Marspedia - User contributions [en]

Air

2019-06-04T04:05:41Z

Timfduffy: Added a section on pressure, wrote a couple subsections for it and moved in some existing sections. Also added more sources to existing sections.

[[Image:carbon_cycle_simplified.png|thumb|right|300px|Breathing keeps the Carbon Cycle running]]

Settlers on [[Mars]] will depend on manufactured '''air''' for breathing, since the planet's [[atmosphere]] is too thin and lacks Oxygen.

Standard air on Earth is composed of Nitrogen (78%) and Oxygen (21%), with traces of other gases at 101,3 kPa (14,7 psi) of pressure.

==Gases==

===Oxygen===
[[Oxygen]] is the one essential component of any breathing gas. At sea level on Earth, the partial pressure of oxygen is about 22 kPa, habitats on Mars will likely have a similar amount. However, high oxygen concentrations and high oxygen partial pressures both contribute to increased flammability, so it may be best to supplement oxygen with other inert gases.

===Inert gases===
[[Nitrogen]] and [[argon]] are available in similar concentrations in Mars’ atmosphere and would both be suitable for use in habitats. Because inert gases slow the spread fire by absorbing heat, and nitrogen has about 65% more heat capacity per volume than argon<ref>[http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/heatcap.html Molar Heat Capacities, Gases]</ref>, nitrogen may be preferred. But it is also plausible that a nitrogen/argon mix would be used since the mix would be easier to obtain, or that argon would be used, since nitrogen has other uses like production of fertilizer.

===Carbon dioxide===
Carbon dioxide is a low concentration atmospheric component produced by the human metabolism and industrial processes. Excess carbon dioxide concentrations can produce a variety of negative health effects, even at low concentrations. But CO2 is a also a requirement for plant metabolism. A study on astronauts on the International Space Station found that headache risk was significantly affected by CO2 levels even at concentrations below 10,000 ppm<ref>[https://journals.lww.com/joem/Abstract/2014/05000/Relationship_Between_Carbon_Dioxide_Levels_and.4.aspx Relationship Between Carbon Dioxide Levels and Reported Headaches on the International Space Station]</ref>. Nuclear submarines can operate with up to 9000 ppm in their atmosphere. In Mars habitats carbon dioxide will have to be separated and removed, or converted back into oxygen by plants.
==Pressure==
It may be worthwhile to keep Mars habitats at a lower pressure than we generally experience on Earth. This was done on the Apollo and Skylab missions, which both had total pressures of 5 psi (34 kPa). Robert Zubrin advocates for a Skylab-type habitat air mix on Mars, with 3.5 psi (24 kPa) O2 and 1.5 psi (10 kPa) N2<ref>Zubrin, Robert (2011). ''The Case for Mars: The Plan to Settle the Red Planet and Why We Must'' (2nd ed.) p. 159</ref>. There are several key considerations in determining the optimal air pressure.

=== Structural stress ===
Using sea level Earth air pressure, the force on each square meter of a habitat’s surface would be around 100 kN, equivalent to the weight of more than 10 tonnes on Earth. Habitats on Mars will need to have high tensile strength to withstand this great force. Using a lower pressure would reduce the strain, possibly leading to more lightweight and less expensive habitats.

=== Oxygen partial pressure ===
The level of oxygen in the air must be high enough to supply sufficient oxygen to the bloodstream. To do this, the partial pressure of oxygen reaching the alveoli in the lungs must be comparable to what we experience on Earth. Because our lungs are saturated with water vapor, oxygen is partially crowded out at very low total pressures, so at those pressures, the partial pressure of oxygen in the air required to properly supply our lungs is actually higher.
{| class="wikitable"
|+Oxygen concentrations to provide sea level O2 absorption<ref>[https://spacecraft.ssl.umd.edu/old_site/design_lib/HSSWG_3-02.pdf Guidelines and Capabilities for Designing Human Missions]</ref>
!Total pressure (kPa)
!Oxygen partial pressure (kPa)
!Percent oxygen
|-
|25.5
|25.5
|100
|-
|34.5
|23.8
|69.0
|-
|48.3
|22.7
|47.0
|-
|62.1
|22.1
|35.5
|-
|101.4
|21.2
|21.0
|}
Since humans can survive at pressures significantly below sea level on Earth, lower oxygen pressures than shown above would certainly be tolerable. However, physical and mental performance are diminished at high altitudes on Earth, so the same is likely true for partial pressures significantly below those in the chart.

