Space Research Institute

Because of Mercury’s close orbital position to the Sun and its low mass, the planet cannot retain a dense atmosphere and instead possesses an exosphere. The gaseous species detected so far - such as H, (Mariner 10, MESSENGER), He (Mariner 10, MESSENGER, BepiColombo flyby), (possibly) O (Mariner 10), Na, K, Ca (ground-based and MESSENGER), Mg (MESSENGER), and Li and H2 (inferred from MESSENGER magnetic field data) - yield a column content in the order of about 1012 cm−2, which is lower than the expected column content of an exosphere which is in the order of about 1014 cm−2. In addition to these elements, MESSENGER’s FIPS instrument also detected C, OH, H2O, Ne, Al, Si, O2, Ar, CO2, Ti, and Fe ions at the downstream of Mercury. Atmospheric measurements from the Mariner 10 occultation experiment indicate that the electron density near the planet's surface is less than 103 cm-3 on both sides of the planet, implying an upper limit to the dayside surface gas number density of about 106 cm-3. The observed elements are expected to represent only a small fraction of Mercury’s exosphere, as the total surface pressure contributed by these known species is far lower than the upper limit for the exospheric surface pressure of 10-11 - 10-12 bar. While H and He appear to originate from the solar wind (i.e., thermal release of implanted solar wind ions), heavier elements are sourced from the planet’s regolith and may be delivered by meteoroids of various sizes. In this study, we investigate the role of meteoroids and their contribution to the elemental input on Mercury's surface and exosphere. We also discuss the potential effects of meteoritic material on the volatile components of the planet's surface composition and examine which currently undetected elements, potentially delivered from meteoroids, may contribute to the still-unknown surface pressure.

In this study we investigate intermittent phenomena in VLF/LF electric fields and particle outbursts caused by solar activity fluctuations and affecting principally the Earth’s ionosphere. Strong events from the current solar cycle 25, e.g., x-ray flares, generate electric field amplitude and phase variations occurring on the ray-path between the VLF/LF transmitter stations and the reception facilities. These variations in the sub-ionospheric waveguide, with the lower ionosphere as upper boundary (D/E-layer during day/night), are complementary to secondary cosmic ray data measured by ground-based (muon) detectors. VLF/LF measurements are from the European INFREP receiver network and muon particle observations are collected from the Belgrade detector in Serbia. With the combined observation sets we analyze and characterize single events and corresponding statistical parameters. The study benefits from continuous ground based long-term measurements and the multi-parameter approach using complementary instrumentations.

Venus lacks an intrinsic magnetic field, and its induced magnetosphere differs significantly from Earth's stable dipolar magnetic field. Although magnetic reconnection was detected in the near Venusian magnetotail, the drivers and impacts of magnetic reconnection at Venus remain poorly understood. In this study, we present the global magnetohydrodynamic simulation of Venusian magnetotail reconnection. The results reproduce characteristic reconnection signatures in the Venusian magnetotail and delineate the formation of three-dimensional magnetic structures consistent with reconnection topologies. We demonstrate that reconnection is triggered by the compression of the draped interplanetary magnetic field following an interplanetary shock, a mechanism previously associated with terrestrial dynamics. We further explore the roles of velocity, density and magnetic field of the solar wind in this process. This work highlights new insights into magnetic reconnection in unmagnetized plasma environments.

Auroral arcs in the high latitude are frequently observed during periods of northward interplanetary magnetic field (IMF). However, their generation mechanisms are not yet fully understood, due to the limited availability of simultaneous in-situ and optical auroral observations. In this talk, we present observations of recurrent tailward-propagating auroral arcs in the dawnside during a period of northward IMF. THEMIS satellites located near the dawnside magnetopause in the equatorial plane observed strong fluctuations in magnetic field and plasma parameters with periods of 5–7 minutes, suggesting the presence of surface waves or ULF waves. Subsequently, shorter-period fluctuations of 2-3 minutes were observed for an hour, which may indicate the development of Kelvin–Helmholtz instability (KHI). During these intervals, a ground-based all-sky imager detected recurrent auroral arcs detached from the poleward boundary of the auroral oval, with a period of 5–10 minutes, propagating predominantly tailward. DMSP observations revealed multiple auroral arcs on the dawnside, accompanied by electron precipitation associated with paired upward and downward field-aligned currents. Based on these coordinated space- and ground-based observations, we discuss several possible generation mechanisms for the observed auroral arcs, including surface waves, ULF waves, and KHI.

