Panspermia (from Ancient Greek πᾶν (pan) 'all' and σπέρμα (sperma) 'seed') is the hypothesis that life exists throughout the Universe , distributed by space dust , meteoroids , asteroids , comets , and planetoids , as well as by spacecraft carrying unintended contamination by microorganisms , known as directed panspermia . The theory argues that life did not originate on Earth, but instead evolved somewhere else and seeded life as we know it.
118-410: Panspermia comes in many forms, such as radiopanspermia, lithopanspermia, and directed panspermia . Regardless of its form, the theories generally propose that microbes able to survive in outer space (such as certain types of bacteria or plant spores) can become trapped in debris ejected into space after collisions between planets and small solar system bodies that harbor life. This debris containing
236-634: A future. An early example of the idea of directed panspermia dates to the early science fiction work Last and First Men by Olaf Stapledon , first published in 1930. It details the manner in which the last humans, upon discovering that the Solar System will soon be destroyed, send microscopic "seeds of a new humanity" towards potentially habitable areas of the universe. In 1966, Shklovskii and Sagan speculated that life on Earth may have been seeded through directed panspermia by other civilisations, and, in 1973, Crick and Orgel also discussed
354-521: A boat trip along the Berwickshire coast with John Playfair and the geologist Sir James Hall , and found a dramatic unconformity showing the same sequence at Siccar Point . Playfair later recalled that "the mind seemed to grow giddy by looking so far into the abyss of time", and Hutton concluded a 1788 paper he presented at the Royal Society of Edinburgh , later rewritten as a book, with
472-415: A capsule to hit the target area with radius r target {\displaystyle r_{\text{target}}} (m) is given by the ratio of the targeting scatter and the target area. To apply these equations, the precision of astrometry of star proper motion of 0.00001 arcsec/year, and the solar sail vehicle velocity of 0.0005 c (1.5 × 10 m s ) may be expected within
590-482: A certain degree today within the asteroid belt. 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. 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
708-423: A distinctive 'signature' message were found, deliberately implanted into either the genome or the genetic code of the first microorganisms by our hypothetical progenitor. In 2013 a team of physicists claimed that they had found mathematical and semiotic patterns in the genetic code which, they believe, is evidence for such a signature. This claim has not been substantiated by further study, or accepted by
826-521: A few decades. For a chosen planetary system, the area A target {\displaystyle A_{\text{target}}} may be the width of the habitable zone , while for interstellar clouds, it may be the sizes of the various density zones of the cloud. Solar sail missions to Sun-like stars can decelerate by radiation pressure in reverse dynamics of the launch. The sails must be properly oriented at arrival, but orientation control may be avoided using spherical sails. The vehicles must approach
944-422: A few hundred new stars, still leaving a hundred billion pristine for local life and for research. A technical objection is the uncertain survival of the messenger organisms during long interstellar transit. Research by simulations, and the development on hardy colonizers is needed to address these questions. A third argument against engaging in directed panspermia derives from the view that wild animals do not — on
1062-519: A mechanism of transferring between planets. Thus, the modern treatment of panspermia began in earnest. Lord Kelvin , in a presentation to The British Association for the Advancement of Science in 1871, proposed the idea that similarly to how seeds can be transferred through the air by winds, so can life be brought to Earth by the infall of a life-bearing meteorite. He further proposed the idea that life can only come from life, and that this principle
1180-408: A message over long periods of time. In 1972, both abiogenesis and panspermia were seen as viable theories by different experts. Given this, Crick and Orgel argued that experimental evidence required to validate one theory over the other was lacking. That being said, evidence strongly in favor of abiogenesis over panspermia exists today, whereas evidence for panspermia, particularly directed panspermia,
1298-565: A miniaturized gene laboratory for the in situ cell synthesis of the microbes. The Genesis project extends directed panspermia to eukaryotic life, arguing that it is more likely that complex life is rare, and not bacterial life. In 2020, the theoretical physicist Avi Loeb wrote about a similar 3-D printer that can manufacture seeds of life in the Scientific American . Directed panspermia aims to secure and expand our family of organic gene/protein life. It may be motivated by
SECTION 10
#17327979359481416-543: A model for estimating the probability of interplanetary panspermia, similar to studies in the past done about Earth-Mars panspermia. This study found that lithopanspermia is 'orders of magnitude more likely to occur' 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
1534-481: A new environment. Though both plant seeds and bacterial spores have been proposed as potentially viable vehicles, their ability to not only survive in space for the required time, but also survive atmospheric entry is debated. Space probes may be a viable transport mechanism for interplanetary cross-pollination within the Solar System. Space agencies have implemented planetary protection procedures to reduce
1652-477: A panbiotic ethics aimed to secure this future. The main objection to directed panspermia is that it may interfere with local life at the targets. The colonizing microorganisms may out-compete local life for resources, or infect and harm local organisms. However, this probability can be minimized by targeting newly forming planetary systems, accretion discs and star-forming clouds, where local life, and especially advanced life, could not have emerged yet. If there
1770-456: A plant is partially damaged during its travel in space, the pieces could still seed life in a sterile environment. Sterility of the environment is relevant because it is unclear if the novel plant could out-compete existing life forms. This idea is based on previous evidence showing that cellular reconstruction can occur from cytoplasms released from damaged algae. Furthermore, plant cells contain obligate endosymbionts , which could be released into
