Zita Martins

Astrobiology and habitability studies in preparation for future Mars missions: Trends from investigating minerals, organics and biota

Several robotic exploration missions will travel to Mars during this decade to investigate habitability and the possible presence of life. Field research at Mars analogue sites such as desert environments can provide important constraints for instrument calibration, landing site strategies and expected life detection targets. We have characterized the mineralogy, organic chemistry and microbiology of ten selected sample sites from the Utah desert in close vicinity to the Mars Desert Research Station (MDRS) during the EuroGeoMars 2009 campaign (organized by International Lunar ExplorationWorking Group (ILEWG), NASA Ames and ESA ESTEC). Compared with extremely arid deserts (such as the Atacama), organic and biological materials can be identified in a larger number of samples and subsequently be used to perform correlation studies. Among the important findings of this field research campaign are the diversity in the mineralogical composition of soil samples even when collected in close proximity, the low abundances of detectable polycyclic aromatic hydrocarbons (PAHs) and amino acids and the presence of biota of all three domains of life with significant heterogeneity. An extraordinary variety of putative extremophiles, mainly Bacteria and also Archaea and Eukarya was observed. The dominant factor in measurable bacterial abundance seems to be soil porosity and lower small (clay-sized) particle content. However, correlations between many measured parameters are difficult to establish. Field research conducted during the EuroGeoMars 2009 campaign shows that the geological history and depositional environment of the region, as well as the mineralogy influence the ability to detect compounds such as amino acids and DNA. Clays are known to strongly absorb and bind organic molecules often preventing extraction by even sophisticated laboratory methods. Our results indicate the need for further development and optimization of extraction procedures that release biological compounds from host matrices to enable the effective detection of biomarkers during future sampling campaigns on Earth and Mars.

Extraction of amino acids from soils close to the Mars Desert Research Station (MDRS), Utah

Future space missions that aim to detect life should search for molecules that are vital to all living organisms. Although the Viking landers did not find any signs of organic molecules on Mars, signatures of past and/or present life may still exist in the Martian regolith. In this paper, we describe amino acid analyses performed in several Martian analogue soil samples collected close to the Mars Desert Research Station (MDRS), Utah, during the International Lunar Exploration Working Group (ILEWG) EuroGeoMars campaign in February 2009. The Utah desert around Hanksville is characterized as shale desert and is cold and arid with an average annual temperature of 12°C. It is subjected to wind erosion and was shaped by fluvial erosion. The data show large differences in the total amino acid abundances between all the collected soil samples, with values ranging from non-detectable to 100 000 parts per billion (ppb). These results are explained in the context of mineralogical differences (namely different clay content) among the soil samples. The data have implications for future life-detection missions and the target mineralogy that may host biological signatures.

Field astrobiology research in Moon–Mars analogue environments: instruments and methods

We describe the field demonstration of astrobiology instruments and research methods conducted in and from the Mars Desert Research Station (MDRS) in Utah during the EuroGeoMars campaign 2009 coordinated by ILEWG, ESA/ESTEC and NASA Ames, with the contribution of academic partners. We discussthe entire experimental approach fromdetermining the geological context using remote sensing, in situ measurements, sorties with sample collection and characterization, analysis in the field laboratory, to the post sample analysis using advanced laboratory facilities. We present the rationale for terrestrial field campaigns to strengthen astrobiology research and the link between in situ and orbital remote sensing data. These campaigns are supporting the preparation for future missions such as Mars Science Laboratory, ExoMars or Mars Sample Return. We describe the EuroGeoMars 2009 campaign conducted by MDRS crew 76 and 77, focused on the investigation of surface processes in their geological context. Special emphasis was placed on sample collection and pre-screening using in-situ portable instruments. Science investigations included geological and geochemical measure- ments as well as detection and diagnostic of water, oxidants, organic matter, minerals, volatiles and biota. EuroGeoMars 2009 was an example of a Moon-Mars field research campaign dedicated to the demonstration of astrobiology instruments and a specific methodology of comprehensive measurements fromselected samplingsites. Wediscuss in sequence: the campaign objectivesand trade-off based on science, technicaloroperationalconstraints.Thisincludes remotesensingdataandmaps, andgeologicalcontext; the monitoring of environmental parameters; the geophysical context and mineralogy studies; geology and geomorphology investigations; geochemistry characterization and subsurface studies. We describe sample handling (extraction and collection) methods, and the sample analysis of soils and rocks performed in the MDRS laboratory using close inspection, initial petrological characterization, microscopy, Visible-NIR spectrometry, Raman spectrometry, X-ray diffraction/X-ray fluorescence spectrometry, soil analysis, electrochemical and biological measurements. The results from post-mission analysis of returned samples using advanced facilities in collaborator institutes are described in companion papers in this issue. We present examples of in-situ analysis, and describe an example investigation on the exploration and analysis of endolithic microbial mats (from reconnaissance, in-situ imaging, sampling, local analysis to post-mission sample analysis).We describe the field demonstration of astrobiology instruments and research methods conducted in and from the Mars Desert Research Station (MDRS) in Utah during the EuroGeoMars campaign 2009 coordinated by ILEWG, ESA/ESTEC and NASA Ames, with the contribution of academic partners. We discuss the entire experimental approach from determining the geological context using remote sensing, in situ measurements, sorties with sample collection and characterization, analysis in the field laboratory, to the post sample analysis using advanced laboratory facilities. We present the rationale for terrestrial field campaigns to strengthen astrobiology research and the link between in situ and orbital remote sensing data. These campaigns are supporting the preparation for future missions such as Mars Science Laboratory, ExoMars or Mars Sample Return. We describe the EuroGeoMars 2009 campaign conducted by MDRS crew 76 and 77, focused on the investigation of surface processes in their geological context. Special emphasis was placed on sample collection and pre-screening using in-situ portable instruments. Science investigations included geological and geochemical measurements as well as detection and diagnostic of water, oxidants, organic matter, minerals, volatiles and biota. EuroGeoMars 2009 was an example of a Moon-Mars field research campaign dedicated to the demonstration of astrobiology instruments and a specific methodology of comprehensive measurements from selected sampling sites. We discuss in sequence: the campaign objectives and trade-off based on science, technical or operational constraints. This includes remote sensing data and maps, and geological context; the monitoring of environmental parameters; the geophysical context and mineralogy studies; geology and geomorphology investigations; geochemistry characterization and subsurface studies. We describe sample handling (extraction and collection) methods, and the sample analysis of soils and rocks performed in the MDRS laboratory using close inspection, initial petrological characterization, microscopy, Visible-NIR spectrometry, Raman spectrometry, X-ray diffraction/X-ray fluorescence spectrometry, soil analysis, electrochemical and biological measurements. The results from post-mission analysis of returned samples using advanced facilities in collaborator institutes are described in companion papers in this issue. We present examples of in-situ analysis, and describe an example investigation on the exploration and analysis of endolithic microbial mats (from reconnaissance, in-situ imaging, sampling, local analysis to post-mission sample analysis).

