Origin of life

thumb|Nucleic acids may not be the only [[biomolecules in the universe capable of coding for life processes.]]

thumb|upright=2|Stages in the origin of life process range from the well understood, such as the planetary habitability|habitable Earth and the abiotic synthesis of simple molecules, to the largely unknown, like the derivation of the [[last universal common ancestor (LUCA) with its complex molecular functionalities.]]

Soviet biochemist (1894-1980)

thumb |upright=1.3 |Panspermia proposes that organisms such as [[bacteria, complete with their DNA, could be transported by means such as comets through space to planets including Earth.]] Panspermia () is the hypothesis that life exists throughout the universe, distributed by cosmic 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.

chemical experiment that simulated conditions on the early Earth, and tested the origin of life

most recent common ancestor of all current life on Earth

geometric property of some molecules and ions

hypothetical phase of the history of life, in which self-replicating RNA proliferated

American scientist (1930–2007)

disproven theory of life arising from nonliving matter

hydrocarbons composed of multiple aromatic rings

Paleoproterozoic surge in atmospheric oxygen

thumb|Neverland Regio, a dark region on Charon's north pole. The region is stained a dark brown by deposits of tholins Tholins (after the Greek ('''') "hazy" or "muddy"; from the ancient Greek word meaning "sepia ink") are a wide variety of organic compounds formed by solar ultraviolet or cosmic ray irradiation of simple carbon-containing compounds such as carbon dioxide (), methane () or ethane (), often in combination with nitrogen () or water (). Tholins are disordered polymer-like materials made of repeating chains of linked subunits and complex combinations of functional groups, typically

hypothesis that complex extraterrestrial life is a very improbable phenomenon and likely to be extremely rare

current scientific theory outlining the major events during the development of life

thumb|class=skin-invert-image|right|150px|General structure of a thioester, where R and R' are organyl groups, or H in the case of R. In organic chemistry, thioesters are organosulfur compounds with the molecular structure . They are analogous to carboxylate esters () with the sulfur in the thioester replacing oxygen in the carboxylate ester, as implied by the thio- prefix. They are the product of esterification of a carboxylic acid () with a thiol (). In biochemistry, the best-known thioesters are derivatives of coenzyme A, e.g., acetyl-CoA. The R and R' represent organyl groups, or H in the

biological molecule

A protocell (or protobiont) is a self-organized, membrane-bound or membraneless compartment that concentrates biomolecules, proposed as a rudimentary precursor to cells during the origin of life. A central question in evolution is how simple protocells first arose and how their progeny could diversify, thus enabling the accumulation of novel biological emergences over time (i.e. biological evolution). Although a functional protocell has not yet been achieved in a laboratory setting, the goal to understand the process appears well within reach.

theoretical conditions under which life on earth might have begun

thumb|Coacervate droplets dispersed in a dilute phaseCoacervate ( or ) is an aqueous phase rich in macromolecules such as synthetic polymers, proteins or nucleic acids. It forms through liquid-liquid phase separation (LLPS), leading to a dense phase in thermodynamic equilibrium with a dilute phase. The dispersed droplets of dense phase are also called coacervates, micro-coacervates or coacervate droplets. These structures draw a lot of interest because they form spontaneously from aqueous mixtures and provide stable compartmentalization without the need of a membrane—they are protocell candida

thumb|Two enantiomers of a generic amino acid that is chiral

British chemist (1927–2007)

pathway leading to the fixation of two molecules of CO2 and the production of one molecule of acetyl-CoA; essentially the oxidative TCA cycle running in reverse. Acetyl-CoA is reductively carboxylated to pyruvate, from which all other central metab

Akilia Island is an island in southwestern Greenland, about 22 kilometers south of Nuuk. Akilia is the location of a rock formation that has been proposed to contain the oldest known sedimentary rocks on Earth, and perhaps the oldest evidence of life on Earth.

Hypothesis about the origin of life

hypothetical scenario for the origin of life

Collodictyon is a genus of single-celled, omnivorous eukaryotes belonging to the collodictyonids, also known as diphylleids. Due to their mix of cellular components, collodictyonids do not belong to any well-known kingdom-level grouping of that domain and this makes them distinctive from other families. Recent research places them in a new "super-group" called CRuMs together with rigifilids and Mantamonas.

species of Methanomicrobia

Monogenism or sometimes monogenesis is the theory of human origins which posits a common descent for all humans. The negation of monogenism is polygenism. This issue was hotly debated in the Western world in the nineteenth century, as the assumptions of scientific racism came under scrutiny both from religious groups and in the light of developments in the life sciences and human science. It was integral to the early conceptions of ethnology.

chemical reaction involving the formation of sugars from formaldehyde

Homochirality is a uniformity of chirality, or handedness. Objects are chiral when they cannot be superposed on their mirror images. For example, the left and right hands of a human are approximately mirror images of each other but are not their own mirror images, so they are chiral. In chemistry, chirality is a geometric property of some compounds and ions. These compounds exist in two different chiral conformations, enantiomers, often described as the left-handed and right-handed isomers of a compound (denoted by L- (levorotatory to the left) and D- (dextrorotatory to the right), respectivel

term

the argument against abiogenesis of chance

possible earliest ancestor of the LUCA ancestral cell

collection of chemical entities

Proteinoids, or thermal proteins, are protein-like, often cross-linked molecules formed abiotically from amino acids. Sidney W. Fox initially proposed that they may have been precursors to the first living cells (protocells). The term was also used in the 1960s to describe peptides that are shorter than twenty amino acids found in hydrolysed protein, but this term is no longer commonly used.

thumb|right|200px|Gamma-ray bursts might have regulated the advent of intelligent life Neocatastrophism is the hypothesis that life-exterminating events such as gamma-ray bursts have acted as a galactic regulation mechanism in the Milky Way upon the emergence of complex life in its habitable zone. It is one of several proposed solutions to the Fermi paradox since it provides a mechanism which would have delayed the advent of intelligent beings in local galaxies near Earth.

Hemolithin (sometimes confused with the similar space polymer hemoglycin) is a proposed protein containing iron and lithium, of extraterrestrial origin, according to an unpublished preprint. The result has not been published in any peer-reviewed scientific journal. The protein was purportedly found inside two CV3 meteorites, Allende and Acfer-086, by a team of scientists led by Harvard University biochemist Julie McGeoch. The report of the discovery was met with some skepticism and suggestions that the researchers had extrapolated too far from incomplete data.

thumb|300px|Aristeas and bugonia. Virgil's Georgics. Lyon. 1517 Bugonia (; bougoníā) was a folk practice in the ancient Mediterranean region based on the belief that bees were spontaneously generated from a cow's carcass. By extension, it was thought that fumigation with cow dung was beneficial to the health of the hive.

thumb|400px|Reaction scheme of the chemoton, showing the interplay of metabolism, information and structural closure. Based on Fig. 1.1 of Gánti (2003)The term chemoton (short for 'chemical automaton') refers to an abstract model for the fundamental unit of life introduced by Hungarian theoretical biologist Tibor Gánti. Gánti conceived the basic idea in 1952 and formulated the concept in 1971 in his book The Principles of Life (originally written in Hungarian, and translated to English only in 2003). He suggested that the chemoton was the original ancestor of all organisms.

proposed sample-return mission to a comet

theory of molecules organization

stratigraphic layer in Western Australia

Spanish astrobiology research center