Photoprocessing of formamide ice: route towards prebiotic chemistry in space

Aims. Formamide (HCONH2) is the simplest molecule containing the peptide bond first detected in the gas phase in Orion-KL and SgrB2. In recent years, it has been observed in high temperature regions such as hot corinos, where thermal desorption is responsible for the sublimation of frozen mantles into the gas phase. The interpretation of observations can benefit from information gathered in the laboratory, where it is possible to simulate the thermal desorption process and to study formamide under simulated space conditions such as UV irradiation. Methods. Here, two laboratory analyses are reported: we studied formamide photo-stability under UV irradiation when it is adsorbed by space relevant minerals at 63 K and in the vacuum regime. We also investigated temperature programmed desorption of pure formamide ice in the presence of TiO2 dust before and after UV irradiation. Results. Through these analyses, the effects of UV degradation and the interaction between formamide and different minerals are compared.We find that silicates, both hydrates and anhydrates, offer molecules a higher level of protection from UV degradation than mineral oxides. The desorption temperature found for pure formamide is 220 K. The desorption temperature increases to 250 K when the formamide desorbs from the surface of TiO2 grains. Conclusions. Through the experiments outlined here, it is possible to follow the desorption of formamide and its fragments, simulate the desorption process in star forming regions and hot corinos, and constrain parameters such as the thermal desorption temperature of formamide and its fragments and the binding energies involved. Our results offer support to observational data and improve our understanding of the role of the grain surface in enriching the chemistry in space.Comment: In press Astronomy and Astrophysics, 13 pages, 12 figure

Life detection in Martian returned samples: correlation between analytical techniques and biological signatures

As soon as samples collected from Mars will be brought back to Earth, the samples will be placed inside a receiving facility to check for the presence of life. There is a large number of approaches that were proposed on the techniques to be used to investigate the presence of life and any biological risk in the returned samples. Another interesting approach was reported by Kminek in which suggestions were provided on how to organize the sample analysis sequence within the facility. Finally, another study suggested a long list of techniques capable of measuring biological signatures based on their general characteristics: global, morphological, mineralogical, organic, molecular and biochemical, isotopic analysis. Despite the effort of the cited studies, there is still the need of a critical approach to make an actual comparison between the techniques, with the aim to find a ranking. In this work, we focused on the construction of a correlation matrix with which to correlate biosignatures to analytical techniques. It is known that a number of techniques can detect biological signatures and, at the same time, each technique can be applied to multiple biological signatures. Using this method, it is possible to summarize all this information to be easily consulted, but also to define in a quantitative way how strong each correlation is

Ultraviolet Photoprocessing of Glycine Adsorbed on Various Space-Relevant Minerals

The discovery of amino acids such as glycine on meteorites and comets confirms the role of small bodies as transport and delivery vehicles of building blocks of life on Earth and possibly on other planetary bodies of our Solar System. Glycine is quite interesting because it is the simplest of the 20 biogenic amino acids, from which complex organic molecules might have originated in our evolved Solar System. To investigate the possible chemical evolution of this molecule in space, it is important to consider how the interaction with mineral matrices influences its photostability. Indeed, the presence of minerals can mediate the effects of electromagnetic radiation, catalyzing photoreactions, or protecting molecules against degradation. Such interactions are responsible for the preservation/degradation mechanisms of organic molecules in space environments. Laboratory simulations of UV processing may provide key insights into the survival of organic molecules in space environment and rocky surfaces, which is of particular relevance for current missions of sample return from asteroids, such as NASA OSIRIS-REx and JAXA Hayabusa 2, and in particular, upcoming space exploration missions on planetary surfaces, such as ESA-Roscosmos ExoMars 2022 and NASA Mars 2020. In this article, we report a laboratory study of UV irradiation of glycine adsorbed on various space relevant minerals: forsterite, antigorite, spinel, and pyrite. We monitored possible changes of glycine functional groups due to UV irradiation through in situ infrared (IR) spectroscopic analysis. Results show that degradation of glycine occurs with a half-life of 0.5–2 h depending on the mineral substrate. Appearance of new IR bands suggests the occurrence of catalytic reactions mediated by minerals and UV

The Marco Polo mission: a sample return from a low-albedo Near Earth Object in the ESA Cosmic Vision Program 2015-2025

Marco Polo is a sample return mission to a Near-Earth Object (NEO) which was originally proposed as a joint European-Japanese mission for the scientific program Cosmic Vision 2015-2025 of the European Space Agency (ESA) in June 2007 and selected for an assessment study until fall 2009. The main goal of this mission is to return a sample from a dark taxonomic type (low albedo) NEO for detailed laboratory analysis in order to answer questions related to planetary formation, evolution and the origin of Life. In addition, it will provide detailed information on the physical and chemical properties of a body belonging to the population of potential Earth impactors, and therefore it is also directly relevant to the problems of risk assessment and mitigation. We review basic information on NEOs, potential targets for a sample return mission and the Marco Polo mission, with emphasis on their relevance to impact risk assessment and mitigation. More details on the Marco Polo mission and scientific objectives can be found in [1]