=== Flammability ===
Flammability is influenced by both the concentration (percentage) and partial pressure of oxygen in an environment, with concentration having the greater effect<ref>[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160001047.pdf Oxygen Partial Pressure and Oxygen Concentration Flammability: Can They Be Correlated?]</ref>. So for a given partial pressure of oxygen, reducing the total pressure increases the fire risk.

===Heat transfer===
Air convection is one of the main heat transfer mechanisms. Reduced pressure air has less capacity for convective heat transfer, and added ventilation is required for work in low density air. Most plants function more efficiently if there is air movement to remove heat and evaporation from their surface.

==Open Issues==

*What air pressure, combined with different oxygen levels, is required for persons to survive?
*What air pressure, combined with different oxygen levels, is required for persons to live and work?
*What are the results from the [[Biosphere 2]] experiment? Ideas for mitigation and/or compensation?
*What is known about the behaviour of dusty air under low [[gravity]]?

==References==
<references />

[[Category:Air]]

Oxygen

2019-06-03T03:49:39Z

Timfduffy: Added a link to the page for air

{{element
|float=right
|elementName=Oxygen
|elementSymbol=O
|protons=8
|abundance=0.13% ([[atmosphere]])
}}

'''Oxygen''' (''periodic table symbol:'' O8) is a chemical element that can be found in the [[atmosphere]] and in most [[minerals]] on [[Mars]].

[[Image:alga_and_bubbles.jpg|thumb|right|200px|Alga producing oxygen]]

==Relevance for life==
The metabolism of [[human|human beings]], [[:category:animals|animals]] and various [[microbes]] depends on oxygen. The atmosphere of Mars contains only 0.2 % oxygen, which is not enough to support animal or human life.

==Production==
Oxygen can be produced [[Atmospheric processing|in situ]]:

*in [[greenhouse]]s by plants.
*by reduction of [[carbon dioxide]] from the martian atmosphere
*by reduction of oxide minerals
*by [[electrolysis]] of [[water]]

==Uses==

*[[Propellant]]. Oxygen is often chosen as an oxidizer for chemical propulsion.
*[[Air|Atmospheric component]]. Standard atmosphere contains 21% Oxygen.
*Chemical reagent

==Related Articles==

[[lunarp:Oxygen|Oxygenlunarp]] on Lunarpedia.

[[category:Air]]

Nitrogen

2019-06-03T03:48:40Z

Timfduffy: Added a link to the page for air

{{element|elementName=Nitrogen|elementSymbol=N|protons=7|abundance=2.7%}}
'''Nitrogen''' (''chemical symbol:'' N7) is the most abundant atmospheric element in the [[Earth]]'s atmosphere, making up 78% of the total atmospheric gas. [[Mars]], however, has less nitrogen in it's [[atmosphere]], only 3% of the total atmospheric gas. This relative scarcity of nitrogen will cause an expense for colonists on Mars as the existing atmosphere must be processed to separate out CO2. As the CO2 is required for propellant production, the concentration of Nitrogen to breathable levels becomes part of the propellant production cycle.

Producing [[In-situ resource utilization|in-situ]] nitrogen is a rather straightforward operation in which the cooling needed to liquefy the carbon dioxide is mainly provided by evaporating the liquid carbon dioxide after the nitrogen has been removed. Likewise the power for compressing the carbon dioxide is partially provided by expanding the output waste through a turbine with a common shaft with the compressor. however some energy is required to offset system losses, and the CO2 may not always be expanded as it will normally be used to produce propellant.

The "[[nitrogen cycle]]" is an essential terrestrial process that produces organic compounds intrinsic to life on Earth. "Fixing" by [[lightning]] strikes or [[bacteria|bacterial]] processes combine atmospheric nitrogen with other elements (such as hydrogen, producing [[ammonia]]) producing organic compounds required for plants ([[fertilizer|sustaining growth]] and used in [[photosynthesis]]), thereby supporting [[ecosystem]]s. Nitrogen can be found in [[amino acids]], proteins and DNA, making it an essential component of life as we know it.

