Editing Panspermia (section)

== Varieties of panspermia theory ==
[[File:ISS space station modules in the SSPF.jpg|thumb|Some microbes appear able to survive the [[planetary protection]] procedures applied to spacecraft in [[cleanroom]]s, intended to prevent accidental planetary contamination.<ref name="NAT-20140519"/><ref name="NASA-20131106"/>]]
Panspermia is generally subdivided into two classes: either transfer occurs between planets of the same system (interplanetary) or between stellar systems (interstellar). Further classifications are based on different proposed transport mechanisms, as follows.

===Radiopanspermia===
In 1903, [[Svante Arrhenius]] proposed radiopanspermia, the theory that singular microscopic forms of life can be propagated in space, driven by the [[radiation pressure]] from stars.<ref>{{Citation |title=V. Die Verbreitung des organischen Lebens auf der Erde |date=1885-12-31 |url=http://dx.doi.org/10.1515/9783112690987-006 |work=Anthropologische Studien |pages=101–133 |access-date=2023-11-28 |publisher=De Gruyter |doi=10.1515/9783112690987-006 |isbn=978-3-11-269098-7}}</ref> This is the mechanism by which light can exert a force on matter. Arrhenius argued that particles at a critical size below 1.5 μm would be propelled at high speed by radiation pressure of a star.<ref name=":103"/> However, because its effectiveness decreases with increasing size of the particle, this mechanism holds for very tiny particles only, such as single [[Endospore|bacterial spores]].

==== Counterarguments ====
The main criticism of radiopanspermia came from [[Iosif Shklovsky]] and [[Carl Sagan]], who cited evidence for the [[Health threat from cosmic rays|lethal action of space radiation]] ([[UV]] and [[X-ray]]s) in the cosmos.<ref>{{Citation |title=The Intelligent Universe |date=2020-09-24 |url=http://dx.doi.org/10.1017/9781108873154.026 |work=The Biological Universe |pages=318–334 |access-date=2023-11-28 |publisher=Cambridge University Press |doi=10.1017/9781108873154.026 |isbn=978-1-108-87315-4|s2cid=116975371 }}</ref> If enough of these microorganisms are ejected into space, some may rain down on a planet in a new star system after 10<sup>6</sup> years wandering interstellar space.{{cn|date=September 2024}} There would be enormous death rates of the organisms due to radiation and the generally hostile conditions of space, but nonetheless this theory is considered potentially viable by some.{{cn|date=September 2024}}

Data gathered by the orbital experiments [[Exobiology Radiation Assembly|ERA]], [[BIOPAN]], [[EXOSTACK]] and [[EXPOSE]] showed that isolated spores, including those of ''[[B. subtilis]]'', were rapidly killed if exposed to the full space environment for merely a few seconds, but if shielded against solar [[UV]], the spores were capable of surviving in space for up to six years while embedded in clay or meteorite powder (artificial meteorites).<ref>{{Cite journal |last1=Horneck |first1=Gerda |last2=Rettberg |first2=Petra |last3=Reitz |first3=Günther |last4=Wehner |first4=Jörg |last5=Eschweiler |first5=Ute |last6=Strauch |first6=Karsten |last7=Panitz |first7=Corinna |last8=Starke |first8=Verena |last9=Baumstark-Khan |first9=Christa |date=2001 |title=Protection of bacterial spores in space, a contribution to the discussion on Panspermia |url=http://link.springer.com/10.1023/A:1012746130771 |journal=Origins of Life and Evolution of the Biosphere |volume=31 |issue=6 |pages=527–547 |doi=10.1023/A:1012746130771|pmid=11770260 |bibcode=2001OLEB...31..527H |s2cid=24304433 }}</ref> Spores would therefore need to be heavily protected against UV radiation: exposure of unprotected DNA [[UV exposure|to solar UV]] and [[Cosmic ray|cosmic]] [[ionizing radiation]] would break it up into its constituent bases.<ref>{{Cite journal |last1=Patrick |first1=Michael H. |last2=Gray |first2=Donald M. |date=December 1976 |title=INDEPENDENCE OF PHOTOPRODUCT FORMATION ON DNA CONFORMATION* |url=http://dx.doi.org/10.1111/j.1751-1097.1976.tb06867.x |journal=Photochemistry and Photobiology |volume=24 |issue=6 |pages=507–513 |doi=10.1111/j.1751-1097.1976.tb06867.x |pmid=1019243 |s2cid=12711656 |issn=0031-8655}}</ref> Rocks at least 1 meter in diameter are required to effectively shield resistant microorganisms, such as bacterial spores against galactic [[cosmic radiation]].<ref>{{Cite journal |last=Mileikowsky |first=C |date=June 2000 |title=Natural Transfer of Viable Microbes in Space 1. From Mars to Earth and Earth to Mars |url=http://dx.doi.org/10.1006/icar.1999.6317 |journal=Icarus |volume=145 |issue=2 |pages=391–427 |doi=10.1006/icar.1999.6317 |pmid=11543506 |bibcode=2000Icar..145..391M |issn=0019-1035}}</ref> Additionally, exposing DNA to the [[Ultra-high vacuum|ultrahigh vacuum]] of space alone is sufficient to cause [[DNA damage]], so the transport of unprotected DNA or [[RNA]] during [[Interplanetary spaceflight|interplanetary flights]] powered solely by [[light pressure]] is extremely unlikely.<ref>{{Cite journal |last1=Nicholson |first1=Wayne L. |last2=Schuerger |first2=Andrew C. |last3=Setlow |first3=Peter |date=2005-04-01 |title=The solar UV environment and bacterial spore UV resistance: considerations for Earth-to-Mars transport by natural processes and human spaceflight |url=https://linkinghub.elsevier.com/retrieve/pii/S0027510704004981 |journal=Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis |language=en |volume=571 |issue=1–2 |pages=249–264 |doi=10.1016/j.mrfmmm.2004.10.012|pmid=15748651 |bibcode=2005MRFMM.571..249N }}</ref>