1888-445: A protostellar condensation in the cloud. As for approach to accretion discs about stars, a millimetre size capsule entering the 1000 km thick disc face at 0.0005 c will be captured at 100 km into the disc. Therefore, 1 mm sized objects may be the best for seeding protoplanetary discs about new stars and protostellar condensations in interstellar clouds. The captured panspermia capsules will mix with dust. A fraction of
2006-426: A required first principle in scientific research. Other scientists disagree and consider that nature is not absolutely uniform, even though it does exhibit certain regularities. In geology , uniformitarianism has included the gradualistic concept that "the present is the key to the past" and that geological events occur at the same rate now as they have always done, though many modern geologists no longer hold to
2124-500: A satisfying resolution of this predicament, humanity should abstain from any acts of cosmic preservation." The discovery of an ancient directed panspermia effort is the central theme of " The Chase ," an episode of Star Trek: The Next Generation . In the story, Captain Picard must work to complete the penultimate research of his late archaeology professor's career. That professor, Galen, had discovered that DNA fragments seeded into
2242-671: A self-sustaining ecosystem with cyanobacteria , would combine ideally the features needed for survival and higher evolution. For advanced missions, ion thrusters or solar sails using beam-powered propulsion accelerated by Earth-based lasers can achieve speeds up to 0.01 c (3 × 10 m/s). Robots may provide in-course navigation, may control the reviving of the frozen microbes periodically during transit to repair radiation damage , and may also choose suitable targets. These propulsion methods and robotics are under development. Microbial payloads may be also planted on hyperbolic comets bound for interstellar space. This strategy follows
2360-527: A single idea: None of these connotations requires another, and they are not all equally inferred by uniformitarians. Gould explained Lyell's propositions in Time's Arrow, Time's Cycle (1987), stating that Lyell conflated two different types of propositions: a pair of methodological assumptions with a pair of substantive hypotheses . The four together make up Lyell's uniformitarianism. The two methodological assumptions below are accepted to be true by
2478-505: A strict gradualism. Coined by William Whewell , uniformitarianism was originally proposed in contrast to catastrophism by British naturalists in the late 18th century, starting with the work of the geologist James Hutton in his many books including Theory of the Earth . Hutton's work was later refined by scientist John Playfair and popularised by geologist Charles Lyell 's Principles of Geology in 1830. Today, Earth's history
SECTION 20
#17327979359482596-425: A testable theory. Though it has yet to be tested, panspermia is still explored today in some mathematical treatments, and as its long history suggests, the appeal of the theory has stood the test of time. Panspermia requires: The creation and distribution of organic molecules from space is now uncontroversial; it is known as pseudo-panspermia . The jump from organic materials to life originating from space, however,
2714-590: A total biomass of 10 kg. The required biomass to launch for a successful mission is given by following equation. m biomass (kg) = 10 / P planet Using the above equations for P target with transit velocities of 0.0005 c, the known distances to the targets, and the masses of the dust in the target regions then allows calculating the biomass that needs to be launched for probable success. With these parameters, as little as 1 gram of biomass (10 microorganisms) could seed Alpha PsA and 4.5 gram could seed Beta Pictoris. More biomass needs to be launched to
2832-616: Is a type of panspermia that implies the deliberate transport of microorganisms into space to be used as introduced species on other astronomical objects . Historically, Shklovskii and Sagan (1966) and Crick and Orgel (1973) hypothesized that life on the Earth may have been seeded deliberately by other civilizations. Conversely, Mautner and Matloff (1979) and Mautner (1995, 1997) proposed that humanity should seed other planetary systems, protoplanetary discs or star-forming clouds with microorganisms , to secure and expand its organic gene/protein lifeform. To avoid interference with local life,
2950-493: Is considered to have been a slow, gradual process, punctuated by occasional natural catastrophic events. Abraham Gottlob Werner (1749–1817) proposed Neptunism , where strata represented deposits from shrinking seas precipitated onto primordial rocks such as granite . In 1785 James Hutton proposed an opposing, self-maintaining infinite cycle based on natural history and not on the Biblical account. The solid parts of
3068-476: Is decidedly lacking. Pseudo-panspermia is the well-supported hypothesis that many of the small organic molecules used for life originated in space, and were distributed to planetary surfaces. Life then emerged on Earth , and perhaps on other planets , by the processes of abiogenesis . Evidence for pseudo-panspermia includes the discovery of organic compounds such as sugars, amino acids , and nucleobases in meteorites and other extraterrestrial bodies, and
3186-456: Is given by the equation below, where P target {\displaystyle P_{\text{target}}} is the probability that the capsule reaches the target accretion disc or cloud zone, and P capture {\displaystyle P_{\text{capture}}} is the probability of capture from this zone by a planet. The probability P planet {\displaystyle P_{\text{planet}}} depends on
3304-450: Is hypothetical and currently untestable. Bacterial spores and plant seeds are two common proposed vessels for panspermia. 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). This naturally requires that these spores and seeds have formed somewhere else, maybe even in space in
3422-421: Is in contrast with the previous two philosophical assumptions that come before one can do science and so cannot be tested or falsified by science. Stephen Jay Gould 's first scientific paper, "Is uniformitarianism necessary?" (1965), reduced these four assumptions to two. He dismissed the first principle, which asserted spatial and temporal invariance of natural laws, as no longer an issue of debate. He rejected
