Editing Atmosphere

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The [[Atmosphere|Atmosphere Code]] is the [[UWP]] code to represent the mixture of gases constituting an an atmosphere encountered on a [[world]] or [[moon]]. Some types of atmospheres require the use of [[protective clothing]] or [[mask]]s. {{Page cite|name=Worlds and Adventures|version=Classic Traveller|page=7}} The code shows the requirements for using protective gear on the world.  The [[Atmospheric Pressure|Atmospheric Code]] is a standard [[Metric]]. 

== Description ([[Specifications]]) == <!--T:2-->
Atmospheres have a mix of different gases, some in great amounts, while others are barely detectable. Atmospheric mixes include active and inert gases. On Earth, oxygen (02) is active, but forms less than 25% of the total atmosphere. Three times as much is nitrogen (N2), plus a few trace elements such as argon. These inert gases are not usually required by animal or plant life, and take no part in the chemical reactions essential for [[life]] (except for nitrogen, a special case). They are, nonetheless, part of the atmosphere. In this [[AAB]] article, when we refer to a specific gas such as methane making up an atmosphere, we are referring to the active element, which may make up only a fraction of the total atmospheric mix. {{Page cite|name=Exotic Atmospheres|page=3-4}}
 
=== World Atmosphere Classification Codes Table ===
As a generality, small [[world]]s have insufficient [[gravity]] to maintain an atmosphere and tend to have [[Thin Atmosphere|thin]] or [[trace atmosphere]]s while larger worlds grow increasingly dense. [[Corrosive World|Corrosive]] and [[insidious world]]s tend to be at extreme ends of the tolerable temperature spectrum. 
{| class="wikitable sortable"
|-
!colspan="9"| Atmospheric Code Descriptions
|-
! [[Symbol]]
! Code 
! Specific Description
! General Description 
! Pressure ([[Atm]])
! Remarks
|-
| [[File: ATM-0-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 0 
| [[Vacuum]] 
| [[Vacuum]] 
| < 0.001
| Vacuum requires a [[vacc suit]]. The atmosphere has a pressure of less than 0.001 atmospheres, which requires the use of a [[vacc suit]].
|-
| [[File: ATM-1-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 1  
| [[Trace Atmosphere|Trace]]
| [[Vacuum]] 
| 0.001-0.09
| The atmosphere has a pressure of less than 0.1 atmospheres, which requires the use of a [[vacc suit]].
|-
| [[File: ATM-2-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 2  
| [[Very Thin Atmosphere|Very Thin]] / [[Tainted Atmosphere|Tainted]] 
| [[Vacuum]] 
| 0.10-0.42
| [[Very Thin Atmosphere|Very Thin]] tainted requires a [[filter respirator combination]]
|-
| [[File: ATM-3-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 3  
| [[Very Thin Atmosphere|Very Thin]]
| [[Vacuum]]  
| 0.10-0.42
| [[Very Thin Atmosphere|Very Thin]] requires a [[respirator]]. The atmosphere has a pressure of 0.1 to 0.42 atmospheres, which requires the use of a [[respirator]] to ensure sufficient oxygen.
|-
| [[File: ATM-4-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 4  
| [[Thin Atmosphere|Thin]] / [[Tainted Atmosphere|Tainted]]
| [[Thin Atmosphere|Thin]] 
| 0.43-0.70
| [[Tainted Atmosphere|Tainted]] requires a [[filter mask]]. The atmosphere contains an unusual taint such as such as [[Diseases & Plagues of Charted Space|disease]], a hazardous gas mix, [[pollutant]]s, or sulfur compounds which requires the use of a [[filter mask]]. 
|-
| [[File: ATM-5-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 5  
| [[Thin Atmosphere|Thin]] 
| [[Thin Atmosphere|Thin]] 
| 0.43-0.70
| ''[[Shirtsleeve World]]:'' No survival gear required. The atmosphere has a pressure of 0 43 to 0.70 atmospheres. The atmosphere is a standard oxygen/nitrogen mix, which is breathable without assistance.
|-
| [[File: ATM-6-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 6  
