Search

Progress towards understanding catalytically 'dead' protein kinases - pseudokinases - in biology and disease has hastened over the past decade. An especially lively area for structural biology, pseudokinases appear to be strikingly similar to their kinase relatives, despite lacking key catalytic residues. Distinct active- and inactive-like conformation states, which are crucial for regulating bona fide protein kinases, are conserved in pseudokinases and appear to be essential for function. We discuss recent structural data on conformational transitions and nucleotide binding by pseudokinases, from which some common principles emerge. In both pseudokinases and bona fide kinases, a conformational toggle appears to control the ability to interact with signaling effectors. We also discuss how biasing this conformational toggle may provide opportunities to target pseudokinases pharmacologically in disease.

Clouds on Mars are primary elements for understanding the past and present climate of the planet. Cloud particles can affect the energy balance of the planet, and so the atmospheric dynamic, as well as influence the vertical distribution of dust particles through dust scavenging. The dust scavenging by clouds has critical consequences in the water cycle of the planet; e.g. regions in the atmosphere with insufficient quantity of dust particles (or condensation nuclei) can inhibit the formation of H2O clouds and thus lead to the presence of water vapor in excess of saturation. The study of these interactions requires observations whose analysis allows us to infer simultaneously the properties of both the clouds and dust. To address these observations, the Radiation and Dust Sensor (RDS) is part of the Mars Environmental Dynamics Analyzer (MEDA) payload onboard of the Mars 2020 rover Perseverance.In this work we analysed the RDS observations made during twilight in the period Ls 39◦-262◦ to characterize the clouds above ∼ 30 km over the Perseverance rover site. From the ratio between the irradiance measured at zenith at 450 nm and 750 nm, we inferred that from Ls= 39◦ to 150◦ (referred as the cloudy period), water ice is the main constituent of the detected high-altitude aerosol layers. For Ls 150◦-262◦ dust is the main aerosol present. A total of 161 twilights were analysed in the cloudy period with a radiative transfer code in spherical geometry. Among other results we found: i) signatures of clouds or hazes on the RDS signals in the 58 % of the twilights; ii) most of the clouds were at altitudes between 40 km and 50 km and with particle sizes between 0.6 μm and 2 μm (in effective radius); iii) the cloud activity at sunrise is slightly higher that at sunset (65 % against 52 %), likely due to the differences in temperature; iv) the cloudiest time in Perseverance site and with the greatest cloud opacities is in Ls 120◦-150◦; and v) a notable decrease in the cloud activity around the aphelion (Ls ∼ 70◦), along with lower cloud altitudes and opacities. The drop in cloud activity around Ls ∼ 70◦ indicates lower concentrations of water vapor or cloud nuclei (dust) around this period in the Martian mesosphere. In this presentation, we will discuss the implications of our results on the water cycle of the planet.

Aeolian activity, the movement of sand and dust by the wind, is common on Earth and has been observed on other planets [1]. Under the current climatic conditions on Mars, aeolian activity is the primary process of surface modification driven by winds, dust storms and wind vortices. Landed and orbiting cameras show that widespread aeolian activity occurs despite low measured and modelled winds, challenging Earth-based theories [2, 3]. Dust particles enter into long-term suspension forming global dust storms which drastically alter the Martian atmospheric dynamics and present hazards to robotic and human missions.Several models have been proposed on the long-standing conundrum of sediment transport on Mars, however, none of these have been verified on the planet. The outstanding question of what wind shear velocities mobilize sediments on Mars has remained elusive despite multiple spacecrafts carrying wind sensors and studying aeolian activity on finer spatial and temporal scales than can be achieved in orbit. Quantitative examination of aeolian activity under natural Martian surface conditions is imperative in validating transport models.The InSight lander has provided a unique opportunity for monitoring simultaneous coverage of aeolian activity on Mars by combining, for the first time, imaging with atmospheric, seismic and magnetic measurements. Previous studies spanned over just half of the first Martian year, from the end of northern winter to midsummer, and observed minor aeolian activity limited to sporadic grain motion and dust devil tracks [4, 5].In this study, we extend observations of aeolian activity for two Martian years, allowing us to infer the seasonal evolution at the landing site. We report a series of remarkable daytime vortex-induced events with pressure excursions up to 10 Pa, including an investigation of the burst in daytime vortices and emergence of nighttime vortices in northern autumn. Despite our observations reinforcing the quiescent aeolian surface environment at InSight, we observe further evidence and constrain timings of surface track formation, saltation, dust lifting and surface creep of coarser particles both on the surface of Mars and lander elements. Such an investigation was previously impossible due to power constraints allowing only intermittent meteorological measurements in the second year and wind-sensor saturation from energetic close vortex encounters that cause surface changes. Here, we derive estimates of vortex-induced peak wind speeds responsible for grain motion based on strong correlations from the excitation of high-frequency lander resonances sensitive to wind forcing measured continuously by the seismometers [6]. This wealth of data allows us to obtain a unique catalogue of complete wind-induced surface activity at InSight over two Martian years. Our findings provide an insight into the long-standing paradox of aeolian transportation on Mars by quantifying the environmental variables responsible for sand motion which help constrain current threshold and transport models.[1] Hayes (2018) Sci. [2] Kok et al. (2012) RPP [3] Newman et al. (2022) Auth. [4] Charalambous et al. (2021) JGR 126(6) e2020JE006538 [5] Baker et al., (2021) JGR [6] Charalambous et al. (2021) JGR 126(4) e2020JE006514.

