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Astroecology

Astroecology concerns the interactions of biota with space environments. It studies resources for life on planets (and asteroids and comets), about various stars, in galaxies, and in the overall universe. The results allow estimating the future prospects of life, from planetary to galactic and cosmological scales (Mautner, 2002) [1] (Mautner, 2002) [2] (Mautner, 2005) [3]

Experimental astroecology studies biological resources in actual space materials in meteorites. (The term “astroecology” was first applied in this context) (Mautner, 2002) [4]. Early results showed that meteorite/asteroid materials can support microorganisms, algae and and plant cultures. Analysis of essential nutrients (C, N, P, K) in the meteorites allows calculating the biomass that can be constructed from these resources. (Mautner, 2002) [5] For example, the results suggest that carbonaceous asteroids can yield biomass on the order of 6e20 kg (six hundred million trillion kg). Available energy, and microgravity, radiation, pressure and temperature also affect astroecology. Also relevant are the ways by which that life can reach space environments, including natural (Thomson (Lord Kelvin), 1871) [6] (Weber and Greenberg, 1985) [7] or directed panspermia (Crick and Orgel) [8] (Mautner and Matloff, 1977) [9] (Mautner, 1995) [10] 

For human-based biological expansion in space`, life-centered astroethics  with a panbiotic commitment to propagate life are also relevant. (Mautner and Matloff, 1977) [11] (Mautner, 1995) [12] (Mautner, 2009) [13]

Theoretical astroecology can quantify the potential amounts of life, or the total biomass supported over the duration of a biosphere (Biomass Integrated Over Times Available (BIOTA) (kg-years). The biological resources, biomass and time-integrated BIOTA have been estimated for solar systems and for habitable zones about various stars, and for the galaxy and the universe. (Mautner, 2002) [14] (Mautner, 2005) [15]

For example, the limiting elements N and P in the estimated 1e22 kg carbonaceous asteroids could support 6e20 kg biomass for the expected 5e9 years of the main-sequence Sun, yielding a future time-integrated BIOTA of 3e30 kg-years in the Solar System. (Mautner, 2002) [16] (Mautner, 2002) [17] (Mautner, 2005) [18]

On the largest scale, cosmoecology concerns life in the galaxy and in the universe over cosmological times. On these scales life may be energy-limited. BAsed on biological requirements of 100 W/kg biomass, radiated energy about red giant stars and white and red dwarf stars could support BIOTA up to 1e46 kg-years in the galaxy and 1e57 kg-years in the universe. As an upper limit, the ultimate amount of life would be achieved if all matter was incorporated into biomass and then slowly converted to energy to sustain the biomass. This would yield 1e48 kg-years of time-integrated biomass in the galaxy and 1e59 kg-years of time-integrated biomass in the universe. [2] (Mautner, 2002) [19] (Mautner, 2005) [20]

In summary, the results of experimental and theoretical astroecology indicate an immense potential for future life in the universe. It may depend on human action and a life-centered astroethics if this potential will be realized.

Experimental Astroecology: Biological Cultures on Meteorites

Experimental astroecology uses meteorites to assess nutrients in asteroids and planets. Chemical analysis of carbonaceous chondrite meteorites (Jarosewich, 1973) [21] (Fuchs et al, 1973)[22] (Mautner, 2002) [23] shows that they contain extractable bioavailable water, organic carbon, and the phosphate, nitrate and potassium. The results allow assessing the soil fertilities of the parent asteroids and planets, and the amounts of biomass that they can sustain. (Mautner, 2002) [24] (Mautner, 2002) [25]

Can these resources actuallly support life? Experiments showed that extracts of the Murchison CM2 meteorite can support high populations of organisms including bacteria (Nocardia asteroides), algae, and plant cultures including potato and asparagus. The microorganisms used organics in the carbonaceous meteorites as carbon sources. Algae and plant cultures also grew well on Mars meteorites.

The biomass that can be constructed from these resources is found by comparing the concentration of elements in the resource materials and in biomass (Equation 1). (Mautner, 2002) [26] (Mautner, 2002) [27] (Mautner, 2005) [28] A given mass of resource materials (m¬resource) (kg) can support mbiomass,x (kg) of biomass containing element x (considering x as the limiting nutrient), where cresource,x is the concentration of element x in the resource material (g/kg) and cbiomass,x is its concentration in the biomass (g/kg).

mbiomass,x = mresource,x x (cresource,x / cbiomass,x) (1)

Carbonaceous asteroids contain about 1e22 kg potential resource materials. (Lewis, 1997) [29] (Lewis, 1996) [30] (O’Leary, 1977) [31] (O’Neill, 1974) [32] (O’Neill, 1977) [33] (Hartmann, 1985) [34]

From Equation (1), their critical resources (C (carbon), N (nitrogen) and P (phosphorus) ) can yield about 6e20 kg biomass (Table 1).

