View source for Astroecology

{{Short description|Study of the interactions of biota with space environments}}
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'''Astroecology'''  concerns the interactions of [[Biota (ecology)|biota]] with [[space]] environments. It studies resources for [[life]] on [[planet]]s, [[asteroid]]s and [[comet]]s, around various [[star]]s, in [[Galaxy|galaxies]], and in the [[universe]].  The results allow estimating the future prospects for life, from [[planet]]ary to [[galaxy|galactic]] and [[cosmology|cosmological]] scales.<ref name="Mautner-2002">{{Citation |last=Mautner |first=Michael N. |title = Planetary Bioresources and Astroecology. 1. Planetary Microcosm Bioassays of Martian and Meteorite Materials: Soluble Electrolytes, Nutrients, and Algal and Plant Responses |url=http://www.astro-ecology.com/PDFBioresourcesIcarus2002Paper.pdf |journal=[[Icarus (journal)|Icarus]] |volume=158 |issue=1 |pages=72–86 |year=2002 |doi=10.1006/icar.2002.6841  |bibcode=2002Icar..158...72M }}</ref><ref name="Mautner-2005">{{Citation |last=Mautner |first=Michael N. |title=Life in the Cosmological Future: Resources, Biomass and Populations |journal=[[Journal of the British Interplanetary Society]] |volume=58 |pages=167–180 |year=2005 |url=http://www.astro-ecology.com/PDFCosmologyJBIS2005Paper.pdf |bibcode=2005JBIS...58..167M}}</ref><ref name= "Mautner-2000">{{Citation |last=Mautner |first=Michael N. |title=Seeding the Universe with Life: Securing Our Cosmological Future |publisher=Legacy Books, Washington D. C |year=2000 |url=http://www.astro-ecology.com/PDFSeedingtheUniverse2005Book.pdf }}</ref>

Available [[energy]], and [[microgravity]], [[radiation]], [[pressure]] and [[temperature]] are physical factors that affect astroecology. The ways by which life can reach [[space environment]]s, including [[panspermia|natural panspermia]] and [[directed panspermia]] are also considered.<ref name="Kelvin-1871">{{Cite journal| last = Thomson (Lord Kelvin) | first = W. | title =Inaugural Address to the British Association Edinburgh | journal = Nature | volume = 4 | pages = 261–278 [263] | year = 1871 |doi=10.1038/004261a0| issue = 92 |bibcode = 1871Natur...4..261. | doi-access = free }}</ref><ref name="Weber-1985">{{Citation |last1=Weber |first1=P. |last2=Greenberg |first2=Jose |title=Can spores survive in interstellar space? |journal=[[Nature (journal)|Nature]] |volume=316 |issue=6027 |pages=403–407 |year=1985 |doi=10.1038/316403a0 |bibcode=1985Natur.316..403W |s2cid=4351813 }}</ref><ref name="Crick-1975">{{Citation |last1=Crick |first1=F.H. |last2=Orgel |first2= L.E. |title=Directed Panspermia |journal=[[Icarus (journal)|Icarus]] |volume=19 |issue=3 |pages=341–348 |year=1973 |doi=10.1016/0019-1035(73)90110-3 |bibcode=1973Icar...19..341C }}</ref><ref name="Mautner-1979">{{Citation |last1=Mautner |first1 = Michael N. |last2=Matloff |first2=G.L. |title=A Technical and Ethical Evaluation of Seeding Nearby Solar Systems |journal=Bulletin of the American Astronomical Society |volume=32 |pages=419–423 |year=1979 | url=http://www.astro-ecology.com/PDFDirectedPanspermia1JBIS1979Paper.pdf }}</ref><ref name="Mautner-1997">{{Citation |last=Mautner |first=Michael N. |title=Directed Panspermia. 2. Technological Advances Toward Seeding Other Solar Systems, and the Foundations of Panbiotic Ethics |journal=[[Journal of the British Interplanetary Society]] |volume=50 |pages=93–102 |year=1997|bibcode = 1997JBIS...50...93M }}</ref> Further, for human expansion in space and directed panspermia, motivation by life-centered [[biotic ethics]], panbiotic ethics and  planetary [[bioethics]] are also relevant.<ref name="Mautner-1979" /><ref name="Mautner-1997" /><ref name="Mautner-2009">{{Citation |last=Mautner |first=Michael N. |title=Life-Centered Ethics, and the Human Future in Space |url =http://www.astro-ecology.com/PDFLifeCenteredBioethics2009Paper.pdf |journal=Bioethics |volume=23 |issue=8 |pages=433–440 |year=2009 |doi=10.1111/j.1467-8519.2008.00688.x |pmid=19077128 |s2cid=25203457 }}</ref>