Organic host analogues and the search for life on Mars

Mars analogue sites represent vital tools in our continued study of the Red Planet; the similar physico-chemical processes that shape a given analogue environment on Earth allow researchers to both prepare for known Martian conditions and uncover presently unknown relationships. This review of organic host analogues – sites on Earth that mimic the putatively low organic content of Mars – examines specific locations that present particular Mars-like obstacles to biological processes. Low temperatures, aridity, high radiation and oxidizing soils characterise modern-day Mars, while acid–saline waters would have presented their own challenges during the planets warmer and wetter past. By studying each of these hurdles to life on Earth, scientists can prepare instruments headed for Mars and identify the best locations and approaches with which to look for biological signatures. As our use of organic host analogues becomes increasingly sophisticated, researchers will work to identify terrestrial sites exhibiting multiple Mars-like conditions that are tailored to the distinct mineralogical and physical characteristics of Martian locations. Making use of organic host analogues in these ways will enhance the search for signs of past or present life on Mars.

Inconclusive evidence for nonterrestrial isoleucine enantiomeric excesses in primitive meteorites

Pizzarello et al. (1) recently described the soluble organic content of eight Antarctic Renazzo-type (CR) carbonaceous chondrites and reported large enantiomeric excesses (ee) of l-isoleucine and d-alloisoleucine. The reported values of ee decrease with inferred increases in aqueous alteration. We believe the conclusions presented in the paper are not fully justified and the data are potentially flawed.

Analysis of mineral matrices of planetary soil analogues from the Utah Desert

Phyllosilicate minerals and hydrated sulphate minerals have been positively identified on the surface of Mars. Studies conducted on Earth indicate that micro-organisms influence various geochemical and mineralogical transitions for the sulphate and phyllosilicate minerals. These minerals in turn provide key nutrients to micro-organisms and influence microbial ecology. Therefore, the presence of these minerals in astrobiology studies of Earth–Mars analogue environments could help scientists better understand the types and potential abundance of micro-organisms and/or biosignatures that may be encountered on Mars. Bulk X-ray diffraction of samples collected during the EuroGeoMars 2009 campaign from the Mancos Shale, the Morrison and the Dakota formations near the Mars Desert Research Station in Utah show variable but common sedimentary mineralogy with all samples containing quantities of hydrated sulphate minerals and/or phyllosilicates. Analysis of the clay fractions indicate that the phyllosilicates are interstratified illite–smectites with all samples showing marked changes in the diffraction pattern after ethylene glycol treatment and the characteristic appearance of a solvated peak at ∼17 A. The smectite phases were identified as montmorillonite and nontronite using a combination of the X-ray diffraction data and Fourier–Transform Infrared Spectroscopy. The most common sulphate mineral in the samples is hydrated calcium sulphate (gypsum), although one sample contained detectable amounts of strontium sulphate (celestine). Carbonates detected in the samples are variable in composition and include pure calcium carbonate (calcite), magnesium-bearing calcium carbonate (dolomite), magnesium, iron and manganese-bearing calcium carbonate (ankerite) and iron carbonate (siderite). The results of these analyses when combined with organic extractions and biological analysis should help astrobiologists and planetary geologists better understand the potential relationships between mineralogy and microbiology for planetary missions.