The Thermal Infrared Sensor (TIRS; Sebastián et al., 2021; Martínez et al., 2023) is one of the six sensor packages of the Mars Environmental Dynamics Analyzer (MEDA; Rodríguez-Manfredi et al., 2021), which in turn is one of the seven science instruments on board Perseverance. Here we show a summary of TIRS scientific highlights during the first Martian year of operations. In particular, TIRS is providing the first in situ determination of the surface radiative budget, direct determination of broadband albedo and thermal inertia (Martínez et al., 2023; Savijärvi et al., 2022), and around-the-clock determination of aerosol opacities (Smith et al., 2023). In addition, TIRS is providing ground-truth to orbital retrievals of thermal inertia and albedo, as well as geophysical characterization of the uppermost surface of the regolith during Phobos and Deimos eclipses. In synergy with other instruments, TIRS is being used to determine vertical profiles of temperature (Munguira et al., 2023), to detect dust lifting from sudden changes in albedo (Vicente-Retortillo et al., 2023), and to assess changes in the water content of the Martian soil (Hausrath et al., 2023), including the potential formation of frost. TIRS observations are critical to achieve MEDA’s first programmatic objective (validate global atmospheric models by measuring the radiative surface budget in preparation for future human exploration). Also, TIRS observations are important in support of flights of Ingenuity and therefore for the design and operations of future drones. References: Hausrath, E. M. et al. (2023), The SuperCam team and the Regolith working group, An Examination of Soil Crusts on the Floor of Jezero crater, Mars, Journal of Geophysical Research: Planets (accepted). Martínez, G. M. et al. (2023), Surface Energy Budget, Albedo and Thermal Inertia at Jezero Crater, Mars, as Observed from the Mars 2020 MEDA Instrument, Journal of Geophysical Research: Planets (accepted). Munguira, A. et al. (2023), Near Surface Atmospheric Temperatures at Jezero from Mars 2020 MEDA measurements, Journal of Geophysical Research: Planets (under review). Rodriguez-Manfredi, J.A. et al. (2021), The Mars Environmental Dynamics Analyzer, MEDA. A suite of environmental sensors for the Mars 2020 mission, Spa. Sci. Rev., 217(3), 1-86. Savijärvi, H. I. et al. (2022), Surface energy fluxes and temperatures at Jezero crater, Mars, Journal of Geophysical Research: Planets: e2022JE007438. Sebastián, E. et al. (2021), Thermal calibration of the MEDA-TIRS radiometer onboard NASA's Perseverance rover, Acta Astronautica, 182,144-159. Smith, M. D. et al. (2023), Diurnal and Seasonal Variations of Aerosol Optical Depth Observed by MEDA/TIRS at Jezero Crater, Mars, Journal of Geophysical Research: Planets (accepted). Vicente-Retortillo, A. et al. (2023), Dust Lifting Through Changes in Albedo at Jezero Crater, Mars, Journal of Geophysical Research: Planets (under review).

