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

Experimental astroecology studies the biological resources in actual space materials from meteorites; the term “astroecology” was first applied in this context.[1] Early results showed that meteorite/asteroid materials can support microorganisms, algae and plant cultures. Analysis of the essential nutrients (C, N, P, K) in meteorites yielded information for calculating the amount of biomass that can be constructed from asteroid resources.[1] For example, the results suggest that carbonaceous asteroids can yield a biomass on the order of 6·1020 kg.

Available energy, and microgravity, radiation, pressure and temperature also affect astroecology. Also relevant are the ways by which life can reach space environments, including natural [4][5] and directed panspermia [6][7][8]

For human expansion in space, life-centered astroethics, and panbiotic ethics committed to propagate and expand life, are also relevant.[7][8][9]

Theoretical astroecology can quantify the amount of biomass that could be supported over the duration of a biosphere (BIOTA, Biomass Integrated Over Times Available, measured in kilogram-years). The resources, and the potential time-integrated biomass were estimated for solar systems, for habitable zones around stars, and for the galaxy and the universe.[2][3]

For example, the limiting elements N and P in the estimated 1022 kg carbonaceous asteroids could support 6·1020 kg biomass for the expected five billion future years of the Sun, yielding a future time-integrated BIOTA of 3·1030 kg-years in the Solar System.[1][2][3]

On the largest scale, cosmoecology concerns the scope of life in the galaxy and in the universe over cosmological time, based on the available energy. Based on biological requirements of 100 W kg-1 biomass, radiated energy about red giant stars and white and red dwarf stars could support BIOTA up to 1046 kg-years in the galaxy and 1057 kg-years in the universe.

The ultimate amount of life would be achieved if all matter was incorporated into biomass and then slowly converted to sustaining energy. This would yield 1048 kg-years of time-integrated biomass in the galaxy and 1059 kg-years of time-integrated biomass in the universe.[2][3]

Contents

Biological cultures on meteorites

Experimental astroecology uses meteorites to assess nutrients in asteroids and on planets. Chemical analysis of carbonaceous chondrite meteorites [10][11][12] shows that they contain extractable bioavailable water, organic carbon, and essential phosphate, nitrate and potassium nutrients. The results allow assessing the soil fertilities of the parent asteroids and planets, and the amounts of biomass that they can sustain.[1][12]

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 can be calculated by comparing the concentration of elements in the resource materials and in biomass (Equation 1).[1][2][3] A given mass of resource materials (mresource) can support mbiomass, X of biomass containing element X (considering X as the limiting nutrient), where cresource, X is the concentration (mass per unit mass) of element X in the resource material and cbiomass, X is its concentration in the biomass.

m_{biomass,\, X} = m_{resource,\, X} \frac{c_{resource,\, X}}{c_{biomass,\, X}} (1)

Carbonaceous asteroids contain about 1022 kg potential resource materials.[13][14][15][16][17][18]

From Equation (1), the elemental contents of asteroids (C (carbon), N (nitrogen) and P (phosphorus) ) can yield about 6·1020 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
Elements in meteorite Elements in biomass [note 1] Wet biomass constructible from element X per kg of meteorite [note 2]
Water-soluble elemental contents [note 3]: C, 1.8; N, 0.008; S,7.6; P,0.005; Ca, 3.0; Mg, 4.0; K, > 0.34, water, 100 C, 116; N, 17; S, 1.8; P, 3.9; Ca, 5.3; Mg, 0.85; K, 8.6 From water-soluble elements: C, 0.016; N, 0.00048; S, 4.1; P, 0.0013; Ca, 0.57; Mg, 5.3; K, 0.04
Total contents [note 4]: C, 18.6; N, 1.0; S, 32.4; P, 1.1; Ca, 13; Mg, 114; K, > 0.28; water, 100 From total elemental contents: C, 0.16; N, 0.06; S, 18; P, 0.28; Ca, 2.5; Mg, 140; K, >0.03

Notes

  1. ^ Elements in wet biomass, based on elements in dry biomass.[19]
  2. ^ Full wet biomass that can be constructed from element x in 1 kg of meteorite if x is the limiting element (based on Equation (1)). To calculate the total biomass (in kg) that can be constructed from the extractable or total materials of asteroids or comets, multiply the numbers in the bottom rows by the estimated 1022 kg total mass of carbonaceous asteroids or the estimated 1026 kg total mass of comets, respectively.[13][14]
  3. ^ 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- [1][12]
  4. ^ Total concentrations[10][11]

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 the present population). Similar materials in the comets could support biomass and populations about one hundred times larger. Solar energy can sustain these populations for the predicted further five billion years of the Sun. These considerations yield a maximum time-integrated BIOTA of 3e30 kg-years in the Solar System. After the Sun becomes a white dwarf star,[20] and other white dwarf stars, can provide energy for life much longer, for trillions of eons [21] (Table 2)

Effects of wastage

Astroecology also concerns wastage, such as the leakage of biological matter into space. This will cause an exponential decay of space-based biomass [2][3] as given by Equation (2), where M(biomass,o) is the mass of the original biomass, k is its rate of decay (the fraction lost in a unit time) and M_{biomass} (t) is the remaining biomass after time t.