| [[Standard Atmosphere|Standard]]
| [[Standard Atmosphere|Standard]] 
| 0.71-1.49
| ''[[Shirtsleeve World]]:'' No survival gear required. The atmosphere has a pressure of 0.71 to 1.49 atmospheres. The atmosphere is a standard oxygen/nitrogen mix, which is breathable without assistance.
|-
| [[File: ATM-7-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 7  
| [[Standard Atmosphere|Standard]] / [[Tainted Atmosphere|Tainted]]
| [[Standard Atmosphere|Standard]]
| 0.71-1.49
| [[Tainted Atmosphere|Tainted]] requires a [[filter mask]].
|-
| [[File: ATM-8-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 8 
| [[Dense Atmosphere|Dense]] 
| [[Dense Atmosphere|Dense]] 
| 1.50-2.49
| ''[[Shirtsleeve World]]:'' No survival gear required. The atmosphere has a pressure of 1.50 to 2.49 atmospheres The atmosphere is a standard oxygen/nitrogen mix, which is breathable without assistance.
|-
| [[File: ATM-9-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| 9 
| [[Dense Atmosphere|Dense]] / [[Tainted Atmosphere|Tainted]]
| [[Dense Atmosphere|Dense]] 
| 1.50-2.49
| [[Tainted Atmosphere|Tainted]] requires a [[filter mask]].
|-
| [[File: ATM-A-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| A (10) 
| [[Exotic Atmosphere|Exotic]]
| [[Exotic Atmosphere|Exotic]] , Conventional   
| varies
| An unusual gas mix which requires the use of [[oxygen tank]]s, but [[protective suit]]s are not needed.
|-
| [[File: ATM-B-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| B (11)
| [[Corrosive Atmosphere|Corrosive]]
| [[Exotic Atmosphere|Exotic]] , Conventional   
| varies
| A concentrated gas mix or unusual temperature creates a [[Corrosive Atmosphere|corrosive environment]], which requires the use of a [[Hostile environment suit]] or [[vacc suit]].
|-
| [[File: Atm-C-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| C (12)
| [[Insidious Atmosphere|Insidious]]
| [[Exotic Atmosphere|Exotic]], Conventional  
| varies
| The atmosphere is similar to a [[corrosive atmosphere]], but extreme conditions cause the corrosive effects to defeat any protective measures in 2 to 12 hours.
|-
| [[File: ATM-D-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| D (13) 
| [[Dense Atmosphere|Dense]], [[High Pressure Atmosphere|high]]
| [[Exotic Atmosphere|Exotic]], Unusual 
| 2.5 or greater {{Page cite|name= Core Rulebook|version=Mongoose Traveller|page=170}}
| Typically no survival gear required under many conditions. Pressure at or below sea level is too great to support life but is breathable at higher altitudes.
|-
| [[File: ATM-E-T5-Fan-Andy-Bigwood 22-Oct-2019a.jpg|100px]]
| E (14) '''<sup>†</sup>'''
| [[Ellipsoid Atmosphere|Ellipsoid]] '''<sup>†</sup>'''
| [[Exotic Atmosphere|Exotic]], Unusual 
| 0.5 or less {{Page cite|name= Core Rulebook|version=Mongoose Traveller|page=170}}
| Typically no survival gear required under many conditions. The world’s surface is [[Ellipsoid World|ellipsoidal]], not spherical. Because the atmosphere remains spherical, surface atmospheric pressure ranges from very high at the middle to very low at the ends. Breathable bands may exist at some point within the range of pressure.
|-
| [[File: TBD|100px]]
| F (15) '''<sup>†</sup>'''
| [[Thin Atmosphere|Thin]], [[Low Pressure Atmosphere|low]] '''<sup>†</sup>'''
| [[Exotic Atmosphere|Exotic]], Unusual  
| varies
| Typically no survival gear required under some conditions. This [[world]] is large and massive, with a [[thin atmosphere]] which settles to the lowest levels of the terrain. The atmosphere is un-breathable at most altitudes except the very low ones (…as in depressions or deep valleys).
|-
|}
'''<sup>†</sup>''' - '''''NOTE''':  In '''MgT''' and '''T5''', Atm type '''E''' is "'''Thin, Low'''", and Atm type '''F''' is "'''Unusual'''", which includes (but is not limited to) Ellipsoidal atmospheres.''