==Overview==
The term "astroecology" was first applied in the context of performing studies in actual [[meteorite]]s to evaluate their potential resources favorable to sustaining life.<ref name="Mautner-2002" /> Early results showed that meteorite/asteroid materials can support [[microorganisms]], [[algae]] and [[plant]] cultures under Earth's atmosphere and supplemented with water.

Several observations suggest that diverse planetary materials, similar to meteorites collected on Earth, could be used as agricultural soils, as they provide nutrients to support microscopic life when supplemented with water and an atmosphere.<ref name="Mautner-2002"/> Experimental astroecology has been proposed to rate planetary materials as targets for astrobiology exploration and as potential biological in-situ resources.<ref name="Mautner-2002"/> The biological fertilities of planetary materials can be assessed by measuring water-extractable [[electrolyte]] nutrients. The results suggest that [[carbonaceous asteroid]]s and Martian [[basalt]]s can serve as potential future resources for substantial biological populations in the [[Solar System]].<ref name="Mautner-2002"/>

Analysis of the essential [[nutrient]]s ([[carbon|C]], [[Nitrogen|N]], [[Phosphorus|P]], [[Potassium|K]]) in meteorites yielded information for calculating the amount of [[biomass]] that can be constructed from asteroid resources.<ref name="Mautner-2002" /> For example, [[carbonaceous asteroid]]s are estimated to contain about 10<sup>22</sup> kg potential resource materials,<ref name ="Lewis-1997">{{Citation |last=Lewis |first=J.S |author-link=J. S. Lewis | title=Physics and Chemistry of the Solar System |publisher=[[Academic Press]], New York |year=1997}}</ref><ref name="Lewis-1996">{{Citation |last=Lewis |first=J. S. |author-link=J. S. Lewis |title=Mining the Sky |publisher=Helix Books, Reading, Massachusetts |year=1996 }}</ref><ref name="OLeary-1977">{{Citation |last=O'Leary |first=B. T.|title=Mining the Apollo and Amor Asteroids |journal=[[Science (journal)|Science]] |volume=197 |issue=4301 |pages=363–6 |year=1977 |pmid=17797965 |doi=10.1126/science.197.4301.363-a |bibcode=1977Sci...197..363O |s2cid=45597532}}</ref><ref name="ONeill-1974">{{Citation |last=O'Neill |first=G.K. |title=The Colonization of Space |journal=[[Physics Today]] |volume=27 |pages=32–38|year=1974 |doi=10.1063/1.3128863 |issue=9 |bibcode = 1974PhT....27i..32O |doi-access=free }}</ref><ref name="ONeill-1977">{{Citation |last=O'Neill |first=G. K. |title=The High Frontier |publisher=William Morrow |year=1977}}</ref><ref name="Hartmann-1985">{{Citation |last=Hartmann |first=K. W. |title=The Resource Base in Our Solar System, in Interstellar Migration and Human Experience |publisher=ed Ben R. Finney and Eric M. Jones, [[University of California Press]], Berkeley, California |year=1985 }}</ref> and laboratory results suggest that they could yield a biomass on the order of 6·10<sup>20</sup> kg, about 100,000 times more than biological matter presently on [[Earth]].<ref name="Mautner-2005" />