M_{biomass}(t) = M_{biomass} (0) e^{-kt}\, (2)

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

BIOTA = \frac{M_{biomass} (0)}{k} (3)

For example, if 0.01% of the biomass is lost per year, then the time-integrated BIOTA will be 10,000M_{biomass} (0). For the 6·1020 kg biomass constructed from asteroid resources, this yields 6·1024 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 3·1030 kg-years under the main-sequence Sun would decrease by a factor of 5·105, although a still substantial population of 1.2·1012 biomass-supported humans could exist through the habitable lifespan of the Sun.[2][3] 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, the construction rate of the biomass and its steady-state amounts may be reduced allowing a steady-state biomass and population that lasts throughout the lifetime of the habitat.

An issue that arises is whether we should build immense amounts of life that decays fast, or smaller, but still large, populations that last longer. Life-centered ethics suggests that life should last as long as possible.[22]

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 of the materials resources, and sustainable life will be defined by the available energy. The maximum amount of biomass about any star is then determined by the energy requirements of the biomass and by the luminosity of the star.[2][3] For example, if 1 kg biomass needs 100 Watts, we can calculate the steady-state amounts of biomass that can be sustained by stars with various energy outputs. These amounts are multiplied by the life-time of the star to calculate the time-integrated BIOTA over the life-time of the star. Such results were obtained for various types of stars in the future galaxy.[2][3] Using cosmological projections,[20] the potential amounts of future life can then be quantified.[2]

For our Solar System from its origins to the present, the current 1015 kg biomass over the past four billion years gives a time-integrated biomass (BIOTA) of 4·1024 kg-years. In comparison, carbon, nitrogen, phosphorus and water in the 1022 kg asteroids allows 6·1020 kg biomass that can be sustained with energy for the 5 billion future years of the Sun, giving a BIOTA of 3·1030 kg-years in the Solar System and 3·1039 kg-years about 1011 stars in the galaxy. Materials in comets could give biomass and time-integrated BIOTA a hundred times larger. After the Sun turns into a red giant, life in the outer Solar System can contribute significant further biomass for a billion years.[2]

The Sun will then become a white dwarf star, radiating 1015 Watts that sustains 1e13 kg biomass for an immense hundred million trillion (1020) years, contributing a time-integrated BIOTA of 1033 years. The 1012 white dwarfs that may exist in the galaxy during this time can then contribute a time-integrated BIOTA of 1045 kg-years. Red dwarf stars with luminosities of 1023 Watts and life-times of 1013 years can contribute 1034 kg-years each, and 1012 red dwarfs can contribute 1046 kg-years, while brown dwarfs can contribute 1039 kg-years of time-integrated biomass (BIOTA) in the galaxy. In total, the energy output of stars during 1020 years can sustain a time-integrated biomass of about 1045 kg-years in the galaxy. This is one billion trillion (1020) times more life than has existed on the Earth to date. In the universe, stars in 1011 galaxies could then sustain 1057 kg-years of life. These vast amounts of living matter can allow unimaginable diversity in biology and in intelligence.,[2]

The maximum amount of potential life in the universe

It is of interest to estimate the maximum amount of potential life in this universe. This would be achieved if all the 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.[2][3] Assume that the power requirement is P_{biomass} (measured in J sec-1 kg-1) and the energy yield is Eyield) (measured in J kg-1). 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 [5]

-\frac{d M_{biomass}}{d t} E_{yield, biomass} = P_{biomass} M_{biomass} (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} (0) e^{- \frac{P_{biomass}}{E_{yield, biomass}} t} (5)

With an energy requirement of 100 W kg-1 biomass and with the maximum energy yield of E = mc2 a fraction of 3.5·10-8 of the biomass per year would need to be converted to energy, yielding about 3·107 kg-years of time-integrated BIOTA per kg biomass. An estimated 1041 kg baryonic matter in the galaxy and 1052 kg in the universe, all converted to biomass, would then yield 3·1048 kg-years of time-integrated biomass in the galaxy and 3·1059 kg-years of time-integrated biomass in the universe.[2][3]

If all the biomass consisted of 100 kg humans, this would allow 1039 humans in the galaxy living 3·1046 human-years and 1057 human-years in the universe. This illustrates the immense potential amounts of biological and human life in the universe.

Can life last indefinitely?

We can expand life in the galaxy through space travel [23][24] or directed panspermia (www.panspermia-society.com) The amounts of possible life that can be established in the galaxy, as projected by astroecology, are immense, but still finite. These projections are based on information about 15 billion past years since the Big Bang, but the habitable future is much longer, spanning trillions of eons. Our descendants may need to observe the cosmos on that time-scale to predict the future. Some cosmological scenarios may allow organized life to last indefinitely at an ever slowing rate,[25][26] or maybe even the laws of physics can be restructured, creating ever expanding universes [2][3] permanently hospitable to life.

