑄
2 𝑘 𝑅5
3𝐺𝑚𝑃
2
(15)
Where 𝜔 is the initial spin rate in radians per second, a is
the semi-major axis of the satellite (Pluto), I is the moment of
inertia of the satellite, Q is the dissipation function (which for
simplicity purposes is approximated to be roughly 100), G is
the gravitational constant, mP is the mass of the planet, k2 is
the tidal love number of the satellite, and R is the mean radius
of the satellite. These figures or their approximations are
16
straightforward with the exception of the moment of inertia
and the tidal love number, so let’s delve into these two
concepts before we find the time to tidal locking. The
equation to find the moment of inertia of a satellite like Pluto
is approximated by
𝐼 ≈ 0.4𝑚𝑠 𝑅2
(16)
This makes the moment of inertia of Pluto 7.3176x10 33 kg
m . The tidal love number is the tricky one to determine for
Pluto, however. The tidal love number is basically a measure
of the flexibility of a celestial body, and thus with this you can
get a determination of how much the gravity acting upon the
body will affect its spin rate. The equation for the love
number of Pluto is approximated as [26]
2
𝑘2 ≈
1.5
(17)
19𝜇
2𝜌𝑔𝑅
1+
Where 𝜇 is the rigidity of the satellite (3x1010 N/m2 for
rocky objects and 4x109 N/m2 for icy objects), 𝜌 is the density
of the satellite (2.03 g/cm3 for Pluto), R remains as the radius
of the satellite, and g remains as the gravitational pull of the
satellite at its surface. For Pluto, since it is theorized to be
comprised of a mixture of equal parts rocky and icy material
[9], a rigidity of 1.7x1010 N/m2 will be used. This gives a tidal
love number of
this case, to maintain a rotational velocity, large celestial
bodies could be used to speed up the orbit of Pluto.
Additionally, with such a far-reaching engineering project,
there would likely be a plethora of technologies available at
the disposal of humanity 10 million years in the future to
perpetuate a sufficient rotational velocity for Pluto, such as,
perhaps inter-dimensional wormholes used for teleportation
and propulsion purposes. The possibilities are endless. Such
engineering feats have already been discussed with regards to
culling entire asteroids into orbits around Earth for mining
purposes, so this is not an unimaginable task [27].
XI. A FEW MORE INTERESTING FACTS
As it appears, the development of a habitable Pluto is
highly possible, but there are always more variables to take
into consideration due to humanity’s ever-limited
understanding of the cosmos. One interesting concept to
understand is that of barycenters. In Pluto’s current orbit, it
has a giant moon relative to its own size, a moon that is over
10% the mass of Pluto itself: Charon. This moon-dwarf
planet pair is so close in mass and the celestial bodies far
enough away from one another that the barycenter of the
system lies outside the surfaces of both Pluto and Charon.
1.5
𝑘2 ≈
1+(
19 ∙ [1.7𝑥1010 𝑁⁄𝑚2 ]
)
𝑘𝑔
2 ∙ [2030 ⁄𝑚3 ] [0.658 𝑚⁄𝑠 2 ] [1.184𝑥106 𝑚]
= 0.01455
This falls in line with other celestial bodies close to Pluto’s
size. For example, the moon has a tidal love number of
0.0266. The larger the celestial body, the bigger the love
number. PH’s tidal love number is 0.59024. Jupiter-sized
planets have love numbers in the tens to hundreds of
thousands. Let’s assume that Pluto has an initial spin rate that
would give it roughly a 24-hour day. This spin rate in radians
per second is 7.2722x10-5 radians/second. Thus, the length of
time it would take Pluto to tidally lock to P H is 11,320,896
years. This is a relatively short period of time. But it also
must be noted that this calculation is a rough approximation.
It has been known to be off by as much as a factor of 10. For
instance, the time it would take for the Earth to tidally lock to
the moon is believed by a consensus of scientists to be
roughly 2.1 billion years, but using this approximation, the
answer comes out to roughly 20 billion years. As such, this
tidal locking time could be anywhere from 110 million years
to 1.1 million years. Under any of these scenarios, such a
problem would make photosynthesis on the surface of Pluto a
highly difficult task. Though, it still is not impossible.
I’m going to push you as far as you can go. Nothing that
you can perceive is impossible. There is a way to do it. In
Fig. 22 This figure shows the barycenter of the Pluto-Charon system. As can
be seen, the barycenter lies beyond the radius of Pluto.
It brings up an interesting idea: where would the barycenter
of a Pluto-PH system be? As it turns out, this is exceptionally
easy to calculate. Calculating the barycenter of a planetary
system involves taking the mass of the less massive of the two
bodies in the system, and dividing by the overall mass of the
entire system. You multiply this number by the overall orbital
radius of the system, and you get the system’s barycenter.
This gives the distance away from the center of mass of the
larger of the two bodies. The calculation is as follows:
𝑏𝑠𝑦𝑠𝑡𝑒𝑚 =
𝑚𝑃𝑙𝑢𝑡𝑜 𝑟
(𝑚𝑃𝐻 +𝑚𝑃𝑙𝑢𝑡𝑜 )
𝑏𝑠𝑦𝑠𝑡𝑒𝑚 =
(18)
(1.305𝑥1022 𝑘𝑔)(390,000 𝑘𝑚)
(8.80951𝑥1024 𝑘𝑔)
= 577.72 𝑘𝑖𝑙𝑜𝑚𝑒𝑡𝑟𝑒𝑠
In this case, the barycenter would be well within the radius
of PH itself, preventing the possibility of any egregious orbital
17
perturbations. One can do this calculation with any two
bodies in the universe, assuming the masses of the two objects
are known.
