Establishing robust environmental proxies at newly investigated terrestrial sedimentary archives is a challenge, because straightforward climate reconstructions can be hampered by the complex relationship between climate parameters and sediment composition, proxy preservation or (in)sufficient sample material. We present a minimally invasive hyperspectral bidirectional reflectance analysis on discrete samples in the wavelength range from 0.25 to 17 µm on 35 lacustrine sediment core samples from the Chew Bahir Basin, southern Ethiopia for climate proxy studies. We identified and used absorption bands at 2.2 μm (Al–OH), at 2.3 μm (Mg–OH), at 1.16 μm (analcime), and at 3.98 μm (calcite) for quantitative spectral analysis. The band depth ratios at 2.3/2.2 μm in the spectra correlate with variations in the potassium content of the sediment samples, which also reflect periods of increased Al-to-Mg substitution in clay minerals during drier climatic episodes. During these episodes of drier conditions, absorption bands diagnostic of the presence of analcime and calcite support this interpretation, with analcime indicating the driest conditions. These results could be compared to qualitative analysis of other characteristic spectral properties in the spectral range between 0.25 and 17 µm. The results of the hyperspectral measurements complement previous sedimentological and geochemical analyses, allowing us in particular to resolve more finely the processes of weathering in the catchment and low-temperature authigenic processes in the sediment. This enables us to better understand environmental changes in the habitat of early humans.

The Mars Exploration Program Analysis Group has identified measurements of the state and the variability of the Martian atmosphere as high priority investigations for the upcoming years. Balloon-borne instruments could bridge the gap in both temporal and spatial resolution in mesoscale distances between local, stationary landers and global orbiter observations. The idea to use a balloon system for such a purpose is not new in essence and has been proposed already in past decades. While those concepts considered an aerial deployment during entry and descent, the concept outlined in this study revisits a launch off the payload deck of a lander from the Martian surface. This deployment option profits today mainly from the technological advance in micro-electronics and sensor miniaturization, which enables the design of a balloon-probe significantly smaller than earlier proposed systems. This paper presents the feasibility assessment for this instrument and gives further details on the scientific and operational concept, a strawman sensor suite, its system components and the associated size and budget estimates. It is complemented by the analysis scheme proposed to assess, manage and mitigate the deployment risk involved in automatically launching such a balloon-system off a planetary surface.

Introduction The MErcury Radiometer and Thermal Infrared Spectrometer (MERTIS) onboard BepiColombo is designed to study and map Mercury surface mineralogy and temperatures. It combines an imaging push-broom infrared spectrometer (TIS, 7-14 µm) with a radiometer (TIR, 7-40 µm) that share the same in-flight optics, electronics, and calibration unit [1]. During the two Venus flybys of BepiColombo spacecraft in October 2020 and August 2021, MERTIS-TIS acquired several hundred thousand spectra in the mid-infrared range with spectral resolution down to 90 nm [2, 3, 4]. The MERTIS measurements were the first spectrally resolved observations of Venus in the mid-IR range since the Venera 15 mission in 1983 [8]. We report on the results of MERTIS mid IR measurements and show average brightness temperature spectra. Basing on a multi-channel radiative transfer simulation and retrieval algorithm we extract atmospheric temperature profiles and cloud parameters of Venus’ upper troposphere and mesosphere. Method A multi-channel radiative transfer simulation and retrieval algorithm has been adapted to investigate MERTIS-TIS data and to extract atmospheric temperature altitude profiles and cloud mode factors MF1/2 of Venus’ atmosphere. The Radiative Transfer Model (RTM) includes the discrete ordinate package DISORT [5]. It considers absorption, emission, and multiple scattering by gaseous and particulate atmospheric constituents and makes simultaneous use of information from different spectral ranges of an individual spectrum [6,7]. Mesospheric temperature profiles are retrieved using Smith’s relaxation method [8]. It employs initial and measured brightness temperatures in the 15 µm CO2 band. The results of the MERTIS measurements were compared with mid-infrared data recorded by the FS-1/4 spectrometer (PMV) aboard the Venera-15 mission in 1983 [8]. Results We show that Venusian mesospheric parameters like temperature profiles and cloud properties can reliable determined from MERTIS flyby data (Fig. A). The short-wave edge of the 15-µm CO2 band was used to determine atmospheric temperature profiles in an altitude range of about 58-77 km (Fig. B). The retrieved temperature profiles well agree both with VIRA [9] and corresponding profiles obtained from Venera 15 PMV data.  Atmospheric cloud factors were investigated from MERTIS spectral data around 10 µm. They are also well coinciding with earlier analyses.   Still ongoing refinements of calibration will allow the use of data between 7 and 10 μm for the analysis of further atmospheric properties. Fig. MERTIS-TIS FB2, A: Comparison of measured and simulated MERTIS brightness temperature spectra, B: Comparison of initial and retrieved temperature profiles.   References [1] Hiesinger, H. and Helbert, J., Planet. Space Sci. 58, (2010). [2] Maturilli, A., et al., 52nd LPSC, 1435, (2021). [3] Helbert, H., et al., 52nd LPSC, 1521, (2021). [4] Arnold, G., et al., SPIE Optics+Photonics, IR Remote Sensing and Instrumentation XXIX, 1183009, (2021). [5] Stamnes, K. et al., Appl.Opt. (12), 2502-2509, (1988). [6] Haus, R., Kappel, D., Arnold, G., Icarus 232C, 232-248, (2014) [7] Haus, R., Kappel, D., Arnold, G., Planet. Space Sci. 89, 77-101, (2013). [8] Smith, W.L., Appl. Opt.9(9), 1993-1999, (1970). [8] Oertel, R. et al., Adv. Space Res. 5(9), 25-36, (1985). [9] Zasova, L.V. et al., Cosmic Res. 44(4), 364-383, (2006).