3540-407: Is invariant under philosophical uniformitarianism , similar to how matter can neither be created nor destroyed . This argument was heavily criticized because of its boldness, and additionally due to technical objections from the wider community. In particular, Johann Zollner from Germany argued against Kelvin by saying that organisms carried in meteorites to Earth would not survive the descent through
3658-419: Is known today, however, is not identical to this original theory. The name, as applied to this theory, was only first coined in 1908 by Svante Arrhenius , a Swedish scientist. Prior to this, since around the 1860s, many prominent scientists were becoming interested in the theory, for example Sir Fred Hoyle , and Chandra Wickramasinghe . In the 1860s, there were three scientific developments that began to bring
Panspermia - Misplaced Pages Continue
3776-410: Is local life that is fundamentally different, the colonizing microorganisms may not harm it. If there is local organic gene/protein life, it may exchange genes with the colonizing microorganisms, increasing galactic biodiversity . Another objection is that space should be left pristine for scientific studies, a reason for planetary quarantine. However, directed panspermia may reach only a few, at most
3894-484: Is no concrete evidence that lithopanspermia has occurred in the Solar System, the various stages have become amenable to experimental testing. Lithopanspermia, described by the mechanism above can exist as 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 planetary system, presents
4012-462: Is probably a result of the way evolution by natural selection operates, and that evolutionary processes are therefore likely to result, in due time, in similar suffering wherever life evolves. Sivula discusses all sides of the issue and concludes that "... the risk of suffering objection constitutes a serious ethical problem – planetary seeding may be extremely good or it might be a moral disaster – depending on one's moral theory. Until we have identified
4130-477: Is that required conditions for the origin of life may have been more favorable somewhere other than Earth, and second that life on Earth exhibits properties that are not accounted for by assuming an endogenic origin. 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. Critically, Hoyle argued that this chemical evolution
4248-483: Is the resolution of proper motion of the target object (arcsec/year), d {\displaystyle d} d is the distance from the Earth (m) and v {\displaystyle v} is the velocity of the vehicle (m s ). Given the positional uncertainty, the vehicles may be launched with a scatter in a circle about the predicted position of the target. The probability P target {\displaystyle P_{\text{target}}} for
4366-474: Is to say, of interpreting the past by means of the processes that are seen going on at the present day, so long as we remember that the periodic catastrophe is one of those processes. Those periodic catastrophes make more showing in the stratigraphical record than we have hitherto assumed." Modern geologists do not apply uniformitarianism in the same way as Lyell. They question if rates of processes were uniform through time and only those values measured during
4484-465: Is worth noting that Orgel was less serious about the claim. 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. These theories are often considered more science fiction, however, Crick and Orgel use
4602-847: The Kepler mission that will identify nearby star systems with habitable astronomical objects . Alternatively, directed panspermia may aim at star-forming interstellar clouds such as Rho Ophiuchi cloud complex (427 ly), that contains clusters of new stars too young to originate local life (425 infrared-emitting young stars aged 100,000 to a million years). Such clouds contain zones with various densities (diffuse cloud < dark fragment < dense core < protostellar condensation < accretion disc) that could selectively capture panspermia capsules of various sizes. Habitable astronomical objects or habitable zones about nearby stars may be targeted by large (10 kg) missions where microbial capsules are bundled and shielded. Upon arrival, microbial capsules in
4720-714: The Rho Ophiuchi cloud complex , mainly because of its larger distance. A biomass on the order of 300 tons would need to be launched to seed a protostellar condensation or an accretion disc, but two hundred kilograms would be sufficient to seed a young stellar object in the Rho Ophiuchi cloud complex . Consequently, as long as the required physical range of tolerance are met (e.g.: growth temperature, cosmic radiation shielding, atmosphere and gravity), lifeforms viable on Earth may be chemically nourished by watery asteroid and planetary materials in this and other planetary systems. The seeding organisms need to survive and multiply in
4838-459: The history of geology are to be accepted. The present may not be a long enough key to penetrating the deep lock of the past. Geologic processes may have been active at different rates in the past that humans have not observed. "By force of popularity, uniformity of rate has persisted to our present day. For more than a century, Lyell's rhetoric conflating axiom with hypotheses has descended in unmodified form. Many geologists have been stifled by
Panspermia - Misplaced Pages Continue
4956-434: The lethal action of space radiation ( UV and X-rays ) in the cosmos. If enough of these microorganisms are ejected into space, some may rain down on a planet in a new star system after 10 years wandering interstellar space. 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. Data gathered by
5074-429: The ultrahigh vacuum of space alone is sufficient to cause DNA damage , so the transport of unprotected DNA or RNA during interplanetary flights powered solely by light pressure is extremely unlikely. 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
5192-642: The Alpha PsA star will last 50,000 y, and to the Rho Opiuchus cloud, 824,000 years. At the targets, the microbial payload would decompose into 10 (100 billion) 30 μm capsules to increase the probability of capture. In the swarm strategy to protoplanetary discs and interstellar clouds, 1 mm radius, 4.2 × 10 kg microbial capsules are launched from 1 au using sails of 4.2 × 10 kg with radius of 0.37 m and area of 0.42 m to achieve cruising speeds of 0.0005 c . At
