Wooden owl that redefines Earth's biosphere may yet catapult a fungus into space

Hallsworth, John E.

doi:10.1111/1462-2920.14510

Cited by 14 publications

(9 citation statements)

References 64 publications

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“…The fungus (A. penicillioides) that is able to differentiate and grow at 0.585, the lowest water activity for active life 14,32 , is also acidotolerant (see below). At this water activity, differentiation and cell division were observed on a nutrient medium supplemented with 7.7 M glycerol, at pH 6.1 ref.14 .…”

Section: Methodsmentioning

confidence: 99%

Water activity in Venus’s uninhabitable clouds and other planetary atmospheres

et al. 2021

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The recent suggestion of phosphine in Venus' atmosphere has regenerated interest in the idea of life in clouds. However, such analyses usually neglect the role of water activity, which is a measure of the relative availability of water, in habitability. Here, we compute the water activity within the clouds of Venus and other Solar-System planets from observations of temperature and water-vapour abundance. We find water-activity values of sulphuric acid droplets, which constitute the bulk of Venus' clouds, of ≤0.004, two orders of magnitude below the 0.585 limit for known extremophiles. Considering other planets, ice formation on Mars imposes a water activity ≤0.537, slightly below the habitable range, whereas conditions are biologically permissive (>0.585) at Jupiter's clouds (although other factors such as their composition may play a role in limiting their habitability). By way of comparison, the Earth's troposphere conditions are, in general, biologically permissive, whereas the atmosphere becomes too dry for active life above the middle stratosphere. The approach used in the current study can also be applied to extrasolar planets.

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Section: Methodsmentioning

confidence: 99%

Water activity in Venus’s uninhabitable clouds and other planetary atmospheres

et al. 2021

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“…These restrictions are based on the expectation that liquid water is necessary for life, in accordance with [17,18]. Indeed, the presence of water is observed to place rather strict limits for life, with very few microbes capable of being biologically active under extreme desiccation [19,20]. Our discussion presupposes both that water retains its properties which are deemed essential for habitability as the physical constants are varied, that water will be present on planets where it has the potential to be liquid, and, for some planets at least, in moderate enough abundance to maintain some land.…”

Section: Introductionmentioning

confidence: 99%

Multiverse Predictions for Habitability: Element Abundances

et al. 2022

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We investigate the dependence of elemental abundances on physical constants, and the implications this has for the distribution of complex life for various proposed habitability criteria. We consider three main sources of abundance variation: differing supernova rates, alpha burning in massive stars, and isotopic stability, and how each affects the metal-to-rock ratio and the abundances of carbon, oxygen, nitrogen, phosphorus, sulfur, silicon, magnesium, and iron. Our analysis leads to several predictions for which habitability criteria are correct by determining which ones make our observations of the physical constants, as well as a few other observed features of our universe, most likely. Our results indicate that carbon-rich or carbon-poor planets are uninhabitable, slightly magnesium-rich planets are habitable, and life does not depend on nitrogen abundance too sensitively. We also find suggestive but inconclusive evidence that metal-rich planets and phosphorus-poor planets are habitable. These predictions can then be checked by probing regions of our universe that closely resemble normal environments in other universes. If any of these predictions are found to be wrong, the multiverse scenario would predict that the majority of observers are born in universes differing substantially from ours, and so can be ruled out, to varying degrees of statistical significance.

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“…Whereas other studies of water availability on Mars have drawn similar conclusions for the surface and shallow subsurface (Rummel et al, 2014;Hallsworth, 2020). A study of deep-sea brines claims active life at 0.400 water activity (Steinle et al, 2018), although there is no direct biological evidence for this (Hallsworth, 2019b). It is not known how accurate modeling is for extreme acid brines; such modeling may be complicated by the complex chemical compositions, as well as low pH, high salinities, and a wide range of tem-peratures that would be likely on Mars.…”

Section: Implications For Astrobiologymentioning

confidence: 88%

“…It should also be noted that individual salts/ions can exert multiple stresses and multiple extremes on microbial cells (Hallsworth et al, 2007(Hallsworth et al, , 2019bAlves et al, 2015). The close association between microorganisms and organic compounds such as beta carotene suggests that these microorganisms are living in the lake water and not simply getting carried into the lake by wind.…”

Section: Relationships Identified Among Salinity Ph Elemental Concentrations and Water Activitymentioning

confidence: 99%

Water Activities of Acid Brine Lakes Approach the Limit for Life

et al. 2021

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Water activity is an important characteristic for describing unusual waters and is a determinant of habitability for microorganisms. However, few empirical studies of water activity have been done for natural waters exhibiting an extreme chemistry. Here, we investigate water activity for acid brines from Western Australia and Chile with pH as low as 1.4, salinities as high as 32% total dissolved solids, and complex chemical compositions. These acid brines host diverse communities of extremophilic microorganisms, including archaea, bacteria, algae, and fungi, according to metagenomic analyses. For the most extreme brine, its water activity (0.714) was considerably lower than that of saturated (pure) NaCl brine. This study provides a thermodynamic insight into life within end-member natural waters that lie at, or possibly beyond, the very edge of habitable space on Earth.

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Wooden owl that redefines Earth's biosphere may yet catapult a fungus into space

Cited by 14 publications

References 64 publications

Water activity in Venus’s uninhabitable clouds and other planetary atmospheres

Water activity in Venus’s uninhabitable clouds and other planetary atmospheres

Multiverse Predictions for Habitability: Element Abundances

Water Activities of Acid Brine Lakes Approach the Limit for Life

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