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Identifying unequivocal signs of life on Mars is one of the most important objectives for sending missions to the red planet. Here we report Red Stone, a 163-100 My alluvial fan-fan delta that formed under arid conditions in the Atacama Desert, rich in hematite and mudstones containing clays such as vermiculite and smectites, and therefore geologically analogous to Mars. We show that Red Stone samples display an important number of microorganisms with an unusual high rate of phylogenetic indeterminacy, what we refer to as "dark microbiome", and a mix of biosignatures from extant and ancient microorganisms that can be barely detected with state-of-the-art laboratory equipment. Our analyses by testbed instruments that are on or will be sent to Mars unveil that although the mineralogy of Red Stone matches that detected by ground-based instruments on the red planet, similarly low levels of organics will be hard, if not impossible to detect in Martian rocks depending on the instrument and technique used. Our results stress the importance in returning samples to Earth for conclusively addressing whether life ever existed on Mars.
Asunto(s)
Medio Ambiente Extraterrestre , Marte , Exobiología/métodos , Fósiles , Límite de Detección , FilogeniaRESUMEN
The Martian subsurface is more favorable for organic preservation than its surface because of the shielding effect of rocks from cosmic rays and UV radiation with increasing depth. Nevertheless, the natural radioactivity on Mars owing to U, Th, and K must be considered to study the possible extant and/or extinct life. Here, we demonstrate the importance of natural radiation on the amino acid glycine in two different chemical environments, GlyFeSO4 5H2O and GlyMgSO4 5H2O, which are coordination compounds considered relevant to Mars. The results show that after a 600 kGy dose of gamma radiation, glycine was more stable when it bonded to Mg in the GlyMgSO4 5H2O coordination compound, it was less stable when it bonded to Fe in the GlyFeSO4 5H2O compound. Studies on the effects of gamma radiation on preservation of organic molecules bound to minerals and other potential compounds on Mars are significantly important in the search for biosignatures.
Asunto(s)
Marte , Radiactividad , Medio Ambiente Extraterrestre , Rayos gamma , GlicinaRESUMEN
In this work, we have analyzed natural samples collected at three hydrothermal areas of Iceland by Raman spectroscopy. The studied high-latitude regions are considered environmentally and mineralogically appropriate Martian analogues since they are rich in weathered basalts that have been altered by hydrothermalism to mineral phases such as silica, clay minerals, sulfates, oxides, and sulfur. The main objective of this work was to assess the relation of the spectroscopic signatures of alteration to hydrothermal processes and biomediation, considering previous studies focused on the detection of lipid biomarkers in the same samples. The recorded Raman spectra, taken with optical parameters similar to the ExoMars 2022 Raman spectrometer, showed structural modifications in all secondary minerals in the form of peak shifts (in the case of sulfur and clay minerals), changes in the relative ratio intensity (in anatase) and/or shape broadening (in sulfates and hematite). These results reveal the suitability of Raman spectroscopy to examine areas rich in water-altered minerals, where a mixture of crystalline and amorphous phases can co-exist. The detection of silica is singularly interesting since, on the one hand, it can imply the past existence of hydrothermal hot springs rich in nutrient and redox gradients and, on the other hand, provides excellent matrix for biosignature preservation. The data can be helpful as an astrobiological database for the forthcoming missions to Mars, where potential upwelling groundwater systems could have altered the mineral phases in a similar way to that observed in this work.
Asunto(s)
Marte , Medio Ambiente Extraterrestre/química , Islandia , Minerales/química , Espectrometría Raman/métodosRESUMEN
Detecting signs of potential extant/extinct life on Mars is challenging because the presence of organics on that planet is expected to be very low and most likely linked to radiation-protected refugia and/or preservative strategies (e.g., organo-mineral complexes). With scarcity of organics, accounting for biomineralization and potential relationships between biomarkers, mineralogy, and geochemistry is key in the search for extraterrestrial life. Here we explored microbial fingerprints and their associated mineralogy in Icelandic hydrothermal systems analog to Mars (i.e., high sulfur content, or amorphous silica), to identify potentially habitable locations on that planet. The mineralogical assemblage of four hydrothermal substrates (hot springs biofilms, mud pots, and steaming and inactive fumaroles) was analyzed concerning the distribution of biomarkers. Molecular and isotopic composition of lipids revealed quantitative and compositional differences apparently impacted by surface geothermal alteration and environmental factors. pH and water showed an influence (i.e., greatest biomass in circumneutral settings with highest supply and turnover of water), whereas temperature conditioned the mineralogy that supported specific microbial metabolisms related with sulfur. Raman spectra suggested the possible coexistence of abiotic and biomediated sources of minerals (i.e., sulfur or hematite). These findings may help to interpret future Raman or GC-MS signals in forthcoming Martian missions.
