Panspermia
Those who accepted Pasteur's rejection of spontaneous generation began to develop the theory that under (unknown) conditions on a primitive Earth, life must have gradually evolved from organic material.In particular, Johann Zollner from Germany argued against Kelvin by saying that organisms carried in meteorites to Earth would not survive the descent through the atmosphere due to friction heating.Support for the theory persisted, however, with Fred Hoyle and Chandra Wickramasinghe using two reasons for why an extra-terrestrial origin of life might be preferred.[14][20] Hoyle studied spectra of interstellar dust, and came to the conclusion that space contained large amounts of organics, which he suggested were the building blocks of the more complex chemical structures.[14] Furthermore, Hoyle and Wickramasinghe concluded that the evolution of life requires a large increase in genetic information and diversity, which might have resulted from the influx of viral material from space via comets.Since the 1970s, a new era of planetary exploration meant that data could be used to test panspermia and potentially transform it from conjecture to a testable theory.According to the theory, they could be encased in a meteorite and transported to another planet from their origin, subsequently descend through the atmosphere and populate the surface with life (see lithopanspermia below).[15] Given that there are such large numbers of these bodies found within the Solar System, an argument can be made that they each provide a potential site for life to develop.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.The main criticism of radiopanspermia came from Iosif Shklovsky and Carl Sagan, who cited evidence for the lethal action of space radiation (UV and X-rays) in the cosmos.[citation needed] 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.[citation needed] Data gathered by the orbital experiments 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).[34] Rocks at least 1 meter in diameter are required to effectively shield resistant microorganisms, such as bacterial spores against galactic cosmic radiation.In line with this, it is suggested that if biosignatures could be detected on two (or more) adjacent planets, that would provide evidence that panspermia is a potentially required mechanism for abiogenesis.[46] 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.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?[47] 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.A separate fragment of the Orgueil meteorite (kept in a sealed glass jar since its discovery) was found in 1965 to have a seed capsule embedded in it, while the original glassy layer on the outside remained undisturbed.Despite great initial excitement, the seed was found to be that of a European Juncaceae or rush plant that had been glued into the fragment and camouflaged using coal dust.While the perpetrator of this hoax is unknown, it is thought that they sought to influence the 19th-century debate on spontaneous generation—rather than panspermia—by demonstrating the transformation of inorganic to biological matter.
Pseudo-panspermiaorganismsbacteriacometsAncient GreekhypothesisUniversespace dustmeteoroidsasteroidsplanetoidsspacecraftcontaminationmicroorganismsdirected panspermiaouter spacedebris ejectedsmall solar system bodiesfringe theoryorigin of lifeorganic moleculesplanetaryAnaxagorasSvante ArrheniusSir Fred HoyleChandra WickramasingheNebular theoryCharles DarwinLouis PasteurJohn Tyndallspontaneous generationabiogenesisLord Kelvinuniformitarianismneither be created nor destroyedradiation pressureFred Hoyleendogenicradiogenic isotopesasteroid beltendosymbiontsSpace probesplanetary protectionTersicoccus phoenicisspacecraft assembly cleaningcleanroomsbacterial sporesIosif ShklovskyCarl Saganlethal action of space radiationX-raysBIOPANEXOSTACKEXPOSEB. subtilisto solar UVcosmicionizing radiationcosmic radiationultrahigh vacuumDNA damageinterplanetary flightslight pressure, jerkextremophilesgranitecyanobacteriaimpact survivalTrappist-1biosignaturesMilky WayFrancis CrickLeslie OrgelThomas Goldgenomegenetic codemutationnatural selectionperhaps on other planetsamino acidsnucleobasesOrgueil meteoriteJuncaceaecoal dustOumuamuaAvi LoebAstrobiologyCryptobiosisList of microorganisms tested in outer spaceBibcodeScience AdvancesCiteSeerXspacecraft assembly clean roomsNaturePurdue UniversityPhys.orgThe New YorkerProceedings of the National Academy of Sciences of the United States of AmericaFogel, Marilyn L.Live ScienceCrick, FrancisHoyle, FredScientific AmericanAstrochemistryAstrophysicsAtmospheric sciencesBiochemistryEvolutionary biologyExoplanetologyGeomicrobiologyMicrobiologyPaleontologyPlanetary oceanographyPlanetary scienceAllan Hills 84001BiomoleculeBiosignatureDrake equationEarliest known life formsEarth analogExtraterrestrial lifeExtraterrestrial sample curationHypothetical types of biochemistryOcean planetSearch for extraterrestrial intelligence (SETI)Yamato meteorite