The feasibility of other means of transport for the more massive shielded spores into the outer Solar System—for example, through gravitational capture by comets—is unknown. There is little evidence in full support of the radiopanspermia hypothesis.

=== Lithopanspermia ===
This transport mechanism generally arose following the growth of planetary science with the discovery of exoplanets and the sudden availability of data.<ref name=":44"/> Lithopanspermia is the proposed transfer of organisms in rocks from one planet to another through planetary objects such as in [[comet]]s or [[asteroid]]s; it remains speculative.  A variant would be for organisms to travel between star systems on nomadic exoplanets or exomoons.<ref>{{Cite journal |last=Sadlok |first=Grzegorz |date=2020-06-01 |title=On A Hypothetical Mechanism of Interstellar Life Transfer Trough Nomadic Objects |journal=Origins of Life and Evolution of Biospheres |language=en |volume=50 |issue=1 |pages=87–96 |doi=10.1007/s11084-020-09591-z |pmid=32034615 |s2cid=211054399 |issn=1573-0875|doi-access=free |bibcode=2020OLEB...50...87S |hdl=20.500.12128/14868 |hdl-access=free }}</ref>

Although there is no concrete evidence that lithopanspermia has occurred in the Solar System, the various stages have become amenable to experimental testing.<ref name=":5">{{Cite journal |last1=Olsson-Francis |first1=Karen |last2=Cockell |first2=Charles S. |date=January 2010 |title=Experimental methods for studying microbial survival in extraterrestrial environments |url=http://dx.doi.org/10.1016/j.mimet.2009.10.004 |journal=Journal of Microbiological Methods |volume=80 |issue=1 |pages=1–13 |doi=10.1016/j.mimet.2009.10.004 |pmid=19854226 |issn=0167-7012}}</ref>

