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The recently adopted Ariel ESA mission will measure the atmospheric composition of a large number of exoplanets. This information will then be used to better constrain planetary bulk compositions. While the connection between the composition of a planetary atmosphere and the bulk interior is still being investigated, the combination of the atmospheric composition with the measured mass and radius of exoplanets will push the field of exoplanet characterisation to the next level, and provide new insights of the nature of planets in our galaxy. In this white paper, we outline the ongoing activities of the interior working group of the Ariel mission, and list the desirable theoretical developments as well as the challenges in linking planetary atmospheres, bulk composition and interior structure., Experimental Astronomy, 53, ISSN:0922-6435, ISSN:1572-9508

Planetary Terrestrial Analogue Library (PTAL) is a newly built collection of rocks and spectral data aiming to support interpretation of data from Mars and small bodies of the Solar System [1]. It contains spectral data by NIR, Raman and LIBS, validated by XRD and microscopic characterization [2,3,4]. Since September 2021, the PTAL library is public and freely accessible (www.ptal.eu), and the physical collection of witness rocks is available for further studies. PTAL is collection of natural rocks and not individual minerals what gives better insight into mineralogy and geochemistry as e.g. overlapping vibrational absorption features of minerals are included. Although the spectral analogy never implies exact parallelism in processes of deposit formation, reliable identification of specific minerals can shed light on recorded evolution and alterations. Here we present the overview of analogues and assess their fidelity in terms of information about composition (mineralogy and geochemistry) of Martian crust and alteration environments.PTAL consists of 106 rock samples from 19 diverse localities on Earth [1]. The collection contains a variety of volcanic rocks, from picrobasalts to phonolites. Sampling sites include tholeiitic basalts from Iceland, ferropicrites from Rum (Scotland), alkali-rich rocks of metasomatized origin from Canary Islands and Tenerife, basaltic tuffs and ash-fall deposits from the Granby formation (USA) with clay-infilled amygdales, as well as serpentinised peridotites from the Leka ophiolite complex (Norway). Collected rocks are good analogues for processes of martian mantle-plume fed volcanism as well as for evolution of alkali-rich crustal units on Noachian Mars. Additionally they record processes of metasomatism, deuteric and hydrothermal alteration. They are never perfect geochemical analogues to Martian crust, which is a consequence of inherited differences between the two planets, e.g. Fe and Mn content or volatile abundances. PTAL initial studies show, however, that studies of alteration pathways as a function of protolith composition are possible with these rocks, despite geochemistry mismatches [5].PTAL contains also samples from diverse surface alteration environments and from range of climatic environments, including hot and cold deserts: John Day Formation in Oregon (USA), Dry Valleys in Antarctica, Otago Formation (New Zealand), Jaroso Ravine and Rio Tinto (Spain). These analogues contain minerals such as jarosite, hematite, or Fe-rich vermiculite and therefore good geochemical and mineralogical analogies to Mars targeted sites can be obtained. However, care is needed when processes of formation inferred [e.g. 5], as peculiar conditions leading to formation of minerals can be obtained in a spectrum of environments. PTAL strength is that it samples a sequence of alteration products, allowing detailed mineralogical and geochemical comparative analyses within alteration environment to shed light on the potential parallelism of formation process [5].Acknowledgement: PTAL was funded by the EU Horizon 2020 Research and Innovation Programme (Grant Agreement 687302).[1] Dypvik et al., 2021. Planetary and Space Science 208, 105339[2] Lantz et al., 2020. Planetary and Space Science 189: 104989[3] Loizeau et al., 2022. Astrobiology, accepted.[4] Veneranda et al., 2020. Journal of Raman Spectroscopy 51: 1731-1749[5] Krzesinska et al. 2021. Astrobiology 21: 997-1016

Global scale temporal assignments for planetary surfaces are made based on craters statistics. Age assignments require a cratering chronology model that links normalized crater frequencies and sample ages. A challenge is that rocks on planetary surface may not belong to the site from which they are collected. We use detailed spectral mapping, cratering statistics and impact basin ejecta column estimates to suggest stratigraphic relationships for lunar sampling sites, and most specifically the Apollo 14 landing site. We confirm previously recognised resurfacing in the crater size-frequency distribution in agreement with a single blanketing layer. Based on our and previously published crater statistics, and mineral relation derived from spectral data, we suggest a cratering chronology model that effectively increase the surface age of the Moon. In this presentation, we will document and outline our reasons and data. This change in cratering chronology model implies significant changes for the early solar system evolution time-scale assessment, small body flux and geological dates and rates on all planetary surface when crater statistics is used to determine ages.

The Planetary Terrestrial Analogues Library (PTAL) project aims at building and exploiting a database involving several analytical techniques, to help characterize the mineralogical evolution of terrestrial bodies, starting with Mars. Around 100 natural Earth rock samples have been collected from selected locations to gather a variety of analogs for martian geology, from volcanic to sedimentary origin with different levels of alteration. All samples are to be characterized within the PTAL project with different mineralogical and elemental analysis techniques, including techniques brought on actual and future instruments at the surface of Mars (near infrared [NIR] spectroscopy, Raman spectroscopy, and laser-induced breakdown spectroscopy). This article presents the NIR measurements and interpretations acquired with the ExoMars MicrOmega spare instrument. MicrOmega is an NIR hyperspectral microscope, mounted in the analytical laboratory of the ExoMars rover Rosalind Franklin. All PTAL samples have been observed at least once with MicrOmega using a dedicated setup. For all PTAL samples, data description and interpretation are presented. For some chosen examples, color composite images and spectra are presented as well. A comparison with characterizations by NIR and Raman spectrometry is discussed for some of the samples. In particular, the spectral imaging capacity of MicrOmega allows detections of mineral components and potential organic molecules that were not possible with other one-spot techniques. In addition, it enables estimation of heterogeneities in the spatial distribution of various mineral species. The MicrOmega/PTAL data shall support the future observations and analyses performed by MicrOmega/Rosalind Franklin instrument.

The PTAL Project: Mars2020/Perseverance 1 and ExoMars/Rosalind Franklin 2 rovers will look for traces of present or past life on Mars. To do so, the spectroscopic systems included in their analytical payloads will investigate the geochemistry and mineralogy of Martian rocks and soils to detect geological samples that could potentially host biomarkers. In order to optimize the scientific exploitation of planetary spectroscopic analysis, the PTAL project will provide the scientific community with a novel library of terrestrial analogue materials that have been selected based on their similarity to well-known Martian geological contexts. Funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement Nº 687302, the PTAL online platform will be released to public in October 2021. As further detailed by Werner et al. during this conference, the core of the database are the spectroscopic data collected by means of multiple Raman (University of Valladolid, UVa, Spain), NIR (University of Paris-Sud, UP-Sud, France) and LIBS (French National Centre for Scientific Research, IRAP, France) systems. Spectroscopic results are additionally supported by X-ray diffractograms and thin section observations (University of Oslo, Uio, Norway) to provide an exhaustive geochemical and mineralogical characterization of the samples. The whole set of data, collected by means of both commercial systems and prototypes/flight spares (FS) of analytical instruments validated for Mars exploration (RLS-Sim, MicrOmega-FS, ChemCam-FS), will be available to the public thanks to a dedicated online platform, which main characteristics are detailed below.The online PTAL platform:The PTAL database will be accessible to public through the following URL: http://erica.uva.es/PTAL/. After login (credentials will be provided by the PTAL consortium upon request), future users will have access to the whole set of diffractometric and spectroscopic data collected from a total of 102 analogue materials. On one side, clicking on the sample name, the metadata associated to the selected terrestrial analogues are provided (e.g., Sample Name and Lithology, Sampling Campaign and coordinates) together with high quality pictures of the terrestrial analogue sample. On the other side, by clicking on “analytical summary”, the PTAL platform displays the list of NIR, LIBS, Raman and XRD analyses associated to the selected terrestrial analogue, together with a table summarizing and comparing the main results gathered from each technique (Figure 1).Figure 1: Screenshots collected from the PTAL online database: a) list of samples, b) summary result of a selected analogue, and c) online visualization of a selected Raman spectrum.At this stage, all NIR, XRD, Raman and LIBS data have been successfully uploaded to the PTAL database 3–5. In detail, the PTAL database provides access to 102 diffractograms (1 per sample), 102 LIBS spectra, 102 NIR spectra collected by means of the commercial spectrometer, and 102 NIR data cubes obtained through the MicrOmega system (of them composed of 62500 spectra collected at steps of 20µm in a field of view of 5x5mm). Regarding Raman results, only the spectra providing the highest mineralogical information were uploaded to the PTAL database. As such, the number of Raman spectra was reduced from over 4500 to 577 (an average of 5-6 spectra per sample). 245 of them were collected by means of the RLS-Sim, while the remaining 332 were obtained with a commercial spectrometer. All data can be either visualized online or downloaded for further data comparison and processing. In this framework, it must be underlined the PTAL platform also gives access to a dedicated software for data treatment. Named SpectPro, the details of this downloadable software are detailed below.The SpectPro software:Developed in the framework of the ExoMars mission 6, the PTAL version of the SpectPro software could be downloaded from the PTAL webpage (download section) for both windows and MacOs operating systems. Through the SpectPro software, PTAL users will be able to run individual and multi-spectra operations such as labelling, trimming, shifting, normalization, baseline correction (see Figure 2).Figure 2: Screenshot of PTAL/SpectPro, in which the main functionalities and characteristics of the software are highlighted.Among the main functionalities, the software also features a general-purpose spectrum calculator to perform lineal combinations, product and derivative of spectra, among others. The software team has been working to facilitate a direct access from SpectPro to the PTAL database, using the same credentials for access to the PTAL web interface. This connection will boost the capability of the scientist working in a planetary mission (but not only) to perform a fast and comprehensive characterization and identification of the mineral phases present in a sample by comparing the data obtained from the sample with the extensive spectral information included in the PTAL database. This will be possible by profiting from the navigation pane included in SpectPro. In addition, using the peak detection capabilities of SpectPro, it will be possible to perform sample identification based on the acquired spectra.Acknowledgments: This work is financed through the European Research Council in the H2020- COMPET-2015 programme (grant 687302).References: 1 Farley, K. A. et al. Space Sci. Rev. 216, 142 (2020); 2 Vago, J. L. et al. Astrobiology 17, 471–510 (2017); 3 Lantz, C. et al. Planet. Space Sci. 189, 104989 (2020); 4 Loizeau, D. et al. Planet. Space Sci. 193, 105087 (2020); 5 Veneranda, M. et al. J. Raman Spectrosc. 1–19 (2019) doi:10.1002/jrs.5652; 6 Lopez-Reyes G. et al. European Planetary Science Congress 2018 vol. 12 1–2 (2018).