We use data from the MEDA instrument on Mars 2020 to study the evolution of atmospheric and surface temperatures at Jezero. The measurements correspond to four height levels from the surface to ~40 m and together they allow us to examine multiple aspects of the near-surface meteorology at Jezero. We extend the analysis of near-surface temperatures of Munguira et al. (JGR:Planets 2023), which covered the period from Ls 13º to Ls 203º, over a full Martian year. We show the seasonal evolution of temperatures, including temperature fluctuations and thermal gradients, which are affected by the properties of the terrain traversed by Perseverance. We will focus on a physical description of the thermal processes that take place in the Convective Boundary Layer at Jezero. We compare near-surface temperatures with the atmospheric opacity around-the-clock retrieved by Smith et al. (2022) and with daily averages of optical depth measured by MastCam-Z (Bell et al. 2022). After Ls 203º, atmospheric waves coming across Jezero predicted by atmospheric models are expected to contribute to shaping temperatures producing thermal oscillations on time-scales of a few sols. This effect is accompanied by an enhanced variability of atmospheric opacity and both effects contribute to produce a higher variability on temperatures. References:[1] Munguira, A. et al. (2023). Near Surface Atmospheric Temperatures at Jezero from Mars 2020 MEDA Measurements. JGR: Planets.[2] Smith, M.D. et al. (2022). Diurnal and Seasonal Variations of Aerosol Optical Depth Observed by MEDA/TIRS at Jezero Crater, Mars. In Seventh international workshop on the Mars atmosphere: Modelling and observations (pp. 14-17).[3] Bell, J.F. et al. (2022). Geological, multispectral, and meteorological imaging results from the mars 2020 perseverance rover in jezero crater. Science Advances, 8 (47), eabo4856. doi: 10.1126/sciadv.abo485

After one year of surface operations at Jezero, the MEDA meteorological sensors have captured the signals produced by the close approach of hundreds of vortices and dust devils over different seasons and terrains. Here we update findings on the vortex and Dust Devils published in Hueso et al. (JGR: Planets, 2023). That work analyzed MEDA data from spring to early autumn identifying vortices as pressure drops and later characterizing them from the ensemble of MEDA measurements. In this updated analysis we show that, in winter, declining surface temperatures and smaller vertical gradients result in a wane of vortex activity. This decreased activity affects more the frequency of intense vortices (Δp >1.5 Pa) without showing a stiff decay in the total number of vortices (Δp>0.5 Pa). In this contribution we concentrate on the specific aspects of the thermodynamics of the vortices from temperature measurements obtained by MEDA that characterize the vertical thermal gradient at the time of the vortex passage. In addition, when vortices approach the rover closely in a favorable geometry (coming from the front of the vortex) we measure the increased temperatures inside the vortex. We also explore the increased nighttime vortex activity found on some sols, when pressure drops equivalent to those created by daytime vortices appear in the early morning before sunrise, with clusters of nighttime activity in winter and early spring.