External links

References

  1. ^ a b c d e f g Mautner, M. N. (2002), "Planetary Bioresources and Astroecology. 1. Planetary Microcosm Bioassays of Martian and Meteorite Materials: Soluble Electrolytes, Nutrients, and Algal and Plant Responses", Icarus 158 (1): 72–86, Bibcode 2002Icar..158...72M, doi:10.1006/icar.2002.6841 
  2. ^ a b c d e f g h i j k l m n o Mautner, M.N. (2005), "Life in the Cosmological Future: Resources, Biomass and Populations", British Interplanetary Soc 58: 167–180 
  3. ^ a b c d e f g h i j k l Mautner, M.N. (2000), Seeding the Universe with Life: Securing Our Cosmological Future, Legacy Books, Washington D. C 
  4. ^ Kelvin, Lord. (1871), Nature 4: 262 
  5. ^ a b Weber, P.; Greenberg, Jose (1985), "Can spores survive in interstellar space?", Nature 316 (6027): 403–407, Bibcode 1985Natur.316..403W, doi:10.1038/316403a0 
  6. ^ Crick, F.H.; Orgel ], L.E. (1973), "Directed Panspermia", Icarus 19 (3): 341–348, Bibcode 1973Icar...19..341C, doi:10.1016/0019-1035(73)90110-3 
  7. ^ a b Mautner, M.; Matloff, G.L. (1979), "A Technical and Ethical Evaluation of Seeding the Universe", Bulletin Amer. Ast. Soc 32: 419–423 
  8. ^ a b Mautner, M.N. (1997), "Directed Panspermia. 2. Technological Advances Toward Seeding Other Solar Systems", J. British Interplanetary Soc 50: 93–102 
  9. ^ Mautner, M.N. (2009), "Life-Centered Ethics, and the Human Future in Space", Bioethics 23 (8): 433–440, doi:10.1111/j.1467-8519.2008.00688.x, PMID 19077128 
  10. ^ a b Jarosewich, E. (1973), "Chemical Analysis of the Murchison Meteorite", Meteoritics 1: 49 
  11. ^ a b Fuchs, L.H.; Olsen, E.; Jensen, K.J. (1973), "Mineralogy, Mineral Chemistry and Composition of the Murchison (CM2) Meteorite", Smithsonian Contributions to the Earth Sciences 10: 1–84 
  12. ^ a b c Mautner, M.N. (2002), "Planetary Resources and Astroecology. Electrolyte Solutions and Microbial Growth. Implications for Space Populations and Panspermia", Astrobiology, 2: 59–76 
  13. ^ a b Lewis, J.S (1997), Physics and Chemistry of the Solar System, Academic Press, New York 
  14. ^ a b Lewis, J. S. (1996), Mining the Sky, Helix Books, Reading, Massachusetts 
  15. ^ O'Leary, B. T. (1977), "Mining the Apollo and Amor Asteroids", Science 197 (4301): 363, Bibcode 1977Sci...197..363O, doi:10.1126/science.197.4301.363-a, PMID 17797965 
  16. ^ O'Neill, G.K. (1974), "The Colonization of Space", Physics Today 27: 32–38 
  17. ^ O'Neill, G. K. (1977), The High Frontier, William Morrow 
  18. ^ Hartmann, K. W. (1985), The Resource Base in Our Solar System", in Interstellar Migration and Human Experience, ed Ben R. Finney and Eric M. Jones, University of California Press, Berkley 
  19. ^ Bowen, H. J. M. (1966), Trace Elements in Biochemistry, Academic Press, New York 
  20. ^ a b Adams, F.; Laughlin (1999.), The Five Ages of the Universe, Touchstone Books, New York 
  21. ^ Ribicky, K. R.; Denis, C. (2001), "On the Final Destiny of the Earth and the Solar System", Icarus 151 (1): 130–137, Bibcode 2001Icar..151..130R, doi:10.1006/icar.2001.6591 
  22. ^ Mautner, M. N. (2009), "Life-Centered Ethics, and the Human Future in Space", Bioethics: in press 
  23. ^ Hart, M. H. (1985), Interstellar Migration, the Biological Revolution, and the Future of the Galaxy", in Interstellar Migration and Human Experience, ed Ben R. Finney and Eric M. Jones, University of California Press, Berkeley 
  24. ^ Mauldin, J. H. (1992), Prospects for Interstellar Travel, AAS Publications, Univelt, San Diego 
  25. ^ Dyson, F. (1979), "Without End: Physics and Biology in an Open Universe", Rev. Modern Phys 51 (3): 447–468, Bibcode 1979RvMP...51..447D, doi:10.1103/RevModPhys.51.447 
  26. ^ Dyson, F. (1988), Infinite in All Directions, Harper and Row, New York 
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