The early evolution of the atmospheres of Venus, Earth, and Mars, and hence their potential habitability, is strongly linked to the early evolution of the Sun, which was significantly more active during the first ~1 billion years than it is at present. The high solar X-ray and extreme ultraviolet (XUV) surface flux received by the three planets during this time heated their upper atmospheres, inducing thermal and non-thermal atmospheric escape rates that are assumed to be significantly higher than at present. However, whether an atmosphere is stable against escape into space depends not only on the incident solar/stellar XUV surface flux but also on planetary size and atmospheric composition. CO2 and other infrared coolants, for instance, cool the thermosphere, making atmospheres with larger CO2 mixing ratios less susceptible to atmospheric erosion. This implies that atmospheres with certain compositions (e.g., CO2-dominated atmospheres) were more likely to survive the harsh conditions of the early Solar System than others (e.g., N2-dominated atmospheres). This, in turn, has implications for prebiotic chemistry and the origin of life since different atmospheric compositions, but also the therewith connected tropospheric temperature and the hydrology of a planet, further affect the photochemical production and rainout of prebiotic molecules into ancient oceans or shallow ponds. This highlights the importance of considering both the upper atmosphere/thermosphere to evaluate atmospheric stability and the lower atmosphere/homosphere to evaluate prebiotic chemistry and climatic conditions if we want to better understand the habitability and evolution of the rocky planets in the Solar System and beyond. We first discuss atmospheric stability on early Venus, Earth, and Mars and investigate the atmospheric compositions needed for the three planets to host stable atmospheres. By investigating the photochemical production and rainout of prebiotic molecules (with a focus on formaldehyde) within thermally stable atmospheres, we finally assess the prebiotic potential and early habitability of the three planets.

This study presents a comprehensive statistical comparison of solar wind measurements between the OMNI database (collected at L1 and shifted to the Earth's bow shock nose), and near-Earth solar wind observations from MMS, Cluster, and THEMIS missions near the bow shock nose. Using a threshold-based classification methodology, the analysis encompasses approximately 353 days (MMS), 283 days (Cluster), and 125 days (THEMIS) of solar wind intervals that are compared to OMNI data. Bisector regression analysis reveals that the anti-sunward flow component (Vx) demonstrates exceptional agreement across all missions with near-unity slopes and correlation coefficients of 0.92 for THEMIS and 0.97 for both MMS and Cluster. However, perpendicular velocity components show progressively degraded performance: Vy exhibits correlation coefficients of 0.63-0.77 with intercepts ranging from 21.57 km/s (MMS) to 47.49 km/s (THEMIS), while Vz shows lower correlations (0.42-0.72) with intercepts of 4.73-11.94 km/s. Ion density measurements reveal systematic mission-specific biases: MMS and THEMIS show ion density regression slopes below unity (0.59 and 0.54, respectively), while Cluster shows a slope above unity (1.14) compared to OMNI measurements. Magnetic field measurements show higher consistency, with near-unity slopes and correlation coefficients exceeding 0.84 for Bx and By components. The northward magnetic field component (Bz) exhibits elevated variance ratios and reduced correlations across all missions, reaching as low as 0.74 for THEMIS. These results quantify inherent uncertainties in cross-platform solar wind comparisons and assess the accuracy of time-shifted solar wind measurements in the OMNI database as proxies for near-Earth conditions. Based on the presented statistics, OMNI-equivalent measurements from near-Earth missions can be generated as alternative data sources to support the upcoming SMILE mission, multispacecraft studies, and magnetohydrodynamic simulations that require accurate upstream boundary conditions.

Abstract We present a nine‐Martian‐year survey (MY 28–MY 36) of solar occultation measurements taken by the SPICAM IR spectrometer on Mars Express to chart the seasonal and spatial variations of dust and water ice in the atmosphere. Total aerosol extinction profiles demonstrate significant seasonal variations, reaching up to 80 km during perihelion and 40 km during aphelion. However, from profiles in the 1–1.7 μm range, we cannot distinguish between dust and water ice. We attribute these two types of aerosols in SPICAM profiles using Mars Climate Sounder (MCS) data from the Mars Reconnaissance Orbiter, water vapor data from SPICAM, and general circulation model (GCM) predictions. We validate the attribution against simultaneous aerosol measurements from the Atmospheric Chemistry Suite on the Trace Gas Orbiter. The retrieved effective radius of dust ranges from 0.3 to 1 μm and the number density ranges from ≤0.1 to 10 cm −3 , slightly depending on seasons. The effective radius of water ice varies from 0.1 to 3 μm with a number density ranging from 0.1 to 100 cm −3 . High‐altitude mesospheric clouds were detected at 70–90 km during global and regional dust events. Polar hood clouds were characterized by an optical depth above 0.1, small particle sizes (0.2–1.2 μm in effective radius), and a number density greater than 5 cm −3 . SPICAM's mass mixing ratio of both water ice and dust is consistent with MCS and GCM values, except during perihelion and C‐storm occurrences, when the model underestimates them.