Table 1. Concentrations of elements in the carbonaceous chondrite (CM2) Murchison meteorite and in biomass, and the amounts of biomass that can be constructed from the meteorite materials.

ELEMENT x C N S P Ca Mg K Water ELEMENTS IN METEORITE Bioavailable water-soluble elemental contentsa 1.8 0.008 7.6 0.005 3.0 4.0 0.34 100b Total contentsb 18.6 1.0 32.4 1.1 13 114 >0.28 100 ELEMENTS IN BIOMASSc 116 17 1.8 3.9 5.3 0.85 8.6 WET BIOMASS (kg) CONSTRUCTED FROM ELEMENT X IN 1 kg OF METEORITEd From Water-Soluble Elements 0.016 0.00048 4.1 0.0013 0.57 5.3 0.04 From Total Element Contents 0.16 0.06 18 0.28 2.5 140 >0.03

a. Elements extracted in pure water at 120 oC for 15 minutes. Calcium (Ca), magnesium (Mg) and potassium (K) are extracted as elements; sulfur (S) as sulfate SO42-, nitrogen (N) as nitrate NO3- and phosphorus (P) as phosphate PO42- (Mautner, 2002) [35] (Mautner, 2002) [36] 

b. Total concentrations (Jarosewich, 1973)[37]  (Fuchs et al, 1973)[38]
c. Elements in wet biomass, based on elements in dry biomass (Bowen, 1966) [39] and a ratio of wet/dry biomass = 4.0 d. Full wet biomass (kg) constructed from element x in 1 kg of meteorite if x is the limiting element (based on Equation (1)). To calculate the total biomass (kg) that can be constructed from the extractable or total materials of asteroids or comets, multiply the numbers in the bottom rows by 1022 kg or 1026 kg, respectively. (Lewis, 1997) [40]  (Lewis, 1996) [41]


Assuming that 100,000 kg biomass supports one human, the asteroids may then sustain about 6e15 (six million billion) people, equal to a million Earths (a million times more than the present world population). Similar materials in the comets could support biomass and populations about one hundred times even larger. Solar energy can readily sustain these populations for the predicted further five billion year lifespan of the Sun. These considerations yield a maximum time-integrated BIOTA of 3e30 kg-year in the Solar System. After the Sun becomes a white dwarf star (Adams and Laughlin, 1999) [42], and other white dwarf stars, can provide energy to life much longer, for trillions of years (Ribicky and Denis, 2001) [43] (Table 2)

Effects of Wastage

Astroecology also concerns unavoidable wastage, such as the leakage of biological matter into space. This will cause an exponential decay of space-based biomass (Mautner, 2002) [44] (Mautner, 2005) [45]as given by Equation (2), where Mo is the mass of the original biomass, k is its rate of decay (the fraction lost in a unit time) and Mt is the remaining biomass after time t.

Mbiomass,t = Mbiomass,oexp(-kt) (2)

Integration from time zero to infinity yields Equation (3) for the total time-integrated BIOTA contributed by this biomass.

BIOTA = Mbiomass,o / k (3)

For example, if 0.01% of the biomass is lost per year, then the time-integrated BIOTA equals 10,000Mo. For the 6e20 kg biomass constructed from asteroid resources, this yields 6e24 kg-years of BIOTA in the Solar System. Even with this small rate of loss, life in the Solar System would disappear in a few hundred thousand years, and the potential total time-integrated BIOTA of 3e30 kg-years under the main-sequence Sun would decrease by a factor of 5x105 but still a substantial population of 1.2x1012 (1.2 trillion) biomass-supported humans could exist through the habitable lifespan of the Sun. (Mautner, 2002) [46] (Mautner, 2005) [47]