==Cultures on simulated asteroid/meteorite materials==
To quantify the potential amounts of life in biospheres, theoretical astroecology attempts to estimate the amount of biomass over the duration of a [[biosphere]]. The resources, and the potential time-integrated biomass were estimated for [[planetary system]]s, for [[habitable zone]]s around [[stars]], and for the [[galaxy]] and the [[universe]].<ref name="Mautner-2005" /><ref name="Mautner-2000" /> Such astroecology calculations suggest that the limiting elements [[nitrogen]] and [[phosphorus]] in the estimated 10<sup>22</sup> kg carbonaceous asteroids could support 6·10<sup>20</sup> kg biomass for the expected five billion future years of the [[Sun]], yielding a future time-integrated ''BIOTA'' (''BIOTA'', '''B'''iomass '''I'''ntegrated '''O'''ver '''T'''imes '''A'''vailable, measured in kilogram-years) of 3·10<sup>30</sup> kg-years in the Solar System,<ref name="Mautner-2002" /><ref name="Mautner-2005" /><ref name="Mautner-2000" /> a hundred thousand times more than life on Earth to date. Considering biological requirements of 100 W kg<sup>−1</sup> biomass, radiated energy about [[red giant]] stars and [[White dwarf|white]] and [[red dwarf]] stars could support a time-integrated ''BIOTA'' up to 10<sup>46</sup> kg-years in the galaxy and 10<sup>57</sup> kg-years in the universe.<ref name="Mautner-2005" />

Such astroecology considerations quantify the immense potentials of future life in space, with commensurate [[biodiversity]] and possibly, [[intelligence]].<ref name="Mautner-2005" /><ref name="Mautner-2000" /> [[Chemical analysis]] of [[carbonaceous chondrite]] meteorites show that they contain extractable bioavailable [[water]], [[organic carbon]], and essential [[phosphate]], [[nitrate]] and [[potassium]] nutrients.<ref name = 'nine'>{{Citation | last = Jarosewich | first = E.| title = Chemical Analysis of the Murchison Meteorite | journal = Meteoritics | volume = 1 | pages = 49–52 | year = 1973 | issue = 1| bibcode = 1971Metic...6...49J | doi=10.1111/j.1945-5100.1971.tb00406.x| doi-access = free }}</ref><ref name = 'ninea'>{{Citation | last1 = Fuchs | first1 = L.H.| last2 = Olsen |first2 = E. |  last3 = Jensen | first3 = K.J. | title = Mineralogy, Mineral Chemistry and Composition of the Murchison (CM2) Meteorite | journal = Smithsonian Contributions to the Earth Sciences | volume = 10 | pages = 1–84 | year = 1973 | issue = 10| doi=10.5479/si.00810274.10.1}}</ref><ref name = 'ten' >{{Citation | last = Mautner | first = Michael N. | title = Planetary Resources and Astroecology. Electrolyte Solutions and Microbial Growth. Implications for Space Populations and Panspermia | series = 2 | journal = [[Astrobiology (journal)|Astrobiology]] | volume = 2 | pages = 59–76 | year = 2002 | issue = 1 | url = http://www.astro-ecology.com/PDFAsteroidAstrobiology2002Paper.pdf | doi = 10.1089/153110702753621349 |bibcode = 2002AsBio...2...59M | pmid=12449855}}</ref> The results allow assessing the soil fertilities of the parent asteroids and planets, and the amounts of biomass that they can sustain.<ref name="Mautner-2002" /><ref name = 'ten' />

Laboratory experiments showed that material from the [[Murchison meteorite]], when ground into a fine powder and combined with Earth's water and air, can provide the nutrients to support a variety of organisms including bacteria ([[Nocardia asteroides]]), algae, and plant cultures such as potato and asparagus.<ref name = 'ten' /> The microorganisms used organics in the carbonaceous meteorites as the carbon source. Algae and plant cultures grew well also on Mars meteorites because of their high bio-available phosphate contents.<ref name="Mautner-2002" /> The Martian materials achieved soil fertility ratings comparable to productive agricultural soils.<ref name="Mautner-2002" /> This offers some data relating to [[terraforming of Mars]].<ref>{{Citation | last1 = Olsson-Francis | first1 = K  | last2 = Cockell | first2 = CS | title = Use of cyanobacteria in in-situ resource use in space applications | journal = Planetary and Space Science | volume = 58 | pages = 1279–1285 | year = 2010 | bibcode = 2010P&SS...58.1279O | doi = 10.1016/j.pss.2010.05.005 | issue = 10 }}</ref>