* '''Planetary ejection''' – For lithopanspermia to occur, microorganisms must first survive ejection from a planetary surface (assuming they do not form on meteorites, as suggested in<ref name=":24"/>), which involves extreme forces of acceleration and shock with associated temperature rises. Hypothetical values of shock pressures experienced by ejected rocks are obtained from Martian meteorites, which suggest  pressures of approximately 5 to 55 GPa, acceleration of 3 Mm/s<sup>2</sup>[[Jerk (physics)|, jerk]] of 6 Gm/s<sup>3</sup> and post-shock temperature increases of about 1 K to 1000 K. Though these conditions are extreme, some organisms appear able to survive them.<ref>{{Cite journal |last1=Horneck |first1=Gerda |last2=Stöffler |first2=Dieter |last3=Ott |first3=Sieglinde |last4=Hornemann |first4=Ulrich |last5=Cockell |first5=Charles S. |last6=Moeller |first6=Ralf |last7=Meyer |first7=Cornelia |last8=de Vera |first8=Jean-Pierre |last9=Fritz |first9=Jörg |last10=Schade |first10=Sara |last11=Artemieva |first11=Natalia A. |date=February 2008 |title=Microbial rock inhabitants survive hypervelocity impacts on Mars-like host planets: first phase of lithopanspermia experimentally tested |url=https://pubmed.ncbi.nlm.nih.gov/18237257/ |journal=Astrobiology |volume=8 |issue=1 |pages=17–44 |doi=10.1089/ast.2007.0134 |issn=1531-1074 |pmid=18237257|bibcode=2008AsBio...8...17H }}</ref>
* '''Survival in transit''' – Now in space, the microorganisms have to make it to their next destination for lithopanspermia to be successful. The survival of microorganisms has been studied extensively using both simulated facilities and in low Earth orbit.<ref>{{Citation |last=Rothschild |first=Lynn |title=Extremophiles: defining the envelope for the search for life in the universe |date=2007-12-06 |url=http://dx.doi.org/10.1017/cbo9780511536120.007 |work=Planetary Systems and the Origins of Life |pages=113–134 |access-date=2023-12-08 |publisher=Cambridge University Press|doi=10.1017/cbo9780511536120.007 |isbn=9780521875486 }}</ref> A large number of microorganisms have been selected for exposure experiments, both human-borne microbes (significant for future crewed missions) and [[extremophile]]s (significant for determining the physiological requirements of survival in space).<ref name=":5" /> Bacteria in particular can exhibit a survival mechanism whereby a colony generates a biofilm that enhances its protection against UV radiation.<ref>{{Cite journal |last1=Frösler |first1=Jan |last2=Panitz |first2=Corinna |last3=Wingender |first3=Jost |last4=Flemming |first4=Hans-Curt |last5=Rettberg |first5=Petra |date=May 2017 |title=Survival of''Deinococcus geothermalis''in Biofilms under Desiccation and Simulated Space and Martian Conditions |url=http://dx.doi.org/10.1089/ast.2015.1431 |journal=Astrobiology |volume=17 |issue=5 |pages=431–447 |doi=10.1089/ast.2015.1431 |pmid=28520474 |bibcode=2017AsBio..17..431F |issn=1531-1074}}</ref>
* '''Atmospheric entry''' – The final stage of lithopanspermia, is re-entry onto a viable planet via its atmosphere. This requires that the organisms are able to further survive potential atmospheric ablation.<ref>{{Cite journal |last=Cockell |first=Charles S. |date=2007-09-29 |title=The Interplanetary Exchange of Photosynthesis |url=http://dx.doi.org/10.1007/s11084-007-9112-3 |journal=Origins of Life and Evolution of Biospheres |volume=38 |issue=1 |pages=87–104 |doi=10.1007/s11084-007-9112-3 |pmid=17906941 |s2cid=5720456 |issn=0169-6149}}</ref> Tests of this stage could use sounding rockets and orbital vehicles.<ref name=":5" /> ''[[B. subtilis]]'' spores inoculated onto [[granite]] domes were twice subjected to hypervelocity atmospheric transit by launch to a ~120&nbsp;km altitude on an Orion two-stage rocket. The spores survived on the sides of the rock, but not on the forward-facing surface that reached 145&nbsp;°C.<ref>{{Cite journal |last1=Fajardo-Cavazos |first1=Patricia |last2=Link |first2=Lindsey |last3=Melosh |first3=H. Jay |last4=Nicholson |first4=Wayne L. |date=December 2005 |title=''Bacillus subtilis''Spores on Artificial Meteorites Survive Hypervelocity Atmospheric Entry: Implications for Lithopanspermia |url=http://dx.doi.org/10.1089/ast.2005.5.726 |journal=Astrobiology |volume=5 |issue=6 |pages=726–736 |doi=10.1089/ast.2005.5.726 |pmid=16379527 |bibcode=2005AsBio...5..726F |issn=1531-1074}}</ref> As photosynthetic organisms must be close to the surface of a rock to obtain sufficient light energy, atmospheric transit might act as a filter against them by ablating the surface layers of the rock. Although [[cyanobacteria]] can survive the desiccating, freezing conditions of space, the STONE experiment showed that they cannot survive atmospheric entry.<ref>{{Cite journal |last1=Cockell |first1=Charles S. |last2=Brack |first2=André |last3=Wynn-Williams |first3=David D. |last4=Baglioni |first4=Pietro |last5=Brandstätter |first5=Franz |last6=Demets |first6=René |last7=Edwards |first7=Howell G.M. |last8=Gronstal |first8=Aaron L. |last9=Kurat |first9=Gero |last10=Lee |first10=Pascal |last11=Osinski |first11=Gordon R. |last12=Pearce |first12=David A. |last13=Pillinger |first13=Judith M. |last14=Roten |first14=Claude-Alain |last15=Sancisi-Frey |first15=Suzy |date=February 2007 |title=Interplanetary Transfer of Photosynthesis: An Experimental Demonstration of A Selective Dispersal Filter in Planetary Island Biogeography |url=http://dx.doi.org/10.1089/ast.2006.0038 |journal=Astrobiology |volume=7 |issue=1 |pages=1–9 |doi=10.1089/ast.2006.0038 |pmid=17407400 |bibcode=2007AsBio...7....1C |issn=1531-1074}}</ref> Small non-photosynthetic organisms deep within rocks might survive the exit and entry process, including [[impact survival]].<ref>{{Cite journal |last=Ball |first=Philip |date=2004-09-02 |title=Alien microbes could survive crash-landing |url=http://dx.doi.org/10.1038/news040830-10 |journal=Nature |doi=10.1038/news040830-10 |issn=0028-0836}}</ref>