On Water Formation in the Interstellar Medium: Laboratory Study of the O+D Reaction on Surfaces

In the interstellar medium (ISM), an important channel of water formation is the reaction of atoms on the surface of dust grains. Here, we report on a laboratory study of the formation of water via the O+D reaction network. While prior studies were done on ices, as appropriate to the formation of water in dense clouds, we explored how water formation occurs on bare surfaces, i.e., in conditions mimicking the transition from diffuse to dense clouds (Av ~ 1-5). Reaction products were detected during deposition and afterward when the sample is brought to a high temperature. We quantified the formation of water and intermediary products, such as D2O2, over a range of surface temperatures (15-25 K). The detection of OD on the surface signals the importance of this reactant in the overall scheme of water formation in the ISM

FORMATION OF MOLECULAR OXYGEN AND OZONE ON AMORPHOUS SILICATES

Oxygen in the interstellar medium is seen in the gas phase, in ices (incorporated in H{sub 2}O, CO, and CO{sub 2}), and in grains such as (Mg{sub x} Fe{sub 1-x} )SiO{sub 3} or (Mg{sub x} Fe{sub 1-x} ){sub 2}SiO{sub 4}, 0 < x < 1. In this investigation, we study the diffusion of oxygen atoms and the formation of oxygen molecules and ozone on the surface of an amorphous silicate film. We find that ozone is formed at low temperature (<30 K), and molecular oxygen forms when the diffusion of oxygen atoms becomes significant, at around 60 K. This experiment, besides being the first determination of the diffusion energy barrier (1785 {+-} 35 K) for oxygen atoms on a silicate surface, suggests bare silicates as a possible storage place for oxygen atoms in low-A{sub v} environments

Activity of comet 103P/Hartley 2 at the time of the EPOXI mission fly-by

Comet 103P/Hartley~2 was observed on Nov. 1-6, 2010, coinciding with the fly-by of the space probe EPOXI. The goal was to connect the large scale phenomena observed from the ground, with those at small scale observed from the spacecraft. The comet showed strong activity correlated with the rotation of its nucleus, also observed by the spacecraft. We report here the characterization of the solid component produced by this activity, via observations of the emission in two spectral regions where only grain scattering of the solar radiation is present. We show that the grains produced by this activity had a lifetime of the order of 5 hours, compatible with the spacecraft observations of the large icy chunks. Moreover, the grains produced by one of the active regions have a very red color. This suggests an organic component mixed with the ice in the grains.Comment: 11 pages, 7 figures, Icarus in pres

UV Irradiation and Near Infrared Characterization of Laboratory Mars Soil Analog Samples

The search for molecular biosignatures at the surface of Mars is complicated by an intense irradiation in the mid- and near-ultraviolet (UV) spectral range for several reasons: (i) many astrobiologically relevant molecules are electronically excited by efficient absorption of UV radiation and rapidly undergo photochemical reactions; (ii) even though the penetration depth of UV radiation is limited, aeolian erosion continually exposes fresh material to radiation; and (iii) UV irradiation generates strong oxidants such as perchlorates that can penetrate deep into soils and cause subsurface oxidative degradation of organics. As a consequence, it is crucial to investigate the effects of UV radiation on organic molecules embedded in mineral matrices mimicking the martian soil, in order to validate hypotheses about the nature of the organic compounds detected so far at the surface of Mars by the NASA Mars Science Laboratory’s (MSL) Curiosity rover, as well as organics that will be possibly found by the next rover missions Mars 2020 (NASA) and ExoMars 2022 (ESA-Roscosmos). In addition, studying the alteration of possible molecular biosignatures in the martian environment will help to redefine the molecular targets for life detection missions and devise suitable detection methods. Here we report the results of mid- and near-UV irradiation experiments of Mars soil analog samples obtained adsorbing relevant organic molecules on a clay mineral that is quite common on Mars, i.e. montmorillonite, doped with 1 wt% of magnesium perchlorate. Specifically, we chose to investigate the photostability of a plausible precursor of the chlorohydrocarbons detected on Mars by the Curiosity rover, namely phthalic acid, along with the biomarkers of extant life L-phenylalanine and L-glutamic acid, which are proteomic amino acids, and adenosine 5’-monophosphate, which is a nucleic acid component. We monitored the degradation of these molecules adsorbed on montmorillonite through in situ spectroscopic analysis, investigating the reflectance properties of the samples in the Near InfraRed (NIR) spectral region. Such spectroscopic characterization of molecular alteration products provides support for two upcoming robotic missions to Mars that will employ NIR spectroscopy to look for molecular biosignatures, through the instruments SuperCam on board Mars 2020, ISEM, Ma_Miss and MicrOmega on board ExoMars 2022