In summary, the integrated biomass can be maximized by minimizing its rate of dissipation. If this rate can be reduced sufficiently, all the constructed biomass can last for the duration of the habitat, and it pays to construct the biomass as fast as possible. However, if the rate of dissipation is significant vs. the lifetime of the habitat, the construction rate of the biomass and its steady-state amounts may be reduced, but the reduced steady-state biomass and population can then last throughout the lifetime of the habitat. Should we build immense amounts of life that decays fast, or smaller, but still large, populations that last longer? Life-centered ethics suggests that life in the Solar System, and in the universe at large, should last as long as possible. (Mautner, 2009) [48]


Galactic Ecology

The possible amounts of life in the Solar System are determined by material resources. However, when life reaches galactic proportions, technology should be able to access all material resources, and the scope of life will be defined by the supply of energy. The maximum amount of biomass about any star is then determined given by the energy requirements of the biomass and by the luminosity of the star. (Mautner, 2002) [49] (Mautner, 2005) [50] For example, if 1 kg biomass needs to be powered by 100 Watts of energy, we can calculate the steady-state amounts of biomass sustained by stars with various luminosities. These amounts are multiplied by the life-time of the star to calculate the time-integrated BIOTA about the star over its duration. Results were obtained for various types of stars and the total time-integrated BIOTA that can be sustained by each type of star in the galaxy. (Mautner, 2002) [51] (Mautner, 2005) [52]

Cosmo-Ecology and the Maximum Amounts of Life in the Universe

It is of interest to estimate the maximum amount of life that is possible in this universe. This amount of life would be achieved if all the mass in ordinary baryonic matter was converted to living matter. However, life requires energy, and a fraction of this mass would then need to be converted to energy to sustain biology. (Mautner, 2002) [53] (Mautner, 2005) [54] 

Assume that the power requirement is P(biomass) (J/sec kg) and the energy yield is E(yield) (J/kg)   (Joules per kg  biomass converted to energy). If the biomass is converted to energy at the rate required to provide the needed power for the remaining biomass, then the rate of decrease of biomass is given by equation (Weber and Greenberg, 1985) [55]

-dM(biomass)/dt) (kg/s) E(yield, biomass) (J/kg) = P(biomass) (J/s kg) M(biomass) (kg) (4)

This is similar to equation (3) with a rate of loss k(waste) = P(biomass)/E(yield,biomass). The remaining biomass after time t is given according to Equation (5) as

M(biomass,t) = M(biomass,o) exp (-(Pbiomass/Eyield, biomass) t) (5)

With an energy requirement of 100W/kg biomass and with the maximum energy yield of e = mc^2 a fraction of 3.5e-8 of the biomass per year would need to converted to energy, yielding about 3e7 kg-years of time-integrated BIOTA per kg biomass. An estimated 1e41 kg baryonic matter in the galaxy and 1e52 kg in the universe, all converted to biomass, would then yield 3e48 kg-years of time-integrated biomass in the galaxy and 3e59 kg-years of time-integrated biomass in the universe. (Mautner, 2002) [56] (Mautner, 2005) [57] 

If all the biomass consisted of 100 kg humans, this would allow 1e39 humans in the galaxy living 3e46 human-years and 1e57 human-years in the universe. These estimates illustrate the immense potential amounts of biological and human life in the universe.

The Ultimate Future: Can Life Last Indefinitely?

We can expand life in the galaxy through space travel (Hart, 1985) [58] (Mauldin, 1992) Mauldin, J. H. (1992). Prospects for Interstellar Travel. AAS Publications, Univelt, San Diego. </ref> or directed panspermia (www.panspermia-society.com) The amounts of possible life projected by astroecology for the galaxy and the universe are immense, but still finite. These projections are based on information about 15 billion past years since the Big Bang, but the future spans trillions of eons. Our descendants may need to observe the cosmos on that time-scale to predict the future, that may be controlled by dark matter and energy whose nature is yet unknown, or by as yet unknown new forces. Some cosmological futures may allow some organized life to last indefinitely at an ever slowing rate, (Dyson, 1979) [59] (Dyson, 1988) [60] or restructuring the laws of physics to our advantage, creating ever expanding universes (Mautner, 2002) [61] (Mautner, 2005) [62] 

that are hospitable to life.

Astroecology and Astroethics

Astroecology shows that life in the universe can have an immense future. [2] (Mautner, 2002) [63] (Mautner, 2005) [64] This future may be in our hands, if we assure that life survives long-term and that expands in space. Our descendants may understand nature more deeply and try to extend life indefinitely, giving human existence can find a cosmic purpose.(Mautner, 2002) [65] (Mautner, 2005) [66](Mautner, 2009) [67](WWW.ASTROETHICS.COM)

References

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