5310-528: The DNA code. Also, shared are the basic mechanisms of energy use and material transport. These self-propagating patterns and processes are the core of organic gene/protein life. Life is unique because of this complexity, and because of the exact coincidence of the laws of physics that allow life to exist. Also unique to life is the pursuit of self-propagation, which implies a human purpose to secure and expand life. These objectives are best secured in space, suggesting
5428-561: The Solar System, an argument can be made that they each provide a potential site for life to develop. A collision occurring in the asteroid belt could alter the orbit of one such site, and eventually deliver it to Earth. Plant seeds can be an alternative transport vessel. Some plants produce seeds that are resistant to the conditions of space, which have been shown to lie dormant in extreme cold, vacuum, and resist short wavelength UV radiation. They are not typically proposed to have originated on space, but on another planet. Theoretically, even if
5546-514: The Sun, then fragmenting the comet. A 1 km radius comet would yield 4.2 × 10 one-kg seeded fragments, and rotating the comet would eject these shielded icy objects in random directions into the galaxy. This increases a trillion-fold the probability of capture in another planetary system, compared with transport by a single comet. Such manipulation of comets is a speculative long-term prospect. The German physicist Claudius Gros has proposed that
5664-546: 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 biosignatures 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
5782-587: The Universe. At this time, it was recently discovered that solar radiation can exert pressure, and thus force, on matter. Arrhenius thus concluded that it is possible that very small organisms such as bacterial spores could be moved around due to this radiation pressure . At this point, panspermia as a theory now had a potentially viable transport mechanism, as well as a vehicle for carrying life from planet to planet. The theory still faced criticism mostly due to doubts about how long spores would actually survive under
5900-427: The Universe. Its long history also lends itself to extensive speculation and hoaxes that have arisen from meteoritic events. Panspermia has a long history, dating back to the 5th century BCE and the natural philosopher Anaxagoras . Classicists came to agree that Anaxagoras maintained the Universe (or Cosmos) was full of life, and that life on Earth started from the fall of these extra-terrestrial seeds. Panspermia as it
6018-430: The accreting solar nebula, and will be delivered to planets in comets and in asteroids. The microorganisms can grow on nutrients in the carrier comets and asteroids in the aqueous planetary environments, until they adapt to the local environments and nutrients on the planets. A number of publications since 1979 have proposed the idea that directed panspermia could be demonstrated to be the origin of all life on Earth if
SECTION 50
#17327979359486136-415: The affected areas. In Britain, geologists adapted this idea into " diluvial theory " which proposed repeated worldwide annihilation and creation of new fixed species adapted to a changed environment, initially identifying the most recent catastrophe as the biblical flood . From 1830 to 1833 Charles Lyell 's multi-volume Principles of Geology was published. The work's subtitle was "An attempt to explain
6254-406: The arrival of major epidemics and the occasions of close encounters with comets, which lead Hoyle to suggest that the epidemics were a direct result of material raining down from these comets. This claim in particular garnered criticism from biologists. 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
6372-433: The atmosphere due to friction heating. The arguments went back and forth until Svante Arrhenius gave the theory its modern treatment and designation. Arrhenius argued against abiogenesis on the basis that it had no experimental foundation at the time, and believed that life had always existed somewhere in the Universe. He focused his efforts of developing the mechanism(s) by which this pervasive life may be transferred through
6490-446: The average — have lives worth living, and thus spreading life would be morally wrong . Yew-Kwang Ng supports this view, and other authors agree or disagree. Unlike the above two objections, which can be minimized by attention to detail, there is no currently-known way to influence from a distance how evolution would progress on a world seeded with life. O'Brien argues that the large amount of suffering among wild animals on this planet
6608-445: The belief that proper methodology includes an a priori commitment to gradual change, and by a preference for explaining large-scale phenomena as the concatenation of innumerable tiny changes." The current consensus is that Earth's history is a slow, gradual process punctuated by occasional natural catastrophic events that have affected Earth and its inhabitants. In practice it is reduced from Lyell's conflation, or blending, to simply
6726-459: The capture of interplanetary dust particles by planets and moons in our Solar System, where 10 of the Zodiacal cloud maintained by comet ablation, and also a similar fraction of asteroid fragments, is collected by the Earth. The probability of capture of an initially launched capsule by a planet (or astronomical object) P planet {\displaystyle P_{\text{planet}}}
6844-570: The case of how panspermia deals with bacteria. Understanding of planetary formation theory and meteorites has led to the idea that some rocky bodies originating from undifferentiated parent bodies could be able to generate local conditions conducive to life. Hypothetically, internal heating from radiogenic isotopes could melt ice to provide water as well as energy. In fact, some meteorites have been found to show signs of aqueous alteration which may indicate that this process has taken place. Given that there are such large numbers of these bodies found within
6962-416: The cloud with a velocity of 0.0005 c (1.5 × 10 m s ) will be captured when decelerated to 2,000 m s , the typical speed of grains in the cloud. The size of the capsules can be designed to stop at zones with various densities in the interstellar cloud. Simulations show that a 35 μm radius capsule will be captured in a dense core, and a 1 mm radius capsule in