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We present the hypothesis that microorganisms can change the freezing/melting curve of cold salty solutions by protein expression, as it is known that proteins can affect the liquid-to-ice transition, an ability that could be of ecological advantage for organisms on Earth and on Mars. We tested our hypothesis by identifying a suitable candidate, the well-known psycrophile and halotolerant bacteria Rhodococcus sp. JG3, and analyzing its response in culture conditions that included specific hygroscopic salts relevant to Mars-that is, highly concentrated magnesium perchlorate solutions of 20 wt % and 50 wt % Mg(ClO4)2 at both end members of the eutectic concentration (44 wt %)-and subfreezing temperatures (263 K and 253 K). Using a combination of techniques of molecular microbiology and aqueous geochemistry, we evaluated the potential roles of proteins over- or underexpressed as important players in different mechanisms for the adaptability of life to cold environments. We recorded the changes observed by micro-differential scanning calorimetry. Unfortunately, Rhodococcus sp. JG3 did not show our hypothesized effect on the melting characteristics of cold Mg-perchlorate solutions. However, the question remains as to whether our novel hypothesis that halophilic/psychrophilic bacteria or archaea can alter the freezing/melting curve of salt solutions could be validated. The null result obtained after analyzing just one case lays the foundation to continue the search for proteins produced by microorganisms that thrive in very cold, high-saline solutions, which would involve testing different microorganisms with different salt components. The immediate implications for the habitability of Mars are discussed.
Asunto(s)
Proteínas Bacterianas/genética , Medio Ambiente Extraterrestre/química , Compuestos de Magnesio/química , Marte , Percloratos/química , Rhodococcus/metabolismo , Proteínas Bacterianas/metabolismo , Exobiología/métodos , Congelación , Regulación Bacteriana de la Expresión Génica , Compuestos de Magnesio/metabolismo , Percloratos/metabolismo , Rhodococcus/química , Temperatura de Transición , Agua/química , Microbiología del AguaRESUMEN
The presence of organic matter in lacustrine mudstone sediments at Gale crater was revealed by the Mars Science Laboratory Curiosity rover, which also identified smectite clay minerals. Analogue experiments on phyllosilicates formed under low temperature aqueous conditons have illustrated that these are excellent reservoirs to host organic compounds against the harsh surface conditions of Mars. Here, we evaluate whether the capacity of smectites to preserve organic compounds can be influenced by a short exposure to different diagenetic fluids. We analyzed the stability of glycine embedded within nontronite samples previously exposed to either acidic or alkaline fluids (hereafter referred to as "treated nontronites") under Mars-like surface conditions. Analyses performed using multiple techniques showed higher photodegradation of glycine in the acid-treated nontronite, triggered by decarboxylation and deamination processes. In constrast, our experiments showed that glycine molecules were preferably incorporated by ion exchange in the interlayer region of the alkali-treated nontronite, conferring them a better protection against the external conditions. Our results demonstrate that smectite previously exposed to fluids with different pH values influences how glycine is adsorbed into their interlayer regions, affecting their potential for preservation of organic compounds under contemporary Mars surface conditions.
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The aim of the European Space Agency's ExoMars rover mission is to search for potential traces of present or past life in the swallow subsurface (2 m depth) of Mars. The ExoMars rover mission relies on a suite of analytical instruments envisioned to identify organic compounds with biological value (biomarkers) associated with a mineralogical matrix in a highly oxidative environment. We investigated the feasibility of detecting basic organics (linear and branched lipid molecules) with Raman laser spectroscopy, an instrument onboard the ExoMars rover, when exposed to oxidant conditions. We compared the detectability of six lipid molecules (alkanes, alkanols, fatty acid, and isoprenoid) before and after an oxidation treatment (15 days with hydrogen peroxide), with and without mineral matrix support (amorphous silica rich vs. iron rich). Raman and infrared spectrometry was combined with gas chromatography-mass spectrometry to determine detection limits and technical constraints. We observed different spectral responses to degradation depending on the lipid molecule and mineral substrate, with the silica-rich material showing better preservation of organic signals. These findings will contribute to the interpretation of Raman laser spectroscopy results on cores from the ExoMars rover landing site, the hydrated silica-enriched delta fan on Cogoon Vallis (Oxia Planum).
