A thin, patchy layer of airfall dust covers rock surfaces examined by the Mars Science Lab rover Curiosity and complicates interpretation of textures in Mars Hand Lens Imager images and compositions determined by Alpha Particle X-ray Spectrometer (APXS). Using three image processing methods, we estimate dust coverages for Mars Hand Lens Imager images of APXS targets to Sol 1512. Dust coverages of as is rock targets range from 6% to 77% (±5% to 10% estimated error). Targets brushed by the Dust Removal Tool range to lower coverages than as is targets, but quality depends on surface type; brushed mudstones have the narrowest range and lowest coverages (11-25%), while sandstones vary, ranging to higher coverages (12-58%). Groups of rocks with similar compositions (APXS classes) can have strong correlations between dust coverage and SO 3 /Cl (up to r = 0.985). Dust can also strongly affect the lightest elements measured (Na to Ca). By comparing paired as is and Dust Removal Tool analyses, using the determined dust coverages, and finding a best fit dust thickness (generally~10 μm), we model relative contributions of the dust and bedrock to extrapolate dust-free compositions for homogeneous APXS classes. The dust is basaltic with high S and Cl. Dust-free rocks have higher SiO 2 and Na 2 O (up to 6.5 wt% and 0.5 wt% higher, respectively) and lower SO 3 and CaO (up to 5.5 wt% and 1.3 wt% lower, respectively) than dusty equivalents. Dust most influences compositions that are very different from average Mars, including the alkali-rich, MgO-poor Jake M class.

Retroviruses create permanently integrated proviruses that exist in the host genome. Retroviral genomes encode for functionally conserved gag, pro, pol, and env regions, as well as integrase (IN), which is required for retroviral integration. IN mediates viral genome insertion through 3′ end processing of the viral DNA and the strand transfer reaction. This process requires the formation of a pre-integration complex, comprised of IN, viral DNA, and cellular proteins. Viral insertion causes DNA damage, leading to the requirement of host DNA repair mechanisms. Therefore, a failure of DNA repair pathways may result in genomic instability and potentially cause host cell death. Considering the numerous human diseases associated with genomic instability, the endogenous retrovirus-K (ERVK) IN should be considered as a putative contributor to DNA damage in human cells. Future research and drug discovery should focus on ERVK IN activity and its role in human conditions, such as neurological disease and cancers.

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