An Aquatic Habitability Index is proposed, based on Quantitative Habitability Theory, and considering a very general model for life. It is a primary habitability index, measuring habitability for phytoplankton in the first place. The index is applied to some case studies, such as the habitability changes in Earth due to environmental perturbations caused by asteroid impacts.
We do a preliminary modelling of the photosynthetic rates of phytoplankton at
the very beginning of the Paleogene, just after the impact of the Chicxulub
asteroid, which decisively contributed to the last known mass extinction of the
Phanerozoic eon. We assume the worst possible scenario from the photobiological
point of view: an already clear atmosphere with no ozone, as the timescale for
soot and dust settling (years) is smaller than that of the full ozone
regeneration (decades). Even in these conditions we show that most
phytoplankton species would have had reasonable potential for photosynthesis in
all the three main optical ocean water types. This modelling could help explain
why the recovery of phytoplankton was relatively rapid after the huge
environmental stress of that asteroid impact. In a more general scope, it also
reminds us of the great resilience of the unicellular biosphere against huge
environmental perturbations.Comment: Accepted in Astrophysics and Space Scienc
Abstract:We perform a quantitative assessment for the potential for photosynthesis in hydrothermal vents in the deep ocean. The photosynthetically active radiation in this case is from geothermal origin: the infrared thermal radiation emitted by hot water, at temperatures ranging from 473 up to 673 K. We find that at these temperatures the photosynthetic potential is rather low in these ecosystems for most known species. However, species which a very high efficiency in the use of light and which could use infrared photons till 1300nm, could achieve good rates of photosynthesis in hydrothermal vents. These organisms might also thrive in deep hydrothermal vents in other planetary bodies, such as one of the more astrobiologically promising Jupiter satellites: Europa.
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