Lithopanspermia, described by the mechanism above, can be either interplanetary or interstellar. It is possible to quantify panspermia models and treat them as viable mathematical theories. For example, a recent study of planets of the [[TRAPPIST-1|Trappist-1]] planetary system presents a model for estimating the probability of interplanetary panspermia, similar to studies in the past done about Earth-Mars panspermia.<ref name=":33"/> This study found that lithopanspermia is 'orders of magnitude more likely to occur'<ref name=":33" /> in the Trappist-1 system as opposed to the Earth-to-Mars scenario. According to their analysis, the increase in probability of lithopanspermia is linked to an increased probability of abiogenesis amongst the Trappist-1 planets. In a way, these modern treatments attempt to keep panspermia as a contributing factor to abiogenesis, as opposed to a theory that directly opposes it. In line with this, it is suggested that if [[biosignature]]s could be detected on two (or more) adjacent planets, that would provide evidence that panspermia is a potentially required mechanism for abiogenesis. As of yet, no such discovery has been made.

Lithopanspermia has also been hypothesized to operate between stellar systems. One mathematical analysis, estimating the total number of rocky or icy objects that could potentially be captured by planetary systems within the [[Milky Way]], has concluded that lithopanspermia is not necessarily bound to a single stellar system.<ref name=":62" /> This not only requires these objects have life in the first place, but also that it survives the journey. Thus intragalactic lithopanspermia is heavily dependent on the survival lifetime of organisms, as well as the velocity of the transporter. Again, there is no evidence that such a process has, or can occur.

==== Counterarguments====
The complex nature of the requirements for lithopanspermia, as well as evidence against the longevity of bacteria being able to survive under these conditions,<ref name=":112"/> makes lithopanspermia a difficult theory to support. That being said, impact events did occur often in the early solar system and still occur today, such as within the asteroid belt.<ref>{{Citation |last=Ivanov |first=Boris |title=Size-Frequency Distribution Of Asteroids And Impact Craters: Estimates Of Impact Rate |url=http://dx.doi.org/10.1007/978-1-4020-6452-4_2 |work=Catastrophic Events Caused by Cosmic Objects |date=2007 |pages=91–116 |access-date=2023-12-08 |place=Dordrecht |publisher=Springer Netherlands |doi=10.1007/978-1-4020-6452-4_2 |isbn=978-1-4020-6451-7}}</ref>

