Life on Mars (LoMars): A bibliometric study of current research and future perspectives

A quest for life on Mars (LoMars) started in the early 1960s when several research articles were published by the most prestigious scientific journals. The rise in annual literature production started in the late 1990s, most likely associated with the launch of the National Aeronautics and Space Administration’s (NASA) first Sojourner Rover in 1996. This trend predicts that the articles on Mars would further increase in the future given the fact that the recent launch and landing of the Mars 2020 Perseverance Rover is of utmost importance to find and understand the present or past life on the planet. So far, USA dominated the citations and collaborations with the rest of the world on Mars research given its facilities equipped with relevant infrastructure and researchers’ capacity to explore the Solar System beyond Earth. Majority of these frequently cited papers report results of observational and theoretical research; however, the highly cited paper (MCKAY D. S. et al. 1996) is based on analytical studies of a unique Martian meteorite (i.e., Allan Hills 84001) found in the Antarctica. It is expected that the sample return mission associated with the Perseverance Rover could possibly increase the LoMars research exponentially in the coming decades if Martian samples are successfully brought back to Earth. Based on the total number of publications on LoMars, highly influential institute, author, and journal represent Caltech, McKay C. P., and Icarus, respectively. Both the institute and the author are directly affiliated with the NASA, suggestive of the leadership offered by the organization in LoMars research.

EXAFS Determination of Clay Minerals in Martian Meteorite Allan Hills 84001 and Its Implication for the Noachian Aqueous Environment

The aqueous environment of ancient Mars is of significant interest because of evidence suggesting the presence of a large body of liquid water on the surface at ~4 Ga, which differs significantly from the modern dry and oxic Martian environment. In this study, we examined the Fe-bearing minerals in the 4 Ga Martian meteorite, Alan Hills (ALH) 84001, to reveal the ancient aqueous environment present during the formation of this meteorite. Extended X-ray absorption fine structure (EXAFS) analysis was conducted to determine the Fe species in ALH carbonate and silica glass with a high spatial resolution (~1–2 μm). The μ-EXAFS analysis of ALH carbonate showed that the Fe species in the carbonate were dominated by a magnesite-siderite solid solution. Our analysis suggests the presence of smectite group clay in the carbonate, which is consistent with the results of previous thermochemical modeling. We also found serpentine in the silica glass, indicating the decrease of water after the formation of carbonate, at least locally. The possible allochthonous origin of the hematite in the carbonate suggests a patchy redox environment on the ancient Martian surface.