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Exobiología/instrumentación , Medio Ambiente Extraterrestre/química , Lípidos/análisis , Marte , Espectrometría Raman/instrumentación , Biomarcadores/análisis , Europa (Continente) , Exobiología/métodos , Vehículos a Motor Todoterreno , Oxidación-Reducción , Vuelo Espacial , Simulación del EspacioRESUMEN
At present, the study of diverse habitable environments of astrobiological interest has become a major challenge. Due to the obvious technical and economical limitations on in situ exploration, laboratory simulations are one of the most feasible research options to make advances both in several astrobiologically interesting environments and in developing a consistent description of the origin of life. With this objective in mind, we applied vacuum and high pressure technology to the design of versatile simulation chambers devoted to the simulation of the interstellar medium, planetary atmospheres conditions and high-pressure environments. These simulation facilities are especially appropriate for studying the physical, chemical and biological changes induced in a particular sample by in situ irradiation or physical parameters in a controlled environment. Furthermore, the implementation of several spectroscopies, such as infrared, Raman, ultraviolet, etc., to study solids, and mass spectrometry to monitor the gas phase, in our simulation chambers, provide specific tools for the in situ physico-chemical characterization of analogues of astrobiological interest. Simulation chamber facilities are a promising and potential tool for planetary exploration of habitable environments. A review of many wide-ranging applications in astrobiology are detailed herein to provide an understanding of the potential and flexibility of these unique experimental systems.
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Death receptors (DRs) and their ligands are expressed in developing nervous system. However, neurons are generally resistant to death induction through DRs and rather their activation promotes neuronal outgrowth and branching. These results suppose the existence of DRs antagonists expressed in the nervous system. Fas apoptosis inhibitory molecule (FAIM(S)) was first identified as a Fas antagonist in B-cells. Soon after, a longer alternative spliced isoform with unknown function was identified and named FAIM(L). FAIM(S) is widely expressed, including the nervous system, and we have shown previously that it promotes neuronal differentiation but it is not an anti-apoptotic molecule in this system. Here, we demonstrate that FAIM(L) is expressed specifically in neurons, and its expression is regulated during the development. Expression could be induced by NGF through the extracellular regulated kinase pathway in PC12 (pheochromocytoma cell line) cells. Contrary to FAIM(S), FAIM(L) does not increase the neurite outgrowth induced by neurotrophins and does not interfere with nuclear factor kappaB pathway activation as FAIM(S) does. Cells overexpressing FAIM(L) are resistant to apoptotic cell death induced by DRs such as Fas or tumor necrosis factor R1. Reduction of endogenous expression by small interfering RNA shows that endogenous FAIM(L) protects primary neurons from DR-induced cell death. The detailed analysis of this antagonism shows that FAIM(L) can bind to Fas receptor and prevent the activation of the initiator caspase-8 induced by Fas. In conclusion, our results indicate that FAIM(L) could be responsible for maintaining initiator caspases inactive after receptor engagement protecting neurons from the cytotoxic action of death ligands.
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Proteínas Reguladoras de la Apoptosis/biosíntesis , Proteínas Reguladoras de la Apoptosis/genética , Apoptosis/fisiología , Proteínas Inhibidoras de la Apoptosis/fisiología , Neuronas/metabolismo , Receptores de Muerte Celular/antagonistas & inhibidores , Receptores de Muerte Celular/fisiología , Animales , Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/fisiología , Células Cultivadas , Regulación de la Expresión Génica/fisiología , Variación Genética/fisiología , Humanos , Ratones , Neuronas/patología , Células PC12 , Isoformas de Proteínas/biosíntesis , Isoformas de Proteínas/genética , Isoformas de Proteínas/fisiología , Ratas , Receptores de Muerte Celular/genéticaRESUMEN
Resumen: El rol de la Medicina Legal en derechos humanos y acción forense humanitaria es cada vez más visible. La ley Nº 18.596 indemiza a quienes acrediten haber sufrido lesiones gravísimas por el accionar de agentes del Estado. Objetivo: contribuir al conocimiento público de la actuación ilegítima y el terrorismo de Estado en Uruguay (13/6/1968 y 28/2/1985) y del aporte de la Medicina Legal en materia de verdad, justicia, memoria, reparación y garantía de no repetición. Material y método: se estudiaron las solicitudes de indemnización por lesiones gravísimas recibidas en los primeros diez años de vigencia de la ley. Resultados y discusión: de 166 peticiones, se admitieron 115. En el 95% fue requerido informe médico-legal o psiquiátrico, o ambos. Aunque fue dificultoso demostrar el nexo causal, en 55 casos se estableció un nexo con razonable grado de certeza. La edad media de las víctimas al momento de producirse las lesiones era de 26 años. La edad media al momento de la indemnización fue de 66 años. Las lesiones demostradas se corresponden con la referida en la bibliografía nacional y extranjera. Se destaca el hallazgo de una considerable presencia de trastornos psicóticos. Conclusiones: se indemnizaron 115 víctimas por lesiones gravísimas causadas en su amplia mayoría por prisión política prolongada y tortura. Se observó alta prevalencia de patologías osteoarticulares, trastornos por estrés postraumático crónico y depresión, pero también un alto número de psicosis crónicas. Los informes médico-legales fueron relevantes para demostrar las lesiones gravísimas y su nexo causal con el accionar de los agentes del Estado.