Biomass preservation in impact melt ejecta

Meteorites can have played a role in the delivery of the building blocks of life to Earth only if organic compounds are able to survive the high pressures and temperatures of an impact event. Although experimental impact studies have reported the survival of organic compounds, there are uncertainties in scaling experimental conditions to those of a meteorite impact on Earth and organic matter has not been found in highly shocked impact materials in a natural setting. Impact glass linked to the 1.2-km-diameter Darwin crater in western Tasmania is strewn over an area exceeding 400 km2 and is thought to have been ejected by a meteorite impact about 800 kyr ago into terrain consisting of rainforest and swamp. Here we use pyrolysis–gas chromatography–mass spectrometry to show that biomarkers representative of plant species in the local ecosystem—including cellulose, lignin, aliphatic biopolymer and protein remnants—survived the Darwin impact. We find that inside the impact glass the organic components are trapped in porous carbon spheres. We propose that the organic material was captured within impact melt and preserved when the melt quenched to glass, preventing organic decomposition since the impact. We suggest that organic material can survive capture and transport in products of extreme impact processing, at least for a Darwin-sized impact event.

UV to far-IR reflectance spectra of carbonaceous chondrites - I. Implications for remote characterization of dark primitive asteroids targeted by sample-return missions

We analyse here a wide sample of carbonaceous chondrites from historic falls (e.g. Allende, Cold Bokkeveld, Kainsaz, Leoville, Murchison, Murray, Orgueil and Tagish Lake) and from NASA Antarctic collection. With the analysis of these meteorites we want to get new clues on the role of aqueous alteration in promoting the reflectance spectra diversity evidenced in the most primitive chondrite groups. The selected meteorite specimens are a sample large enough to exemplify how laboratory reflectance spectra of rare groups of carbonaceous chondrites exhibit distinctive features that can be used to remotely characterize the spectra of primitive asteroids. Our spectra cover the full electromagnetic spectrum from 0.2 to 25µ mb y using two spectrometers. First one is an ultraviolet (UV)–near-infrared (NIR) spectrometer that covers the 0.2–2µm window, while the second one is an attenuated total reflectance infrared spectrometer covering the 2–25µm window. In particular, laboratory analyses in the UV–NIR window allow obtaining absolute reflectance by using standardized measurement procedures. We obtained reflectance spectra of specimens belonging to the CI, CM, CV, CR, CO, CK, CH, R and CB groups of carbonaceous chondrites plus some ungrouped ones, and it allows identifying characteristic features and bands for each class, plus getting clues on the influence of parent body aqueous alteration. These laboratory spectra can be compared with the remote spectra of asteroids, but the effects of terrestrial alteration forming (oxy)hydroxides need to be considered.

Type IV Kerogens as Analogues for Organic Macromolecular Materials in Aqueously Altered Carbonaceous Chondrites

Understanding the processes involved in the evolution of organic matter in the early Solar System requires extensive experimental work. The scientifically valuable carbonaceous chondrites are principal targets for organic analyses, but these meteorites are rare. Meteoritic analog materials available in larger quantities, on which experiments can be performed, would be highly beneficial. The bulk of the organic inventory of carbonaceous chondrites is made up of solvent-insoluble macromolecular material. This high-molecular-weight entity provides a record of thermal and aqueous parent-body alteration of precursor organic structures present at the birth of the Solar System. To identify an effective analogue for this macromolecular material, we analyzed a series of terrestrial kerogens by pyrolysis-gas chromatography-mass spectrometry. Type I and II kerogens are unsuitable analogues owing to their highly aliphatic nature. Type III kerogens show some similarities to meteoritic macromolecular materials but display a substantial biological heritage. Type IV kerogens, in this study derived from Mesozoic paleosols and produced by the reworking and oxidation of organic matter, represent an effective analogue. Some isomeric differences exist between meteoritic macromolecular materials and type IV kerogens, and stepped pyrolysis indicates variations in thermal stability. In addition to being a suitable material for novel experimentation, type IV kerogens also have the potential to aid in the optimization of instruments for deployment on Mars.

Quantitative enantioseparation of amino acids by comprehensive two-dimensional gas chromatography applied to non-terrestrial samples

This work presents an improved analytical procedure for the resolution and quantification of amino acid enantiomers by multidimensional gas chromatography. The procedure contains a derivatization step, by which amino acids were transformed into N(O,S)-ethoxycarbonylheptafluorobutyl esters. It was optimized for the resolution of non-proteinogenic amino acids in the matrix of complex non-terrestrial samples. The procedure has proven to be highly sensitive and shows a wide linearity range with 0.005-3 pmol detection limits for quantitative determinations. The developed procedure was tested on a sample of the Murchison meteorite, for which obtained chromatograms show excellent peak resolution, minimal co-elution and peak overlap. We conclude that comprehensive two dimensional chromatography, in combination with the optimized derivatization method is a highly suitable technique for the analysis of samples with very limited quantities and containing potentially prebiotic molecules, such as interstellar ice analogs and meteorites.