Ákos Kereszturi’s research while affiliated with Eötvös Loránd University and other places

Identifying surface sites with significant astrobiological potential on Mars requires a comprehensive understanding of past geological processes and conditions there, including the shallow subsurface region. Numerical modelling could distinguish between regions dominated by erosion and those characterized by sediment accumulation in ancient wet environments. The target area of Jezero Crater is relatively well explored and thus is an ideal site to evaluate model calculations; however, important works are still missing on expectations related to its shallow subsurface . In this work, the best available approaches were followed, and only surface morphology was considered (supposedly formed by the last fluvial episode). The shallow subsurface became an important target recently, and this model could provide new inputs in this area. Erosion–accumulation models are suitable for terrestrial surface features, but few have been applied to Mars. This work addresses this challenge using the SIMWE (SIMulated Water Erosion) model on the Jezero Crater delta, the landing site of the Perseverance rover. For calculations, the average grain size according to the THEMIS TI data was applied to the target area. The flow depth varied between 1.89 and 34.74 m (average of 12.66 m). The water-filled channel width ranged from 35.3 to 341.42 m. A flow velocity of 0.008–11.6 m/s, a maximum erosion rate of 5.98 g/m²/h, and a deposition 4.07 g/m²/h were estimated. These calculated values are close to the range of estimations from other authors assuming precipitation of 1–20 mm/h and discharges of 60–400 m³/s. The model was able to distinguish between erosion- and accumulation-dominated areas about 1 m above Jezero Crater’s delta that are not visible from above. This model helps to identify the accumulation-dominated areas with the finest grain size with good preservation capability for the shallow but invisible subsurface.

A model-based surface fluvial erosion and deposition approach was adapted to Martian conditions to forecast the potential locations for shallow subsurface sampling by the Rosalind Franklin ExoMars rover at Oxia Planum. While remote and on-site images show only the surface visible features, former fluvial-related accumulation sites might be hidden. During the fluvial activity, most accumulation-related areas are interesting with regard to clay-like sediments, which could adsorb organics effectively-such sites could be identified by modeling. By applying the SIMWE fluvial erosion/deposition model, substantial variability in accumulation and deposition-dominated areas with their specific pattern and spatial distribution could be outlined, indicating that sophisticated targeting of future sampling could use such a model-based approach. At the main valley-like feature, former water flow tracks were identified, as well as deposition-dominated locations, which are the best targets for shallow subsurface sampling. Joint evaluation of safety aspects like slope angle and loose sand dunes with scientific aspects provide the best sampling locations. Such model-based targeting is important as by using only orbital images, these locations could not be identified.

A medium‐grade, poorly weathered CO3‐type meteorite was subjected to artificial space weathering by 1 keV protons in three subsequent steps, with gradually increasing doses from 10 ¹¹ to 10 ¹⁷ protons per cm ² . The resulting mineral modifications were identified by Raman spectroscopy, with specific emphasis on main minerals such as olivine (bands: 817, 845 cm ⁻¹ ), pyroxene (1007 cm ⁻¹ ), and partly amorphous feldspar (509 cm ⁻¹ ), considering variation in band shift and bandwidth (full width at half maximum, FWHM). After the first and second irradiations, variable band position changes were observed, probably from metastable alterations by Mg loss of the minerals, while the third stronger irradiation showed band shift dominated by amorphization. The olivine and pyroxene show weak increase in FWHM after the first irradiation, while more changes happened after the second and third irradiations. The flux after the third irradiation was higher than in other works, caused stronger damage in crystal lattice, partly resembling to dimerization as described by shock metamorphism. The glassy feldspar was characterized by high FWHM values already at the beginning, indicating weak crystallinity already that become even less crystallized, thus their bands disappeared after the third irradiation. Bands of hydrous minerals (goethite clay, chlorite) were not visible after the third irradiation, confirming some earlier results in the literature. Based on our results, moderately fresh surfaces could show stochastic but small spectral differences compared to the fresh most meteorites by metastable mineral alterations. The interpretation of Raman spectra of heavily space‐weathered surfaces could further benefit from the joint evaluation of alteration induced by both shock impact alteration and space weathering.