=== Directed panspermia ===
{{Main|Directed panspermia}}

First proposed in 1972 by Nobel prize winner [[Francis Crick]] along with [[Leslie Orgel]], directed panspermia is the theory that life was deliberately brought to Earth by a higher intelligent being from another planet.<ref name=":7">{{Cite journal |last1=Crick |first1=F. H. C. |last2=Orgel |first2=L. E. |date=1973-07-01 |title=Directed panspermia |url=https://dx.doi.org/10.1016/0019-1035%2873%2990110-3 |journal=Icarus |volume=19 |issue=3 |pages=341–346 |doi=10.1016/0019-1035(73)90110-3 |bibcode=1973Icar...19..341C |issn=0019-1035}}</ref> In light of the evidence at the time that it seems unlikely for an organism to have been delivered to Earth via radiopanspermia or lithopanspermia, Crick and Orgel proposed this as an alternative theory, though it is worth noting that Orgel was less serious about the claim.<ref>{{Cite book |last=Plaxco |first=Kevin |url=http://dx.doi.org/10.56021/9781421441306 |title=Astrobiology |date=2021 |publisher=Johns Hopkins University Press |doi=10.56021/9781421441306 |isbn=978-1-4214-4130-6}}</ref> They do acknowledge that the scientific evidence is lacking, but discuss what kinds of evidence would be needed to support the theory. In a similar vein, [[Thomas Gold]] suggested that life on Earth might have originated accidentally from a pile of 'Cosmic Garbage'  dumped on Earth long ago by extraterrestrial beings.<ref>{{Cite book |last=Gold |first=Thomas |chapter=Reasons for expecting subsurface life on many planetary bodies |editor-first1=Richard B. |editor-last1=Hoover |date=1997-07-11 |title=Instruments, Methods, and Missions for the Investigation of Extraterrestrial Microorganisms |chapter-url=http://dx.doi.org/10.1117/12.278775 |series=SPIE Proceedings |volume=3111 |pages=7–14 |publisher=[[SPIE]] |doi=10.1117/12.278775|s2cid=97077011 }}</ref> These theories are often considered more science fiction, however, Crick and Orgel use the principle of cosmic reversibility to argue for it.

This principle is based on the fact that if our species is capable of infecting a sterile planet, then what is preventing another technological society from having done that to Earth in the past?<ref name=":7" /> They concluded that it would be possible to deliberately infect another planet in the foreseeable future. As far as evidence goes, Crick and Orgel argued that given the universality of the genetic code, it follows that an infective theory for life is viable.<ref name=":7" />

Directed panspermia could, in theory, be demonstrated by finding a distinctive 'signature' message had been deliberately implanted into either the [[genome]] or the [[genetic code]] of the first microorganisms by our hypothetical progenitor, some 4 billion years ago.<ref>{{Citation |last=Marx |first=George |title=Message through time |date=1979 |url=http://dx.doi.org/10.1016/b978-0-08-024727-4.50021-4 |work=Communication with Extraterrestrial Intelligence |pages=221–225 |access-date=2023-12-08 |publisher=Elsevier|doi=10.1016/b978-0-08-024727-4.50021-4 |isbn=9780080247274 }}</ref> However, there is no known mechanism that could prevent [[mutation]] and [[natural selection]] from removing such a message over long periods of time.<ref name=":122">{{Cite journal |last1=Yokoo |first1=Hiromitsu |last2=Oshima |first2=Tairo |date=April 1979 |title=Is bacteriophage φX174 DNA a message from an extraterrestrial intelligence? |url=http://dx.doi.org/10.1016/0019-1035(79)90094-0 |journal=Icarus |volume=38 |issue=1 |pages=148–153 |bibcode=1979Icar...38..148Y |doi=10.1016/0019-1035(79)90094-0 |issn=0019-1035}}</ref>

==== Counterarguments ====
In 1972, both abiogenesis and panspermia were seen as viable theories by different experts.<ref name=":44"/> Given this, Crick and Orgel argued that experimental evidence required to validate one theory over the other was lacking.<ref name=":7" /> That being said, evidence strongly in favor of abiogenesis over panspermia exists today{{Citation needed|date=October 2024}}, whereas evidence for panspermia, particularly directed panspermia, is decidedly lacking.

