doi:10.1038/nindia.2016.44 Published online 28 March 2016
The temple of Goddess Ashapura Mata has traditionally been an attraction for religious tourists thronging Matanumadh in Kachchh district of Gujarat. Now, thanks to a new discovery, this sleepy village in Western India is set to draw tourists of a different kind – planetary geologists from around the world.
Researchers report1 that Matanumadh (also spelt Matanamadh), situated around 86 km northwest of Bhuj, is actually a terrestrial clone of Mars. In other words, experiments to understand the geology of the Martian surface can be conducted in this "analog locality" in India instead of sending robots to the red planet.
A team of scientists from the Space Applications Center in Ahmedabad, Indian Institute of Technology Kharaghpur, and National Geophysical Research Institute (NGRI) in Hyderabad reached this conclusion after studying rock samples collected from weathered basalts of the Deccan Volcanic Province and overlying shales and sandstones of the Matanumadh Formation.
Using detailed spectroscopic studies supplemented with X-ray diffraction patterns, they identified the presence of the sulfate mineral jarosite [(K,Na)Fe3(SO4)2 (OH)6] — a key mineralogical indicator of hydrous, acidic and oxidizing conditions on the surface of early Mars.
"Though jarosite has been mentioned in earlier literature without any structure and detailed compositional data, our study is the first to provide detailed field data, X- ray, mineralogical, geochemical and infra-red spectral data on jarosite from India," Gopalakrishnarao Parthasarathy, chief scientist at NGRI and one of the authors told Nature India.
According to the report, the overall geological setting of the Matanumadh area, with this unusual mineral assemblage developing within altered basalts and in the overlying sedimentary sequence, "mimics the geological environment of many of the identified jarosite localities on Mars." Jarosite comprises about 10% in outcrop at the Meridiani Planum, the landing site of NASA's Mars rover Opportunity.
"The positive identification of jarosite, in addition to the previously reported minerals natroalunite and minamiite considerably strengthen the case for this locality to be considered as a terrestrial Martian analog site," the researchers said. They speculate that the jarosite-forming mechanism at Matanumadh, currently being investigated, "may ultimately be applicable to some Martian localities."
Jarosite can only be precipitated from highly acidic, oxidizing aqueous fluids in a sulfur-bearing system, the report said. "The limited natural terrestrial regimes in which jarosite is found testifies to the extreme, unusual conditions required for its stabilization. The Martian surface must, at some time, have experienced these conditions and therefore the positive identification of jarosite is a major argument in favour of the Matanumadh Formation representing a Martian analog locality."
Broadly, jarosite formation at Matanumadh requires an initial phase of wet weathering of basaltic crust, subsequent subsidence to form restricted basins, followed by marine transgression and then regression, the report said. "A similar sequence of events may be conceived for the documented Martian jarosite occurrences. Understanding how jarosite formed in the Matanumadh Formation may shed light on the final stages of aqueous activity in parts of the Martian surface," it said.
1. Bhattacharya, S. et al. Jarosite occurrence in the Deccan Volcanic Province (DVP) of Kachchh, western India: spectroscopic studies on a Martian analog locality. J. Geophysical. Res.— Planet (2016) doi: 10.1002/2015JE004949