Terrestrial analogues of planetary materials are also used in such experiments for comparison, and to test the effects of space conditions on microorganisms.<ref>{{Citation | last1 = Billi | first1 = D | last2 = Viaggiu | first2 = E | last3 = Cockell | first3 = CS | last4= Rabbow | first4 = E | last5 = Horneck | first5 = G | last6 = Onofri | first6 = S | title = Damage escape and repair in dried Chroococcidiopsis spp. from hot and cold deserts exposed to simulated space and martian conditions | journal = [[Astrobiology (journal)|Astrobiology]] | volume = 11 | pages = 65–73 | year = 2010 | issue = 1 | bibcode = 2011AsBio..11...65B | doi = 10.1089/ast.2009.0430 | pmid=21294638}}</ref>

The biomass that can be constructed from resources can be calculated by comparing the concentration of elements in the resource materials and in biomass (Equation 1).<ref name="Mautner-2002" /><ref name="Mautner-2005" /><ref name="Mautner-2000" /> A given mass of resource materials (''m<sub>resource</sub>'')  can support ''m<sub>biomass, X</sub>'' of biomass containing element ''X'' (considering ''X'' as the limiting nutrient), where ''c<sub>resource, X</sub>'' is the concentration (mass per unit mass) of element ''X'' in the resource material and ''c<sub>biomass, X</sub>'' is its concentration in the biomass.

<math>m_{biomass,\, X} = m_{resource,\, X} \frac{c_{resource,\, X}}{c_{biomass,\, X}}</math>  (1)

<!--I still can't figure out the information within this table. Rendered invisible for later edit or delete:
 
From Equation (1), the elemental contents of asteroids ([[Carbon|C]] (carbon), [[Nitrogen|N]] (nitrogen) and [[Phosphorus|P]] (phosphorus) ) can yield about 6·10<sup>20</sup> kg biomass (Table 1).

{| class="wikitable"
|+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''' {{refn|Elements in wet biomass, based on elements in dry biomass.<ref name= 'fifteen' >{{Citation | last = Bowen  | first = H. J. M. | author-link = H. J. M Bowen | title = Trace Elements in Biochemistry | publisher = Academic Press, New York | year = 1966 }}</ref>|group="note"}}
!'''Wet biomass constructible from element X per kg of meteorite''' {{refn|Full wet biomass that can be constructed from element x in 1&nbsp;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 10<sup>22</sup> kg total mass of carbonaceous asteroids or the estimated 10<sup>26</sup> kg total mass of comets, respectively.<ref name ="Lewis-1997" /><ref name="Lewis-1996" />|group="note"}}

|-
|Water-soluble elemental contents {{refn|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-<ref name="Mautner-2002" /><ref name = 'ten'/>|group="note"}}: 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 {{refn|Total concentrations<ref name = "nine" /><ref name = "ninea" /> 
|group="note"}}: 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
|-
|}
-->
Assuming that 100,000&nbsp;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).{{Citation needed|date=September 2012}} Similar materials in the comets could support biomass and populations about one hundred times larger.{{Citation needed|date=September 2012}} [[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,<ref name = 'sixteen'>{{Citation | last1 = Adams | first1 = F. | last2 = Laughlin | first2 = G. | title = The Five Ages of the Universe | publisher = Touchstone Books, New York | year = 1999 }}</ref> and other white dwarf stars, can provide energy for life much longer, for trillions of eons.<ref name = 'seventeen'>{{Citation | doi = 10.1006/icar.2001.6591 | last1 = Ribicky | first1 = K. R. | last2 = Denis | first2 = C. | title = On the Final Destiny of the Earth and the Solar System | journal = [[Icarus (journal)|Icarus]]  | volume = 151 | issue = 1 | pages = 130–137 | year = 2001 | bibcode=2001Icar..151..130R }}</ref> (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<ref name="Mautner-2005" /><ref name="Mautner-2000" /> as given by Equation (2), where M (biomass 0) is the mass of the original biomass, ''k'' is its rate of decay (the fraction lost in a unit time) and ''biomass t'' is the remaining biomass after time ''t''. 
			