Using a variety of instruments onboard the Perseverance Rover, a substantial amount of data has been collected and analyzed to understand the environment and atmosphere of the landing site, Jezero Crater. A vital component in understanding this unique environment is studying the local and regional variations of water over diurnal and seasonal timescales. We specifically study the variations of water ice in the atmosphere by observing cloud activity over Jezero Crater using data collected by the Navigation Cameras, NavCam, on board the Mars2020 Rover, Perseverance. IntroductionWater Ice clouds on Mars have been observed for a long time from both the surface and from orbit to understand the role of water in the atmosphere. Using Viking era data, Tamppari (2000, 2003) observed water ice clouds with peak activity seen during the northern spring and summer time. Opportunity Rover acquired images of water ice clouds during the Aphelion Cloud Belt (ACB) season with peak activity seen from Ls 50o to 115o (Lemmon et al., 2015). From the past activity, we have seen that between the solar longitude (Ls) of 45o to 150o, the Aphelion Cloud Belt (ACB) forms every Mars Year (MY) in the equatorial region (10oS–30oN). (Tamppari et al., 2000) (Smith et al., 2004) Furthermore, the Surface Stereo Imager (SSI) on-board the Phoenix Lander showed a large variety of cloud types over the course of the 151-sol mission (Moores et al., 2010). The navigation camera, NavCam aboard the Mars Science Laboratory (MSL, Curiosity) rover has observed cloud activity at Gale crater through cloud movies and surveys. The diurnal and seasonal patterns were comparable with previous observations. The peak cloud activities were observed in the morning/afternoon time and around the ACB period. (Kloos et al., 2018) They have also been reported to leave a thermal signature at night on Gale’s surface (Cooper et al. 2021). NAVCAM dataAt Jezero Crater, water ice clouds have been observed through cloud movies and cloud surveys collected using the Perseverance NavCam instrument that collects colour stereo images with a 96ox73o field of view at 0.33 mrad/pixel. (Maki et al., 2020) Compared to the NavCam on Curiosity, the NavCam on Perseverance holds the capability of imaging in colour which may provide advantages in highlighting water ice clouds in the atmosphere. Cloud surveys are single images taken facing the horizon, generally twice a week, at various times of the day. Similarly, cloud movies are collected by taking 8 frames of images looking towards the horizon with an interval of 15 seconds, producing a movie. A combination of cloud surveys and movies collected by the mission are used to study water ice clouds. Data ProcessingVarious image processing techniques are used on these data sets to emphasize the presence of water ice clouds in the atmosphere. For example, the NavCam Cloud movies can be processed using an imaging technique known as Mean Frame Subtraction (MFS) to enhance cloud features (Campbell et al., 2020) (Moores et al., 2015). This technique takes the average frame of the whole movie and subtracts it from each frame (Moores et al., 2015). This reveals the time-variable component, displaying the cloud movement within the movie. Figure 1 shows an example of raw (left) versus MFS processed frames (right) of a NavCam cloud movie. In addition to these processed images and movies, we have explored techniques such as two-dimensional fast Fourier transforms to recognize patterns in clouds. Figure 1: Comparison between raw and Mean Frame Subtraction frames. The raw frame (left) only shows faint clouds but when the Mean Frame Subtraction method is applied (right), the cloud features become visible. We will be presenting the water-ice cloud activity at Jezero Crater with details on various image processing techniques used to determine the characteristics of Martian clouds. The full data set from the start of the Mars2020 mission up to now will be analyzed to determine any seasonal patterns in the cloud activity seen at Jezero. BibliographyCampbell et al., 2020. Planet. Space Sci. 182 104785, http://dx.doi.org/10.1016/j.pss.2019. 104785.Cooper, B., et al., 221 JGR: Planets, 126(12), doi:10.1029/2020JE006737, 2021Kloos et al., 2018. Geophys. Res. Planets. (2018)123, 233–245. https://doi.org/10.1002/2017JE005314Lemmon et al., 2015. Icarus 251, 96–111. https://doi.org/10.1016Moores et al., 2010. J. Geophys. Res. Planets. https://doi.org/10.1029/ Maki et al., 2020. Space Science Reviews https://doi.org/10.1007/s11214-020-00765-9Moores et al., 2015. Adv. Space Res. 55 2217–2238, http://dx.doi.org/10.1016/j.asr.2015.02.007.Smith, M. D. 2004, Icarus, 167, 148–165. https://doi.org/10.1016/j.icarus.2003.09.010Tamppari et al., 2000, J. Geophys. Res., 105, E2, 4087–4107. https://doi.org/10.1029/1999JE001133Tamppari et al., 2003, J. Geophys. Res., 108, https://doi.org/10.1029/2002JE001911

Clouds on Mars are primary elements for understanding the past and present climate of the planet. Cloud particles can affect the energy balance of the planet, and so the atmospheric dynamic, as well as influence the vertical distribution of dust particles through dust scavenging. The dust scavenging by clouds has critical consequences in the water cycle of the planet; e.g. regions in the atmosphere with insufficient quantity of dust particles (or condensation nuclei) can inhibit the formation of H2O clouds and thus lead to the presence of water vapor in excess of saturation [1]. The study of these interactions requires observations whose analysis allows us to infer simultaneously the properties of both the clouds and dust. To address these observations, the Radiation and Dust Sensor (RDS) [2] is part of the Mars Environmental Dynamics Analyzer (MEDA) [3] payload onboard of the Mars 2020 rover Perseverance. RDS instrument compromises two sets of 8 photodiodes (RDS-DP) and a camera (RDS-SkyCam). One set of photodiodes is pointed upward (TOP sensors), with each one covering a different wavelength range between 190-1200 nm. The other set is pointed sideways (LAT sensors), 20 degrees above the horizon, and they are spaced 45 degrees apart in azimuth to sample all directions at a single wavelength.In this work we will present the radiative transfer analysis of the RDS TOP sensors observations at twilight for the first 365 sols. The twilight period was selected to: i) better constrain the vertical distribution of dust particles for the cloud-free days; ii) detect aerosol layers with very low opacities (lower than 0.1); iii) estimate the cloud altitude [4]. We will discuss the implication of our observations and analyses for Mars aerosol structure and timescales. For example, we find a period of a few days with a notable increase in the presence of clouds during twilight, and for which we derived cloud altitudes higher than 40 km and settling timescales of a few hours (involving a rapid vertical transport of dust particles).References:[1] Maltagliati, Luca, et al. "Evidence of water vapor in excess of saturation in the atmosphere of Mars." science 333.6051 (2011): 1868-1871.[2] Apestigue, Victor, et al. "Radiation and Dust Sensor for Mars Environmental Dynamic Analyzer Onboard M2020 Rover." Sensors 22.8 (2022): 2907.[3] Rodriguez-Manfredi, José Antonio, et al. "The Mars Environmental Dynamics Analyzer, MEDA. A suite of environmental sensors for the Mars 2020 mission." Space science reviews 217.3 (2021): 1-86.[4] Toledo, D., et al. "Measurement of aerosol optical depth and sub-visual cloud detection using the optical depth sensor (ODS)." Atmospheric Measurement Techniques 9.2 (2016): 455-467.