Summary: The role of Legal Medicine in human rights, forensic science and humanitarian action is increasingly visible. Act 18,596 compensates those who prove to have experienced severe lesions by state agents. Objective: to contribute to public awareness of the illegitimate actions and state terrorism in Uruguay (June 13, 1968 to February 28, 1985) and the input of Legal Medicine in terms of truth, justice, memory, reparation and guarantees of non-repetition. Method: the compensation requests for severe lesions received during the first 10 years the law was in force were studied. Results and discussion: 115 out of 166 requests were admitted. In 95% of cases, a medico-legal and or psychological report was requested. Despite it being hard to prove the causal link, a link with a reasonable degree of certainty was found in 55 cases. Average age of victims at the time the lesions were caused was 26 years old. Average age at the time of compensation was 66 years old. Lesions proved match those referred to in the national and international bibliography. The study points out the finding of a considerable number of psychotic disorders. Conclusions: 115 victims were compensated for severe lesions caused, in the wide majority of cases, by long imprisonment and torture. A high prevalence of osteoarticular diseases was observed, chronic post-traumatic stress disorders and depression, although a high number of chronic psychoses, too. Medico-legal reports were relevant to demonstrate severe lesions and the causal link with the action of state agents.
Resumo: O papel da Medicina Legal nos direitos humanos e ação forense humanitária é cada vez mais visível. A Lei Nº 18.596 indeniza aquelas pessoas que acreditem ter sofrido lesões gravíssimas causadas pela ação de agentes do Estado. Objetivo: contribuir para o conhecimento público da ação ilegítima e o terrorismo de Estado no Uruguai no período 13 de junho de 1968 a 28 de fevereiro de 1985 e da contribuição da Medicina Legal em termos de verdade, justiça, memoria, reparação e garantia de não repetição. Material e método: foram estudados os pedidos de indenização por lesões gravíssimas recebidas durante os primeiros dez anos de vigência da lei. Resultados e discussão: das 166 solicitações recebidas, foram incluídas 115. Em 95% dos casos o laudo médico-legal e/ou psiquiátrico foi exigido. Embora fosse difícil demonstrar a relação causal, em 55 casos foi estabelecida com um razoável grau de certeza. A idade média das vítimas no momento em que as lesões foram produzidas era de 26 anos. A idade média no momento da indenização era de 66 anos. As lesões demostradas correspondem às referidas na bibliografia nacional e estrangeira. Destaca-se o achado da presença considerável de transtornos psicóticos. Conclusões: foram indenizadas 115 vítimas por lesões gravíssimas causadas na grande maioria por prisão política prolongada e tortura. Observou-se uma alta prevalência de patologias osteoarticulares, transtornos por estresse pós-traumático crônico e depressão, mas também um número alto de psicoses crônicas. Os laudos médico-legais foram relevantes para demonstrar as lesões gravíssimas e sua relação causal com a ação dos agentes do Estado.
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Tortura , Violaciones de los Derechos Humanos , Medicina Legal , Prisioneros , Heridas y LesionesRESUMEN
Several lines of evidence indicate the existence of salty liquid water below the icy surface of the satellite Europa. Depending on the chemical composition of the original interior brines, minerals that precipitate will be varied as will be the resulting physicochemical parameters of the evolving solutions such as pH and salinity. These parameters are determinants apropos to the study of the possible habitability of the satellite. In this work, experiments of fractional precipitation by cooling of several brines with different chemical composition (acid, alkaline, and neutral) were performed at 1 and 300 bar. The gradual decrease in temperature leads to mineral precipitation and changes in salinity and pH values. During the experiment, Raman spectroscopy was used to analyze quantitatively the variation of the salt concentration in the aqueous solutions. The obtained laboratory data indicate the manner in which cryomagma differentiation might occur on Europa. These endogenous processes of differentiation require planetary energy, which seems to have been plentiful during Europa's geological history. Ultimately, the dissipation of part of that energy is translated to a higher complexity of the cryopetrology in Europa's crust. From the results, we conclude that fractional differentiation processes of briny cryomagmas produce several types of igneous salty mineral suites on icy moons.