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(a) FE-SEM image of the varnish layer showing the presence of a magnetotactic multicellular aggregate (MMA)-like entity embedded in the varnish layer marked by yellow arrows; inset a1 shows the magnified morphology of the MMA-like entity, displaying clear morphological features; inset a2 is an SEM image of a magnetotactic multicellular aggregate (MMA). (b) FE-SEM image showing clusters of magnetosomes with chain morphology in the varnish layer; (d) High-resolution magnified FE-SEM image of panel c indicated by the leftmost blue arrow illustrating the chain morphology of magnetosomes present in the varnish layer, with inset depicting a graphical depiction of the shape of the magnetosomes. — Ministry of Science and Technology, India
Magnetofossils, fossil remains of magnetic particles produced by magnetotactic bacteria, have been discovered in layers of rock varnish in Ladakh. The study, which suggests that there are biotic processes involved in the formation of rock varnish, indicates how life can exist in extreme environments, providing valuable information for astrobiology as well as for planning future space missions aimed at identifying habitable environments in space.
Ladakh, known as the “cold desert of India,” experiences extreme climatic conditions such as high ultraviolet radiation, significant temperature variations, and limited water availability, making it a suitable terrestrial analogue for Martian studies.
Researchers at Lucknow’s Birbal Sahni Institute of Palaeosciences (BSIP), an autonomous institute under the Department of Science and Technology (DST), were inspired by the similarity between the rock varnish observed in Ladakh and that observed on Mars, particularly during the operations of the Perseverance rover.
Field photographs of rocks sampled for rock varnish studies from the northwestern Himalayas (Leh, Ladakh). Panel I (a) to (d) photographs depict rocks designated as RV-1 to RV-4 respectively. Panel II shows striking similarities between rock coatings on Mars and the environment of Ladakh. — Ministry of Science and Technology, India
They collected rock varnish samples from the Ladakh region, picked them, and used XPS to analyze the surface chemistry of the rock varnish. The analysis by lead author Dr. Amritpal Singh Chaddha and Dr. Anupam Sharma at BSIP with its Sophisticated Analytical Instrumentation Facility (SAIF) established by DST, helped identify the magnetofossil nanochains.
In addition, higher concentrations of oxidized manganese (Mn4) were found+) and carboxylic acid functions were identified on the varnish surface, indicating organic signatures.
The study published in Planetary and Space Science showed that the rock varnish from Ladakh, a possible Mars analogue site, contains enriched concentrations of magnetic minerals likely derived from biotic sources.
The findings highlighted the potential of rock varnish as an archive of ancient environmental records and as a geomaterial for astrobiological studies.
By identifying biotic signatures in rock varnish, scientists can better identify potential biosignatures on Mars and other planetary bodies, thereby aiding the search for extraterrestrial life. This information is crucial for planning future space missions by ISRO and other space agencies, including the exploration of Mars, where identifying habitable environments is a primary objective.
Exploring the astrobiological potential of rock varnish from a Mars analogue field site in Ladakh, India, Science Direct
Abstract — Rock varnish, a dark-colored natural feature rich in manganese (Mn), iron (Fe), and clay minerals that forms on rock surfaces and in subsurface rock fractures in extremely dry and cold environments, is thought to provide nutritional support to the microbiota. Because varnish supports an extensive microbial community, this rock coating is considered a substrate for potential microbial life to thrive in extreme environments on Earth. Although research in recent decades has advanced the understanding of the varnish microbiome, little is known about this microbial community in high-altitude (lower oxygen), dry, and cold environments. We present here new morphological, chemical, and magnetic rock results from the rock varnish from this environmental setting, Ladakh, a potential analogue site for life in extreme environments. Our results include the presence of putative magnetofossils, in the form of nanochains present in the rock varnish layer. Furthermore, higher concentrations of oxidized Mn4+ and carboxylic acid functionality on the varnish surface revealed organic signatures. These collective results point towards the enriched concentration of magnetic minerals in the varnish layer possibly originating through biotic forms. Consequently, the rock varnish may serve as an archive of ancient environmental records as well as a potential geomaterial for astrobiological studies of the location of the Ladakh Martian analogue field, which needs to be further explored for extensive biogeochemical studies.
Astrobiology