=== Origination and distribution of organic molecules: Pseudo-panspermia ===
{{main|Pseudo-panspermia}}

[[Pseudo-panspermia]] is the well-supported hypothesis that many of the small [[Organic compound|organic molecule]]s used for [[life]] originated in space, and were distributed to [[planet]]ary surfaces. Life then emerged on [[Earth]], and [[Extraterrestrial life|perhaps on other planets]], by the processes of [[abiogenesis]].<ref name="Klyce 2001">{{cite web |last=Klyce |first=Brig |date=2001 |title=Panspermia Asks New Questions |url=http://www.panspermia.org/oseti.htm |access-date=25 July 2013}}</ref><ref name="SETI 2001">{{cite book |last1=Klyce |first1=Brig I |title=The Search for Extraterrestrial Intelligence (SETI) in the Optical Spectrum III |chapter=Panspermia asks new questions |date=2001 |editor1-last=Kingsley |editor1-first=Stuart A |volume=4273 |pages=11–14  |bibcode=2001SPIE.4273...11K |doi=10.1117/12.435366 |editor2-last=Bhathal |editor2-first=Ragbir |s2cid=122849901}}</ref> Evidence for pseudo-panspermia includes the discovery of organic compounds such as sugars, [[amino acid]]s, and [[nucleobase]]s in meteorites and other extraterrestrial bodies,<ref name="NASA-20191118">{{cite news |last1=Steigerwald |first1=Bill |last2=Jones |first2=Nancy |last3=Furukawa |first3=Yoshihiro |title=First Detection of Sugars in Meteorites Gives Clues to Origin of Life |url=https://www.nasa.gov/press-release/goddard/2019/sugars-in-meteorites |date=18 November 2019 |work=[[NASA]] |access-date=18 November 2019 }}</ref><ref name="PNAS-20191118">{{cite journal |last=Furukawa |first=Yoshihiro |display-authors=et al. |title=Extraterrestrial ribose and other sugars in primitive meteorites |date=18 November 2019 |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=116 |issue=49 |pages=24440–24445 |doi=10.1073/pnas.1907169116 |pmid=31740594 |pmc=6900709 |bibcode=2019PNAS..11624440F |doi-access=free }}</ref><ref name="Furukawa Chikaraishi Ohkouchi 2019">{{Cite journal |last1=Furukawa |first1=Yoshihiro |last2=Chikaraishi |first2=Yoshito |last3=Ohkouchi |first3=Naohiko |last4=Ogawa |first4=Nanako O. |last5=Glavin |first5=Daniel P. |last6=Dworkin |first6=Jason P. |last7=Abe |first7=Chiaki |last8=Nakamura |first8=Tomoki |display-authors=3 |date=13 November 2019 |title=Extraterrestrial ribose and other sugars in primitive meteorites |journal=Proceedings of the National Academy of Sciences |volume=116 |issue=49 |pages=24440–24445 |doi=10.1073/pnas.1907169116 |pmid=31740594 |bibcode=2019PNAS..11624440F |doi-access=free |pmc=6900709}}</ref><ref name="Martins Botta Fogel 2008">{{cite journal |doi=10.1016/j.epsl.2008.03.026 |title=Extraterrestrial nucleobases in the Murchison meteorite |date=2008 |last1=Martins |first1=Zita |last2=Botta |first2=Oliver |last3=Fogel |first3=Marilyn L. |author-link3=Marilyn Fogel |last4=Sephton |first4=Mark A. |last5=Glavin |first5=Daniel P. |last6=Watson |first6=Jonathan S. |last7=Dworkin |first7=Jason P. |last8=Schwartz |first8=Alan W. |last9=Ehrenfreund |first9=Pascale |display-authors=3 |journal=Earth and Planetary Science Letters |volume=270 |issue=1–2 |pages=130–136 |bibcode=2008E&PSL.270..130M |arxiv=0806.2286 |s2cid=14309508 }}</ref><ref>{{Cite journal |last1=Rivilla |first1=Víctor M. |last2=Jiménez-Serra |first2=Izaskun |last3=Martín-Pintado |first3=Jesús |last4=Colzi |first4=Laura |last5=Tercero |first5=Belén |last6=de Vicente |first6=Pablo |last7=Zeng |first7=Shaoshan |last8=Martín |first8=Sergio |last9=García de la Concepción |first9=Juan |last10=Bizzocchi |first10=Luca |last11=Melosso |first11=Mattia |date=2022 |title=Molecular Precursors of the RNA-World in Space: New Nitriles in the G+0.693−0.027 Molecular Cloud |journal=Frontiers in Astronomy and Space Sciences |volume=9 |page=876870 |doi=10.3389/fspas.2022.876870 |arxiv=2206.01053 |bibcode=2022FrASS...9.6870R |issn=2296-987X|doi-access=free }}</ref> and the formation of similar compounds in the laboratory under outer space conditions.