==Storage==
Nitrogen from [[atmospheric processing]] will probably be used immediately to create the settlement atmosphere. If any excess nitrogen is produced it can be stored in some form of containment, or pressure vessel. The boiling point of nitrogen is -195.79 °C at atmospheric pressure. Unless the nitrogen is actively cooled by a refrigeration system, it will eventually heat up to ambient temperatures and the pressure will increase. If the nitrogen is obtained though CO2 compression to 520 kPa (about 5 atmosphere, or 75 psi) it can remain a liquid if cooled to about -170°C. To keep the nitrogen liquid at a room temperature of 23°C requires a pressure of about 1500 kPa (220 psi). This can be easily maintained in small pressure vessels but requires extremely strong and heavy vessels in large volumes.

It is likely that all the nitrogen obtain through atmospheric processing will become part of the colony atmosphere, at least in the early stages. So large scale storage is not an immediate problem. In all cases nitrogen can be stored at lower pressures when cooled bellow ambient temperatures. However, a refrigeration system is required to do this. If there is sufficient insulation, the heat gain can be quite small and the refrigeration system will also be minimum.

The surface temperature of Mars aids for refrigeration as the average global temperature is approximately -63°C. So the storage location for liquid nitrogen would not be inside [[settlement|habitats]] (where the average temperature should be as close to 23 °C as possible), but outside, on the cooler surface. Or preferably underground in pressure vessels. '''''{{PersPosSection}} [[User:Ioneill|Ioneill]]'''''

==Uses==

*[[Air|Settlement atmosphere]] (main usage).
*Fertilizer, when transformed into ammonia as part of the nitrogen cycle.
**Nitrogen is an essential element of all the amino acids in plant structures which are the building blocks of plant proteins, important in the growth and development of vital plant tissues and cells like the cell membranes and chlorophyll.
**Nitrogen is a component of nucleic acid that forms DNA a genetic material significant in the transfer of certain crop traits and characteristics that aid in plant survival. It also helps hold the genetic code in the plant nucleus.
**Chlorophyll being an organelle essential for carbohydrate formation by photosynthesis and a substance that gives the plant their green color, nitrogen is a component in it that aids in enhancing these features.
**Nitrogen is essential in plant processes such as photosynthesis. Thus, plants with sufficient nitrogen will experience high rates of photosynthesis and typically exhibit vigorous plant growth and development.
*Inert gas for certain industrial processes.
*Explosives component (nitrates).
*May be used to [[funeral|prepare dead bodies]] prior to disposal. Freezing bodies with liquid nitrogen and then powdering the remains (through vibration) may be a viable means to reuse valuable biomass (in [[greenhouse]]s etc.).

==External links==

*[http://en.wikipedia.org/wiki/Nitrogen_cycle The nitrogen cycle on Wikipedia.]

[[category:Air]]

Argon

2019-06-03T03:48:11Z

Timfduffy: Added a link to the page for air

{{element
|float=right
|elementName=Argon
|elementSymbol=Ar
|protons=18
|abundance=1.6% ([[atmosphere]])
}}
'''Argon''' is the third most abundant element in the martian [[atmosphere]], 1.6%.<ref>[http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html NASA ''Mars Fact Sheet'']</ref> It is an oderless, colorless [[nobel gas|noble gas]]. Like the other noble gasses, it is chemically inert. As such, it has many uses in industry. Argon is easily produced [[In-situ resource utilization|in-situ]] from the martian atmosphere by cooling to condense out carbon dioxide and [[distillation]] to separate out the nitrogen. For use as a buffer gas in a colony atmosphere, the nitrogen need not be separated. Mixed nitrogen and argon can be added to oxygen to dilute it to 20% mole fraction oxygen, the concentration of the standard Earth atmosphere. The substitution of nitrogen by argon for a breathable atmosphere seems straightforward.

== Uses ==

* As an [[Air|atmospheric filler]] produced alongside nitrogen
* As an inert gas in certain industrial processes
* As propellant for electrical space propulsion

==Reference==
<references />

{{stub}}

[[Category:Materials]]

Talk:Air

2019-06-03T03:44:01Z

Timfduffy: Created page with "==Replacing low pressure effects== I'd like to replace the low pressure effects section with a section about necessary oxygen pressure for survival, since quite low pressures..."

