Assuntos
Meio Ambiente Extraterreno/química , Plutão , Amônia/análise , Exobiologia , Gelo/análise , Metano/análise , Estações do Ano , Telescópios , Água/análiseRESUMO
Carbon-based compounds are widespread throughout the Universe, including abiotic molecules that are the components of the life as we know it. This article reviews the space missions that have aimed to detect organic matter and biosignatures in planetary bodies of our solar system. While to date there was only one life-detection space mission, i.e., the Viking mission to Mars, several past and present space missions have searched for organic matter, paving the way for the future detection of signatures of extra-terrestrial life. This review also reports on the in-situ analysis of organic matter and sample-return missions from primitive bodies, i.e. comets and asteroids, providing crucial information on the conditions of the early solar system as well as on the building blocks of life delivered to the primitive Earth.
Assuntos
Carbono/química , Meio Ambiente Extraterreno/química , Compostos Orgânicos/química , Sistema Solar/química , Exobiologia , Cromatografia Gasosa-Espectrometria de Massas , História do Século XX , História do Século XXI , Marte , Meteoroides , Planetas Menores , Plutão , Saturno , Voo Espacial/história , Estados Unidos , United States National Aeronautics and Space AdministrationRESUMO
We present the case for the presence of complex organic molecules, such as amino acids and nucleobases, formed by abiotic processes on the surface and in near-subsurface regions of Pluto. Pluto's surface is tinted with a range of non-ice substances with colors ranging from light yellow to red to dark brown; the colors match those of laboratory organic residues called tholins. Tholins are broadly characterized as complex, macromolecular organic solids consisting of a network of aromatic structures connected by aliphatic bridging units (e.g., Imanaka et al., 2004; Materese et al., 2014, 2015). The synthesis of tholins in planetary atmospheres and in surface ices has been explored in numerous laboratory experiments, and both gas- and solid-phase varieties are found on Pluto. A third variety of tholins, exposed at a site of tectonic surface fracturing called Virgil Fossae, appears to have come from a reservoir in the subsurface. Eruptions of tholin-laden liquid H2O from a subsurface aqueous repository appear to have covered portions of Virgil Fossae and its surroundings with a uniquely colored deposit (D.P. Cruikshank, personal communication) that is geographically correlated with an exposure of H2O ice that includes spectroscopically detected NH3 (C.M. Dalle Ore, personal communication). The subsurface organic material could have been derived from presolar or solar nebula processes, or might have formed in situ. Photolysis and radiolysis of a mixture of ices relevant to Pluto's surface composition (N2, CH4, CO) have produced strongly colored, complex organics with a significant aromatic content having a high degree of nitrogen substitution similar to the aromatic heterocycles pyrimidine and purine (Materese et al., 2014, 2015; Cruikshank et al., 2016). Experiments with pyrimidines and purines frozen in H2O-NH3 ice resulted in the formation of numerous nucleobases, including the biologically relevant guanine, cytosine, adenine, uracil, and thymine (Materese et al., 2017). The red material associated with the H2O ice may contain nucleobases resulting from energetic processing on Pluto's surface or in the interior. Some other Kuiper Belt objects also exhibit red colors similar to those found on Pluto and may therefore carry similar inventories of complex organic materials. The widespread and ubiquitous nature of similarly complex organic materials observed in a variety of astronomical settings drives the need for additional laboratory and modeling efforts to explain the origin and evolution of organic molecules. Pluto observations reveal complex organics on a small body that remains close to its place of origin in the outermost regions of the Solar System.
Assuntos
Atmosfera/análise , Meio Ambiente Extraterreno/química , Plutão , Purinas/análise , Pirimidinas/análise , Atmosfera/química , Gelo , Metano/análise , Espectrofotometria Infravermelho , Compostos Orgânicos Voláteis/análise , Água/químicaRESUMO
Data from the New Horizons mission to Pluto show no craters on Sputnik Planum down to the detection limit (2 km for low resolution data, 625 m for high resolution data). The number of small Kuiper Belt Objects that should be impacting Pluto is known to some degree from various astronomical surveys. We combine these geological and telescopic observations to make an order of magnitude estimate that the surface age of Sputnik Planum must be less than 10 million years. This maximum surface age is surprisingly young and implies that this area of Pluto must be undergoing active resurfacing, presumably through some cryo-geophysical process. We discuss three possible resurfacing mechanisms and the implications of each one for Pluto's physical properties.