7080-423: The colonizers should include anaerobic microorganisms . Colonizing anaerobic cyanobacteria may later establish atmospheric oxygen that is needed for higher evolution , as it happened on Earth. Aerobic organisms in the biological payload may be delivered to the astronomical objects later when the conditions are right, by comets that captured and preserved the capsules. The development of eukaryote microorganisms
7198-681: The concept. In the controversial documentary Expelled: No Intelligence Allowed starring Ben Stein , Richard Dawkins mentioned directed panspermia as a possible scenario and that scientists may find evidence of it hidden in our chemistry and molecular biology . Conversely, Mautner and Matloff proposed in 1979, and Mautner examined in detail in 1995 and 1997 the technology and motivation to secure and expand our organic gene/protein life-form by directed panspermia missions to other planetary systems, protoplanetary discs and star-forming clouds. Technological aspects include propulsion by solar sails, deceleration by radiation pressure or viscous drag at
SECTION 60
#17327979359487316-455: The conditions of their transport from one planet, through space, to another. Despite all the emphasis placed on trying to establish the scientific legitimacy of this theory, it still lacked testability; that was and still is a serious problem the theory has yet to overcome. 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. First
7434-428: The cruising speeds of the vehicles. The positional uncertainty and size of the target object then allow estimating the probability that the panspermia vehicles will arrive at their targets. The positional uncertainty δ y {\displaystyle \delta y} (m) of the target at arrival time is given by the following equation, where α p {\displaystyle \alpha _{p}}
7552-457: The desire to perpetuate the common genetic heritage of all terrestrial life. This motivation was formulated as biotic ethics , that value the common gene/protein patterns of organic life, and as panbiotic ethics that aim to secure and expand life in the universe. Molecular biology shows complex patterns common to all cellular life, a common genetic code and a common mechanism to translate it into proteins , which in turn help to reproduce
7670-446: The dust and a proportional fraction of the captured capsules will be delivered to astronomical objects. Dispersing the payload into delivery microcapsules will increase the chance that some will be delivered to habitable objects. Particles of 0.6 – 60 μm radius can remain cold enough to preserve organic matter during atmospheric entry to planets or moons. Accordingly, each 1 mm, 4.2 × 10 kg capsule captured in
7788-601: The evolution of many humanoid species. Some variation of directed panspermia was also included in the plot of anime Neon Genesis Evangelion and Ridley Scott's 2012 sci-fi film Prometheus . Uniformitarianism Uniformitarianism , also known as the Doctrine of Uniformity or the Uniformitarian Principle , is the assumption that the same natural laws and processes that operate in our present-day scientific observations have always operated in
7906-696: The focus of the scientific community to the problem of the origin of life. Firstly, the Kant-Laplace Nebular theory of solar system and planetary formation was gaining favor, and implied that when the Earth first formed, the surface conditions would have been inhospitable to life as we know it. This meant that life could not have evolved parallel with the Earth, and must have evolved at a later date, without biological precursors. Secondly, Charles Darwin 's famous theory of evolution implied some elusive origin, because in order for something to evolve, it must start somewhere. In his Origin of Species , Darwin
8024-450: The following definition: If language was normally acquired in the past in the same way as it is today – usually by native acquisition in early childhood – and if it was used in the same ways – to transmit information, to express solidarity with family, friends, and neighbors, to mark one's social position, etc. – then it must have had the same general structure and organization in the past as it does today, and it must have changed in
8142-431: The following equation, where v {\displaystyle v} is the velocity, r c {\displaystyle r_{c}} the radius of the spherical capsule, ρ c {\displaystyle \rho _{c}} is density of the capsule and ρ m {\displaystyle \rho _{m}} is the density of the medium. A vehicle entering
8260-533: The formation of similar compounds in the laboratory under outer space conditions. A prebiotic polyester system has been explored as an example. On May 14, 1864, twenty fragments from a meteorite crashed into the French city of Orgueil. 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
8378-422: The former changes of the Earth's surface by reference to causes now in operation". He drew his explanations from field studies conducted directly before he went to work on the founding geology text, and developed Hutton's idea that the earth was shaped entirely by slow-moving forces still in operation today, acting over a very long period of time. The terms uniformitarianism for this idea, and catastrophism for
8496-859: The genetic code requires design, and the authors haven’t demonstrated otherwise. In a later peer-reviewed article, the authors address the operation of natural law in an extensive statistical test, and draw the same conclusion as in the previous article. In special sections they also discuss methodological concerns raised by PZ Myers and some others. Significantly, panspermia missions can be launched by present or near-future technologies. However, more advanced technologies may be also used when these become available. The biological aspects of directed panspermia may be improved by genetic engineering to produce hardy polyextremophile microorganisms and multicellular organisms, suitable to diverse astronomical objects environments. Hardy polyextremophile anaerobic multicellular eukaryotes with high radiation resistance, that can form
8614-403: The inorganic world, there are eight different systems of beliefs in the development of the terrestrial sphere. All geoscientists stand by the principle of uniformity of law. Most, but not all, are directed by the principle of simplicity. All make definite assertions about the quality of rate and state in the inorganic realm. Lyell's uniformitarianism is a family of four related propositions, not