==Replacing low pressure effects==

I'd like to replace the low pressure effects section with a section about necessary oxygen pressure for survival, since quite low pressures are acceptable as long as the oxygen partial pressure is high enough.
[https://spacecraft.ssl.umd.edu/old_site/design_lib/HSSWG_3-02.pdf This source] has some good information on normoxic oxygen pressure that could be inserted there. I'd like to confirm that I wouldn't be stepping on anyone's toes by doing this though since I'm new to wiki editing. I'd also like to rework part of the article into a series of subsections about the pros and cons of higher and lower total habitat pressures.

Air

2019-06-03T03:36:16Z

Timfduffy: Just fixing a typo

Air

2019-06-03T03:31:53Z

Timfduffy: Added section on gases

Atmosphere

2019-06-03T02:19:55Z

Timfduffy: Fixed an error in my previous edit

[[Image:sunset.jpg|thumb|right|300px|Sunset photographed by Mars Rover Spirit]]
The '''Atmosphere''' of [[Mars]] is not breathable. The pressure is too low, and there is too little [[oxygen]]. And yet, it gives Mars something that makes it the most habitable of all planets in our [[solar system]], except [[Earth]] of course. It provides valuable [[:category:chemistry|chemicals]], and it forms a visible sky, mostly from dispersed dust.

==Composition (gaseous parts)==
Composition of Mars atmosphere by volume<ref>[https://science.sciencemag.org/content/341/6143/263 Abundance and Isotopic Composition of Gases in the Martian Atmosphere from the Curiosity Rover]</ref><ref>[http://www.daviddarling.info/encyclopedia/M/Marsatmos.html Water and trace gases based on table from David Darling Space Encyclopedia]</ref>
{|
|Percentage
|Gas
|-
|96.0%
|[[Carbon dioxide]] (CO2)
|-
|1.93%
|[[Argon]] (Ar)
|-
|1.89%
|[[Nitrogen]] (N)
|-
|0.145%
|[[Oxygen]] (O2)
|-
|0.09%
|[[Carbon monoxide]] (CO)
|-
|0.03%
|[[water|Water vapor]] (H2O)
|-
|''trace''
|[[Neon]] (Ne), [[Krypton]] (Kr), [[Xenon]] (Xe), [[Ozone]] (O3), [[Methane]] (CH4)
|}

==Mars surface pressure==
1-9 millibars (depending on altitude).

==References==
<references />

{{stub}}
[[Category:Atmospheric Sciences]]

Atmosphere

2019-06-03T02:19:23Z

Timfduffy: Replaced concentrations of gases with more modern data from Curiosity rover

[[Image:sunset.jpg|thumb|right|300px|Sunset photographed by Mars Rover Spirit]]
The '''Atmosphere''' of [[Mars]] is not breathable. The pressure is too low, and there is too little [[oxygen]]. And yet, it gives Mars something that makes it the most habitable of all planets in our [[solar system]], except [[Earth]] of course. It provides valuable [[:category:chemistry|chemicals]], and it forms a visible sky, mostly from dispersed dust.

==Composition (gaseous parts)==
Composition of Mars atmosphere by volume<ref>[https://science.sciencemag.org/content/341/6143/263 Abundance and Isotopic Composition of Gases in the Martian Atmosphere from the Curiosity Rover]</ref><ref>[http://www.daviddarling.info/encyclopedia/M/Marsatmos.html Water and trace gases based on table from David Darling Space Encyclopedia]</ref>
{|
|
|Gas
|-
|96.0%
|[[Carbon dioxide]] (CO2)
|-
|1.93%
|[[Argon]] (Ar)
|-
|1.89%
|[[Nitrogen]] (N)
|-
|0.145%
|[[Oxygen]] (O2)
|-
|0.09%
|[[Carbon monoxide]] (CO)
|-
|0.03%
|[[water|Water vapor]] (H2O)
|-
|''trace''
|[[Neon]] (Ne), [[Krypton]] (Kr), [[Xenon]] (Xe), [[Ozone]] (O3), [[Methane]] (CH4)
|}

==Mars surface pressure==
1-9 millibars (depending on altitude).

==References==
<references />

{{stub}}
[[Category:Atmospheric Sciences]]