A CaSSIS and HiRISE map of the Clay-bearing Unit at the ExoMars 2022 landing site in Oxia Planum

 In preparation for the operations of the ExoMars Rosalind Franklin rover, characterising its landing site in Oxia Planum is essential. Of particular interest is the extensive Clay-bearing Unit present at the site, a key target in the search for biosignatures. In this paper we provide a map based on variations in colour and spectral information within this unit, covering the 1σ landing envelope of the rover along with a 1 ​km buffer to account for minor shifts of the landing envelope ahead of launch (referred to going forward as the 1σ+ landing envelope). We used imagery from the Colour and Stereo Surface Imaging System (CaSSIS) and High Resolution Imaging Science Experiment (HiRISE) instruments, along with CaSSIS Band Ratio Composites with enhanced colour sensitivity to the presence of ferric (Fe3+) and ferrous (Fe2+) iron bearing materials. Our map is of a far higher resolution (map-scale 1:2000) than those previously available and, in contrast to previously available maps of this unit, differentiates between an Orange Subunit and a Blue Subunit which make up the Clay-bearing Unit. This mapping covered the ∼91% of the 1σ+ landing envelope where there was CaSSIS coverage and split the Clay-bearing Unit into three categories: one for each of the clay subunits, and another for exposures of the Clay-bearing Unit where either both subunits were too intermixed to reliably separate, or where it was difficult to determine which of the two were present. The results from our mapping shows that at least ∼35% of the 1σ+ envelope is covered by exposures of the Clay-bearing Unit: ∼18% by the Orange Subunit, ∼9% the Blue Subunit, and ∼12% were classified as Indeterminate. The spread of these two subunits varied substantially over the 1σ+ landing envelope, with the south-east half of the landing envelope dominated by the Orange Subunit (∼70% exposures in this area belonging to the Orange Subunit, ∼10% to the Blue Subunit and ∼20% to the Indeterminate category), while the north-west has more sporadic exposures of the Clay-bearing Unit (∼22% Orange, ∼37% Blue and ∼41% Indeterminate). The colour distinction between the two subunits is thought to be due to constituent mineralogical differences rather than differences in dust coverage of the two subunits. The scale of the fracturing present in the two subunits has also been assessed in this study, via qualitative observations of the fracture length and quantitative mapping out of fracture networks. While there were differences in the scale of fracturing between the two subunits, these were not as great as had previously been identified.</p

4EASO transfection suppresses mesothelioma proliferation.

<p>Normal mesothelial cells (LP9) and mesothelioma cell lines H2373, H2461 and H2596 were treated with the indicated concentration of mmASO (open columns) and 4EASO (filled columns), and viable cells were counted. Normal LP9 cells were most resistant to 4EASO treatment, while growth of mesothelioma cell lines was reduced extensively. <i>Columns</i>, the mean of three independent determinations of cell number normalized to untreated cells, <i>bars</i>, s.d.</p

eIF4E expression is reduced by 4EASO treatment in mesothelioma.

<p>Cultured normal mesothelial and mesothelioma cells were transfected with mmASO or 4EASO and eIF4E and β-actin protein expression was evaluated by immunoblot analysis from lysates harvested after 72 hours. The mmASO does not alter eIF4E levels in mesothelial cells or mesothelioma cells. The band intensity levels for eIF4E following 4EASO treatment was normalized to untreated cells for each cell line and was determined using ImageJ. β-actin level does not change upon treatment and serves as a loading control.</p

4EASO transfection induces apoptosis in mesothelioma.

<p>Mesothelioma cell lines H2373 and H2461 along with human mesothelial cells (LP9) were treated with the indicated concentration of 4EASO for 48 hours. Lysates were immunoblotted with anti-PARP antibody. In mesothelioma cell lines PARP cleavage was substantially increased in 4EASO treated compared to untreated cells.</p

Enhanced susceptibility of mesothelioma cells treated with 4EASO to cytotoxic drugs.

<p>Mesothelioma cell lines transfected with mmASO or 4EASO were treated with the indicated concentration of gemcitabine (GEM) or pemetrexed (PEM) and viable cells were counted. Elevated cell death was found for cells treated in combination with 4EASO and pemetrexed or gemcitabine compared to each treatment alone. Concurrent treatment of mesothelioma cells with 4EASO combined with pemetrexed or gemcitabine suppresses proliferation compared to treatment with mmASO combined with pemetrexed or gemcitabine. <i>Columns</i>, the mean of three independent determinations of cell number normalized to untreated cells, <i>bars</i>, s.d. Averages of combination treatment was compared to either agent alone by Student’s <i>t</i>-test. * denotes a p value <0.05. NS = not statistically significant.</p