^1,2Claire I. O. Nichols,²James F.J. Bryson,³Rory D. Cottrell,⁴Roger R. Fu,¹Richard J. Harrison,^5,6Julia Herrero-Albillos,⁷Florian Kronast,³John A. Tarduno,⁴Benjamin P. Weiss
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006900]
¹Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Insitute of Technology, Cambridge, MA, 02139 USA
²Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN UK
³Department of Earth and Environmental Sciences, University of Rochester, NY, 14627 USA
⁴Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
⁵Centro Universitario de la Defensa, Carretera de Huesca s/n, E-50090 Zaragoza, Spain
⁶Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC—Universidad de Zaragoza, Zaragoza, 50009 Spain
⁷Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
Copyright Elsevier

Several paleomagnetic studies have been conducted on five main group pallasites: Brenham, Marjalahti, Springwater, Imilac and Esquel. These pallasites have distinct cooling histories, meaning that their paleomagnetic records may have been acquired at different times during the thermal evolution of their parent body. Here we compile new and existing data to present the most complete time-resolved paleomagnetic record for a planetesimal, which includes a period of quiescence prior to core solidification as well as dynamo activity generated by compositional convection during core solidification. We present new paleomagnetic data for the Springwater pallasite, which constrains the timing of core solidification. Our results suggest that in order to generate the observed strong paleointensities ( ∼ 65 – 95 μT), the pallasites must have been relatively close to the dynamo source. Our thermal and dynamo models predict that the main group pallasites originate from a planetesimal with a large core (> 200 km) and a thin mantle (< 70 km).

¹M.Grott et al. (>10)
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2021JE006861]
¹German Aerospace Center (DLR), Institute of Planetary Research, Berlin, Germany
Published by arrangment with John Wiley & Sons

The heat flow and physical properties package (HP³) of the InSight Mars mission is an instrument package designed to determine the martian planetary heat flow. To this end, the package was designed to emplace sensors into the martian subsurface and measure the thermal conductivity as well as the geothermal gradient in the 0-5 m depth range. After emplacing the probe to a tip depth of 0.37 m, a first reliable measurement of the average soil thermal conductivity in the 0.03 to 0.37 m depth range was performed. Using the HP³ mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 ± 0.002 W m⁻¹ K⁻¹, consistent with the results of orbital and in-situ thermal inertia estimates. This low thermal conductivity implies that 85 to 95 % of all particles are smaller than 104-173 μm and suggests that soil cementation is minimal, contrary to the considerable degree of cementation suggested by image data. Rather, cementing agents like salts could be distributed in the form of grain coatings instead. Soil densities compatible with the measurements are  kg m⁻³, indicating soil porosities of  %.

¹G.Alemanno,¹A.Maturilli,¹M.D’Amore,¹J.Helbert
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114622]
¹Institute for Planetary Research, German Aerospace Center DLR, Rutherfordstr. 2, 12489 Berlin, Germany
Copyright Elsevier

New spectral orbital thermal infrared data of Mars are being acquired by the thermal infrared channel TIRVIM (in honor of Vassily Ivanovich Moroz) of the Atmospheric Chemistry Suite (ACS) of spectrometers on board of ExoMars2016 mission. TIRVIM encompasses the spectral range of 1.7–17 μm. A major challenge brought by the analysis of these data of planetary bodies with atmospheres is the ability to extract from the data the relevant information about the surface. Thus, laboratory work plays an essential role, providing end-member and mixture spectral data of planetary analogs to fit the orbital data by means of deconvolution techniques. At the Planetary Spectroscopy Laboratory (PSL) of the German Aerospace Center (DLR), we are performing new laboratory experiments on Martian analogs in order to provide a new and updated library of spectra optimized for the interpretation of TIRVIM data. Emissivity measurements, recorded at increasing temperatures, are coupled with reflectance measurements on fresh and thermally processed samples acquired between 1.7 and 17 μm. Building on measurements previously collected on Martian analogues, we have paid particular attention to the study of the spectral behaviour of mixtures of carbonates and phyllosilicates. The main goal of this analysis is to study the variation of the main carbonate spectral features in mixtures with a phyllosilicate component, an important factor for understanding the story of carbonates detections on planetary surfaces and to provide insights for new detections. The results obtained in this work show that the presence of a phyllosilicate component affect the appearance of the carbonate spectral features in the spectral range studied, with a stronger effect in the range between 1.7 and 5 μm. Effects of mineral type and particle size are also investigated and shown to strongly affect the spectral behaviour of laboratory samples. Finally, deconvolution techniques of laboratory emissivity spectra are studied in preparation for the interpretation of atmospherically corrected TIRVIM spectral data, showing that modelled mixtures spectra represent an acceptable reproduction of laboratory spectra of mixtures.