Jesús Martínez Frías
Planetary geologist and astrobiologist at the IGEO (CSIC-UCM). Academician of the Royal Academies of Sciences and Doctors of Spain. President of the Planetary Geology Commission of the Geological Society of Spain and of the Spanish Network of Planetology and Astrobiology.
It is a very interesting study that connects mineralogy with other aspects related to Martian habitability. It does so by combining different techniques from in-orbit instruments, in situ (field analysis) and also with laboratory materials. The conclusions are therefore based on solid methodologies that address the objectives very well.
The first published studies linking ferrihydrite to Mars date back to the 1990s (e.g. Robbins et al. 1991, Bishop et al. 1993). Although the presence of this mineral and other [ferro] oxides and water-related mineral phases (sulphates such as jarosite, gypsum, etc.) has subsequently been raised by numerous investigations, probably the first study that experimentally confirmed the presence of ferrihydrite on Mars was by the Mars Exploration Rover (MER) in the Meridiani area (Farrand et al. 2007). Since that year, many other works have addressed the relevance of iron oxides, along with that of other mineral ores, with different objectives, including the characterisation of Martian palaeoenvironments and their habitability conditions.
The main novelties of this research focus on the set of methodologies from different sources and on the importance of water, whose imprint has been captured in the hydrated iron oxides (ferrihydrite) of Martian dust and other mineral phases also related to water, as opposed to the more anhydrous nature, which was classically assumed.
Until we have well-selected and sampled minerals, rocks and regolith on Mars, such as those brought to Earth by a mission like the Mars Sample Return, and experiments that allow us to drill into the surface, such as those that the Rosalind Franklin rover intends to perform, we will not be able to carry out detailed experimentation (including well-defined isotopic studies) and an assessment of the transformations, cycles and sequences of processes and environments over the billions of years of Mars' geological evolution. For the moment, we only have the Martian meteorites and the characterisations that we can carry out with orbiters, rovers and experimental laboratory simulations (including terrestrial analogues as natural laboratories). Nevertheless, this study is an important step forward and a further step in understanding the complex puzzle of Martian geology and mineralogy.