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Context:  Ladakh’s rock varnish may help identify habitable environments in space.

Details

Key Findings

• Magnetofossils, which are fossil remains of magnetic particles produced by magnetotactic bacteria, have been spotted in rock varnish layers in Ladakh.
• Researchers noticed similarities between the rock varnish observed in Ladakh and that seen on Mars, particularly during the Perseverance rover operations.
• Samples of rock varnish from the Ladakh region showed higher concentrations of oxidised manganese (Mn4+) and carboxylic acid functionality on the varnish surface were identified, indicating organic signatures.
• Rock varnish is rich in manganese, iron and clay minerals that forms on rock surfaces and subsurface rock fractures in extremely dry and cold environments and are believed to provide nutritional support to micro-organisms.
• Rock varnish from Ladakh contains enriched concentrations of magnetic minerals likely derived from biotic sources.

Rock Varnish

• Rocks that are exposed to harsh conditions in desert and arid landscapes often develop a hard, sometimes reddish-brown but usually dark brown to almost black color coating.
• This outer layer substance which forms over time and darkens the surface of rocks is called 'desert varnish' or 'rock varnish.'
• Rock varnish can also form on the surface of desert soil if it remains undisturbed for thousands of years.
• However, rock varnish coatings are not unique to arid climates.
• The phenomenon is more widespread and also occurs at high-altitudes and in tropical environments. 

Formation/Composition

• The orange, gray, brown, or black veneer coatings have physiochemical and biological origins.
• Rock varnish is made up of a coating of clay particles (approximately 70%) combined with mineral deposits of iron and manganese oxides all probably wind-blown material that settled on the surface of rock.
• Other minerals mixed into varnish composition include hydroxides plus silica and calcium carbonate. These ingredients are cemented to the rock surface by living bacteria.
• Varnish formation is a means by which these microbes protect themselves in their exposed, extreme environments.
• Manganese oxides in rock varnish block the transmission of ultraviolet radiation.

Implications of the findings

• 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 target potential biosignatures on Mars and other planetary bodies, aiding the search for extraterrestrial life.
• These studies would play a pivotal role in planning future space missions by ISRO and other space agencies, including Mars exploration, where identifying habitable environments is a primary goal.

Comprehensive details about magneto fossils and Magnetotactic bacteria: https://www.iasgyan.in/daily-current-affairs/magneto-fossils

Sources:

PIB, eduscapes.com.

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