Planetary Geomorphology Image of the Month, April 29, 2016: Sandro Rossato (University of Padova, Italy). Terrestrial maar-diatremes are small volcanoes (see this previous post for a general description) which have craters whose floor lies below the pre-eruptive surface and are surrounded by a tuff ejecta ring 2-5 km wide (Figure 1) that depends on the size of the maar itself and on the depth of the explosion (Lorenz, 2003). Maar-diatremes constitute highly valuable sites for in situ investigations on planetary bodies, because they expose rocks at the surface from a great range of crustal depths and are sites which could preferentially preserve biomarkers.
The explosive eruptions that produce maar-diatremes can penetrate down to at least 2.2 km (Valentine, 2012), meaning that material deriving from different depths in the crust can be analyzed and sampled quite easily by a rover at the surface, having been exposed and fragmented. Secondly, but more importantly in the search for signs of life, many maar-diatreme structures on Earth host, or have hosted long-lived lakes… [More at link]