Martian Interior Research Articles

Hydrothermal Fluid Activity on Mars Recorded in Phosphates of the Gabbroic Shergottite Northwest Africa 13581

AbstractApatites record crucial information on the origin, composition, and chemical evolution of volatiles on terrestrial planets. As a martian intrusive rock, the gabbroic shergottite Northwest Africa (NWA) 13581 provides key information on the volatile evolution related to magmatic processes in the interior, shedding light on the intricate volatile circulation on Mars. The textural and chemical characteristics of the phosphates in NWA 13581 indicate a complex formation history involving fractional crystallization, degassing, and fluid interaction. Degassing of the NWA 13581 parent melt is capable of exsolving chlorine‐rich fluids, resulting in the formation of notably fluorine‐rich apatite with a high x‐site occupancy of fluorine up to 90%. The degassed/exsolved volatile‐rich fluids could subsequently continue to migrate and interact with surrounding magmatic suites, leading to highly heterogeneous compositions of active fluids. The crystallization of apatite is initiated by the interaction of fluids with merrillite at the late stage of the magmatic process, leading to the formation of phosphate intergrowths. Influenced by the composition and chemical evolution of volatiles in fluids and melts, apatite exhibits notable variability in chlorine compositions both within individual grains and among different grains. Moreover, the presence of magnetite associated with phosphate intergrowth highlights the transportation of metallic components in addition to volatiles from deep layers to shallower depths or to the surface of Mars. This process, which is observed in young shergottites, indicates the persistent presence of hydrothermal systems until recent geological periods, contributing to the generation and circulation of volatiles within the martian interior and on the surface.

Likely Ferromagnetic Minerals Identified by the Perseverance Rover and Implications for Future Paleomagnetic Analyses of Returned Martian Samples

AbstractAlthough Mars today does not have a core dynamo, magnetizations in the Martian crust and in meteorites suggest a magnetic field was present prior to 3.7 billion years (Ga) ago. However, the lack of ancient, oriented Martian bedrock samples available on Earth has prevented accurate estimates of the dynamo's intensity, lifetime, and direction. Constraining the nature and lifetime of the dynamo are vital to understanding the evolution of the Martian interior and the potential habitability of the planet. The Perseverance rover, which is exploring Jezero crater, is providing an unprecedented opportunity to address this gap by acquiring absolutely oriented bedrock samples with estimated ages from ∼2.3 to >4.1 Ga. As a first step in establishing whether these samples could contain records of Martian paleomagnetism, it is important to determine their ferromagnetic mineralogy, the grain sizes of the phases, and the forms of any natural remanent magnetization. Here, we synthesize data from various Perseverance instruments to achieve those goals and discuss the implications for future laboratory paleomagnetic analyses. Using the rover's instrument payload, we find that cored samples likely contain iron oxides enriched in Cr and Ti. The relative proportions of Fe, Ti, and Cr indicate that the phases may be titanomagnetite or Fe‐Ti‐Cr spinels that are ferromagnetic at room temperature, but we cannot rule out the presence of non‐ferromagnetic ulvöspinel, ilmenite, and chromite due to signal mixing. Importantly, the inferred abundance of iron oxides in the samples suggests that even <1 mm‐sized samples will be easily measurable by present‐day magnetometers.

Evaluating the Use of Seasonal Surface Displacements and Time‐Variable Gravity to Constrain the Interior of Mars

AbstractThe mass transport of volatiles on Mars represents a seasonally changing load on the surface of the planet. Like on Earth, as mass is redistributed across the planet, the surface responds in a complex manner becoming displaced downwards or upwards. The magnitude and extent of displacement depend on the properties of the load and mechanical properties of the planetary interior. Based on new estimates of the height variation of the seasonal polar caps (SPCs), we predict local surface displacements of up to tens of millimeters with a strong degree 1 signal throughout the Martian year. The long‐wavelength portion of the displacement is potentially observable, with a magnitude of a few millimeters, located away from the SPC where one could realistically measure it with a landed or orbital mission. We also model the direct contribution of this process to observable time variable gravity, where we find the zonal coefficients to be in line with previous measurements, although with a smaller magnitude. Future measurements of this displacement could be used to help elucidate the composition of the interior of Mars using this process as a probe into the Martian interior. Furthermore, more refined measurements of time‐variable gravity would be a powerful tool in constraining the pole‐to‐pole volatile cycle present on Mars.