=== Protective Measures Based on Atmosphere === <!--T:3-->
The various atmosphere types require specific personal equipment for survival and protection. {{Page cite|name=Worlds and Adventures|version=Classic Traveller|page=9|citeName=WA9}}
; Codes 0 and 1
: [[Vacuum|No atmosphere]] and [[trace atmosphere]] require use of a [[vacc suit]] and associated support equipment.
; Codes 2, 4, 7, and 9
: [[Tainted atmosphere]]s require the use of specialized [[filter mask]]s.
; Codes 2 and 3
: [[Very thin atmosphere]]s require the use of [[compressor]]s to insure sufficient oxygen to breathe. The tainted very thin atmosphere requires a [[combination respirator/filter mask]] for survival.
; Codes 5, 6, 8
: [[Thin Atmosphere|Thin]], [[Standard Atmosphere|standard]], and [[dense atmosphere]] are breathable without assistance.
; Codes A
: [[Exotic atmosphere]]s require the use of [[oxygen tank]]s, but [[protective suit]]s are not usually required unless corrosive or insidious.
; Code B
: [[Corrosive atmosphere]]s require the use of [[protective suit]]s or [[vacc suit]]s.
; Code C
: [[Insidious atmosphere]]s are similar to [[corrosive atmosphere]]s, but will defeat any personal protective measures in two to twelve hours. The only reliable variant for prolonged survival is heavily fortified, reinforced and armored buildings (deep bunkers) and vehicles (Such vehicles were used since TL7 - for example, soviet "Venera" probes/landers - so future materials should definitely do the job).
:: The strongest variants of powered [[Personal Armor|armor]] (like [[Battle Dress]], Augmented Battle Dress, Power Armor, Battle Pod, and other armor models) ''may'' protect the Sophont, but it wasn't confirmed experimentally - it's unclear if they will wistand the atmosphere, melt in 2 to 12 hours, or melt for longer than [[Protective Equipment]].
:: Yet, as written in Techno-Environmental Limits, Sophonts of [[TL:10-12|TL10]] and higher '''do manage to somehow live there'''.
; Codes D, E, and F
: These represent "[[Unusual Atmosphere]]s" with special conditions such as [[Ellipsoid Atmosphere]]s. The worlds are partly covered with a breathable atmosphere. The survival gear required depends upon where you are located.

=== Basic Atmosphere Types === <!--T:4-->
Combinations of the below atmospheres may exist and are not comprehensively listed: 
# [[Corrosive Atmosphere]]
# [[Dense Atmosphere]]
# [[Ellipsoid Atmosphere]]
# [[Exotic Atmosphere]]
# [[High Pressure Atmosphere]]
# [[High Temperature Atmosphere]]
# [[Insidious Atmosphere]]
# [[Low Pressure Atmosphere]]
# [[Low Temperature Atmosphere]]
# [[Standard Atmosphere]] (Tolerable pressure, temperature, constituent gases, etc. for [[Conventional Life|conventional]] [[lifeform]]s)
# [[Tainted Atmosphere]]
# [[Thin Atmosphere]]
# [[Trace Atmosphere]]
# [[Unusual Atmosphere]]
# [[Vacuum]] ([[Interstellar Medium]])
# [[Very Thin Atmosphere]]

=== UWP & Atmospheres === <!--T:5-->
The third digit in the [[UWP]] identifies the type of atmosphere that the [[world]] has. As a rule, only larger worlds have a [[Gravity|gravitational field]] large enough to hold on to an atmosphere, but there certainly are exceptions. An atmosphere is essentially a layer of gas or gasses that cloak the surface of the [[planet]] and there are a number of reasons why a world may or may not be lucky enough to have one. As we have already mentioned, a big world has the muscle to keep its atmosphere and the bigger the world, in all likelihood the denser (...or thicker) the atmosphere will be. Conversely, [[moon]]s and [[Planetoid|small planet]]s with relatively low surface gravities will generally have only [[trace atmosphere]]s, if they have anything at all. {{Page cite|name=The Universal World Profile|page=13}}

<!--T:6-->
Other factors also come into play. A [[world]] sitting close to the [[Star|main star]] might have its atmosphere stripped away by the destructive energy of the star's [[solar wind]] sweeping past. The only chance a planet has of retaining its layer of gasses in this situation, is if it also benefits from a molten core that is producing a protective [[magnetosphere]]. Compare the [[Earth]], whose atmosphere is shielded by its magnetosphere, with [[Mars]]. The [[Mars|red planet]] has a [[Trace Atmosphere|trace]] or [[very thin atmosphere]] that was considerably thicker in ancient times, but as the planet cooled it first lost its magnetosphere and then its atmosphere. {{Page cite|name=The Universal World Profile|page=13}}

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Yet there are exceptions; in the depths of the solar system, the [[moon]] [[Saturn_(world)#Mainworld_Data|Titan]] orbits the ringed planet [[Saturn (world)|Saturn]]. Titan is cold, far from the [[sun]] and seismically inactive. It has no [[magnetosphere]] and with a surface [[gravity]] of only 0.14 G should not be able to retain an atmosphere - yet it has a [[dense atmosphere]] that is 1.45 times thicker than that of [[Earth]]'s. [[Jupiter_(world)#Ganymede|Ganymede]] and [[Jupiter_(world)#Callisto|Callisto]], comparable-sized [[moon]]s of [[Jupiter]], are of a similar composition but do not have atmospheres. One theory suggests that [[Saturn_(world)#Mainworld_Data|Titan]], being farther from the [[sun]] than the [[moon]]s of [[Jupiter]], was colder during its formation. Gasses were trapped in the ice at those low temperatures and later made their way into [[Saturn_(world)#Mainworld_Data|Titan]]'s atmosphere. {{Page cite|name=The Universal World Profile|page=13-14}}

== History & Background ([[Dossier]]) == <!--T:8-->
All [[TL:4-6|industrial societies]] gain an expanded understanding of atmospheres, air pressure, atmospheric constituents, gas behavior, industrial pollutants, and other factors in order to build a successful, modern interstellar starfaring society.   

