Quantification of water content by laser induced breakdown spectroscopy on Mars

© 2017 Elsevier B.V. Laser induced breakdown spectroscopy (LIBS), as performed by the ChemCam instrument, provides a new technique to measure hydrogen at the surface of Mars. Using a laboratory replica of the LIBS instrument onboard the Curiosity rover, different types of hydrated samples (basalts, calcium and magnesium sulfates, opals and apatites) covering a range of targets observed on Mars have been characterized and analyzed. A number of factors related to laser parameters, atmospheric conditions and differences in targets properties can affect the standoff LIBS signal, and in particular the hydrogen emission peak. Dedicated laboratory tests were run to identify a normalization of the hydrogen signal which could best compensate for these effects and enable the application of the laboratory calibration to Mars data. We check that the hydrogen signal increases linearly with water content; and normalization of the hydrogen emission peak using to oxygen and carbon emission peaks (related to the breakdown of atmospheric carbon dioxide) constitutes a robust approach. Moreover, the calibration curve obtained is relatively independent of the samples types

In situ evidence for continental crust on early Mars

Understanding of the geologic evolution of Mars has been greatly improved by recent orbital in situ and meteorite data, but insights into the earliest period of Martian magmatism (4.1 to 3.7 billion years ago) remain scarce. The landing site of NASA’s Curiosity rover, Gale crater, which formed 3.61 billion years ago within older terrain, provides a window into this earliest igneous history. Along its traverse, Curiosity has discovered light-toned rocks that contrast with basaltic samples found in younger regions. Here we present geochemical data and images of 22 specimens analysed by Curiosity that demonstrate that these light-toned materials are feldspar-rich magmatic rocks. The rocks belong to two distinct geochemical types: alkaline compositions containing up to 67 wt% SiO2 and 14 wt% total alkalis (Na2O + K2O) with fine-grained to porphyritic textures on the one hand, and coarser-grained textures consistent with quartz diorite and granodiorite on the other hand. Our analysis reveals unexpected magmatic diversity and the widespread presence of silica- and feldspar-rich materials in the vicinity of the landing site at Gale crater. Combined with the identification of feldspar-rich rocks elsewhere and the low average density of the crust in the Martian southern hemisphere, we conclude that silica-rich magmatic rocks may constitute a significant fraction of ancient Martian crust and may be analogous to the earliest continental crust on Earth

Elimination of rabies—a missed opportunity

Rabies is one of the oldest known zoonoses. Recognized etiological agents consist of at least 15 proposed species of lyssaviruses with primary reservoirs residing in the Orders Carnivora and Chiroptera. A plethora of viral variants, maintained by a diverse set of abundant hosts, presents a formidable challenge to a strict concept of true disease eradication. Despite the availability of affordable and efficacious animal and human vaccines, today however dog rabies continues to escalate unabated across much of Asia and Africa, causing millions of suspect human exposures and tens of thousands of human rabies deaths annually. By identifying what hampers global human rabies elimination this chapter emphasizes that, given the global epidemiology of rabies, the “One Health” concept is key to solving the problem. Next to state of the art human rabies prevention, immunization and experimental therapy, it is obvious that human rabies can only be eliminated through rabies control at the animal source. This ‘paradigm shift’, however, needs new grassroot initiatives as well as political will and the closing of ranks of all stakeholders in the near future