Serpentinization and carbonation have affected ultramafic rocks on Noachian Mars in several places called here serpentinization-carbonation systems (SCS). Among the most prominent SCS revealing mineral assemblages characteristic of serpentinization/carbonation is the Nili Fossae region [1]. Jezero crater – the target of the Mars 2020 rover –hosted a paleolake which constitutes a sink for sediments from Nili Fossae [1]. Thanks to the near infrared spectrometer onboard Mars2020 [2], the mission has the potential to offer ground truth measurement for other putative serpentinization/carbonation system documented on Mars. Several important aspects that may be addressed are: Do carbonates result from primary alteration of olivine-rich lithologies or are they derived by reprocessing of previous alteration minerals [3]? What is the composition? and nature of the protolith, which appear to be constituted of considerable amounts of olivine [4]? To reveal critical information regarding the conditions of serpentinization/carbonation, accessory minerals need detailed studies [1; 5]. In case of Jezero Crater, and serpentinization on Mars in general, the main alteration minerals are identified, but little is known about the accessory minerals. The Nili Fossae-Jezero system has potential analogues in terrestrial serpentinized and carbonated rocks, such as the Leka Ophiolite Complex, Norway (PTAL collection, https://www.ptal.eu). Here, distinct mineral assemblages record different stages of hydration and carbonation of ultramafic rocks [6]. We perform petrological and mineralogical analyses on thin sections to characterize the major and trace minerals and combine with Near Infrared (NIR) spectroscopy measurements. A set of spectral parameters are defined and compare to spectral parameters previously used on CRISM and OMEGA data [1, 4, 7, 8]. We study the significance of the mineralogical assemblages including nature of accessory minerals. Effect of the presence of accessory minerals on the NIR signal is investigated and their potential incidence on the amount of H2/CH4 production in mafic or ultramafic system is discussed [5]. We started to apply the newly defined spectral parameters on several SCS on Mars. Results confirm local carbonation of earlier serpentinized rocks and suggest that different protoliths could have led to diversity of mineralogical associations in SCS on Mars. Multiple detection of brucite are also suggested for the first time on Mars. Altogether our results help to better describe key geochemical conditions of the SCS on Mars for habitability potential of the martian crust and Mars’s evolution. References: Brown, A. J., et al. EPSL1-2 (2010): 174-182. Wiens, R.C., et al. Space Sci Rev217, 4 (2021). Horgan, B., et al. Second International Mars Sample Return. Vol. 2071. 2018. Ody, A., et al. JGR: Planets2 (2013): 234-262. Klein, F., et al. Lithos178 (2013): 55-69. Bjerga, A., et al. Lithos227 (2015): 21-36. Viviano-Beck et al, JGR: Planets 118.9 (2013) Viviano-Beck et al, JGR: Planets 119.6 (2014)

Impact craters are the predominant geological features on the lunar surface. Data about the craters are crucial for inferring information about surface age, the generation processes of the geological units, and the sequences of geological events. The higher-resolution remote sensing datasets collected by recent lunar missions enable the investigation of impact craters of smaller size and provide more accurate information. This paper presents an investigation of the distribution and population characteristics of impact craters in and around the Orientale Basin based on high-resolution datasets. First, an update to the crater catalogue for the Orientale Basin and its surrounding area is provided, including craters as small as 1 km in diameter. Based on the updated crater catalogue, the crater densities and depth-to-diameter ratios in and around the Orientale Basin are investigated. The inclusion of small craters enables a crater density map with higher resolution, revealing a significantly higher crater density of the study area. Also, the surface age of Orientale Basin is estimated from the size–frequency distribution (SFD) using the new crater catalogue, showing an age of 3.75 Ga using the production function of Neukum et al. (2001), which is in good agreement with previous studies. Finally, distribution patterns of secondary craters around the Orientale Basin are investigated, indicating the Orientale Basin may be caused by an oblique impact with a downrange direction of about 235°–260° and an offset strength towards the direction of about 305°–350°.

The intensity and effects of early impact bombardment on the major satellites of the giant planets during an episode of giant planet migration is still poorly known. We use a combination of dynamical N-body and Monte Carlo simulations to determine impact probabilities, impact velocities, and expected masses that collide with these satellites to determine the chronology of impacts during the migration. Volatile loss through bombardment is typically 20% for Miranda, a few percents for the larger Uranian satellites and negligible for the Galilean satellites. Due to its small size and the high impact velocity there is a >99% chance that Miranda suffered a catastrophic impact that shattered the satellite. Subsequent re-accretion from a circum-Uranian ring could account for its peculiar surface morphology and low density. The probability to destroy Ariel and Umbriel is 15% and 1% for Titania and Oberon. Approximately 90% of the mass in planetesimals that passes through the Jovian and Uranian satellite systems (about $4 {\rm \ M_{\oplus}}$ and $2 {\rm \ M_{\oplus}}$ respectively) does so in about 15 Myr. This extremely rapid and intense bombardment causes repeated local crustal melting on all satellites. The combination of these effects results in an entirely different impact chronology than that of the inner solar system. We conclude that the simple extrapolation of the lunar chronology to the outer solar system satellites is not correct. The tail end (after 25 Myr) of the chronology function has an e-folding time of 100 Myr at Jupiter, but follows a cumulative Weibull distribution at Uranus, making direct comparisons between the gas and ice giant planets difficult. Based on our results the surfaces of the Uranian satellites, Callisto, and possibly Ganymede, are all about the same age, and are roughly 150 Myr younger than the timing of the dynamical instability., 24 pages, 5 figures, accepted for publication in Earth and Planetary Science Letters