The Mars 2020 Perseverance rover is developing its mission in Jezero crater [1], a north tropical location that is rich in vortices and dust devils [2]. The MEDA instrument [3] collects atmospheric data at a typical frequency of 1 Hz with several sensors including pressure and winds. It also registers data about atmospheric dust with its set of photodiodes [4]. Together, these data are providing a large set of detections of vortices and dust devils [2, 5] that can be used to investigate the physical properties of the vortices and their effects on the environment though the combination of additional data obtained by MEDA. Here we present a physical characterization of dust devils detected with the pressure data and confirmed as dust devils from the set of photodiodes on MEDA. We show that the combination of pressure, winds and a simple model of drifting vortices [6] can fit the observations of many of these events determining their true central pressure drop, diameter and maximum circulation winds. The quality of the comparisons depend on the varying quality of the wind measurements and is better in short encounters with small vortices than in long encounters with large dust devils. We examine how the vortices characteristics, i.e. their true diameter, minimum distance of the encounter, central pressure drop and maximum wind intensity compare with the detection of dust and its basic inferred abundance and explore the consequences for the efficiency of vortices of different sizes and intensities to raise dust from the Martian surface. We also compare these vortex parameters with environment thermal properties, such as the thermal gradient from the surface and the air, and the thermal perturbations caused by the vortex in a selection of the best observed cases. A comparison with main properties of vortices observed in the different surveys of dust devil activity carried on by the cameras onboard Perseverance will be also presented. References:[1] Farley, K.A. et al. Mars2020 Mission Overview, Space Sci. Rev., 216, 142 (2020). Doi: 10.1007/s11214-020-00762-y[2] Newman, C.E. et al. The dynamic atmospheric and aeolian environment of Jezero crater, Mars, Science Advances (in press).[3] Rodriguez-Manfredi, J.A. et al. The Mars Environmental Dynamics Analyzer, MEDA. A Suite of Environmental Sensors for the Mars 2020 Mission, Space Science Reviews, 217, 48 (2021), doi:10.1007/s11214-021-00816-9.[4] Apestigue, V. et al. Radiation and Dust Sensor for Mars Environmental Dynamic Analyzer Onboard M2020 Rover. Sensors, 22, 2907 (2022). doi:10.3390/s22082907[5] Jackson, B. Vortices and Dust Devils as Observed by the Mars Environmental Dynamics Analyzer Instruments on Board the Mars 2020 Perseverance Rover, The Planetary Science Journal, 3, 20 (2022). Doi: 103847/PSJ/ac4586[6] Lorenz, R., Heuristic estimation of dust devil vortex parameters and trajectories from single-station meteorological observations: Application to InSight at Mars. Icarus, 271, 326-337 (2016). doi: 10.1016/j.icarus.2016.02.001

Perseverance's Mars Environmental Dynamics Analyzer (MEDA) is collecting data at Jezero Crater, characterizing the physical processes in the lowest layer of the atmosphere as no previous instrument did before. Here we show that temperature measurements at four heights capture the response of the atmospheric surface layer to multiple phenomena. We observe the transition from a stable nighttime thermal inversion to a diurnal, highly turbulent convective regime, with large vertical thermal gradients, and where local surface properties (such as Thermal Inertia) play an essential role. Recording multiple daily optical depths yielded higher aerosol concentrations in the morning than in the afternoon. Measured wind patterns are mainly driven by local topography, with a small contribution from regional winds. Daily and seasonal variability of relative humidity shows a complex hydrologic cycle. These observations raise new puzzles in which changes in surface albedo and thermal inertia may play an influential role. On a larger scale, surface pressure shows typical signatures of gravity waves and baroclinic eddies in a part of the seasonal cycle characterized before as low wave activity. These observations, combined and simultaneous, show the rich Jezero’s meteorology, and unveil the diversity of processes driving change on today’s Martian surface.