A heterogeneous mantle and crustal structure formed during the early differentiation of Mars.

Highly siderophile element abundances and Os isotopes of nakhlite and chassignite meteorites demonstrate that they represent a comagmatic suite from Mars. Nakhlites experienced variable assimilation of >2-billion-year-old altered high Re/Os basaltic crust. This basaltic crust is distinct from the ancient crust represented by meteorites Allan Hills 84001 or impact-contaminated Northwest Africa 7034/7533. Nakhlites and chassignites that did not experience crustal assimilation reveal that they were extracted from a depleted lithospheric mantle distinct from the deep plume source of depleted shergottites. The comagmatic origin for nakhlites and chassignites demonstrates a layered martian interior comprising ancient enriched basaltic crust derived from trace element-rich shallow magma ocean cumulates, a variably metasomatized mantle lithosphere, and a trace element-depleted deep mantle sampled by plume magmatism.

Source and parental melts of poikilitic shergottites: Implications for martian magmatism

Martian poikilitic shergottites are cumulate rocks that can help advance the understanding of magmatic evolution from near the base of the crust (∼10 kbar) to near-surface conditions. Through a comprehensive petrographic and geochemical study, we aim to better understand poikilitic shergottite formation and the evolution in the martian interior. A suite of poikilitic shergottites, including Northwest Africa (NWA) 7755, NWA 11043, NWA 11065, NWA 10618 and Alan Hills (ALHA) 77005, were investigated for their major, minor, and trace element compositions of olivine-hosted melt inclusions (MI). The MI occur within both the early-evolutional stage textural and late-evolution stage textural domains in olivine. Major element compositions of MI indicate fractional crystallization between the early and late-crystallizing domains. Calculated parental melt compositions from these MI data yielded results that also petrogenetically link the poikilitic shergottites with the olivine-phyric shergottite subgroup. Trace element compositions of MI show that the later-crystallizing MI could have undergone open-system processes, such as fluid exsolution. Lutetium-Hf and Sm-Nd isotopic analyses were performed on NWA 7755 and NWA 11043 to constrain their age and source isotopic compositions. Northwest Africa 7755 shows a 176Lu/177Hf crystallization age of 223 ± 46 Ma, which fits into the expected range for enriched shergottites of ∼165 Ma to 225 Ma. A similar crystallization age and 176Lu/177Hf and 147Sm/144Nd source composition of NWA 7755 to the other enriched shergottites suggest that this specimen likely shares a long-lived geochemical source with these samples that has lasted for at least 60 Ma. Northwest Africa 11043 shows scatter throughout the Lu-Hf and Sm-Nd isotopic data, suggesting that this sample is not in isotopic equilibrium. This sample was possibly inherited from high-temperature processes, such as incomplete magmas mixing from a similar, but distinct, source. We conducted in situ U-Th-Pb isotope analyses of Ca-phosphate minerals for NWA 11043 and found an unreliable crystallization age of 59.2 ± 138.4 Ma: phosphates are likely recording the period of shock metamorphism related to the ejection event. Consistent crystallization ages and magmatic histories support previous work that suggest there is a common magmatic system on Mars that is responsible for the formation of enriched shergottites.

Role of 26Al and impact-generated atmosphere in the early thermal evolution, differentiation, and volatile-rich core of Mars