The PTAL project [1] aims to build an Earth analogues database, the Planetary Terrestrial Analogues Library, to help characterizing the mineralogical evolution of terrestrial bodies, with a focus on Martian analogues (www.PTAL.eu). A set of natural Earth rock samples have been collected, compelling a variety of igneous and sedimentary rocks with variable compositions and levels of alteration. Those samples are characterized with thin section observations and XRD analysis, NIR spectroscopy, Raman spectroscopy and LIBS.This abstract focuses on the NIR (Near Infrared) spectroscopy analysis performed using the MicrOmega instrument, a NIR hyperspectral microscope (e.g. [2]). The MicrOmega instrument used within the PTAL project is the spare model of the ExoMars rover laboratory. It has a total field of view of 5 mm x 5 mm, with resolution of 20 µm/pixel in the focal plane. It covers the spectral domain from 0.98 µm to ~3.6 µm. Its capabilities enable the identification of grains of different mineralogy in the samples [2].Each MicrOmega observation produces >65,000 spectra, hence automatic analysis is needed as a first step. After data calibration, a quick-look data analysis based on a set of ~16 spectral parameters based on the detection of single or multiple absorption bands was performed to produce spectral indices maps and average spectra, then guiding the manual analysis in a second step. After spectral endmembers are identified, they are compared to reference spectral libraries to identify the presence of minerals species in the sample. Spectral parameter maps can then be used to map the extent of the identified mineral species on the surface of the sample. Final products of the analyses will feed the online PTAL spectral database, and a paper describing these analyses has recently been submitted to Astrobiology.Mineral species detected with MicrOmega in the PTAL samples include: Olivine, High Calcium Pyroxene, Low Calcium Pyroxene, Amphiboles, Epidotes, Zeolites, Opals, Phyllosilicates, Oxides and Hydroxides, Carbonates, and Sulfates.Preliminary comparisons with XRD and Raman analyses show general consistency in the identification of olivine, pyroxene and hydrated phases. As expected, quartz and plagioclase for example are challenging to be identified in NIR, but MicrOmega shows well the capacity in hydrated minerals identification and qualitative estimation of major and minor mineral species thanks to its spectral-imaging capabilities.The PTAL spectral database will assist in particular in interpreting in situ data from the next Mars surface missions. The target-rocks in Oxia Planum and Jezero Crater, the landing sites of the next surface missions, have compositional similarities with some samples of the PTAL collection, in particular with the orbital identification of clay minerals and serpentine. The NIR spectrometers on board the rovers will be involved at multiple stages of the surface operations and will be crucial to understand the geologic history of each landing site, and in particular the context of the water alteration of the rocks.References: [1] Werner et al. (2018) Second International Mars Sample Return, No. 2071, 6060. [2] Pilorget and Bibring (2014) PSS 99, 7-18.Acknowledgements: This project is financed through the European Research Council in the H2020-COMPET-2015 program (grant 687302).

NASA/Mars2020 and ESA/ExoMars missions will look for traces of present or past life on Mars. To do so, both Perseverance and Rosalind Franklin rovers have been equipped with a wide set of spectroscopic systems to investigate the geochemistry and mineralogy of Martian rocks and soils. As spectroscopic techniques are acquiring an increasing importance in the field of Mars exploration, many research groups are trying to estimate and optimize their potential scientific return by carrying out representative analytical studies in the laboratory.In this framework, PTAL is a research project founded by the European Commission through the H2020 program, which is aimed to provide the scientific community with a novel library of terrestrial analogue materials that have been selected based on their similarity to well-known Martian geological contexts. Planned to be released to public on January 2022, the PTAL platform (http://erica.uva.es/PTAL/) will provide future users with access to complementary spectroscopic and diffractometric data gathered from over 100 terrestrial analogues.In detail, the XRD analysis of each analogue was carried out to gather a reliable overview of samples mineralogy. Then, LIBS, IR and Raman spectrometers were used to collect additional elemental and molecular data, these being the key analytical tools onboard NASA/Perseverance and ESA/Rosalind Franklin rovers. Beside the use of commercial spectrometers, the RLS ExoMars Simulator, the MicrOmega-Flight (FS) (Spare Model) and the ChemCam-FS were also employed to collect LIBS, Raman and NIR spectra (respectively) qualitatively comparable to those that will soon gathered on Mars.In addition to analytical data, the PTAL platform will also provide direct access to a dedicated software (SpectPro) for spectral visualization and treatment [1]To conclude, future users can also request physical access to the terrestrial analogues, so that the data contained in the PTAL library can be combined with further analysis in the laboratory.To obtain further information about the PTAL project, please use the QR code provided in Figure 01.Figure 01: PTAL QR codeAcknowledgements: This work is financed through the European Research Council in the H2020- COMPET-2015 programme (grant 687302) and the Ministry of Economy and Competitiveness (MINECO, grant PID2019-107442RB-C31).References: [1] Saiz J. et al., (2019) EGU general Assembly, 21, 17904.

In 2022, ESA/ROSCOSMOS will launch the ExoMars2022 rover mission to Mars. The selected landing site for the mission is Oxia Planum, a wide, Noachian-age, phyllosilicate-bearing plain located on the SE border of Chryse Planitia. The Fe,Mg-rich clay mineral deposits at Oxia Planum are one of the largest exposures of this type on Mars, with a thickness of more than 10 m. They clearly record complex water-rock interactions and as such are a promising target to answer scientific questions posed by the ExoMars 2022 mission pertaining to the history of water and the geochemical environment in the shallow Martian subsurface, and the ancient and present habitability of the planet.From the spectral analysis by CRISM and OMEGA, bedrock deposits at Oxia appear to contain vermiculite, a hydrous 2:1 phyllosilicate. But the exact mineralogy of the deposits and their origin is not yet fully understood. To fill this gap, and to better prepare for in-situ analyses by the ExoMars2022 rover, we performed a survey of potential terrestrial analog rocks by determining their mineralogy and NIR spectra for comparison with CRISM and OMEGA spectra of bedrock deposits at Oxia. The study focused on Fe-rich, trioctahedral vermiculite.Two terrestrial sites were identified and studied: Otago, New Zealand with vermiculitized chlorite-schists that underwent alteration without significant oxidation; and Granby, Massachusetts with basaltic tuffs containing Fe-rich clays of apparent hydrothermal origin filling amygdales. Both analogues have been added to a newly built Planetary Terrestrial Analogue Library (PTAL) collection. The PTAL collection aims to provide the scientific community with analogue rocks to help characterize and define the mineralogy and geochemistry of landing sites on Mars chosen for in-situ analyses (www.ptal.eu).The analogue comparisons reveal that Oxia bedrock deposits consist of Fe-rich, trioctahedral vermiculite, which is well crystallized and probably mixed with minor saponite. Additionally, NIR data analysis suggests that the deposits were not oxidized, nor illitized after formation. Based on this study, Oxia’s bedrock deposits may have formed from: (1) hydrothermal or magma fractionation-related origin of phyllosilicates and formation as an ash-fall deposits or (2) chlorite-rich sediment transported to a basin where chlorite was subsequently altered to vermiculite under anoxic, reducing conditions. The detailed characterization of the analogues and discussion of processes inferred for the evolution of Oxia Planum will be presented during the meeting.Vermiculite, with its high surface area and exchange capacity, has great potential to store organic compounds. The mineralogy of the bedrock deposits at Oxia, along with the anoxic, reducing conditions that might have been prevalent during Noachian time would be advantageous for retaining and preserving organic matter and make it a promising site for future analysis.

Oxia Planum is a Noachian plain on Mars. It was chosen as the final landing site for in situ studies by ExoMars 2022 rover. The main scientific objectives of the mission are to understand the mineralogy and aqueous evolution of ancient Mars with relevance to habitability. Oxia is covered by vast deposits of Fe,Mg-phyllosilicates, but the exact nature of these deposits is not yet fully understood. We performed a survey of potential terrestrial analog rocks, and here we show combined mineralogical characterization of these rocks with their near-infrared spectral analysis. Samples from two terrestrial sites were studied: (1) vermiculitized chlorite-schists from Otago, New Zealand, which underwent an alteration process without significant oxidation; and (2) basaltic tuffs from Granby, Massachusetts, USA, with Fe-rich clays filling amygdales of supposedly hydrothermal origin. Both analogues are incorporated into the newly built Planetary Terrestrial Analogue Library (PTAL) collection. Oxia bedrock clay-rich deposits are spectrally matched best by a well-crystallized trioctahedral vermiculite/saponite mixture from the basaltic tuff, although the contribution of saponite must be minor. Otago vermiculite is a good analogue to Oxia vermiculite in terms of overall mineralogy and Fe content. However, spectral inconsistencies related to the Al content in the Otago clays indicate that illitization of vermiculite, which results from postalteration oxidation, did not occur at Oxia. This implies limited water/rock interactions and reducing conditions during deposition of sediments now constituting the bedrock at Oxia. Whereas the spectral match does not conclusively imply the mineralogy, trioctahedral vermiculite should be considered a likely mineral component of the bedrock unit at Oxia Planum. Vermiculite has great potential to store organic matter, and the postdeposition geological context of Oxia Planum derived from understanding of environmental conditions in analog sites is promising for organic matter preservation.