And finally, probably the most interesting artifact of
creating a habitable atmosphere on Pluto is the terminal
velocity. Due to the far lower gravitational pull on Pluto, the
terminal velocity has the potential to be much slower than on
Earth (122 miles per hour for a human being). A good
example of this is Titan. On Titan, the terminal velocity is a
mere 12 miles per hour, slow enough to fall from the top of
the Titanian atmosphere all the way to the moon’s surface and
safely touch down without a parachute! A similar effect
would be experienced on Pluto, though, since Pluto has only
half the surface pressure of Earth, this factor slightly increases
the terminal velocity. The overall terminal velocity of Pluto
would become roughly 16.4 miles per hour. Typically, a
parachutist on Earth will touch down between five and 15
miles per hour. This means that, as with Titan, one would not
ever need a parachute to safely touch down on the surface of
Pluto!
XII.
A FEW MORE LIMITATIONS
It must be noted, there was one assumption not previously
mentioned in this analysis with regards to super greenhouse
gases that would likely be the most prohibitive. The
temperatures on Pluto, even if culled into an orbit around P H
are extremely low, so low that very few compounds are
scarcely anything more than frozen solid. The boiling point of
sulfur hexafluoride is 209 Kelvin, and this paper assumed that
sulfur hexafluoride would be gaseous on Pluto. This means
that sulfur hexafluoride would likely be solid ice on the
surface of Pluto. Nevertheless, the numerical analysis, for the
most part, remains valid. In the future, when new types of
greenhouse gases are discovered that could potentially be
gaseous at low temperatures, the same temperatures that affect
a wispy atmosphere on Pluto when it comes close to the Sun,
the engineering endeavor can be attempted with a high
probability of success. As it is, the next paper in this series
will be addressing how to overcome this issue.
Additionally, though sulfur hexafluoride would likely be a
solid at these temperatures, a significant vapor pressure could
still be present if bulk composition of the compound on Pluto
is made to be large enough. For instance, tetrafluoromethane
has a boiling point of 145 Kelvin, and methane which is 20
times more effective at trapping heat compared to CO 2 has a
boiling point of 111 Kelvin. These gases would have a
significant vapor pressure even at extremely low temperatures
which could potentially increase the equilibrium temperature
of Pluto enough to cause a runaway greenhouse effect up to
somewhere around 100 Kelvin.
Beyond this, there are other possible ways to affect a
temperature on Pluto that would be conducive to a primordial
atmosphere of significant enough density to begin retaining
higher temperatures for other greenhouse gases. Among these
is a planet-wide dome. Not only would this planet-wide dome
retain an atmosphere, it would also act in the same way that
greenhouses act on Earth, causing the dwarf planet to reach a
new, higher equilibrium temperature.
Fig. 23. The figure above shows an artist’s concept of a potential planetwide dome on Pluto for atmospheric retention.
XIII. CONCLUSION
Now we have had two papers expanding upon the idea of
artificial habitability zones around stars. So, what defines an
artificial habitability zone? In truth, it is the human desire to
actually make a celestial body habitable—there is no real limit
to the human ability to engineer a habitable environment on
planets, no matter the distance from a star. Nevertheless, this
definition that I am putting forward is due to current
limitations in economic and technological feasibility, and is
highly subjective.
If it would take more than 6,000,000 MW of power
production more than 1,000,000 years to increase the surface
temperature enough to sustain life, as well as produce surface
atmospheric pressures above the Armstrong limit [28], then
the planet falls outside the artificial habitability zone.
Additionally, if sputtering effects outpace atmospheric
production, the planet falls outside the artificial habitability
zone.
True habitability is thus determined less by orbital
proximity to the host star and more by the intrinsic properties
of the celestial body (i.e. size, gravitational pull, magnetic
field, elemental/chemical composition, etc.).
This definition is subject to as much refinement as any third
party wishes, and is by no means final. What is artificially
habitable is truly a function of the limitations humanity puts in
place. As those factors continuously change in the course of
human events, assuming humanity does not lose its vision and
continues to progress, this artificial habitability zone will
continuously push farther and farther out.
One way or another, what was shown in this paper is that if
we can as a society eliminate our perceived limitations, the
possibilities in the universe expand explosively. Who would
have thought that it was theoretically possible to terraform a
dwarf planet with minimal gravitational pull? Who would
have thought that a planet orbiting the Sun 16.043 times
farther away than the Earth would get sufficient solar energy
to warm up to habitable temperatures? Once more, who
18
would have thought that a planet such as Venus could be
made habitable if the atmosphere were stripped down to Earth
pressures, and the albedo were increased to roughly 0.60 Bond
(this produces a surface temperature that averages out to be
approximately 85 degrees Fahrenheit, as opposed to 58
degrees Fahrenheit for Earth)? Strip away these limitations
and start thinking of grander possibilities. That is what
science truly is all about.
Let’s put this engineering thought experiment in
perspective. 1,000 years ago, an airplane would have been
thought of as impossible; for that matter, the simple
technology that is a pocket lighter would have been
considered magic. During the 17th century, Giordano Bruno
was burned at the stake for believing that there were worlds
beyond Earth [29]. About a century later, Isaac Newton was a
social pariah for many of the same reasons. Galileo Galilei
was put on house arrest for explaining the motion of the
planets around the Sun and other celestial bodies. All of these
people pushed the boundaries of what was considered true or
even possible. It is the responsibility of the scientist, or all of
us for that matter, to never settle for the currently understood,
but continually push back the curtains of ignorance.
Nothing is impossible. The only impossibilities are those
created from human-perceived limitations. But, in order for
anything to be accomplished, you must first believe that it can
be.
ACKNOWLEDGMENTS
1LT William Giguere was integral in the initial review of
papers in this series, providing ample support. 1LT Michael
K. Seery (MS, CpE.) and 1LT Phaelen French also took part
in the review process.
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