<!--T:9-->
[[Tent World]]s are an example of a world ordinarily too small to contain an atmosphere, but artificially and technologically modified to possess an atmosphere using [[paraterraforming]].

=== Techno-Environmental Limits === <!--T:10-->
The typical [[sophont]] species needs to invent various kinds of protective equipment in order to colonize atmospheres to which it is not native.

<!--T:11-->
:{| class="wikitable sortable" width="90%"
|+ Techno-Environmental Limits
! Atmosphere <br> (Nomenclature) Code 
! Minimum <br> [[TL]]
! Remarks
|-
| [[Thin Atmosphere|5]], [[Standard Atmosphere|6]] or [[Dense Atmosphere|8]]
| [[TL-0]]
| No [[survival equipment]] required.
|-
| [[Tainted Atmosphere|4, 7 or 9]]          
| [[TL:1-3|TL-3]]
| [[Tainted atmosphere]]s require [[filter]]s.
|-
| [[Very Thin Atmosphere|2 or 3]]
| [[TL:4-6|TL-5]]
| [[Very thin atmosphere]]s require [[compressor]]s.
|-
| [[High Pressure Atmosphere|13 (D)]] or [[Low Pressure Atmosphere|14 (E)]]    
| [[TL:4-6|TL-5]]
| [[Unusual atmosphere]]s require a variety of protective equipment.
|-
| [[Vacuum|0]] or [[Trace Atmosphere|1]]           
| [[TL:7-9|TL-8]]
| [[Trace Atmosphere|Trace]] or [[vacuum]] atmospheres require a [[vacc suit]] and [[oxygen tank]]s.
|-
| [[Exotic Atmosphere|10 (A)]]             
| [[TL:7-9|TL-8]]
| Unbreathable atmospheres require [[oxygen tank]]s.
|-
| [[Unusual Atmosphere|15 (F)]]             
| [[TL:7-9|TL-8]]
| Unusual atmospheres such as [[ellipsoid]]s require [[survival equipment]] under selected conditions.
|-
| [[Corrosive Atmosphere|11 (B)]]             
| [[TL:7-9|TL-9]]
| [[Corrosive atmosphere]]s require a variety of capable protective equipment.
|-
| [[Insidious Atmosphere |12 (C)]]           
| [[TL:10-12|TL-10]]
| [[Insidious atmosphere]]s require a variety of heavy-duty protective equipment.
|-
|}

== See also == <!--T:12-->
{{Goods title list|Atmosphere equipment}}

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{{Referral-Tree-U-Universal-World-Profile}}

== References & Contributors ([[Sources]]) == <!--T:14-->
{{Advanced}}
{{Sources
 | {{Ludography cite|name= Worlds and Adventures|version=Classic Traveller|page=5, 9, 17, 19}}
 | {{Ludography cite|name= Exotic Atmospheres|page=1-16}} 
 | {{Ludography cite|name= Grand Survey |page=19, 27-28, 34-35, 45}}  
 | {{Ludography cite|name= Referee's Manual|page=22}}
 | {{Ludography cite|name= World Builder's Handbook|page=64-68}}
 | {{Ludography cite|name= World Tamer's Handbook|page=11-17, 84, 90-91}}
 | {{Ludography cite|name= First In|page=67-73}}
 | [[Robert O'Connor]], ''[http://freelancetraveller.com/features/science/atmos/index.html Atmospheres]'' ([[Freelance Traveller]] 2003) 
 | {{Ludography cite|name= Interstellar Wars|page=125-6}} 
 | {{Ludography cite|name= Core Rulebook|version=Mongoose Traveller|page=41, 137, 170-171, 179}}
 | {{Ludography cite|name= T5 Core Rules|page=409}}
 | {{Ludography cite|name= The Universal World Profile|page=13-18}}
 | {{Ludography cite|name=Core Rule Book | version=Mongoose 2nd|page=217-218}}
 | Author & Contributor: Lord (Marquis) [[Jonathan Sherlock]]
 | Author & Contributor: Lord (Marquis) and Master Scout Emeritus [[Adie Alegoric Stewart]] of the [[IISS]]
 | Contributor: Lord (Marquis) and Master of Sophontology [[Maksim-Smelchak]] of the [[Ministry of Science]]
}}

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{{LE|Planets|Planetology}}
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