International audience; The Planetary Terrestrial Analogues Library (PTAL) is a dedicated lithological collection that currently consists of 102 terrestrial rock samples selected to be possible Mars analogues. The ultimate goal is improving future remote mineralogical and petrological analysis on Mars and other planetary bodies based on selected analysis such as Near- Infrared Reflectance Spectroscopy (NIR), Raman spectroscopy, Laser Induced Breakdown Spectroscopy (LIBS) and X-ray diffraction (XRD). Most international standards applied in the remote martian mineralogical and petrological analysis have so far been based on single, pure mineral analysis, with minimal interferences from other naturally occurring minerals. Here we present detailed lithological sample evaluations based on field appearance along with optical and XRD analysis of key terrestrial rock types. The detailed mineralogical and petrological descriptions give good basis for more complete lithological understanding. In combination with NIR, LIBS and Raman analysis of the very same samples PTAL aims at improving mineralogical and petrographical information from future rovers on Mars e.g. NASA's Mars2020-Perseverance and ESA and Roscosmos's ExoMars - Rosalind Franklin. The PTAL sample collection covers exclusively collected volcanic, magmatic and various sedimentary rocks and regoliths from well-known locations all over the world. These samples have a general composition comparable to what is currently known from Mars. The strength of this sample collection is its origin as common whole rock samples, in which minerals occur in their natural settings. It thereby allows studying possible detection interferences and a comparison of the sensitivity of the different techniques. The collection, in addition, forms the base for various alteration studies to better understand and explain alteration and weathering conditions on Mars. The complete results and sample preparations will be available to all scientists interested.

A selective compilation of paleomagnetic data from North America indicates that a vast amount of rapid polar motion occurred in Late Jurassic time. The over 30° polar shift that accumulated during a relatively short time interval (~160–145 Ma) suggests an episode of fast true polar wander (TPW) and was referred to as the Jurassic “monster polar shift” by some workers. However, this rapid TPW event is not supported by paleomagnetic data on a global scale . Here, we scrutinize the Jurassic apparent polar wander path (APWP) by virtue of a new paleomagnetic and 40Ar/39Ar geochronology study of Mesozoic coast-parallel dykes exposed in southwest Greenland. Combined with existing geochronological data, our results show that the dykes were emplaced during a prolonged period centered at 147.6 ± 3.4 Ma (2σ). A primary nature of the characteristic remanent magnetization is supported by multiple positive baked contact tests and a reversal test. The paleomagnetic pole calculated from 40 site-mean paleomagnetic directions is located at Plat = 69.3°S, Plong = 5.0°E (A95 = 4.6°), or at Plat = 73.9°S and Plong = 0.4°E when reconstructed to North America. Our new high-quality paleomagnetic pole and an updated global APWP do not support the fast Jurassic polar shift but instead indicate steady polar motion with moderate rates of about 0.7°/Myr. The new pole effectively reduces the mismatch between the APWPs for Laurentia and Europe. Our critical reassessment of the monster polar shift indicates that it may be an artifact of paleomagnetic and geochronological data that were previously used to argue for its existence.

We evaluated the effectiveness of the ExoMars Raman laser spectrometer (RLS) to determine the degree of serpentinization of olivine-rich units on Mars. We selected terrestrial analogs of martian ultramafic rocks from the Leka Ophiolite Complex (LOC) and analyzed them with both laboratory and flight-like analytical instruments. We first studied the mineralogical composition of the samples (mostly olivine and serpentine) with state-of-the-art diffractometric (X-ray diffractometry [XRD]) and spectroscopic (Raman, near-infrared spectroscopy [NIR]) laboratory systems. We compared these results with those obtained using our RLS ExoMars Simulator. Our work shows that the RLS ExoMars Simulator successfully identified all major phases. Moreover, when emulating the automatic operating mode of the flight instrument, the RLS ExoMars Simulator also detected several minor compounds (pyroxene and brucite), some of which were not observed by NIR and XRD (e.g., calcite). Thereafter, we produced RLS-dedicated calibration curves (R2 between 0.9993 and 0.9995 with an uncertainty between ±3.0% and ±5.2% with a confidence interval of 95%) to estimate the relative content of olivine and serpentine in the samples. Our results show that RLS can be very effective in identifying serpentine, a scientific target of primary importance for the potential detection of biosignatures on Mars—the main objective of the ExoMars rover mission., Proyecto MINECO Retos de la Sociedad. Ref. ESP2017-87690-C3-1-R

International audience; Multiple spectroscopic techniques have been selected on previous, present and forthcoming missions to explore planetary surfaces in the Solar System. In particular, forthcoming ESA/Roscosmos and NASA missions to the surface of Mars will bring instruments capable of near-infrared (NIR), Raman and Laser Induced Breakdown Spectroscopies to analyze the mineralogy and chemistry of rocks. The PTAL (Planetary Terrestrial Analogues Library) project aims at building a multi-instrument spectral database of a large variety of natural Earth rock samples, including Mars analogues. The NIR hyperspectral microscope MicrOmega was selected to characterize the mineralogy of these analogues within the PTAL project. The instrument model used for the PTAL project is a spare flight model that requires specific care. For the safety of the instrument, and because of the large number of samples in the PTAL library and the requirement to optimize the observational conditions, a dedicated and semiautomated setup was built for the use of the MicrOmega instrument for this project. This paper presents the requirements specified for this setup, the technical solutions that have been selected, their implementation and the performances of the setup. Sample preparation and operations during sample observations are explained, and a characterization example is presented to briefly illustrate the capabilities of MicrOmega in this setup. The complete results from the MicrOmega characterizations of the PTAL rock analogues will be presented in a forthcoming paper (Loizeau et al. in prep).

NASA/Mars 2020 [1] and ESA/ExoMars [2] missions are scheduled to be launched in 2020 and 2022 respectively. For the first time in history, the analytical payload of both exploration rovers will be equipped with Raman systems that will work in combination with complementary spectroscopic techniques such as LIBS and NIR. Prior to science operations, detailed laboratory investigations are necessary to constrain the potential scientific outcome of Raman spectrometers, as well as to facilitate the comprehension of the advantages provided by combined Raman/LIBS (e.g. the SuperCam analytical suite [3] onboard the Perseverance rover) and Raman/NIR (as is the case of ExoMars RLS [4] and MicrOmega coordinated studies) analysis.In this framework, beside coordinating the development of Mars 2020/SuperCam Calibration Target (SCCT) and ExoMars/Raman Laser Spectrometer (RLS), the ERICA research group is developing novel tools that are meant to facilitate both science operation teams in the analysis and interpretation of the spectroscopic data soon gathered from Mars. As such, the three main tools under development are presented below:1) Planetary Terrestrial Analogue Library (PTAL) Funded by the European Research Council through the H2020-Compet-2015 programme (grant 687302), the Planetary terrestrial analogue library (PTAL) project will provide science operation teams (and, in a broader extent, the whole scientific community) with free access to an extended multi spectral database of terrestrial analogues materials that have been selected basing on their congruence to well-known Martian geological and environmental contexts [5]. Through the collaboration of the Universities of Valladolid (UVa, Spain), Oslo (UiO, Norway) and Paris-Sud (UPSud, France) the PTAL database will offer Raman, LIBS, NIR and XRD data collected from 1) natural geological samples collected from terrestrial analogues sites and 2) artificial samples replicating Martian protoliths composition and altered in the laboratory under controlled physical-chemical conditions. Beside the use of conventional laboratory instruments, the mineralogical and geochemical composition of PTAL samples is characterized by means of spacecraft derived instrumentation, as is the case of the RLS ExoMars Simulator, MicrOmega and ChemCam spare models. Furthermore, the PTAL platform will provide the opportunity to request physical access to Martian analogue materials thus enabling future users to combine PTAL spectroscopic data with further laboratory analysis.2) Analytical DAtabase of Martian Minerals (ADAMM) Complementary to PTAL, the ADAMM database will include diffractometric (XRD) and spectroscopic (Raman, NIR, LIBS) data from a wide collection of pure mineral phases that have been detected on Mars by orbital and on-ground analytical systems, as well as from the laboratory study of Martian meteorites. Financed by the Ministry of Economy and Competitiveness (MINECO, grant ESP2017-87690-C3-1-R) the ADAMM database also includes additional phases that, according to the modern knowledge about the geological evolution of Mars, are most likely to be present at the (sub)surface of the red planet. As such, over 300 specimens are being analyzed using both commercial and spacecraft derived instrumentations. Besides the previously mentioned RLS ExoMars Simulator, mineral samples will be also analyzed by means of SimulCam, a remote Raman/LIBS system recently developed by the ERICA research group to reliably simulate SuperCam analytical outcomes. After comparing ADAMM database with the mineralogy detected from orbit at Jezero Crater and Oxia Planum (the landing site for Mars 2020 and ExoMars missions, respectively) a more detailed analysis of selected samples will be carried out. Thus, complementary analysis will be performed in the framework of the SIGUE-Mars consortium by using additional instruments (including the RLS spare model), and under Martian conditions (temperature and atmospheric pressure). In this way, a reliable estimation of the potential scientific outcome of the forthcoming rover missions to Mars will be provided.3) IDAT/SpectPro The Instrument Data Analysis Tool (IDAT)/SpectPro software was developed by the University of Valladolid to receive, decodify, calibrate and verify the telemetries generated by the RLS instrument on Mars [6]. IDAT/SpectPro is able to open and process data in PDS4 format, as required by the ExoMars mission. In this way, as soon as the data from the processors is available, IDAT/SpectPro will automatically process it to obtain science and engineering (housekeeping) calibrated data and even generate autolooks.IDAT/SpectPro also provides access to an extended set of analytical tools for spectral analysis such as labelling, trimming, shifting, normalization, baseline correction, and features a general-purpose spectrum calculator to perform lineal combinations, product, division and derivative of spectra. An automated identification algorithm to classify Raman spectra is also under development. This algorithm is based on the comparison of peak positions and intensities, which has provided good results, even for the detection of all samples present in simple mixtures.The mentioned analytical tools will be made available to PTAL and ADAMM users through a dedicated version of IDAT/SPectPro software, which will have a direct interface to access the two databases.Acknowledgements:This work is financed through the European Research Council in the H2020- COMPET-2015 programme (grant 687302) and the Ministry of Economy and Competitiveness (MINECO, grant ESP2017-87690-C3-1-R). The authors gratefully acknowledge the support of the SIGUE-Mars consortium (MINECO, grant RDE2018-102600-T). References:[1] Williford, K. H. et al. From Habitability to Life on Mars (Elsevier Inc., 2018). [2] Vago, J. L. et al. Astrobiology 17, 471–510 (2017). [3] Wiens, R. C., Maurice, S. & Perez, F. R. Spectrosc. (Santa Monica) 32, 50–55 (2017). [4] Rull, F. et al. Astrobiology 17, 627–654 (2017). [5] Veneranda, M. et al. J. Raman Spectrosc. 50, 1–19 (2019). [6] Lopez-Reyes G. et al. European Planetary Science Congress 2018 12 1–2 (2018).