8732-695: The late 19th and early 20th centuries, most geologists took this interpretation to mean that catastrophic events are not important in geologic time; one example of this is the debate of the formation of the Channeled Scablands due to the catastrophic Missoula glacial outburst floods. An important result of this debate and others was the re-clarification that, while the same principles operate in geologic time, catastrophic events that are infrequent on human time-scales can have important consequences in geologic history. Derek Ager has noted that "geologists do not deny uniformitarianism in its true sense, that
8850-427: The lifeforms is then transported by meteors between bodies in a solar system, or even across solar systems within a galaxy. In this way, panspermia studies concentrate not on how life began but on methods that may distribute it within the Universe. This point is often used as a criticism of the theory. Panspermia is a fringe theory with little support amongst mainstream scientists. Critics argue that it does not answer
8968-606: The majority of scientists and geologists. Gould claims that these philosophical propositions must be assumed before you can proceed as a scientist doing science. "You cannot go to a rocky outcrop and observe either the constancy of nature's laws or the working of unknown processes. It works the other way around." You first assume these propositions and "then you go to the outcrop." The substantive hypotheses were controversial and, in some cases, accepted by few. These hypotheses are judged true or false on empirical grounds through scientific observation and repeated experimental data. This
9086-420: The mechanisms of natural panspermia by comets, as suggested by Hoyle and Wikramasinghe. The microorganisms would be frozen in the comets at interstellar temperatures of a few kelvins and protected from radiation for eons. It is unlikely that an ejected comet will be captured in another planetary system, but the probability can be increased by allowing the microbes to multiply during warm perihelion approach to
9204-495: The mixing ratio of the capsules with the dust and on the fraction of the dust delivered to planets. These variables can be estimated for capture in planetary accretion discs or in various zones in the interstellar cloud. After determining the composition of chosen meteorites , astroecologists performed laboratory experiments that suggest that many colonizing microorganisms and some plants could obtain most of their chemical nutrients from asteroid and cometary materials. However,
9322-452: The new habitats. They may be sent in 10 kg, 60 μm diameter capsules that allow intact atmospheric entry at the target planets, each containing 100,000 diverse microorganisms suited to various environments. Both for bundled large mass missions and microbial capsule swarms, solar sails may provide the most simple propulsion for interstellar transit. Spherical sails will avoid orientation control both at launch and at deceleration at
9440-467: The opposing viewpoint, was coined by William Whewell in a review of Lyell's book. Principles of Geology was the most influential geological work in the middle of the 19th century. Geoscientists support diverse systems of Earth history, the nature of which rests on a certain mixture of views about the process, control, rate, and state which are preferred. Because geologists and geomorphologists tend to adopt opposite views over process, rate, and state in
9558-770: 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). Spores would therefore need to be heavily protected against UV radiation: exposure of unprotected DNA to solar UV and cosmic ionizing radiation would break it up into its constituent bases. Rocks at least 1 meter in diameter are required to effectively shield resistant microorganisms, such as bacterial spores against galactic cosmic radiation . Additionally, exposing DNA to
9676-436: 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 . The outer "fusion layer" was in fact glue. 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
9794-444: The payload may be dispersed in orbit for capture by planets. Alternatively, small microbial capsules may be sent in large swarms to habitable planets, protoplanetary discs , or zones of various density in interstellar clouds. The microbial swarm provides minimal shielding but does not require high precision targeting, especially when aiming at large interstellar clouds. Panspermia missions should deliver microorganisms that can grow in
9912-465: The phrase "we find no vestige of a beginning, no prospect of an end". Both Playfair and Hall wrote their own books on the theory, and for decades robust debate continued between Hutton's supporters and the Neptunists. Georges Cuvier 's paleontological work in the 1790s, which established the reality of extinction , explained this by local catastrophes, after which other fixed species repopulated
10030-414: The present land appear in general, to have been composed of the productions of the sea, and of other materials similar to those now found upon the shores. Hence we find a reason to conclude: Hence we are led to conclude, that the greater part of our land, if not the whole had been produced by operations natural to this globe; but that in order to make this land a permanent body, resisting the operations of
10148-415: The presumed primordial rock had been molten after the strata had formed. He had read about angular unconformities as interpreted by Neptunists, and found an unconformity at Jedburgh where layers of greywacke in the lower layers of the cliff face have been tilted almost vertically before being eroded to form a level plane, under horizontal layers of Old Red Sandstone . In the spring of 1788 he took
10266-476: The primordial genetic material of 19 worlds could be rearranged to assemble a computer algorithm . Amid competition (and, later, with begrudging cooperation) from Cardassian , Klingon and Romulan expeditions also exploring Galen's research clues, the Enterprise crew discovers that an alien progenitor race had indeed, 4 billion years prior, seeded genetic material across many star systems, thus directing
10384-417: 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? 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