:Equation 2:  <math>M_{biomass}(t) = M_{biomass} (0) e^{-kt}\,</math>

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

:Equation 3:  <math>BIOTA  = \frac{M_{biomass} (0)}{k}</math>

For example, if 0.01% of the biomass is lost per year, then the time-integrated ''BIOTA'' will be 10,000<math>M_{biomass} (0)</math>. For the 6·10<sup>20</sup> kg biomass constructed from asteroid resources, this yields 6·10<sup>24</sup> 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 3·10<sup>30</sup> kg-years under the main-sequence Sun would decrease by a factor of 5·10<sup>5</sup>, although a still substantial population of 1.2·10<sup>12</sup> biomass-supported humans could exist through the habitable lifespan of the Sun.<ref name="Mautner-2005" /><ref name="Mautner-2000" /> 
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 biotic ethics suggests that life should last as long as possible.<ref name="Mautner-2009" />

==Galactic ecology==
If 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.<ref name="Mautner-2005" /> 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.<ref name="Mautner-2005" /><ref name="Mautner-2000" /> For example, if 1&nbsp;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.<ref name="Mautner-2005" /><ref name="Mautner-2000" /> Using similar projections, the potential amounts of future life can then be quantified.<ref name="Mautner-2005" />

For the Solar System from its origins to the present, the current  10<sup>15</sup> kg biomass over the past four billion years gives a time-integrated biomass (''BIOTA'') of 4·10<sup>24</sup> kg-years. In comparison, carbon, [[nitrogen]], [[phosphorus]] and water in the 10<sup>22</sup> kg asteroids allows 6·10<sup>20</sup> kg biomass that can be sustained with energy for the 5 billion future years of the Sun, giving a ''BIOTA'' of 3·10<sup>30</sup> kg-years in the Solar System and 3·10<sup>39</sup> kg-years about  10<sup>11</sup> stars in the galaxy. Materials in comets could give biomass and time-integrated ''BIOTA'' a hundred times larger. <!--In space colonies? Certainly not on the outer planets as we know them. Lots of assumptions are loaded in this statement, when the research was limited to water-soluble chemicals: After the Sun turns into a red giant, life in the outer Solar System can contribute significant further biomass for a billion years.<ref name="Mautner-2005" /> -->

The Sun will then become a [[white dwarf]] star, radiating 10<sup>15</sup> Watts that sustains 1e13 kg biomass for an immense hundred million trillion (10<sup>20</sup>) years, contributing a time-integrated ''BIOTA'' of 10<sup>33</sup> years. The 10<sup>12</sup> white dwarfs that may exist in the galaxy during this time can then contribute a time-integrated ''BIOTA'' of 10<sup>45</sup> kg-years. Red dwarf stars with luminosities of 10<sup>23</sup> Watts and life-times of 10<sup>13</sup> years can contribute 10<sup>34</sup> kg-years each, and 10<sup>12</sup> red dwarfs can contribute 10<sup>46</sup> kg-years, while [[brown dwarf]]s can contribute 10<sup>39</sup> kg-years of time-integrated biomass (''BIOTA'') in the galaxy. In total, the energy output of stars during 10<sup>20</sup> years can sustain a time-integrated biomass of about 10<sup>45</sup> kg-years in the galaxy. This is one billion trillion (10<sup>20</sup>) times more life than has existed on the Earth to date. In the universe, stars in 10<sup>11</sup> galaxies could then sustain 10<sup>57</sup> kg-years of life.