In 2020, ESA/ROSCOSMOS will launch ExoMars2020 rover mission to Mars. The selected landing site for the mission is Oxia Planum, a wide Noachian-aged clay mineral-bearing plain. The Fe,Mg-rich clay mineral deposits in Oxia are one of the largest exposures of this type on Mars, with a thickness of more than 10 m and as such are an important source of information about Martian Noachian (>3.9 Ga) water-mediated interactions between lithosphere, hydrosphere, and atmosphere. The regional compositional mapping of Oxia Planum conducted in spectroscopic studies by OMEGA and CRISM suggests that the clay minerals are mainly trioctahedral Fe,Mg-rich in nature, with a local presence of dioctahedral Al-rich varieties. Although no exact spectral match was found for Oxia clay minerals among terrestrial analog rocks, the closest consistency is revealed by vermiculite or Fe,Mg-rich di-trioctahedral smectite.The mechanism by which vast deposits of vermiculite may have formed on Mars is, however, not entirely clear. Based on the preliminary geomorphological investigation at Oxia, five major environments of basement clay minerals formation are plausible: pedogenic, hydrothermal in shallow sub-surface, related to metamorphism or to diagenesis as well as connected to glacial alteration. However, it is not obvious whether these early Noachian environments may have provided conditions capable to form vermiculite-like minerals. Furthermore, understanding the mechanisms of alteration in specific environments does not bring sufficient information about fluid alteration conditions such as chemical composition, acidity, oxidation state and amount of fluid (i.e. water to rock ratio).To better understand the plausible mechanism of the formation of vermiculitic-like clay minerals at Oxia Planum as well as fluid alteration conditions, we have been performing laboratory alteration experiments. Comprehended from terrestrial analog environments, we focus our research on possible alteration pathways of biotite and chlorite towards vermiculite. Additionally, considering geomorphological manifestations of plausible past aqueous environments at Oxia Planum, we test various conditions of surface weathering and hydrothermal activity.Our results show that Fe,Mg-vermiculite may form via alteration of Fe-rich biotite in the CO2-rich atmosphere in Noachian Mars. However, critical factors governing the process are the saturation of solution in K dissolved from biotite and oxidation of solution. In laboratory conditions, vermiculitization occurred only under conditions providing relatively high water to rock ratios or in an open system. It implies that if vermiculite-like clay mineral deposits formed in Oxia Planum, a large amount of water must have been delivered to the subsurface to drive alteration through preferential removal of potassium from interlayer space of primary minerals.

In its bulk properties, Venus appears similar to Earth, but both planets have developed substantially different geodynamic regimes. Earth has plate tectonics with a continuously renewed surface and its crustal distribution is very dichotomous in composition, thickness, and age. Venus, on the other hand, presently displays a period of a stagnant-lid regime, which may or may not was interrupted by catastrophic events of tectonic recycling during its history. Venus’ crustal thickness is not well constrained, but likely thicker than Earth’s oceanic crust; pronounced crustal dichotomy may be possible but evidence needs yet to be found. The age of the crust appears rather uniform, which traditionally has been taken as evidence that an episodic overturn must have taken place. However, recent arguments have challenged the episodic overturn hypothesis and favor a more continuous stagnant lid on Venus. To resolve the problem of Venus’ geodynamic regime understanding the generation of Venus’ crust in a dynamic context that also considers the underlying mantle is necessary. This can be achieved using numerical models of mantle convection tailored to Venus, which include the basic complexities of planetary mantle convection in terms of effective rheology, mineralogy and melting processes. Still, previous models have essentially failed to predict the thickness and age characteristics of Venus’ crust. One possible reason is that these models only considered extrusive volcanism, which renews the surface directly, while intrusive magmatism does not. Yet, intrusion seems the dominant mode of magmatism at least on Earth, so we investigate its influence in our model and evaluate whether this ingredient is key to predict Venus’ crustal characteristics. Using the code StagYY, we compute a suite of mantle convection models in 2D spherical annulus geometry that run through the entire solid-state history of Venus. We vary the partitioning of intrusive and extrusive volcanism from purely extrusive to dominantly intrusive and predict the present-day distributions of crustal thickness and surface age in the stagnant lid regime. With more intrusive magmatism, average crustal thickness is reduced by 20-25%, but mean crustal thickness still exceeds other independent estimates. The surface is on average much older, which is more consistent with mean age estimates from crater counting. However, lateral age variations also become stronger with dominantly intrusive volcanism, which indicates that volcanism keeps going on, but is more restricted spatially. Governing parameters like mantle reference viscosity and relative enrichment of heat-producing elements into the crust change the absolute values of mean crustal thickness and surface age, but do not improve surface age uniformity. This is somewhat at odds with Venus’ seemingly uniform surface age, so suitable conditions for this possibility are further evaluated in models featuring episodic overturn events.

As part of the ESA ExoMars rover payload, the Raman Laser Spectrometer (RLS) is scheduled to deploy on Mars in 2021. Together with MicrOmega (NIR) and MOMA (GC-MS), the instrument will analyze Martian subsoil samples to determine their mineralogical composition and investigate the potential presence of biomarkers. Beside the challenges associated with the development of the first Raman spectrometer to be validated for planetary exploration (together with Mars2020/ Sherloc and Supercam systems), to optimize the scientific outcome of RLS spectra gathered on Mars has a crucial importance in the fulfillment of the mission aims. Thus, the RLS team is developing tailored chemometric tools that, taking into account technical specifications and the operational mode of the RLS system, could be used to semi-quantify the main phases composing Martian samples.Considering that 1) the serpentinization of olivine-bearing rocks on Earth plays a key role in the proliferation of microorganisms and in the preservation of biomarkers, and 2) remote sensing systems (e.g. CRISM) detected vast serpentine-bearing deposits on Mars, the present work seek to provide the chemometric tools necessary to correctly define the serpentinization degree of Martian rock samples through the interpretation of RLS data.To do so, olivine and serpentine certified materials were mixed at different concentration ratios and 39 spot of analysis por sample were analyzed by means of the RLS ExoMars Simulator. Data sets were then analyzed using uni-variate (intensity ratio between olivine and serpentine main peaks) and multi-variate (a combination of principal component analysis and artificial neural networks PCA-ANN) methods.The two uni-variate and multi-variate semi-quantification models were finally applied to the study of serpentinized rocks sampled from the Leka Ophiolite Complex (LOC), being those part of the Planetary Terrestrial Analogue Library (PTAL) collection. RLS-based semi-quantification results were finally compared to those obtained from the use of a state-of-the-art laboratory X-ray diffractometer (XRD).Our study suggest that the uni-variate method provide excellent results when the analyzed rocks are mainly composed of olivine and serpentine. However, the estimation reliability decreases when the mineralogical heterogeneity of the sample increases (Raman features of additional mineral phase may overlap the selected olivine and serpentine peaks). In these cases, the multi-variate method based on the combination of PCA and ANN helps to more accurate estimate the serpentinization degree of the terrestrial analogs.In conclusion, the preliminary results summarized in this work indicates that the study of terrestrial analogs is of crucial importance to test and validate RLS-dedicated semi-quantification models. In a broader perspective, it also highlights the importance of developing multiple chemometric tools, since the effectiveness of each of them varies according to mineralogical complexity of the sample under study.

