Lermontov crater on Mercury: Geology, morphology and spectral properties of the coexisting hollows and pyroclastic deposits

Abstract We present a multidisciplinary analysis of Lermontov crater, located at 15.24°N, −48.94°E in the Kuiper quadrangle of Mercury. By means of MESSENGER multiband MDIS-WAC and monochrome MDIS-NAC images, we prepare a high-resolution geological map of the crater and its closest surroundings, highlighting the presence of coexisting hollows and pyroclastic deposits on its floor. On the photometrically corrected MDIS-WAC multiband dataset, we apply an unsupervised clustering technique that spectrally separates the different materials located both inside and outside Lermontov crater. We observe that the pyroclastic deposits located on the crater's floor have a steep, red spectral behaviour dominated by the presence of a mixture of various pyroxenes containing Ti and Ni. On the contrary, the vents' rims are characterised by several hollows whose spectral slope is bluer than that of the pyroclastic deposits. By comparing the vent hollows to the hollows located farther out on the crater floor, we observe a steeper 0.62–0.82 μm spectral trend for those within the vents. The vent hollows' spectrum is more similar to the pyroclastic one in the above mentioned wavelength range. In addition, the vent hollows 0.55 μm absorption band could be related to CaS, while the small differences in slope at 0.48 μm and 0.62 μm could be due to the presence of other volatiles compounds, such as MgS or chlorides. When compared to hollows located in other hermean geological settings, Lermontov hollows are characterised by steeper spectra. This supports the interpretation that when hollows form, their bright deposits do not completely overwrite the spectral signature of the surrounding terrain, and their spectroscopic appearance is mixed with the composition of the terrain where they form

Multidisciplinary Analysis of Lermontov Crater on Mercury

We present the geological, age determination, and spectrophotometric analysis of the Lermontov Crater on Mercury

Spring Deposits and Lakeshore Layered Sediments Inside the Vernal Crater (SW Arabia Terra): A Resource-Rich and Engineering Safe Mars Human Landing Site

We here present the scientific rationale, the resource analysis and the engineering requirements evaluation performed on the Vernal crater and its closest surroundings in SW Arabia Terra, Mars, as a possible future human landing site

Mass movement reconstruction and boulder size-frequency distribution of the Simud Vallis landslide, Mars

International audienc

Change detection analyses using simulated and actual ExoMars TGO-CaSSIS images: A case study based on past and present Gasa Crater gully activity

International audienc

Modelling reconstruction and boulder size-frequency distribution of a young (<5 Myr) landslide located in Simud Vallis floor, Mars

International audienc

Lymphocyte migration and retention properties affected by ibrutibnib in chronic lymphocytic leukemia

International audienceThe Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib is widely used for treatment of patients with relapsed/refractory or treatment-naïve Chronic Lymphocytic Leukemia (CLL). A prominent effect of ibrutinib is to disrupt the retention of CLL cells from supportive lymphoid tissues, by altering BTK-dependent adhesion and migration. To further explore the mechanism of action of ibrutinib and its potential impact on non-leukemic cells, we quantified multiple motility and adhesion parameters of human primary CLL cells and non-leukemic lymphoid cells. In vitro, ibrutinib affected CCL19-, CXCL12- and CXCL13-evoked migration behavior of CLL cells and non-neoplastic lymphocytes, by reducing both motility speed and directionality. Dephosphorylation of BTK induced by ibrutinib in CLL cells was associated with defective polarization over fibronectin and inability to assemble the immunological synapse upon BCR engagement. In patient samples collected during a 6-month monitoring of therapy, chemokineevoked migration was repressed in CLL cells and marginally reduced in T cells. This was accompanied by profound modulation of the expression of chemokine receptors and adhesion molecules. Remarkably, the relative expression of the receptors governing lymph node entry (CCR7) versus exit (S1PR1) stood out as a reliable predictive marker of the clinically relevant treatment-induced lymphocytosis. Together, our data reveal a multifaceted modulation of motility and adhesive properties of ibrutinib on both CLL leukemic cell and T-cell populations and point to intrinsic differences in CLL recirculation properties as underlying cause for variability in treatment response

Change detection and monitoring of active Martian surface phenomena with the Colour and Stereo Surface Imaging System (CaSSIS) onboard the ExoMars Trace Gas Orbiter (TGO)

Mars is host to a variety of active surface processes that relate to changes in seasonal ice/frost, slope activity, wind and processes potentially relating to liquid water. Regular monitoring and change detection of these phenomena is crucial to not only provide us insights into present day Martian surface conditions, but also its past geologic and climatic scenarios. Visual comparisons of high-resolution remote sensing images of the surface from the Mars Reconnaissance Orbiter (MRO) have allowed detailed tracking and monitoring of these changes over time. The CaSSIS instrument onboard the ExoMars Trace Gas orbiter also provides a unique pathway to track areally-large surface changes in colour, that permits us to better constrain origin and evolution of various surface features. Since TGO operates in a non-sun-synchronous orbit, previously adopted qualitative methods like visual image comparisons for MRO cannot be adopted for CaSSIS-based change detection. Consequently, this study lists and describes in detail, the techniques that need to be adopted to conduct such change detection campaigns with CaSSIS, for the variety of active processes currently identified on Mars. This work also proposes and describes two additional semi-quantitative techniques for CaSSIS-based change detection, that may be used in concert with existing visual comparison methods to enable reliable change identification and tracking. It is observed that these supplementary methods work well in characterizing a variety of surface changes related to ice/frost and slope processes, and can provide reasonable spectral constraints to better understand their origin. These methods are not effective in providing quantitative constraints for purely physical changes. Instead, for long-period changes like aeolian bedform movement, digital image correlation techniques on ortho-rectified images, are recommended; while for short period changes like real-time dust devil activity, measurements based on CaSSIS stereo pairs of the region can be used to provide quantitative estimates of change