The Mars 2020 Perseverance rover landed in Mars in February 2021 in Jezero crater at 18.4ºN. One of its instruments is MEDA, the Mars Environmental Dynamics Analyzer, which measures among other properties air pressure, air temperature at different levels, surface temperature from its infrared emission, and the presence of dust. The latter is provided by a set of photodiodes pointing in different directions that constitute the Remote Dust Sensor or RDS. MEDA data are acquired with a frequency of 1 or 2 Hz in data sessions that cover about 50% of a full sol allowing a full characterization of daily and seasonal cycles.Predictions before landing indicated that Jezero should be a location favoring the formation of intense vortices and dust devils in Spring to Summer. These expectations were fulfilled with frequent observations of vortices and dust devils observed with MEDA and the rover cameras. A systematic analysis of MEDA’s pressure sensor shows the close passage of convective vortices. These are detected as events that range from short and sharp pressure drops to long and deep pressure drops. Wind measurements during the vortex passage, combined with their duration, give information about the size and distance of the vortex. Many of the most intense events in terms of the pressure drop and peak winds detected have simultaneous drops of light measured with the RDS and are dust devils equivalent to those observed at much higher distances with Perseverance cameras. The combination of pressure, wind and RDS measurements largely constrain the geometry effects associated to these close passing dust devils. Some of them also have additional clear counterparts in other MEDA sensors including temperatures, which allows for an in-depth investigation of the physical properties of selected dust devils. Some events might also be captured by the SuperCam microphone, that records pressure fluctuations in the audible domain. The acoustic signal can provide insights into the short term behavior of vortices, and can contribute to the determination of the vortex physical properties. Statistics of vortices allow us to determine the probability of finding these events with the SuperCam microphone.We present results for over one Earth year (Ls=6; Feb. 2021, Northern Hemisphere Spring – Ls=180; Feb. 2022; Northern Autumn Equinox). We show the daily cycle of vortex and dust devil activity and how this has evolved from early Spring until the start of the dust storms season. We present results of the distribution of sizes of vortices and dust devils and a selection of some remarkable events. These include direct hits of dust devils passing right through Perseverance, tangential passes in which one wall of the vortex passes over Perseverance, and more distant passages of very dusty events whose diameter in some cases largely exceed 100 m. A comparison of the vortex convective activity observed at Jezero with results from a Large-Eddy-Simulations (LES) using the MarsWRF model helps us to gain insight into how the detected vortices and their properties can constrain other general properties of the atmospheric dynamics at Jezero crater.

The Mars Science Laboratory Curiosity rover has explored over 400 m of vertical stratigraphy within Gale crater to date. These fluvio-deltaic, lacustrine, and aeolian strata have been well-documented by Curiosity's in situ and remote science instruments, including the Mast Camera (Mastcam) pair of multispectral imagers. Mastcam visible to near-infrared spectra can broadly distinguish between iron phases and oxidation states, and in combination with chemical data from other instruments, Mastcam spectra can help constrain mineralogy, depositional origin, and diagenesis. However, no traverse-scale analysis of Mastcam multispectral data has yet been performed. We compiled a database of Mastcam spectra from >600 multispectral observations and quantified spectral variations across Curiosity's traverse through Vera Rubin ridge (sols 0-2302). From principal component analysis and an examination of spectral parameters, we identified nine rock spectral classes and five soil spectral classes. Rock classes are dominated by spectral differences attributed to hematite and other oxides (due to variations in grain size, composition, and abundance) and are mostly confined to specific stratigraphic members. Soil classes fall along a mixing line between soil spectra dominated by fine-grained Fe-oxides and those dominated by olivine-bearing sands. By comparing trends in soil versus rock spectra, we find that locally derived sediments are not significantly contributing to the spectra of soils. Rather, varying contributions of dark, mafic sands from the active Bagnold Dune field is the primary spectral characteristic of soils. These spectral classes and their trends with stratigraphy provide a basis for comparison in Curiosity's ongoing exploration of Gale crater.

The new London Crossrail running tunnels for the future London Rail Elizabeth Line were driven by Tunnel Boring Machine (TBM) and linked at regular intervals by cross passages, constructed with open face techniques. This paper describes the development of the ground model and depressurisation required for a cross passage link between the running tunnels in East London, through the analysis of the existing data and a subsequent targeted ground investigation. The cross passage was 14 m long and included a central sump with a formation level at 48 m below ground surface. Cross passages encompass two risks: Programme risk as they run along the critical path of the project and construction risk, since they are excavated with traditional open face techniques. For cross passage CP6, a pre-construction borehole indicated that the ground conditions at the cross passage horizon comprised predominantly cohesive Lambeth Group soils. The well-known variability of the Lambeth Group, often with sudden lateral and vertical change in facies, make the prediction of ground conditions extremely challenging and critical for safe open face tunnelling. The ground model evolved from the design to the construction stage, using the information provided by: the project ground investigation; TBM drive data and sampling; followed by a targeted probe drilling investigation conducted from within the running tunnels. During the latter investigation, more extensive water bearing sands were identified, than previously identified by the surface borehole, which required a revision to the ground model and subsequently a change in approach to the cross passage excavation. The new ground model allowed the Contractor to manage the ground risk appropriately, which included a change in approach to groundwater control in the form of in-tunnel well-points depressurisation and surface ejector wells.