The InSight mission's high-quality seismic data and cosmochemical models have demonstrated that Mars has a volatile-rich core. It is proposed that Mars formed early, before the solar nebular gas dispersed, and/or it accreted volatile-rich material to account for its volatile-rich interior. The early accreted Mars must have gravitationally attracted proto-atmosphere from the surrounding solar nebula. If its building blocks were rich in volatiles, it might have acquired impact-generated atmosphere during accretion. By considering the decay energy of the short-lived radionuclide (SLR) 26Al and the blanketing effect of the primordial and impact-generated atmosphere during the initial 10 Ma of the formation of the solar system, we present the results of numerical simulations carried out for the early thermal evolution and core formation of Mars. To explain the formation of a large iron core of Mars as suggested by the seismometer of InSight mission, we considered the 60% EH- and 40% CI-chondrite composition for the building blocks of Mars. The blanketing effect of impact generated H2O + CO2+CO + H2 atmosphere caused the melting of surface silicates to form magma ocean at surface. We thoroughly examined the effects of several variables on the timing of complete core formation, including the initial water content in the accreted material, timescale of onset of accretion after the formation of CAIs, duration of accretion, absorption coefficient of CO2, efficiency of degassing of volatiles, and melting temperature. The results of present study show that the decay energy of SLR 26Al caused the widespread heating and melting of interior of Mars. For complete core formation, Mars must accrete within the first ∼2 Ma in order to explain the volatile-rich core. Further, the timescales of core formation were found to be strongly dependent on the assumed melting curve. For longer timescales of accretion, the interior of Mars experienced incomplete differentiation even by assuming high water content in the accreted material and larger absorption coefficient for CO2. However, Mars does not have to accrete within 2 Ma for the core to fully develop if the Rayleigh- Taylor (RT) instability is present in the dense metallic layer on top of the undifferentiated interior. A short accretion time is only valid if RT-instability is neglected. Hence, we expect that the volatiles in the magma ocean could also be transferred to core by Rayleigh-Taylor instability. We also parameterized the thermal influence of gravitational heat produced during the differentiation of Mars to study its influence on the thermal evolution of the planet. The outcomes of the present work have implications to explain the timing of partition of volatiles in the Martian interior and formation of an early atmosphere on Mars.

Origin of nitrogen on Mars: First in situ N isotope analyses of martian meteorites

Martian meteorites are key for assessing the isotopic characteristics of nitrogen in different martian reservoirs (i.e., mantle, crust, and atmosphere), and, ultimately, for constraining the source(s) of nitrogen trapped during the earliest stages of planetary accretion in the terrestrial planet-forming region. In this study, we analysed, for the first time, the nitrogen content and isotopic composition of glassy melt inclusions of Chassigny and of the mesostasis of five nakhlites (MIL 03346, Nakhla, NWA 6148, NWA 998, and Y 000593) by in situ secondary ion mass spectrometry. The nitrogen content of Chassigny melt inclusions, corrected for olivine overgrowth on the inclusion walls, varies from 4 ± 1 to 860 ± 45 ppm N, and the majority of δ15N values range from –35 ± 41 to +73 ± 36‰. The estimated nitrogen isotopic signature of the primitive melt, prior to degassing of N2 or NH3, is 0 ± 32‰. The mesostasis of nakhlites contains 2.7 ± 0.2 to 943 ± 156 ppm N, with δ15N values from –30 ± 37 to +348 ± 43‰. Whereas degassing of N2 or NH3 can explain the lowest nitrogen isotopic ratios measured in the nakhlite mesostasis, the 15N-enriched isotopic composition (δ15N > 150‰) of four nakhlites (MIL 03346, Nakhla, NWA 6148, and Y 000593) likely results from interaction of the mesostasis melt with the martian atmosphere during ejection. The δ15N values (+25 ± 42 and +77 ± 19‰) of two melt inclusions in Y 000593 are comparable to those of Chassigny, further confirming that these meteorites likely sample a common volatile reservoir in the martian interior. Overall, the new results indicate that the chassignite-nakhlite reservoir did not inherit nitrogen from the solar nebula but, instead, from chondritic-like materials. These findings further confirm that planetary bodies in the inner solar system accreted (isotopically) chondritic nitrogen during the first few million years of solar system history.

Tidal Constraints on the Martian Interior

AbstractWe compare several recent Martian interior models and evaluate how these are impacted by the tidal constraints provided by the Love number k2 and the secular acceleration in longitude s of its main moon, Phobos. The expression of the latter is developed up to harmonic degree 5 to match the accuracy of the current observations. We match a number of current interior structure models to the recent measurements of the tidal parameters and derive estimations of the possible core radius, temperature profile, and attenuation in the Martian interior. Our estimation of the core radius is 1,820 ± 80 km, consistent with recent seismic measurements. The attenuation profiles in the Martian interior at the main tidal period of Phobos are similar between the considered models, giving a range for the degree‐2 bulk tidal attenuation Q2 = 93.0 ± 8.40 but diverge at seismic frequencies. At seismic frequencies, model shear attenuation Qμ ranges between 100 and 4,000 in the lower mantle, so that a measurement of seismic shear attenuation could be used as an effective means for distinguishing between the models considered. Other constraints such as elastic lithosphere thickness and Chandler Wobble period favor a thicker elastic lithosphere and models with a frequency dependence α of the shear attenuation between 0.15 and 0.4. Improved constraints on the Martian interior should be possible with additional seismic and radio observations from the InSight mission.