Abstract The Magnetospheric Multiscale (MMS) mission's extended phase introduced an “unbiased campaign” that provided the first high‐resolution data set of the terrestrial magnetosheath obtained without human selection, across complete crossings from the bow shock to the magnetopause. This is achieved by collecting 3 min of burst‐mode data every 9 min. Leveraging this novel data set, we report average plasma parameters and observe the emergence of a range in the magnetic field power spectrum. A distinct ordering of both bulk and turbulence quantities is demonstrated when the Alfvénic Mach number is used as a proxy for the distance from the bow shock. This ordering enables us to obtain clear insights into the occurrence of small‐scale current sheets throughout the magnetosheath by evaluating magnetic field kurtosis. Furthermore, the evolution of the correlation time is opposite to that of kurtosis and aligns with the principle of turbulence relaxation. This information is dispersed when quantities are sorted by geocentric distance. Crucially, striking differences emerge in turbulence‐related quantities when comparing unsupervised and supervised data sets. These findings provide valuable insights into magnetospheric turbulence, establishing the campaign as a critical resource for unbiased statistical analysis of this environment.

ABSTRACT The evolutionary classification of molecular clumps, crucial for understanding star formation, is commonly based on human-assigned categories derived from infrared (IR) emission and well-established morphological criteria. However, due to ambiguous signatures, distance uncertainties or heavily obscured IR emission, a significant fraction of sources often remains unclassified. This work demonstrates the capability of machine learning (ML) as a complementary, data-driven approach to automate the identification and classification of these clumps using data from the MALT90 survey, complemented by Spitzer IR photometry. We applied unsupervised clustering with HDBSCAN on molecular line intensities, revealing distinct groupings that correspond to evolutionary stages. Using only five molecular lines (HCO$^+$, HNC, N$_2$H$^+$, HCN, C$_2$H), we identified stable clusters of protostars and regions without active star formation, driven primarily by C$_2$H and N$_2$H$^+$ emission. Incorporating H$^{13}$CO$^+$ gave rise to a distinct UV-dominant cluster, tracing more evolved regions. Infrared properties appeared as non-significant features implying that envelopes of clumps with different masses are similar in their global infrared characteristics. We then employed supervised learning to classify clumps with previously uncertain categories and provided classifications for 522 objects, predominantly as regions without active star formation. Our results show that ML techniques can effectively uncover intrinsic evolutionary structures in complex astrochemical data and assign categories to uncertain sources, providing a powerful, data-driven complement to traditional methods.

Abstract Introduction The inclusion of Indigenous Peoples and Local Communities (IPLCs) in Forest Landscape Restoration (FLR) is central to international agendas. Yet, the understanding of how national frameworks operationalize this principle through concrete mechanisms for IPLC participation and rights recognition remains limited. Mexico exemplifies this issue: despite 60% of forests under community management and commitments to restore 8.4 million hectares by 2030, very few restoration projects report meaningful community involvement. Objectives This study determines: (1) the extent to which existing policies align with core FLR principles; (2) how these policies incorporate mechanisms for meaningful IPLC inclusion and rights recognition; and (3) what barriers and opportunities constrain or facilitate policy translation into practice. Methods We assessed 24 Mexican policies (1988–2024) using two complementary indices: an FLR alignment index measuring adherence to eight core restoration principles, and an IPLC inclusion index ranging from exclusion to full autonomy in decision‐making. We followed these with a thematic analysis of policy content to identify barriers and opportunities constraining or facilitating policy‐to‐practice translation. Results Policies demonstrated strong alignment with FLR principles: landscape focus, ecological functionality, multiple benefits, and local adaptation. However, although all policies recognized stakeholder involvement in principle, IPLC inclusion in decision‐making remained severely constrained: only four documents positioned IPLCs as equal collaborators, one granted community leadership, and one provided full autonomy. Conclusions Mexican restoration policy recognizes FLR principles but lacks institutional mechanisms to operationalize meaningful IPLC participation. This gap between international standards and national implementation reflects deeper institutional and governance constraints, underscoring the need for structural changes for equitable and effective restoration.