The SuperCam instrument [1,2] onboard Mars2020 disposes of a variety of active and passive techniques, including passive spectroscopy in the 0.40-0.85 (VIS) and 1.3 to 2.6 microns (IR, [3,4]) wavelength ranges. Since the landing on Mars of Perseverance in February 2021, Supercam has acquired numerous observations of its near and distant environment, exploring the geological and mineralogical context of Jezero crater. In addition, several measurements were devoted to probing the atmosphere surrounding the Perseverance rover. The technique of using sky spectra in passive mode, known as "passive sky", has already been demonstrated with ChemCam on the Mars Science Laboratory (MSL) rover [4]. SuperCam provides a superset of the ChemCam capabilities used in [4], and in particular adds a near-infrared component that includes absorption and scattering characteristics of key gases and aerosols/clouds. "Passive sky" measurements have typically been performed every other week to allow a consistent monitoring of the seasonal evolution of the main quantities (CO2, O2, H2O, CO, aerosols/clouds). Particular attention was given to joint measurements of O2 and CO, as they appear as key components of the Martian chemical cycle and have never been measured together at the same time on the surface of Mars. As the 2 m wavelength region is used for the first time at the surface of Mars, it enables the detection of CO (around 2.35 m). CO possesses a small absorption that has made it difficult to identify in SuperCam spectra so far. An overview of SuperCam's progress to date in its attempt to characterize the Martian atmosphere at Jezero will be presented. References : [1] Wiens, R.C., et al. , 2021. Space Sci Rev 217, 4, [2] Maurice, S., et al., 2021. Space Sci Rev 217, 47, [3] Royer, C., et al.., 2020. Review of Scientific Instruments 91, 063105, [4] Fouchet, T., et al., 2021, Icarus, submitted. [5] McConnochie T. H et al., 2018. Icarus 307, 294

The InSight lander (Banerdt et al. 2020) on Mars is equipped with two cameras capable of sky imaging both of which have been used opportunistically to search for meteors. The rate of occurrence of Martian meteors has not been directly measured and initial reports of an imaged meteor by Selsis et al. 2005 were likely incorrect (Domokos et al. 2007). The meteor search is part of the investigation into the flux of impactors at Mars (Daubar et al. 2018).The InSight cameras have been described by Maki et al. (2018). The Instrument Deployment Camera (IDC) can be aimed by a robotic arm and has a 45-degree square field of view (FOV). However, this camera was typically unavailable, and has only been used twice. The Instrument Context Camera (ICC) has a 120-degree fisheye FOV. It is aimed downward, but sees a broad section of the southern sky to around 20-degrees elevation angle.IDC images are shown in Fig. 1. They were aimed to the southwest at an elevation of about 35 degrees, and on sols 126 and 176 (5 April and 27 May 2019), four 5-minute exposures were acquired. Stars are visible in the images, and will be used to determine the sensitivity. Many cosmic rays were seen (e.g., Fig. 2)—long ones can be mistaken for meteors, but they have a distinctive morphology with a narrow end and a diffuse end due to the charge diffusion process after the charged particles pass through the detector (Fisher-Levine and Nomerotski, 2015). Despite the Sun being 60 degrees down, diffuse sky brightness was visible (Banfield et al. 2020). No meteors were detected.ICC images are shown in Fig. 3—about 75% of the images do not include sky. On 25 sols from 254 to 432 (15 August 2019 to 6 February 2020), the ICC acquired four, 5-minute exposures. No meteors were seen.We will present an analysis of the results and their implication for the meteor rate at Mars. While no meteors were seen, the upper limit is likely to be constraining. Total exposure time is 540 minutes, using cameras more sensitive than the limiting exposures of Domokos et al. (2007) and with wider FOVs. However, the complex geometry and the time variable atmospheric dust extinction will be considered.References. Banerdt et al. 2020. Nature Geoscience, 13, 183-189. Banfield et al. 2020. Nature Geoscience, 13, 190-198. Daubar et al. 2018. Space Science Rev. 214, 132. Domokos et al. 2007. Icarus 191, 141-150. Fisher-Levine and Nomerotski 2015. BNL-108381-2015-JA. Maki et al. 2018. Space Sci. Rev. 214, 105. Selsis et al. 2005. Nature 435, 581.

