The Cassini-Huygens mission detected large negative ions in Titan's ionosphere at pressures as low as 10-6 Torr. These ions ultimately polymerize to form Titan's complex organic haze particles, which are observed throughout the atmosphere and potentially on the surface. Laboratory analogs of these hazes, known as tholins, have been used to study Titan's aerosols; however, most are produced at much higher pressures. The influence of formation pressures on key physical properties-such as particle size, density, surface energy, and mechanical strength-remains poorly constrained. These properties govern the haze's aggregation efficiency, radiative behavior, and surface-atmosphere interactions, shaping Titan's climate and surface. To investigate the effects of formation pressure, we generate tholins using a newly developed cold plasma discharge system. A 95% nitrogen and 5% methane gas mixture is exposed to plasma at two pressures, 1 Torr and 0.125 Torr. For both samples, we measure the production rate, particle size, morphology, density, surface free energy, Young's modulus, and nanoindentation hardness. While particle size, morphology, surface energy, and Young's modulus are similar across both pressures, tholins produced at lower pressure exhibited a threefold lower production rate, but a higher density and nanoindentation hardness. These variations likely reflect pressure-dependent changes in chemical structure, porosity, and mechanical strength. Because Titan's hazes form at much lower pressures than investigated here, actual haze particles are potentially even denser and mechanically stronger than our analogs, with implications for aerosol aggregation, aeolian and fluvial transport, and surface modification on Titan.

Lava tubes are potentially important sites for the long-term human presence on the Moon because they provide shelter from surface hazards, including micrometeorites, radiation, extreme temperatures, and dust. The discovery of a lava tube opening or pit at Marius Hills in Oceanus Procellarum is compelling motivation for robotic and eventually human exploration missions to these sites for in situ investigations and site assessments to determine viability for habitation and utilization of lunar resources. We make the case for Marius Hills to be a high-priority landing site and present elements of lunar data analysis, instrument/payload concepts, science justification for robotic missions, and thematic geologic reconnaissance and remote sensing that should be conducted prior to any construction or emplacement of infrastructure. This is described as a "green reconnaissance" approach to lunar exploration and exploitation, which seeks to address such contamination factors as sprayed rocket exhaust and sublimating water in order to preserve science fidelity. We are developing a concept of operations called the Leto mission for a green reconnaissance approach to robotically access the Marius Hills sublunarean void.

We report new measurements of the far-ultraviolet (FUV) bidirectional reflectance of Apollo soil 10084 from the Southwest Research Institute ultraviolet reflectance chamber. The bidirectional reflectance distribution function of this mare soil, enriched in Ti and Fe content, is rather featureless in the FUV wavelength region of 115-180nm, except for a small blue slope, which is attributed to the effects of space weathering. This soil preferentially backscatters FUV photons as indicated by the angular distribution of the bidirectional reflectance. The phase curves are fitted with a simplified Hapke photometric model to derive the average volume single scattering albedo and scattering phase function of the mare lunar grains. The albedo values and the backscattering nature reported here are consistent with Lunar Reconnaissance Orbiter's Lyman-Alpha Mapping Project ultraviolet imaging spectrograph observations, despite expected morphological differences. Plain Language Summary We characterize the reflective properties of Apollo soil 10084 in the far ultraviolet (115-200nm). This is a mare soil retrieved by the Apollo 11 mission from the Mare Tranquillitatis region of the Moon. We have obtained laboratory reflectance spectra of soil 10084, which reveals that the soil is dark (low albedo) in the far-ultraviolet. Furthermore, the spectra are rather featureless but present a blue slope; that is, they reflect more light at shorter wavelengths. This blue slope is caused by the nanophase Fe present in the exterior rims of the soil. This nanophase Fe is generated by reduction of native iron oxide by solar wind and micrometeorites. The soil is also an efficient backscatterer; it reflects more light in the direction of incidence. The laboratory data are in reasonable agreement with measurements made by the Lyman-Alpha Mapping Project instrument, a far-ultraviolet imaging spectrograph onboard the Lunar Reconaissance Orbiter.

Introduction: Lunar reflectance spectra obtained by LRO-LAMP [1, 2] and previously by Apollo 17 ultraviolet spectrometer [3] were spectrally blue with higher albedo reported towards shorter wavelengths. This spectral bluing has been attributed mainly to the presence of nanophase Fe (npFe) in the exterior rims of lunar grains formed as a result of micrometeorite and solar wind space weathering [3]. Less weathered fresh crater ejecta [1] and swirls regions [2] are spectrally flatter or redder compared to surrounding mature regions. The blue slope is also corroborated by laboratory measurements of lunar soils returned by the Apollo missions [4], including our recent effort [5]. In addition to the Apollo soil 10084, we also measured the far-ultraviolet spectra of lunar simulant JSC1A, which surprisingly exhibited a blue slope. The JSC-1A simulant resembles the lunar soil in its chemical composition but lacks space-weathering derived traits such as agglutinates and npFe [6]. This preliminary dataset warrants additional investigation to the origin of the blue slope in the far-ultraviolet spectra of lunar soils. What other factors, besides npFe, contribute the observed spectral bluing? Experimental Setup: The bidirectional reflectance measurements of the Apollo soil and JSC-1A lunar simulant samples were conducted in the Southwest Ultraviolet Reflectance Chamber (SwURC), a highvacuum ultraviolet reflectance chamber [7]. Apollo soil 10084 was obtained from the Curation and Analysis Planning Team for Extraterrestrial Materials (CAPTEM), while the lunar simulant JSC-1A was sourced from Orbital Technology Corporation (ORBITEC). The average grain size of both samples is ~ 50 μm [8, 9]. In the SwURC system, a 30 W deuterium lamp feeds a grating monochromator which provides monochromatic light that is collimated with a pair of reflective cylindrical mirrors, prior to illuminating the samples at a fixed 45° incidence. A channeltron detector (Photonis 5901 Spiraltron, CsI-coated) is rotated in the principal plane over emission angles of -70° to + 75° with respect to the surface normal to collect diffuse light Pr over 115-180 nm reflected by the lunar soil and the simulant placed on the sample tray. Further, we also measure the incident beam intensity Pi by retracting the sample tray and directly intercepting the beam with the detector positioned at 135°. The absolute bidirectional distribution function is given by ( ) ( ) [ cos( 45 )] r r BRDF r i d P f P θ θ = − Ω  , where Ωd is the

Long term settlement of lunar or Mars caves or subsurface features on planetary bodies where large pit openings exist provide an opportunity to substantially increase livable volume areas and allow inhabitants freedom from confines of living in modules or enclosed in a cave environment. Various studies centered on enclosing a lunar skylight pit with a pressurized dome are under investigation by the authors. An intuitive approach of merely placing a dome cap over the skylight pit is fraught with a number of issues. Accomplishing this in a practical fashion without having the seal independent of the regolith surface is a challenge for understanding the porosity of the lunar regolith along the pit walls and outer rim of the pit. Not least among these issues is prevention of the regolith from consuming too much gas and never reaching an equilibrium pressure. Essentially, what happens to gas pumped into the dome? How much of it will simply pass into the surrounding desiccated regolith? How much of this valuable atmospheric resource will simply diffuse away into the skylight walls? Lunar regolith porosity studies investigate various challenges associated with pressurizing a large porous geologic feature.