Norwegian geosciences institutes has as separate and spread entities had limited resources for teaching global, large-scale processes and changes related to the evolution of planetary interior and its interaction with the crust, atmosphere and hydrosphere. The institutes experienced that the courses offered locally were insufficient to educate young academics in fundamental and curiosity-driven Earth sciences. The PhD students also experienced to be alone within their field and without a network around them.The quality of PhD education is highly relying on the supervisor’s ability to give good supervision, but the entire setting that a PhD student is situated in will contribute to their success in science. The short duration of Norwegian PhD programs combined with a course requirement of 30 ECTS points, calls for well-planned and efficient research, good supervision and course work. For a PhD student to work efficient a good workplace, role models and a good network is also of great importance. Under difficult conditions, the universities see higher drop out and longer completion time numbers from the PhD program, especially for already vulnerable groups.The national research school of Dynamics and Evolution of Earth and Planets (DEEP) aims to gather the Norwegian natural science expertise relevant for studying the Earth as part of the Solar System and promotes an environment that enables efficiency, at the same time as the scientific quality remains high. Since 2016 DEEP research school has offered specialised scientific courses and a bigger network for the PhD students and their supervisors. We see an increasing interest in joining the research school as part of the PhD program and increasing cooperation between PhD students within the network. With annual conferences and many smaller gatherings, we also ensure that the PhD students form a network amongst each other and find mentors that will strengthen them in their future careers.

The Planetary Terrestrial Analogues Library project aims to build and exploit a spectral data base for the characterization of the mineralogical and geological evolution of terrestrial planets and small Solar System bodies. Basis for the library is our collection of natural field-collected and artificial planetary (often Martian) analogue materials as well as materials, which have been altered in laboratory experiments. All samples were characterized by XRD, thin sections as base and as input for the spectral library with standard commercial and dedicated spacecraft instrumentation (NIR, RAMAN, LIBS) under laboratory conditions. The database will allow users to jointly interpret laboratory results and newly gathered in-situ or remote sensing data using instruments (LIBS, NIR, Raman) on board of current and future space missions (e.g., Hayabusa-2, Curiosity, ExoMars, Mars2020). The main aim of the database is the use of spectra stored for purposes related to comparison, identification, quantification and spectral calculation when spectroscopic instruments such as NIR, Raman and LIBS operate in planetary missions and/or analyzing materials in the field or in the laboratory. This database features spectral tools allowing for the spectral data treatment implementation plans are the integration of the database management and algorithms in an end-user platform with graphical interfaces for the use of the data and analyzing tools. The public release of the Planetary Terrestrial Analogues Library will be at the end of year 2020. We will have a demonstration and tutorial during the EGU-GA 2020.Acknowledgements: This project is financed through the European Research Council in the H2020-COMPET-2015 programme (grant 687302).

In the present work, NIR, LIBS, Raman and XRD techniques have been complementarily used to carry out a comprehensive characterization of a terrestrial analogue selected from the Chesapeake Bay Impact Structure (CBIS). The obtained data clearly highlight the key role of Raman spectroscopy in the detection of minor and trace compounds, through which inferences about geological processes occurred in the CBIS can be extrapolated. Beside the use of commercial systems, further Raman analyses were performed by the Raman Laser Spectrometer (RLS) ExoMars Simulator. This instrument representsthe most reliable tool to effectively predict the scientific capabilities of the ExoMars/Raman system that will be deployed on Mars in 2021. By emulating the analytical procedures and operational restrictions established by the ExoMars mission rover design, it was proved that the RLS ExoMars Simulator is able to detect the amorphization of quartz, which constitutes an analytical clue of the impact origin of craters. On the other hand, the detection of barite and siderite, compounds crystallizing under hydrothermal conditions, helps to indirectly confirm the presence of water in impact targets. Furthermore, the RLS ExoMars Simulator capability of performing smart molecular mappings was also evaluated. According to the obtained results, the algorithms developed for its operation provide a great analytical advantage over most of the automatic analysis systems employed by commercial Raman instruments, encouraging its application for many additional scientific and commercial purposes., Proyecto MINECO Retos de la Sociedad. Ref. ESP2017-87690-C3-1-R

Detailed spectral mapping, cratering statistics, and impact basin ejecta column estimates document a new and very different stratigraphic relationship for the Apollo 14 landing site. We observe a resurfacing event in the crater size–frequency distribution in agreement with a single blanketing layer. Using the crater size–frequency distribution, we determine two relative ages (cumulative crater frequencies) that match those observed for the Imbrium and Orientale basins, respectively. The pattern and strength of resurfacing and morphological distinction by spectral features suggest the top layer to be about 10–25 m thick. We propose that this top layer at the Apollo 14 landing site is Orientale basin ejecta above Imbrium basin ejecta. Such stratigraphy reattributes the (majority of) Apollo 14 samples to Orientale rather than to Imbrium basin and implies that Orientale basin is about 3.92 Gyr old, 200 million years older than previously suggested. The youngest lunar basin thus formed at the onset, rather than amid, of recorded mare volcanism. This time shift also changes constraints on early planetary and solar system processes, such as the intensity of impact bombardment, and pleads for revision of the crater-statistics-based surface ages of other planetary bodies.

Venus has similar size, density and bulk composition as Earth, but has tectonically evolved clearly differently and this divergence remains enigmatic. Surface observations such as gravity, topography and surface age constrain Venus’ evolution, but interpreting these signals requires understanding of the surface-interior coupling and thus insight into the structure and evolution of the venusian mantle and lithosphere. Here, we investigate how such observables may be generated from interior dynamics using numerical forward models of global mantle convection that consistently link the thermochemical, magmatic and tectonic evolution of Venus. Venus’ present surface gravity spectrum and its relation to topography is matched best by our models with a mantle viscosity profile featuring a sublithospheric minimum of ∼ 2 × 1020 Pa s and a gradual increase by a factor of ∼ 100 down to a depth of ∼ 250 km above the core-mantle boundary. No pronounced viscosity jump around the mantle transition as inferred for Earth is favoured for Venus, which points to a relatively dry venusian upper mantle compared to Earth’s as previously suggested. This holds true for both a pure stagnant-lid scenario and in the presence of episodic catastrophic overturns triggered by cumulative crustal growth due to on-going magmatism and volcanism. Overturns strongly perturb the surface gravity spectrum up to ∼ 150 Myr after overturn cessation. Material deeply recycled by the resurfacing event annihilates the developed plume pattern, which needs much longer than those 150 Myr to recover to a state comparable to the pattern suggested by thermal emissivity anomalies observed on Venus. Moreover, overturns limit crustal thicknesses to reasonable values and are more capable than stagnant-lid evolutions in generating mean surface ages > 500 Myr. These findings seem to confirm previous suggestions that the episodic regime is more applicable to Venus than a purely stagnant-lid regime. Yet, the relatively long time span required to recycle the entire surface ( ∼ 150 − 200 Myr) and the presently on-going volcanic resurfacing predicted by our models complicate the formation of a uniform surface age as indicated by Venus’ crater population and may also suggest that the latest overturn has ceased longer ago than indicated by Venus’ present mean surface age.

The effects of the coefficient of friction and porosity on impact cratering are not sufficiently considered in scaling laws that predict the crater size from a known impactor size, velocity, and mass. We carried out a systematic numerical study employing more than 1000 two-dimensional models of simple crater formation under lunar conditions in targets with varying properties. A simple numerical setup is used where targets are approximated as granular or brecciated materials, and any compression of porous materials results in permanent compaction. The results are found to be consistent with impact laboratory experiments for water, low strength and low porosity materials (e.g., wet sand), and sands. Using this assumption, we found that both the friction coefficient and porosity are important for estimating transient crater diameters as is the strength term in crater scaling laws, i.e. the effective strength. The effects of porosity and friction coefficient on impact cratering were parameterized and incorporated into π-group scaling laws and predict transient crater diameters within an accuracy of ±5 % for targets with friction coefficients f ≥ 0.4 and porosities Φ = 0 – 30 %. Moreover, 90 crater scaling relationships are made available and can be used to estimate transient crater diameters on various terrains and geological units with different coefficient of friction, porosity and cohesion. The derived relationships are most robust for targets with Φ > 10 – 15 %, applicable for a lunar environment, and could therefore yield significant insights into the influence of target properties on cratering statistics.