International audience; The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorus were measured directly as key biogenic elements; by inference, phosphorus is assumed to have been available. The environment probably had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial-lacustrine environments in the post-Noachian history of Mars.

International audience; The Radiation Assessment Detector (RAD) on the Mars Science Laboratory's Curiosity rover began making detailed measurements of the cosmic ray and energetic particle radiation environment on the surface of Mars on 7 August 2012. We report and discuss measurements of the absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the martian surface for similar to 300 days of observations during the current solar maximum. These measurements provide insight into the radiation hazards associated with a human mission to the surface of Mars and provide an anchor point with which to model the subsurface radiation environment, with implications for microbial survival times of any possible extant or past life, as well as for the preservation of potential organic biosignatures of the ancient martian environment.

Mars' Atmosphere from Curiosity The Sample Analysis at Mars (SAM) instrument on the Curiosity rover that landed on Mars in August last year is designed to study the chemical and isotopic composition of the martian atmosphere. Mahaffy et al. (p. 263 ) present volume-mixing ratios of Mars' five major atmospheric constituents (CO 2 , Ar, N 2 , O 2 , and CO) and isotope measurements of 40 Ar/ 36 Ar and C and O in CO 2 , based on data from one of SAM's instruments, obtained between 31 August and 21 November 2012. Webster et al. (p. 260 ) used data from another of SAM's instruments obtained around the same period to determine isotope ratios of H, C, and O in atmospheric CO 2 and H 2 O. Agreement between the isotopic ratios measured by SAM with those of martian meteorites, measured in laboratories on Earth, confirms the origin of these meteorites and implies that the current atmospheric reservoirs of CO 2 and H 2 O were largely established after the period of early atmospheric loss some 4 billion years ago.

Improper regulation of the level and duration of activated erbB family growth factor receptors at the cell surface can lead to uncontrolled cell proliferation and transformation. The GTPase dynamin is a regulator both of transport of receptors to the plasma membrane and down-regulation of receptors via receptor-mediated endocytosis (RME). The localization of specific dynamin isoforms led us to hypothesize that different dynamin isotypes are involved in the distinct processes of vesicle budding from the TGN and receptor-mediated endocytosis from the plasma membrane. This proposal outlines a study of the role of different dynamin isoforms in cellular trafficking to define which members of the dynamin family are involved in up-versus down-regulation of erbB receptors. The analysis of these hypotheses is still on going. I also hypothesized that the pleckstrin homology (PH) domain of dynamin is essential for dynamin targeting. My studies indicate that this is not the case, and that the PH domain may instead be directly involved in vesicle scission. PH domains have characteristics that suggest they will be good targets for small molecule drugs, so understanding the role of the PH domain in dynamin function should allow for modulating dynamin activity to control the level of erbB-mediated signaling.

No Methane to Be Found On Earth, atmospheric methane is mostly produced biologically. Atmospheric methane has also been detected on Mars, but these reports have been controversial. Based on data from the Sample Analysis at Mars instrument suite on the Curiosity rover, which arrived at the surface of Mars in August 2012, Webster et al. (p. 355 , published online 19 September) report no methane, with an upper limit of only 1.3 parts per billion by volume, about 6 times lower than previous measurements.

Specific side-by-side interactions between transmembrane alpha-helices may be important in the assembly and function of integral membrane proteins. We describe a system for the genetic and biophysical analysis of these interactions. The transmembrane alpha-helical domain of interest is fused to the C-terminus of staphylococcal nuclease. The resulting chimera can be expressed at high levels in Escherichia coli and is readily purified. In our initial application we study the single transmembrane alpha-helix of human glycophorin A (GpA), thought to mediate the SDS-stable dimerization of this protein. The resulting chimera forms a dimer in SDS, which is disrupted upon addition of a peptide corresponding to the transmembrane domain of GpA. Deletion mutagenesis has been used to delineate the minimum transmembrane domain sufficient for this behavior. Site-specific mutagenesis shows that a methionine residue, previously implicated as a potential interfacial residue, can be replaced with other hydrophobic residues without disrupting dimerization. By contrast, rather conservative substitutions at a valine on a different face of the alpha-helix disrupt dimerization, suggesting a high degree of specificity in the helix-helix interactions. This approach allows the interface between interacting helices to be defined.