10502-448: The question of the origin of life but merely places it on another celestial body. It is also criticized because it cannot be tested experimentally. Historically, disputes over the merit of this theory centered on whether life is ubiquitous or emergent throughout the Universe. Due to its long history, the theory maintains support today, with some work being done to develop mathematical treatments of how life might migrate naturally throughout
10620-486: The radiopanspermia hypothesis. This transport mechanism generally arose following the discovery of exoplanets, and the sudden availability of data following the growth of planetary science. Lithopanspermia is the proposed transfer of organisms in rocks from one planet to another through planetary objects such as in comets or asteroids , and remains speculative. A variant would be for organisms to travel between star systems on nomadic exoplanets or exomoons. Although there
10738-460: The risk of planetary contamination, but microorganisms such as Tersicoccus phoenicis may be resistant to spacecraft assembly cleaning . 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. In 1903, Svante Arrhenius proposed radiopanspermia,
10856-437: The rotifers can be hardened to survive interstellar transit. Microorganisms or capsules captured in the accretion disc can be captured along with the dust into asteroids. During aqueous alteration the asteroids contain water, inorganic salts and organics, and astroecology experiments with meteorites showed that algae, bacteria, fungi and plant cultures can grow in the asteroids in these media. Microorganisms can then spread in
10974-424: The scientists noted that phosphate (PO 4 ) and nitrate (NO 3 –N) critically limit nutrition to many terrestrial lifeforms. For successful missions, enough biomass must be launched and captured for a reasonable chance to initiate life at the target astronomical object. An optimistic requirement is the capture by the planet of 100 capsules with 100,000 microorganisms each, for a total of 10 million organisms with
11092-465: The target Sun-like stars at radial distances similar to the launch, about 1 au. After the vehicles are captured in orbit, the microbial capsules may be dispersed in a ring orbiting the star, some within the gravitational capture zone of planets. Missions to accretion discs of planets and to star-forming clouds will decelerate by viscous drag at the rate d v d t {\displaystyle {\frac {dv}{dt}}} as determined by
11210-703: The target environments and establish a viable biosphere . Some of the new branches of life may develop intelligent beings who will further expand life in the galaxy. The messenger microorganisms may find diverse environments, requiring extremophile microorganisms with a range of tolerances, including thermophile (high temperature), psychrophile (low temperature), acidophile (high acidity), halophile (high salinity), oligotroph (low nutrient concentration), xerophile (dry environments) and radioresistant (high radiation tolerance) microorganisms. Genetic engineering may produce polyextremophile microorganisms with several tolerances. The target atmospheres will probably lack oxygen, so
11328-416: The target, and capture of the colonizing micro-organisms by planets. A possible objection is potential interference with local life at the targets, but targeting young planetary systems where local life, especially advanced life, could not have started yet, avoids this problem. Directed panspermia may be motivated by the desire to perpetuate the common genetic heritage of all terrestrial life. This motivation
11446-501: The target, each capsule decomposes into 4,000 delivery microcapsules of 10 kg and of 30 micrometer radius that allow intact entry to planetary atmospheres. For missions that do not encounter dense gas zones, such as interstellar transit to mature planets or to habitable zones about stars, the microcapsules can be launched directly from 1 au using 10 kg sails of 1.8 mm radius to achieve velocities of 0.0005 c to be decelerated by radiation pressure for capture at
11564-524: The targets may be young planetary systems where local life is unlikely. Directed panspermia can be motivated by biotic ethics that value the basic patterns of organic gene/protein life with its unique complexity and unity, and its drive for self-propagation. Directed panspermia is becoming possible due to developments in solar sails , precise astrometry , the discovery of extrasolar planets , extremophiles and microbial genetic engineering . Cosmological projections suggest that life in space can then have
11682-517: The targets. For bundled shielded missions to nearby star systems, solar sails with thicknesses of 10 m and areal densities of 0.0001 kg/m seem feasible, and sail/payload mass ratios of 10:1 will allow exit velocities near the maximum possible for such sails. Sails with about 540 m radius and area of 10 m can impart 10 kg payloads with interstellar cruise velocities of 0.0005 c (1.5 × 10 m/s) when launched from 1 au (astronomical unit). At this speed, voyage to
11800-438: The targets. The 1 mm and 30 micrometer radius vehicles and payloads are needed in large numbers for both the bundled and swarm missions. These capsules and the miniature sails for swarm missions can be mass manufactured readily. The panspermia vehicles would be aimed at moving targets whose locations at the time of arrival must be predicted. This can be calculated using their measured proper motions, their distances, and
11918-607: The technology developed by the Breakthrough Starshot initiative may be utilized in a second step to establish a biosphere of unicellular microbes on otherwise only transiently habitable astronomical objects . The aim of this initiative, the Genesis project, would be to fast forward evolution to a stage equivalent of the precambrian period on Earth. Gros argues that the Genesis project would be realizable within 50–100 years, using low-mass probes equipped with
12036-599: The theory that singular microscopic forms of life can be propagated in space, driven by the radiation pressure from stars. 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. However, because its effectiveness decreases with increasing size of the particle, this mechanism holds for very tiny particles only, such as single bacterial spores . The main criticism of radiopanspermia came from Iosif Shklovsky and Carl Sagan , who cited evidence for