Newly formed craters on Mars located using seismic and acoustic wave data from InSight

Meteoroid impacts shape planetary surfaces by forming new craters and alter atmospheric composition. During atmospheric entry and impact on the ground, meteoroids excite transient acoustic and seismic waves. However, new crater formation and the associated impact-induced mechanical waves have yet to be observed jointly beyond Earth. Here we report observations of seismic and acoustic waves from the NASA InSight lander’s seismometer that we link to four meteoroid impact events on Mars observed in spacecraft imagery. We analysed arrival times and polarization of seismic and acoustic waves to estimate impact locations, which were subsequently confirmed by orbital imaging of the associated craters. Crater dimensions and estimates of meteoroid trajectories are consistent with waveform modelling of the recorded seismograms. With identified seismic sources, the seismic waves can be used to constrain the structure of the Martian interior, corroborating previous crustal structure models, and constrain scaling relationships between the distance and amplitude of impact-generated seismic waves on Mars, supporting a link between the seismic moment of impacts and the vertical impactor momentum. Our findings demonstrate the capability of planetary seismology to identify impact-generated seismic sources and constrain both impact processes and planetary interiors. Impact-induced acoustic and seismic wave events on Mars recorded by the InSight lander’s seismometer have been traced to fresh craters observed in spacecraft imagery.

Autocorrelation R2 on Mars

AbstractA purpose of the Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) mission is to reveal the Martian interior structure with seismic data. In this work, ambient noise autocorrelation of the continuously recorded vertical‐component seismic signals has extracted the Rayleigh waves that propagate around Mars for one cycle, R2. The Mars orbiting surface waves are observed at a lag time of ∼6,000 s in the stacked autocorrelation series filtered between 0.005 and 0.01 Hz. Synthetic seismograms from a set of radially concentric velocity models were computed to find the best‐fitting one as the starting model for a Monte Carlo inversion. The starting model was randomly perturbed iteratively to increase the correlation coefficients and reduce the absolute time shifts between the synthetic and observed R2. An S‐wave low‐velocity layer in the inverted velocity model extends to ∼400 km depth, consistent with Marsquake observations, geophysical inversion, and high‐pressure experiments.

Repetitive marsquakes in Martian upper mantle

Marsquakes excite seismic wavefield, allowing the Martian interior structures to be probed. However, the Martian seismic data recorded by InSight have a low signal-to-noise ratio, making the identification of marsquakes challenging. Here we use the Matched Filter technique and Benford’s Law to detect hitherto undetected events. Based on nine marsquake templates, we report 47 newly detected events, >90% of which are associated with the two high-quality events located beneath Cerberus Fossae. They occurred at all times of the Martian day, thus excluding the tidal modulation (e.g., Phobos) as their cause. We attribute the newly discovered, low-frequency, repetitive events to magma movement associated with volcanic activity in the upper mantle beneath Cerberus Fossae. The continuous seismicity suggests that Cerberus Fossae is seismically highly active and that the Martian mantle is mobile.

On the source of the quasi Carrington Rotation periodic magnetic variations on the Martian surface: InSight Observations and Modelling