<!--This section is little more than a though experiment: contemplating the spontaneous conversion of all atoms (barionic matter) in the universe to living matter. No use in Wikipedia.
==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 life.<ref name="Mautner-2005" /><ref name="Mautner-2000" />  Assume that the power requirement is <math>P_{biomass}</math> (measured in J sec<sup>−1</sup> kg<sup>−1</sup>) and the energy yield is ''E<sub>yield</sub>'') (measured in J kg<sup>−1</sup>). 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<ref name="Weber-1985" />

:<math>-\frac{d M_{biomass}}{d t} E_{yield, biomass} = P_{biomass} M_{biomass}</math> (4)

This is similar to equation (3) with a rate of loss <math>k_{waste} =  P_{biomass}{E_{yield, biomass}}</math>. The remaining biomass after time ''t'' is given according to Equation (5) as:

:<math>M_{biomass} (t) = M_{biomass} (0) e^{- \frac{P_{biomass}}{E_{yield, biomass}} t}</math> (5)

With an energy requirement of 100 W kg<sup>−1</sup> biomass and with the maximum energy yield of ''E = mc<sup>2</sup>'' a fraction of 3.5·10<sup>−8</sup> of the biomass per year would need to be converted to energy, yielding about 3·10<sup>7</sup> kg-years of time-integrated BIOTA per kg biomass. An estimated 10<sup>41</sup> kg baryonic matter in the galaxy and 10<sup>52</sup> kg in the universe, all converted to biomass, would then yield 3·10<sup>48</sup> kg-years of time-integrated biomass in the galaxy and 3·10<sup>59</sup> kg-years of time-integrated biomass in the universe.<ref name="Mautner-2005" /><ref name="Mautner-2000" />

If all the biomass consisted of 100&nbsp;kg humans, this would allow 10<sup>39</sup> humans in the galaxy living 3·10<sup>46</sup> human-years and 10<sup>57</sup> human-years in the universe. This illustrates the immense potential amounts of biological and human life in the universe.
-->

==Directed panspermia==
{{further| Directed panspermia}}
The astroecology results above suggest that humans can expand life in the galaxy through [[Interstellar space travel|space travel]] or [[directed panspermia]].<ref name = 'nineteen'  >{{Citation | last =  Hart | first = M. H.  | title =  Interstellar Migration, the Biological Revolution, and the Future of the Galaxy", in Interstellar Migration and Human Experience | publisher = ed Ben R. Finney and Eric M. Jones, University of California Press, Berkeley | year = 1985 }}</ref><ref name = 'nineteena' >{{Citation | last = Mauldin | first = J. H. | title = Prospects for Interstellar Travel | publisher = AAS Publications, Univelt, San Diego | year = 1992 | bibcode = 1992STIA...9325710M | volume = 93 | pages = 25710 | journal = Prospects for Interstellar Travel Univelt }}</ref> The amounts of possible life that can be established in the galaxy, as projected by astroecology, are immense. 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. Therefore, physics, astroeclogy resources, and some cosmological scenarios may allow organized life to last, albeit at an ever slowing rate, indefinitely.<ref name = 'twenty'  >{{Citation | doi = 10.1103/RevModPhys.51.447 | last = Dyson | first = F. | title = Without End: Physics and Biology in an Open Universe | journal = Rev. Mod. Phys. | volume =  51 | issue = 3 | pages = 447–468 | year = 1979 | bibcode=1979RvMP...51..447D}}</ref><ref name = "twentya" >{{Citation | last = Dyson   | first = F.| title =  Infinite in All Directions | publisher = Harper and Row, New York | year = 1988}}</ref> These prospects may be addressed by the long-term extension of astroecology as cosmoecology.

==See also==
{{Portal|Astronomy|Biology}}
*[[Biotic ethics]]
*[[Cosmology]]
*[[Meteorites]]

==References==
{{Reflist|2}}

==External links==
* [http://www.astro-ecology.com Astro-Ecology / Science of expanding life in space]
* [http://www.astroethics.com AstroEthics / Ethics of expanding life in space]    
* [http://www.panspermia-society.com Panspermia-Society / Science and ethics of expanding life in space]

{{Astrobiology}}
{{Extraterrestrial life}}

[[Category:Astrobiology]]
[[Category:Habitat]]
[[Category:Environmental terminology]]
[[Category:Ecology terminology]]