Raman and infrared measurements of the same locations were conducted on a northwest African (NWA) 10580 CO3 meteorite sample, before and after three proton irradiations (1 keV ion energy using 1011, 1014, and 1017 ion/cm2 fluent values), to simulate space weathering effects. In the case of Raman spectroscopy, both FWHM and peak positions of the major olivine and pyroxene bands changed after the irradiation, and the minor bands disappeared. In the FTIR spectra, the minor bands of olivine and pyroxene also disappeared; meanwhile, major IR bands of pyroxene remained visible, demonstrating both positive and negative peak shifts, and the olivines were characterised only by negative peak shifts. The olivines were characterised by negative FWHM changes for major bands, but positive FWHM changes for minor bands. The pyroxenes were characterised by elevated FWHM changes for minor bands after the irradiation. The disappearance of minor bands both of IR and Raman spectra indicates the amorphization of minerals. The negative peak shift in IR spectra indicates Mg loss for olivine and pyroxene, in agreement with the literature. The Raman spectra are characterised by positive peak shift and positive FWHM changes; the IR spectra are characterised by a negative peak shift. The Mg loss, which was detected by negative peak shifts of FTIR bands, may be caused by distortion of the crystal structure, which could be detected by a positive peak shift in Raman spectra. This joint observation and interpretation has not been formulated in the literature, but indicates further possibilities in the confirmation of mineral changes by different instruments. Shock alteration-based observations by other researchers could be used as a reference for irradiation experiments as irradiation makes a similar structural alteration, like a low-grade shock metamorphism.

Context . Identifying minerals on asteroid surfaces is difficult as space weathering modifies the minerals’ infrared spectra. This should be better understood for proper interpretation. Aims . We simulated the space weathering effects on a meteorite and recorded the alterations of the crystalline structure, such as the change in peak positions and full width at half maximum values. Methods . We used proton irradiation to simulate the effects of solar wind on a sample of NWA 10580 CO3 chondrite meteorites. After irradiation in three gradually increased steps with 1 keV ion energy, we used infrared microscopic reflectance and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to identify and understand the consequences of irradiation. Results . We find negative peak shifts after the first and second irradiations at pyroxene and feldspar minerals, similarly to the literature, and this shift was attributed to Mg loss. However, after the third irradiation a positive change in values in wavenumber emerged for silicates, which could come from the distortion of SiO 4 tetrahedra, resembling shock deformation. The full width at half maximum values of major bands show a positive (increasing) trend after irradiations in the case of feldspars, using IR reflection measurements. Comparing DRIFTS and reflection infrared data, the peak positions of major mineral bands were at similar wavenumbers, but differences can be observed in minor bands. Conclusions . We measured the spectral changes of meteorite minerals after high doses of proton irradiation for several minerals. We show the first of these measurements for feldspars; previous works only presented pyroxene, olivine, and phyllosilicates.

Robotic and manned exploration of the Moon is the next target in Solar System exploration. The availability of in situ resources such as water ice, iron oxides, helium-3, and rare earth elements, combined with permanently sunlit areas, provides the opportunity for the first settlement, either human or robotic, on the Moon. We used several selection criteria (abundance of water ice, the slope of terrain, usable energy sources, communications, and base expandability) to identify a suitable area for a future base in the southern polar crater Sverdrup-Henson. Due to the higher abundance of water ice, we found that the Sverdrup-Henson site is better suited to host a base than the nearby craters de Gerlache and Shackleton. The crater floor is partly in permanent shadow and exhibits numerous signatures of water ice. Since water ice is essential for rocket fuel production and human survival, its presence is necessary for a first settlement. Sverdrup-Henson has a flat floor ideal for building and safe traversing, is accessible from the surrounding intercrater plains, and has nearby locations suitable for communications and solar power production. Thus, the Sverdrup-Henson site holds great potential for future missions. We propose further exploration of this area through in situ measurements to better constrain available resources.

More and more attention is devoted to the icy moons of the Solar System, including Europa, the second Galilean satellite of Jupiter, since the discovery of potential liquid water and the possibility of extra-terrestrial life harbored in its subsurface ocean below its icy crust. Along with the renaissance of the study of icy satellites, the ongoing missions, such as Europa Clipper and JUICE (JUpiter ICy moons Explorer), are also part of such rejuvenation of icy satellite research. One of the leading research topics connected to Europa is understanding its surface renewal, including the interaction between the subsurface ocean and the icy crust. One of the longest-lasting and still unsettled debates related to Europa is about the nature of the potentially active cryovolcanism, which may play an essential role in the interaction between the surface of the Jovian moon and the underlying subsurface ocean. Our study focuses on the geological-geomorphological characterization of a newly identified putative cryovolcanic field found on the surface of Europa. Various volcanic structures, possibly in multiple stages of maturity, were identified. The executed geological analysis in the surroundings of the volcanoes suggests strong local influence during the formation of cryovolcanic cones working together with the overall global-scale stress fields appearing in the ice crust of Europa.