[LINK] "Planetary Habitability Quantified"

[rfmcdonald]

My thanks to james_nicoll for linking to an interesting Centauri Dreams post reporting on a new method that can be used to calculate the volume on a world habitable by microorganisms.

“QH Theory is based on two new biophysical parameters: the habitability H, as a relative measure of the potential for life of an environment, or habitat quality, and the habitation M, as a relative measure of biodensity, or occupancy. Both parameters are related to other physiological and environmental variables and can be used to make predictions about the distribution, abundance, and productivity of primary producers, such as plants and phytoplankton, and microbial life in general. Initially, habitability was modeled from the environment’s temperature and humidity because they are easier to measure at planetary scales with ground or orbital instruments. Global habitability and habitations maps were constructed of terrestrial land and ocean areas with data gridded at various spatial and temporal resolutions. Preliminary work shows that the QH Theory is comparable to existing models in predicting terrestrial primary productivity.”

The results, as applied to our planetary system?

Using finely tuned planetary models, Mendez found that among Mars, Venus, Europa, Titan and Enceladus, the latter has the highest subsurface habitability. That makes the Saturnian moon a tempting but difficult target, the inaccessibility of its habitable region rendering Mars and Europa better compromises for near-term missions to places where habitability is still unresolved.

On Earth, the biosphere includes parts of the atmosphere, oceans, and subsurface. The potential global habitats of the other planetary bodies are deep below their surface. Enceladus has the smallest volume but the highest habitat-planet size ratio followed by Europa. Surprisingly, it also has the highest mean habitability H, in the Solar System, although too deep for direct exploration. Mars and Europa are the best compromise between potential for life and accessibility.

[. . .]

Mendez has established a quantity called Standard Primary Habitability that uses a variety of criteria for establishing the surface habitability on a given world. Interestingly, while the current SPH of Earth is close to 0.7, the figure has been as high as 0.9 in earlier periods, including the late Cretaceous, the time of the dinosaurs’ extinction. Earth achieved, in other words, a higher level of habitability in that era than today, at least as quantified by Mendez, until the events that led to the K/T extinction occurred.