What is an atmosphere comparable to Earth's atmosphere?

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Discussion Overview

The discussion revolves around the concept of an atmosphere comparable to Earth's atmosphere, particularly in the context of exoplanets. Participants explore various aspects such as composition, temperature profiles, and the implications for supporting life.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether a comparable atmosphere would consist of the same atoms and molecules as Earth's, and whether its temperature and structural layers would be similar.
  • Another participant suggests that a practical definition of a comparable atmosphere is one that allows humans to breathe normally.
  • A different viewpoint emphasizes that the context and the speaker's intent matter, particularly in exoplanet research, where claims about atmospheric similarity may be influenced by funding considerations.
  • It is proposed that a planet's atmosphere described as "similar to Earth's" would need to support life, potentially including temperatures between 0 to 100 Celsius, and contain gases like CO2 and N2, with O2 being a significant indicator of biological activity.
  • One participant notes that nascent oxygen detected on exoplanets could arise from non-biotic processes, such as the ionization of water or carbon dioxide.

Areas of Agreement / Disagreement

Participants express differing views on what constitutes an atmosphere comparable to Earth's, with no consensus reached on specific definitions or criteria.

Contextual Notes

The discussion highlights the ambiguity in defining "comparable" atmospheres, including assumptions about the necessity of certain gases and temperature ranges, as well as the influence of context on interpretations.

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TL;DR
What does it mean when a planet have an atmosphere comparable to the Earth?
Does it mean that the atmosphere is made of the same atoms and molecules like our atmosphere and that it has the same spheres such as trophosphere? And that the temperatures in these spheres are also the same or very similar like here? And are distances between these spheres the same like here or are they adapted to the planet's size? What do you think?
 
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Lotto said:
What does it mean when a planet have an atmosphere comparable to the Earth?
VERY vague question but the most practical answer is simply "one in which humans can breath normally".
 
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Depends who says it and in what context. Presuming you're talking about exoplanets, it probably means that there's enough oxygen that the lead researcher reckons that bro, you could totally breathe that mix, and knows he's more likely to get more funding for more exoplanet research if he can sell it as earthlike...
 
A comparison between Earth's atmosphere and that of other planets is usually tied to support for life.
So a planet with something "similar to Earth's" would include parts that are within 0 to 100 Celsius and contain some CO2 and perhaps N2. It could also contain a significant portion of O2, but at that point you would probably find the use of descriptions more exclamatory than "similar to Earth's" - since significant amounts of O2 aren't likely to persist without biological activity.
Nascent Oxygen can be detected in some exoplanets - but that can be from the ionization of H2O or CO2.
Here's an article describing how O2 can be produced from non-biotic chemical reactions.
 
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