Abstract
New images from Mars rover Curiosity display millimetric, elongate stick- like structures in the fluvio-lacustrine deposits of Vera Rubin Ridge, the depositional environment of which has been previously acknowledged as habitable. Morphology, size and topology of the structures are yet incompletely known and their biogenicity remains untested. Here we provide the first quantitative description of the Vera Rubin Ridge structures, showing that ichnofossils, i.e., the product of life-substrate interactions, are among their closest morphological analogues. Crystal growth and sedimentary cracking are plausible non-biological genetic processes for the structures, although crystals, desiccation and syneresis cracks do not typically present all the morphological and topological features of the Vera Rubin Ridge structures. Morphological analogy does not necessarily imply biogenicity but, given that none of the available observations falsifies the ichnofossil hypothesis, Vera Rubin Ridge and its sedimentary features are here recognized as a privileged target for astrobiological research.
Highlights
New observations at Vera Rubin Ridge by the Mars Space Laboratory Rover Curiosity show millimetric, elongate structures preserved in sedimentary rocks deposited in fluvio-lacustrine environments within Gale Crater
They consist of horizontal, straight segments that are frequently connected by curved turns (Figure 2a)
The ends of few structures (s1, s11) appear tapered but it is unclear whether tapering results from primary or secondary processes; as such, ends of these structures have been excluded from image analysis
Summary
New observations at Vera Rubin Ridge by the Mars Space Laboratory Rover Curiosity show millimetric, elongate structures preserved in sedimentary rocks deposited in fluvio-lacustrine environments within Gale Crater. On Earth, such settings are inhabited by an enormous diversity of macro- and microorganisms producing traces of life-substrate interactions [1,2] that are similar to the structures of Vera Rubin Ridge. DiGregorio [4] suggested a potential biogenic nature as the fossilized products of life-substrate interactions (ichnofossils) This biogenic hypothesis was informally disputed in a set of blog posts including interviews of Earth and planetary scientists [5,6,7]. Despite of this debate, morphology, size and topology of the stick-like structures are yet incompletely known, and their potential biogenicity remains untested. In this paper we Geosciences 2020, 10, 39; doi:10.3390/geosciences10020039 www.mdpi.com/journal/geosciences
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