Assuntos
Astronomia , Meio Ambiente Extraterreno , Geologia , Gelo/análise , Plutão , Fatores de TempoAssuntos
Ciência , Sistemas CRISPR-Cas/genética , Congressos como Assunto , Microscopia Crioeletrônica , Vacinas contra Dengue/provisão & distribuição , Terremotos/estatística & dados numéricos , Vacinas contra Ebola/imunologia , Engenharia Genética/ética , Engenharia Genética/legislação & jurisprudência , Aquecimento Global/legislação & jurisprudência , Aquecimento Global/prevenção & controle , Humanos , Fraturamento Hidráulico/estatística & dados numéricos , Cooperação Internacional , Vacinas Antimaláricas/imunologia , Paris , Física , Plutão , Medicina de Precisão , Reprodutibilidade dos Testes , Pesquisa/normas , Sexismo/estatística & dados numéricos , Voo EspacialAssuntos
Aquecimento Global/legislação & jurisprudência , Analgésicos Opioides/metabolismo , Astronomia , Benzilisoquinolinas/química , Benzilisoquinolinas/metabolismo , Viés , Sistemas CRISPR-Cas/genética , Diplomacia , Condutividade Elétrica , Eletrônica/instrumentação , Pesquisas com Embriões/ética , Engenharia Genética/ética , Genoma Humano/genética , Genômica , Aquecimento Global/economia , Aquecimento Global/prevenção & controle , História do Século XXI , História Antiga , Migração Humana/história , Humanos , Irã (Geográfico) , Idioma/história , Nanotubos de Carbono , Armas Nucleares/legislação & jurisprudência , Paris , Plutão , Preconceito , Psicologia/normas , Reprodutibilidade dos Testes , Medicina Reprodutiva/ética , Assédio Sexual/prevenção & controle , Voo Espacial/economia , Voo Espacial/tendências , Biologia Sintética/métodos , Temperatura , Leveduras/genética , Leveduras/metabolismoAssuntos
Plutão , Voo Espacial , Meio Ambiente Extraterreno , Gelo , Netuno , Astronave , TemperaturaRESUMO
We compare astronomers' removal of Pluto from the listing of planets and psychiatrists' removal of homosexuality from the listing of mental disorders. Although the political maneuverings that emerged in both controversies are less than scientifically ideal, we argue that competition for "scientific authority" among competing groups is a normal part of scientific progress. In both cases, a complicated relationship between abstract constructs and evidence made the classification problem thorny.
Assuntos
Manual Diagnóstico e Estatístico de Transtornos Mentais , Homossexualidade/psicologia , Plutão , Astronomia/tendências , Classificação , Feminino , Homossexualidade/classificação , Humanos , MasculinoAssuntos
Gelo , Plutão , Sistema Solar , Temperatura Baixa , Meio Ambiente Extraterreno , Temperatura AltaAssuntos
Orçamentos/legislação & jurisprudência , Plutão , Apoio à Pesquisa como Assunto/economia , Ciência/economia , Voo Espacial/economia , Educação de Pós-Graduação/economia , Governo , Pesquisa/economia , Apoio à Pesquisa como Assunto/legislação & jurisprudência , Fatores de Tempo , Estados Unidos , United States Environmental Protection Agency/economia , United States National Aeronautics and Space Administration/economiaRESUMO
Observations have resolved the satellite Charon from its parent planet Pluto, giving separate spectra of the two objects from 1.0 to 2.5 micrometers. The spectrum of Charon is found to be different from that of Pluto, with water ice in crystalline form covering most of the surface of the satellite. In addition, an absorption feature in Charon's spectrum suggests the presence of ammonia ices. Ammonia ice-water ice mixtures have been proposed as the cause of flowlike features observed on the surfaces of many icy satellites. The existence of such ices on Charon may indicate geological activity in the satellite's past.