In a recent paper (Luo H et al., 2022), we found that the peak amplitudes of diurnal magnetic variations, measured during martian days (sols) at the InSight landing site, exhibited quasi Carrington-Rotation (qCR) periods at higher eigenmodes of the natural orthogonal components (NOC); these results were based on ~664 sols of magnetic field measurements. However, the source of these periodic variations is still unknown. In this paper we introduce the neutral-wind driven ionospheric dynamo current model (e.g., Lillis et al., 2019) to investigate the source. Four candidates — the draped IMF, electron density/plasma density, the neutral densities, and the electron temperature in the ionosphere with artificial qCR periodicity, are applied in the modeling to find the main factor likely to be causing the observed surface magnetic field variations that exhibit the same qCR periods. Results show that the electron density/plasma density, which controls the total conductivity in the dynamo region, appears to account for the greatest part of the surface qCR variations; its contribution reaches about 67.6%. The draped IMF, the neutral densities, and the electron temperature account, respectively, for only about 12.9%, 10.3%, and 9.2% of the variations. Our study implies that the qCR magnetic variations on the Martian surface are due primarily to variations of the dynamo currents caused by the electron density variations. We suggest also that the time-varying fields with the qCR period could be used to probe the Martian interior's electrical conductivity structure to a depth of at least 700 km.

The Tharsis mantle source of depleted shergottites revealed by 90 million impact craters

The only martian rock samples on Earth are meteorites ejected from the surface of Mars by asteroid impacts. The locations and geological contexts of the launch sites are currently unknown. Determining the impact locations is essential to unravel the relations between the evolution of the martian interior and its surface. Here we adapt a Crater Detection Algorithm that compile a database of 90 million impact craters, allowing to determine the potential launch position of these meteorites through the observation of secondary crater fields. We show that Tooting and 09-000015 craters, both located in the Tharsis volcanic province, are the most likely source of the depleted shergottites ejected 1.1 million year ago. This implies that a major thermal anomaly deeply rooted in the mantle under Tharsis was active over most of the geological history of the planet, and has sampled a depleted mantle, that has retained until recently geochemical signatures of Mars’ early history.

Shock-induced H loss from pyroxene and maskelynite in a Martian meteorite and the mantle source δD of enriched shergottites

Assessing the water abundance and hydrogen isotopic signature (δD) of the Martian interior dictates our understanding of the formation of inner solar-system planets, the origin of their volatiles, Martian volcanic history, and the potential for life-bearing environments on the surface of the red planet. Although several Martian meteorites, representing the planet's crust, have been analyzed before for this assessment, little is known about the effect of shock on recorded hydrogen (H) in their mineral phases. Here, hydrogen contents and isotopes are measured by secondary ion mass spectrometry (SIMS) in an enriched olivine-phyric shergottite, Larkman Nunatak (LAR) 06319, containing impact-melted zones. Systematic 100 μm-long traverses in pyroxene and maskelynite grains reveal decreases of hundreds of µg/g H2O and increases in δD of thousands of ‰ towards the contact with impact-melted zones, which is interpreted as H diffusive loss during shock-melting. Diffusion modeling reveals that temperatures high enough to permit H diffusion following shock were maintained near the impact-melted zone for a few minutes. By comparison, the interior of pyroxenes > 200 μm away from impact-melted zones have some of the highest H content with 170–480 µg/g H2O and the lowest δD with ∼ 300‰. The latter values, obtained on the most Mg-rich, i.e. earliest crystallized pyroxenes, are used to estimate that the enriched shergottite mantle source contains 300–1000 µg/g H2O and has a δD of ∼ 300‰. This δD is similar to that of depleted shergottite and nakhlite mantle sources, but higher than Earth’s upper mantle, suggesting slightly different water source materials for the two planets. The enriched shergottite mantle source has ∼ 10 times more water than that inferred for the depleted shergottite source and for Earth’s upper mantle. The high water content and wide range of δD in olivine (from 90 µg/g H2O and 2700‰ to 1350 µg/g H2O and −14‰) is interpreted as overprinting by a combination of Martian and terrestrial surface alteration. Finally, the high δD recorded in the impact-melt produced glass (3350–4700‰), its moderate water content (100–230 µg/g H2O), and the presence of vesicles, are likely the result of incorporation of Martian surficial material (ice and atmospheric gases) and degassing during shock melting. This study shows that shock can induce H loss from minerals, accompanied by > 1000‰ δD increases. Additionally, although it confirms that the Martian mantle may be heterogeneous in its water content, it implies that the Martian mantle is homogeneous within uncertainties for δD.

Scattering Attenuation of the Martian Interior through Coda Wave Analysis.

