Habitable Zones & Global Climate

Interior Controls on the Habitability of Rocky Planets

By Keith Cowing
Press Release
Space: Science & Technology
May 14, 2024
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Interior Controls on the Habitability of Rocky Planets
Equilibrium speciation of atmospheres at 2,173 K formed around an Earth-sized planet in equilibrium with a magma ocean of mass equal to that in Earth’s mantle (4.2 × 1024 kg) in the system CHONPS with abundances for the BSE as per Table. The atmospheres are produced given solubility laws for CO, CO2, H2O, H2, N2, SO2, and S2 and their equilibrium gas speciation solved at 3 oxygen fugacities relative to the IW buffer, +3, 0, and −3. Total pressure in the atmosphere is shown below the respective pie chart. CREDIT Space: Science & Technology

Investigations into habitability have provided ample opportunity for not only reflection as to its nature but also planetary evolution processes in general. Agreeing on a definition for habitability has proved troublesome.

Rather than providing a definition, we consider that the concept can be distilled to a simple question: Can life develop there? Unfortunately, the notion of life is heavily biased toward life as we know it on Earth, and even the question of “development” remains vague: Is survival enough? Does it include its proliferation instead? Does it cover the emergence of life? Would the requirements not change with time and because of life itself? The interested reader could consult the review by Cockell et al. [1] for a discussion of the definition of the term.

It is nonetheless possible to draw a list of requirements that any living organism we can imagine would need to remain active. Those would include (a) a solvent (water, on Earth), (b) energy, and (c) the presence of various elements and nutrients in sufficient abundances and forms to facilitate (a) and (b).

It has been argued that energy was likely easily accessible in general, from solar radiation, redox potential, or other processes, and that life as we know it makes use of some of the most common building blocks (elements) in the universe, the CHONPS (carbon–hydrogen–oxygen–nitrogen–phosphorus–sulfur).

Even minor elements that are used by life, such as Fe or Mg, for instance, are relatively abundant on the surface of Earth (even if those may vary from one specific organism to the other). Finally, the solvent common to known life, water, is one of the most abundant molecules in the Solar System.

Interior Controls on the Habitability of Rocky Planets, Space Science & Technology (open access)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