12154-460: The theory that under (unknown) conditions on a primitive Earth, life must have gradually evolved from organic material. This theory became known as abiogenesis , and is the currently accepted one. On the other side of this are those scientists of the time who rejected Pasteur's results and instead supported the idea that life on Earth came from existing life. This necessarily requires that life has always existed somewhere on some planet, and that it has
12272-442: The third (uniformity of rate) as an unjustified limitation on scientific inquiry, as it constrains past geologic rates and conditions to those of the present. So, Lyell's uniformitarianism was deemed unnecessary. Uniformitarianism was proposed in contrast to catastrophism , which states that the distant past "consisted of epochs of paroxysmal and catastrophic action interposed between periods of comparative tranquility" Especially in
12390-476: 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. 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
12508-653: The transformation of inorganic to biological matter. In 2017, the Pan-STARRS telescope in Hawaii detected a reddish object up to 400 meters in length. Analysis of its orbit provided evidence that it was an interstellar object, originating from outside our Solar System. From this Avi Loeb speculated that the object was instead an artifact from an alien civilization and could potentially be evidence for directed panspermia. This claim has been considered unlikely by other authors. Directed panspermia Directed panspermia
12626-413: The two philosophical assumptions. This is also known as the principle of geological actualism, which states that all past geological action was like all present geological action. The principle of actualism is the cornerstone of paleoecology . Uniformitarianism has also been applied in historical linguistics , where it is considered a foundational principle of the field. Linguist Donald Ringe gives
12744-469: The universality of the genetic code, it follows that an infective theory for life is viable. 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. However, there is no known mechanism that could prevent mutation and natural selection from removing such
12862-429: The universe in the past and apply everywhere in the universe. It refers to invariance in the metaphysical principles underpinning science, such as the constancy of cause and effect throughout space-time, but has also been used to describe spatiotemporal invariance of physical laws . Though an unprovable postulate that cannot be verified using the scientific method, some consider that uniformitarianism should be
12980-436: The velocity of the transporter. Again, there is no evidence that such a process has, or can occur. The complex nature of the requirements for lithopanspermia, as well as evidence against the longevity of bacteria being able to survive under these conditions, makes lithopanspermia a difficult theory to get behind. That being said, impact events did happen a lot in the early stages of the solar system formation, and still happen to
13098-617: The viscous medium can be dispersed into 42,000 delivery microcapsules of 30 μm radius, each weighing 10 kg and containing 100,000 microbes. These objects will not be ejected from the dust cloud by radiation pressure from the star, and will remain mixed with the dust. A fraction of the dust, containing the captured microbial capsules, will be captured by planets or moons, or captured in comets and delivered by them later to planets. The probability of capture, P capture {\displaystyle P_{\text{capture}}} , can be estimated from similar processes, such as
13216-474: The waters, two things had been required; Hutton then sought evidence to support his idea that there must have been repeated cycles, each involving deposition on the seabed , uplift with tilting and erosion , and then moving undersea again for further layers to be deposited. At Glen Tilt in the Cairngorm mountains he found granite penetrating metamorphic schists , in a way which indicated to him that
13334-403: The wider scientific community with a seemingly paradoxical situation regarding the origin of life: life must have evolved from non-biological precursors after the Earth was formed, and yet spontaneous generation as a theory had been experimentally disproved. From here, is where the study of the origin of life branched. Those who accepted Pasteur's rejection of spontaneous generation began to develop
13452-495: The wider scientific community. One outspoken critic is biologist PZ Myers who said, writing in Pharyngula : Unfortunately, what they’ve so honestly described is good old honest garbage ... Their methods failed to recognize a well-known functional association in the genetic code; they did not rule out the operation of natural law before rushing to falsely infer design ... We certainly don’t need to invoke panspermia. Nothing in
13570-408: Was a major bottleneck to higher evolution on Earth. Including eukaryote microorganisms in the payload can bypass this barrier. Multicellular organisms are even more desirable, but being much heavier than bacteria, fewer can be sent. Hardy tardigrades (water-bears) may be suitable but they are similar to arthropods and would lead to insects. The body-plan of rotifers could lead to higher animals, if
13688-472: Was formulated as biotic ethics that value the common gene/protein patterns of self propagation, and as panbiotic ethics that aim to secure and expand life in the universe. Directed panspermia may be aimed at nearby young planetary systems such as Alpha PsA (25 ly ( light-years ) away) and Beta Pictoris (63.4 ly), both of which show accretion discs and signs of comets and planets. More suitable targets may be identified by space telescopes such as
13806-400: Was unable or unwilling to touch on this issue. Third and finally, Louis Pasteur and John Tyndall experimentally disproved the (now superseded) theory of spontaneous generation , which suggested that life was constantly evolving from non-living matter and did not have a common ancestor, as suggested by Darwin's theory of evolution. Altogether, these three developments in science presented
13924-419: Was unlikely to have taken place on a prebiotic Earth, and instead the most likely candidate is a comet. 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. Hoyle reported (in a lecture at Oxford on January 16, 1978) a pattern of coincidence between
#947052