<ref name="NASA-20150303">{{cite web |last=Marlaire |first=Ruth |title=NASA Ames Reproduces the Building Blocks of Life in Laboratory |url=http://www.nasa.gov/content/nasa-ames-reproduces-the-building-blocks-of-life-in-laboratory |date=3 March 2015 |work=[[NASA]] |access-date=5 March 2015 |archive-date=5 March 2015 |archive-url=https://web.archive.org/web/20150305083306/http://www.nasa.gov/content/nasa-ames-reproduces-the-building-blocks-of-life-in-laboratory/ |url-status=dead }}</ref><ref name="Krasnokutski Chuang Jäger 2022">{{cite journal |doi=10.1038/s41550-021-01577-9 |title=A pathway to peptides in space through the condensation of atomic carbon |date=2022 |last1=Krasnokutski |first1=S.A. |last2=Chuang |first2=K. J. |last3=Jäger |first3=C. |last4=Ueberschaar |first4=N. |last5=Henning |first5=Th. |display-authors=3 |journal=Nature Astronomy |volume=6 |issue=3 |pages=381–386 |arxiv=2202.12170 |bibcode=2022NatAs...6..381K |s2cid=246768607 }}</ref><ref>{{Cite journal |last1=Sithamparam |first1=Mahendran |last2=Satthiyasilan |first2=Nirmell |last3=Chen |first3=Chen |last4=Jia |first4=Tony Z. |last5=Chandru |first5=Kuhan |date=2022-02-11 |title=A material-based panspermia hypothesis: The potential of polymer gels and membraneless droplets |url=https://onlinelibrary.wiley.com/doi/10.1002/bip.23486 |journal=Biopolymers |volume=113 |issue=5 |pages=e23486 |doi=10.1002/bip.23486 |pmid=35148427 |arxiv=2201.06732 |s2cid=246016331}}</ref><ref>{{Cite journal |last1=Comte |first1=Denis |last2=Lavy |first2=Léo |last3=Bertier |first3=Paul |last4=Calvo |first4=Florent |last5=Daniel |first5=Isabelle |last6=Farizon |first6=Bernadette |last7=Farizon |first7=Michel |last8=Märk |first8=Tilmann D. |date=2023-01-26 |title=Glycine Peptide Chain Formation in the Gas Phase via Unimolecular Reactions |url=https://pubs.acs.org/doi/10.1021/acs.jpca.2c08248 |journal=The Journal of Physical Chemistry A |language=en |volume=127 |issue=3 |pages=775–780 |doi=10.1021/acs.jpca.2c08248 |pmid=36630603 |bibcode=2023JPCA..127..775C |s2cid=255748895 |issn=1089-5639}}</ref> A prebiotic polyester system has been explored as an example.<ref>{{Cite journal |last1=Chandru |last2=Mamajanov |last3=Cleaves |last4=Jia |date=2020-01-19 |title=Polyesters as a Model System for Building Primitive Biologies from Non-Biological Prebiotic Chemistry |journal=Life |volume=10 |issue=1 |pages=6 |doi=10.3390/life10010006 |pmid=31963928 |pmc=7175156 |bibcode=2020Life...10....6C |doi-access=free }}</ref><ref>{{Cite journal |last1=Jia |first1=Tony Z. |last2=Chandru |first2=Kuhan |last3=Hongo |first3=Yayoi |last4=Afrin |first4=Rehana |last5=Usui |first5=Tomohiro |last6=Myojo |first6=Kunihiro |last7=Cleaves |first7=H. James |date=2019-08-06 |title=Membraneless polyester microdroplets as primordial compartments at the origins of life |journal=Proceedings of the National Academy of Sciences |volume=116 |issue=32 |pages=15830–15835 |doi=10.1073/pnas.1902336116 |pmc=6690027 |pmid=31332006 |bibcode=2019PNAS..11615830J |doi-access=free }}</ref>
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