The lunar surface features diverse impact structures originating from its early bombardment; the largest among them are the lunar basins. Basin-forming impacts delivered large amounts of energy to the target and expelled lots of material that deposited as an insulating blanket in the vicinity of the impact. Here, we investigate how such processes may have altered the lunar evolution. We combine lunar basin chronologies with numerical models of basin formation and 3D thermochemical mantle convection and analyse the role of single generic impacts resulting in basins with varying diameter, formation time, location and ejecta properties. The direct effects of a single impact are enhanced melt generation as well as thermal and heat flux anomalies, but these are limited to ∼ 100 Myr following the impact. We use these insights in multi-impact scenarios more relevant for the Moon, which lead to a widespread ejecta blanket and make impact-induced effects more substantial. Lunar contraction history may be altered by the impact bombardment in favour of an early expansion phase as suggested by recent observations. Moreover, imprints of the early bombardment may be kept in the thermal and compositional state of the Moon’s interior until modern times. These can be as large as those induced by uncertainties in bulk lunar heat content, if surface insulation due to ejecta is efficient. In this case, model-predicted present-day thermal profiles match independent constraints better if the bulk Moon is not significantly enriched in refractory elements compared to Earth.

On Mars, mineral sequences have been detected and they are composed of a top layer of Al-rich clay minerals, then (Al, Fe)-rich clay minerals and a bottom layer composed of (Mg, Fe)-rich clay minerals. By analogy with Earth, such sequences are interpreted as weathering profiles formed by the interaction of acidic solutions in equilibrium with the atmosphere and the parent rock. Thus, understanding of the aqueous solution composition leading to the above mineral description allows deciphering the atmosphere composition. We designed an experimental column system with three levels containing powdered basaltic rock to test the influence of different acidic fluids on the mineralogical formation. Five solutions were used: H 2 SO 4 and HCl at pH 3 in equilibrium with N 2 atmosphere, pure water in equilibrium with 0.1 and 1 atmospheric pressure CO 2 leading to pH values of 3.9 and 4.4, respectively and a H 2 SO 4 solution at pH 3 in equilibrium with 0.1 atmospheric pressure CO 2 leading to a pH value of 2.98. The results obtained show that the content of Al-rich clay minerals and the evolution from Al, (Al, Fe) to (Fe, Mg)-rich clay minerals formed are better reproduced with an originally high pCO 2 . Hence, we suggest that acidic alteration driven by a dense CO 2 atmosphere reproduced better the observed martian weathering profiles. The experiments involving CO 2 led to the formation of carbonates. Their identification by near infrared (NIR) detection methods is challenged, because even the laboratory NIR spectra acquired on the experimental products show that: (i) the absorption bands related to carbonates are very weak, and (ii) the strongest feature at 3.95 μm is beyond the CRISM NIR range. Such carbonate formation is consistent with the recent carbonate detection at a planetary scale in weathering profiles, which goes toward that the weathering profiles could have been formed under a dense CO 2 -rich atmosphere as suggested also by climatic models.

Immediately after their formation, the terrestrial planets experienced intense impact bombardment by comets, leftover planetesimals from primary accretion, and asteroids. This temporal interval in solar system evolution, termed late accretion, thermally and chemically modified solid planetary surfaces and may have impeded the emergence of life on the Hadean Earth. The sources and tempo of late accretion are, however, vague. Here, we present a timeline that relates variably retentive radiometric ages from asteroidal meteorites, to new dynamical models of late accretion that invokes giant planet migration. Reconciliation of the geochronological data with dynamical models shows that giant planet migration immediately leads to an intense 30 Myr influx of comets to the entire solar system. The absence of whole-sale crustal reset ages after 4450 Ma for the most resilient chronometers from Earth, Moon, Mars, Vesta and various meteorite parent bodies confines the onset of giant planet migration to no later than ca. 4480 Ma. Waning impacts from planetesimals, asteroids (and a minor cometary component) continue to strike the inner planets through a protracted monotonic decline in impactor flux; this is in agreement with predictions from crater chronology. Amended global 3-D thermal analytical bombardment models derived from our new impact mass-production functions show that persistent niches for prebiotic chemistry on the early Hadean Earth could endure late accretion for at least the last 4400 Myr., Main text: 46564 characters with spaces/7549 words Tables: 3 Figures:7 References: 115

Subsequent to the Moon's formation, late accretion to the terrestrial planets modified their silicate crusts and mantles. We combine dynamical N-body and Monte Carlo simulations to determine impact probabilities, impact velocities, and expected mass augmentation onto the terrestrial planets from three sources: planetesimals left over from primary accretion, asteroids from the E-belt, and comets arriving from the outer Solar System. We present estimates of the amount of cometary material striking the terrestrial planets in an early episode of planetesimal-driven giant planet migration (Mojzsis et al., 2019). The Moon and Mars suffer proportionally higher cometary accretion than Venus and Earth. The background mass addition from small leftover planetesimals to Earth and Mars is far less than independent estimates based on their mantle abundances of highly-siderophile elements. This supports the theory that both planets were struck by single large bodies that delivered most of their mass augmentation since primary accretion. We present fits to the impact chronologies valid from 4500 Ma to ca. 3700 Ma. The lunar timeline thus obtained is at odds with both the calibrated Neukum (Neukum et al., 2001) and Werner (Werner et al., 2014; Werner, 2019) chronologies. For Mars, the match with its calibrated Werner chronology is no better; by increasing the mass of the E-belt by a factor of four the dynamical lunar and martian chronologies are in line with that of Werner (2019) and match constraints from the current population of Hungaria asteroids. Yet, neither of our dynamical timelines fit well with that of Neukum. The dynamical lunar and martian chronologies are also different from each other. Consequently, the usual extrapolation of such chronologies from one planetary body to the other is technically inappropriate., Comment: Accepted in Icarus

Producción Científica, We present the compositional analysis of three terrestrial analogues of Martian olivine-bearing rocks derived from both laboratory and flight-derived analytical instruments. In the first step, state-of-the-art spectroscopic (XRF, NIR and Raman) and diffractometric (XRD) laboratory systems were complementary used. Besides providing a detailed mineralogical and geochemical characterization of the samples, results comparison shed light on the advantages ensured by the combined use of Raman and NIR techniques, being these the spectroscopic instruments that will soon deploy (2021) on Mars as part of the ExoMars/ESA rover payload. In order to extrapolate valuable indicators of the mineralogical data that could derive from the ExoMars/Raman Laser Spectrometer (RLS), laboratory results were then compared with the molecular data gathered through the RLS ExoMars Simulator. Beside correctly identifying all major phases (feldspar, pyroxene and olivine), the RLS ExoMars Simulator confirmed the presence of additional minor compounds (i.e. hematite and apatite) that were not detected by complementary techniques. Furthermore, concerning the in-depth study of olivine grains, the RLS ExoMars simulator was able to effectively detect the shifting of the characteristic double peak around 820 and 850 cm 1 , from which the Fe-Mg content of the analysed crystals can be extrapolated. Considering that olivine is one of the main mineral phases of the ExoMars landing site (Oxia Planum), this study suggests that the ExoMars/RLS system has the potential to provide detailed information about the elemental composition of olivine on Mars., Proyecto MINECO Retos de la Sociedad. Ref. ESP2017-87690-C3-1-R

Producción Científica, The multi analytical study of terrestrial analogues is a useful strategy to deepen the knowledge about the geological and environmental evolution of Mars and other extraterrestrial bodies. In spite of the increasing importance that LIBS, NIR and Raman techniques are acquiring in the field of space exploration, there is a lack web-based platform providing free access to a wide multi-spectral database of terrestrial analogue materials. The Planetary Terrestrial Analogue Library (PTAL) project aims at responding to this critical need by developing and providing free web accessibility to LIBS, NIR and Raman data from more than 94 terrestrial analogues selected according to their congruence with Martian geological contexts. In this framework, the present manuscript provides the scientific community with a complete overview of the over 4500 Raman spectra collected to feed the PTAL database. Raman data, obtained through the complementary use of laboratory and spacecraft-simulator systems, confirmed the effectiveness of this spectroscopic technique for the detection of major and minor mineralogical phases of the samples, the latter being of critical importance for the recognition of geological processes that could have occurred on Mars and other planets. In light of the forthcoming missions to Mars, the results obtained through the RLS ExoMars Simulator offer a valuable insight on the scientific outcome that could derive from the RLS spectrometer that will soon land on Mars as part of the ExoMars rover payload. (13) (PDF) PTAL multi-spectral database of planetary terrestrial analogues: Raman data overview. Available from: https://www.researchgate.net/publication/348675482_PTAL_multi-spectral_database_of_planetary_terrestrial_analogues_Raman_data_overview [accessed Apr 19 2021]., Proyecto MINECO Retos de la Sociedad. Ref. ESP2017-87690-C3-1-R