We investigate the scattering attenuation characteristics of the Martian crust and uppermost mantle to understand the structure of the Martian interior. We examine the energy decay of the spectral envelopes for 21 high-quality Martian seismic events from Sol 128 to Sol 500 of InSight operations. We use the model of Dainty et al. (1974b) to approximate the behavior of energy envelopes resulting from scattered wave propagation through a single diffusive layer over an elastic half-space. Using a grid search, we mapped the layer parameters that fit the observed InSight data envelopes. The single diffusive layer model provided better fits to the observed energy envelopes for High Frequency (HF) and Very High Frequency (VF) than for the Low Frequency (LF) and Broadband (BB) events. This result is consistent with the suggested source depths (Giardini et al., 2020) for these families of events and their expected interaction with a shallow scattering layer. The shapes of the observed data envelopes do not show a consistent pattern with event distance, suggesting that the diffusivity and scattering layer thickness is non-uniform in the vicinity of InSight at Mars. Given the consistency in the envelope shapes between HF and VF events across epicentral distances and the tradeoffs between the parameters that control scattering, the dimensions of the scattering layer remain unconstrained but require that scattering strength decreases with depth and that the rate of decay in scattering strength is fastest near the surface. This is generally consistent with the processes that would form scattering structures in planetary lithospheres.

Potential Pitfalls in the Analysis and Structural Interpretation of Seismic Data from the Mars InSight Mission.

The Seismic Experiment for Interior Structure (SEIS) of the InSight mission to Mars, has been providing direct information on Martian interior structure and dynamics of that planet since it landed. Compared to seismic recordings on Earth, ground motion measurements acquired by SEIS on Mars are made under dramatically different ambient noise conditions, but include idiosyncratic signals that arise from coupling between different InSight sensors and spacecraft components. This work is to synthesize what is known about these signal types, illustrate how they can manifest in waveforms and noise correlations, and present pitfalls in structural interpretations based on standard seismic analysis methods. We show that glitches, a type of prominent transient signal, can produce artifacts in ambient noise correlations. Sustained signals that vary in frequency, such as lander modes which are affected by variations in temperature and wind conditions over the course of the Martian Sol, can also contaminate ambient noise results. Therefore, both types of signals have the potential to bias interpretation in terms of subsurface layering. We illustrate that signal processing in the presence of identified nonseismic signals must be informed by an understanding of the underlying physical processes in order for high fidelity waveforms of ground motion to be extracted. While the origins of most idiosyncratic signals are well understood, the 2.4 Hz resonance remains debated and the literature does not contain an explanation of its fine spectral structure. Even though the selection of idiosyncratic signal types discussed in this paper may not be exhaustive, we provide guidance on best practices for enhancing the robustness of structural interpretations.

Seismic Velocity Variations in a 3D Martian Mantle: Implications for the InSight Measurements

AbstractWe use a large data set of 3D thermal evolution models to predict the distribution of present‐day seismic velocities in the Martian interior. Our models show a difference between maximum and minimum S wave velocity of up to 10% either below the crust, where thermal variations are largest, or at the depth of the olivine to wadsleyite phase transition, located at around 1,000–1,200 km depth. Models with thick lithospheres on average have weak low‐velocity zones that extend deeper than 400 km and seismic velocity variations in the uppermost 400–600 km that closely follow the crustal thickness pattern. For these cases, the crust contains more than half of the total amount of heat‐producing elements. Models with limited crustal heat production have thinner lithospheres and shallower but prominent low‐velocity zones that are incompatible with Interior exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) observations. Seismic events suggested to originate in Cerberus Fossae indicate the absence of S wave shadow zones in 25°–30° epicentral distance. This result is compatible with previous best fit models that require a large average lithospheric thickness and a crust containing more than half of the bulk amount of heat‐producing elements to be compatible with geological and geophysical constraints. Ongoing and future InSight measurements that will determine the existence of a weak low‐velocity zone will directly bear on the crustal heat production.

What Martian Meteorites Reveal About the Interior and Surface of Mars

AbstractMartian meteorites are the only direct samples from Mars, thus far. Currently, there are a total of 262 individual samples originating from at least 11 ejection events. Geochemical analyses, through techniques that are also used on terrestrial rocks, provide fundamental insights into the bulk composition, differentiation and evolution, mantle heterogeneity, and role of secondary processes, such as aqueous alteration and shock, on Mars. Martian meteorites display a wide range in mineralogy and chemistry, but are predominantly basaltic in composition. Over the past 6 years, the number of martian meteorites recovered has almost doubled allowing for studies that evaluate these meteorites as suites of igneous rocks. However, the martian meteorites represent a biased sampling of the surface of Mars with unknown ejection locations. The geology of Mars cannot be unraveled solely by analyzing these meteorites. Rocks analyzed by rovers on the surface of Mars are of distinct composition to the meteorites, highlighting the importance of Mars missions, especially sample return. The Mars 2020 Perseverance rover will collect and cache—for eventual return to Earth—over 30 diverse surface samples from Jezero crater. These returned samples will allow for Earth‐based state‐of‐the‐art analyses on diverse martian rocks with known field context. The complementary study of returned samples and meteorites will help to constrain the evolution of the martian interior and surface. Here, we review recent findings and advances in the study of martian meteorites and examine how returned samples would complement and enhance our knowledge of Mars.

Volatile abundances and hydrogen isotope ratios of apatite in Martian basaltic breccia NWA 11522—A paired stone of NWA 7034

AbstractThis study aimed to determine the volatile content (Cl, F, OH) and hydrogen isotope (D/H) ratios of apatite grains within the Martian meteorite NWA 11522, a paired stone of the ungrouped polymict breccia NWA 7034. Apatite F:Cl:OH ratios were measured via SEM‐EDS analyses, and found to be strikingly similar in all grains, and dominated by Cl. Apatite D/H ratios were measured in situ via the Cameca ims 1280 SIMS at the University of Hawai'i. Results varied between δDvalues of 782 and 52 ‰ and between water contents of 0.127 and 0.510 wt%. The data form a mixing line between two endmembers. The first endmember, a high D/H ratio and low water content endmember, represents a fluid present during the thermal event that lithified the breccia at 1.5 Ga, resetting apatite volatile content, D/H ratio, and U‐Pb ages at this time. The D/H ratio of this fluid suggests that it was derived from the crust/cryosphere (e.g., melted groundwater ice). The second endmember, a low D/H ratio and high water content endmember, represents a second Martian fluid that interacted with the breccia after lithification. The low D/H ratio of this later fluid indicates it was derived from the deeper Martian interior, and may be evidence of an impact‐related hydrothermal system on Mars during the Amazonian period. The presence of these fluids within NWA 11522 suggests that subsurface impact crater environments were still host to liquid water during the past 1.5 Ga on Mars, and still could be to this day.

Vanadium micro-XANES determination of oxygen fugacity in olivine-hosted glass inclusion and groundmass glasses of martian primitive shergottite Yamato 980459

Abstract The redox condition of magma determines the stability and composition of crystallizing and volatile phases in martian meteorites, reflecting the evolution of the martian interior. In the current study, direct analyses on the oxidation states of V, Cr, and Fe were performed based on the X-ray absorption near-edge structure (XANES) measurements equipped with a micro-sized X-ray beam. We first applied the micro-XANES (μ-XANES) technique to the olivine-hosted glass inclusion and groundmass glass of martian meteorite Yamato 980459 (Y98), which is interpreted as representing a primary melt composition. Mass-balance calculations and XANES spectra comparisons indicated that, while chromite and pyroxene affected Cr and Fe K-edge XANES spectra, the contribution of these minerals was minimal for V. The pre-edge peak intensity of V K-edge XANES enabled the estimation of the oxygen fugacity for inclusion and groundmass glasses. The calculated oxygen fugacity (fO2) of the glass inclusions was near the Iron-Wüstite (IW) buffer (IW-0.07 ± 0.32) for the glass inclusion, whereas it was 0.9 log units more oxidized (IW+0.93 ± 0.56) for the groundmass glasses. This result suggests that the redox condition of the parent magma of Y98 evolved during magma ascent and emplacement. Since Y98 is interpreted to have evolved in a closed system, our finding suggests that fractional crystallization and/or ascent of magma potentially induces the fO2 increase. This study shows that the μ-XANES technique enables us to determine the fO2 by only measuring a single phase of glassy compounds, and thus, it is useful to discuss the redox condition of volcanic rocks even if they do not crystallize out several equilibrium phases of minerals.