Subsequent to the Moon's formation, late accretion to the terrestrial planets strongly modified the physical and chemical nature of silicate crusts and mantles. This alteration came in the form of melting through impacts, as well as the belated addition of volatiles and the highly siderophile elements (HSEs). Current debate centres on whether the lunar HSE record is representative of its whole late accretion history or alternatively that these were only retained in the mantle and crust after a particular time, and if so, when. Here we employ improved Monte Carlo impact simulations of late accretion onto the Moon and Mars and present an updated chronology based on new dynamical simulations of leftover planetesimals and the E-belt. We take into account the inefficient retention of colliding material. We compute the crater and basin densities on the Moon and Mars, the largest objects to strike these planets and the amount of material they accreted. Outputs are used to infer the mass in leftover planetesimals at a particular time period, which is then compared to the lunar HSE abundance. From this estimate we calculate a preferred lunar HSE retention age of ca. 4450 Ma which means that the modelled lunar mantle HSE abundances trace almost all of lunar late accretion. Based on our results, the surface ages of the lunar highlands are at least 4370 Ma. We find that the mass of leftover planetesimals with diameters Di, Accepted in Icarus after 5 rounds of review

The dating of the surfaces of the giant planets' regular satellites is hampered by two issues. The first is the lack of known samples from which radiometric ages can be measured. The second is a potentially different cratering chronology compared to those of the Moon and Mars, due to a difference in the impactor population and planetary system architecture, making a direct comparison and absolute ages derivation difficult. That leaves modelling as the only way to obtain something close to absolute surface ages. Here we applied and reported an improved chronological model of the outer solar system during an episode of dynamical instability caused by giant planet migration. We have combined a series of dynamical and Monte Carlo simulations with various crater scaling laws, impactor size-frequency distributions and observational crater densities to compute the expected crater densities on the surfaces of the regular satellites of Jupiter, Saturn and Uranus. From this, we derived their oldest surface ages. Our impactors are sourced from heliocentric planetesimals that originated from the disk of small bodies exterior to the orbit of the giant planets, and the irregular satellites, which were likely captured by the mutual encounters between the giant planets. With both crater scaling laws and the assumption that the giant planets began their migration at 4.5 Ga, most satellites' surfaces were dated to be older than 4.3 Ga, apart from the inner and small satellites, i.e. Mimas, Enceladus, Hyperion and Miranda. Their estimated surface ages are ca. 4 Ga, although these bodies' masses are expected to have been heavily eroded and if they existed prior to giant planet migration they were likely to be destroyed. Our prediction of old surface ages for the mid-sized Saturnian satellites has implications for their formation, their tidal evolution, the interior of Saturn and the ages of the rings.

Whether or not self-secondaries dominate small crater populations on continuous ejecta deposits and floors of fresh impact craters has long been a controversy. This issue potentially affects the age determination technique using crater statistics. Here the self-secondary crater population on the continuous ejecta deposits of the Hokusai crater on Mercury is unambiguously recognized. Superposition relationships show that this population was emplaced after both the ballistic sedimentation of excavation flows and the subsequent veneering of impact melt, but it predated the settlement and solidification of melt pools on the crater floor. Fragments that formed self-secondaries were launched via impact spallation with large angles. Complex craters on the Moon, Mercury, and Mars probably all have formed self-secondaries populations. Dating young craters using crater statistics on their continuous ejecta deposits can be misleading. Impact melt pools are less affected by self-secondaries. Overprint by subsequent crater populations with time reduces the predominance of self-secondaries.

The two neighboring Suvasvesi North and South impact structures in central-east Finland have been discussed as a possible impact crater doublet produced by the impact of a binary asteroid. This study presents 40Ar/39Ar geochronologic data for impact melt rocks recovered from the drilling into the center of the Suvasvesi North impact structure and melt rock from glacially transported boulders linked to Suvasvesi South. 40Ar/39Ar step-heating analysis yielded two essentially flat age spectra indicating a Late Cretaceous age of ~85 Ma for the Suvasvesi North melt rock, whereas the Suvasvesi South melt sample gave a Neoproterozoic minimum (alteration) age of ~710 Ma. Although the statistical likelihood for two independent meteorite strikes in close proximity to each other is rather low, the remarkable difference in 40Ar/39Ar ages of >600 Myr for the two Suvasvesi impact melt samples is interpreted as evidence for two temporally separate, but geographically closely spaced, impacts into the Fennoscandian Shield. The Suvasvesi North and South impact structures are, thus, interpreted as a “false” crater doublet, similar to the larger East and West Clearwater Lake impact structures in Quebec, Canada, recently shown to be unrelated. Our findings have implications for the reliable recognition of impact crater doublets and the apparent rate of binary asteroid impacts on Earth and other planetary bodies in the inner solar system.

The PTAL project aims at building and exploiting a database involving several analytical techniques, the Planetary Terrestrial Analogues Library, to help characterizing the mineralogical evolution of terrestrial bodies, starting with Mars. A total of 94 natural Earth rocks have been collected from selected locations around the world to get a selection of analogues for Martian geology. The PTAL library gathers a variety of igneous rocks from different plutonic and volcanic origins and compositions, associated to different environments and levels of aqueous alteration. Samples of impact craters and sedimentary units are also present. The full set of samples will be characterized with optical thin section analysis and XRD (Oslo University, Norway), NIR spectroscopy (Paris-Saclay University, France), Raman spectroscopy (Valladolid University, Spain) and LIBS (Paul Sabatier University, France). The multianalytical study used within the PTAL project provides an unique opportunity to coordinate minerals/elements detection by different techniques that are similar to the instruments onboard current and forthcoming Martian missions. Such combined analysis should give the opportunity to prepare and improve ExoMars/ESA-Roscosmos and Mars2020/NASA observations. This paper focuses only on the NIR measurements and interpretations. The diversity of the PTAL samples is well revealed by the diversity of spectra from the NIR observations. The detected minerals are representative of various formation, alteration and geochemical environments. The major diagnostic features observed are those of primary Fe2+ bearing silicates like olivine or pyroxene with low and/or high calcium content; altered silicates detected with vibrational features associated to OH and/or H2O and/or metal-OH features; oxides; zeolites; and carbonates. This collection brings together a set of rocks and minerals that have been reported elsewhere in the Solar System and particularly on Mars.

Overprinting of craters by subsequent impacts and topographic degradation complicates crater statistics, especially for old surfaces and small-diameter crater populations. A crater population is regarded as in equilibrium at a particular crater size when smaller craters are being produced at the same rate at which they are being destroyed. Evaluating the equilibrium state of crater populations is challenging, and empirical equilibrium densities are frequently inferred. By performing careful crater counts and cross comparisons on several lunar surfaces, we study the size-frequency distributions (SFD) for the crater populations, which have portions in equilibrium. The results are one of the few observational constraints on the SFD of crater populations in equilibrium, showing that referring to empirical equilibrium densities is not safe for evaluating the equilibrium states of crater populations. Equilibrium densities are not positively correlated with the ages of crater populations, and some populations in equilibrium have crater densities less than those previously believed to represent equilibrium conditions. Besides the SFD of the production population, different crater removal rates at different diameters also affect the SFD of crater populations in equilibrium. The equilibrium onset diameter (Deq) of a crater population can be translated to model ages because older populations have larger Deq, and those for same-aged surfaces are comparable. We show that the crater populations studied here are in equilibrium at much smaller diameters than those predicted for same-aged surfaces by crater degradation models, thus indicating lower crater degradation rates on the Moon, and/or younger ages of the counting areas.

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Both General Relativistic (GR) precession and the Lidov-Kozai mechanism, separately, are known to play an important role in the orbital evolution of solar system bodies. Previous works have studied these two mechanisms independently in great detail. However, both these phenomena occurring at the same time in real solar system bodies have rarely been explored. In this work, we find a continuum connecting the GR precession dominant and Lidov-Kozai like mechanism dominant regimes, i.e. an intermediate regime where the competing effects of GR precession and Lidov-Kozai like oscillations co-exist simultaneously. We find some real examples in the solar system in this intermediate regime. Moreover we identify a rare example amongst them, comet 96P/Machholz 1, which shows significant changes in the rates of GR precession (an order of magnitude higher than Mercury's GR precession rate) due to sungrazing and sun colliding phases induced by Lidov-Kozai like oscillations. This comet's combination of orbital elements and initial conditions (at the present epoch) favour this measurable rapid change in GR precession (at some points peaking up to 60 times Mercury's GR precession rate) along with prograde-retrograde inclination flip (due to Lidov-Kozai like oscillations). Similar tests are performed for hundreds of bodies lying in the moderately low perihelion distance and moderately low semi-major axis phase space in the solar system, the present lowest perihelion distance asteroid 322P/SOHO 1, and further examples connected with 96P/Machholz 1 namely, the Marsden and Kracht families of sungrazing comets plus low perihelion meteoroid streams like Daytime Arietids (ARI) and Southern Delta Aquariids (SDA)., 10 pages, 5 tables, 12 figures; Accepted in MNRAS Main Journal