Wednesday, May 22, 2024

The Luna Structure In India

Image from Wikipedia.

The biggest meteor impact on Earth in the last 10,000 years struck Western India around 6905 BP (i.e. 4955 BCE). 

The impact clearly wasn't related to the fall of the Harappan culture. Indeed, perhaps it destroyed a previous civilizations in the area in a way that made way for it to move in. On the other hand, the location is quite far from the core of the Harappan region, and the civilization didn't really take off for another 1600 years or so, so the link between this civilization and the archaeological culture doesn't really ring true. 

But "[a]round 6500 BCE, agriculture emerged in Balochistan, on the margins of the Indus alluvium," which is a better fit geographically and temporally to this impact. This period was also known as the Mehrgarh, aceramic Neolithic period, in the Indus Valley Civilization. The agriculture that emerged was an expansion of the geographic range of the Fertile Crescent Neolithic. But this first appearance of agriculture in the region was still far north of the Luna structure.

It also isn't obviously related to any major regional or global climate event. This time period is mostly remembered for being in the middle of the Holocene Climatic Optimum that occurred in the interval roughly 9,500 to 5,500 years BP, with a thermal maximum around 8000 years BP. 

It also far predates the South Indian Neolithic Revolution of ca. 2500 BCE, and the arrival of rice as a major food crop in the Harappan culture.
The Luna structure of India has been rumored to be an impact crater for more than a decade without any convincing evidence. This structure (1.5–1.8 km) is prominently visible in the low-lying Banni Plains of the tectonically active Kutch Basin as a circular morphological feature with a less-prominent rim. Luna area is strewn with melt-like rocks having high specific gravity and displaying wide range of magnetic properties. It contains minerals like wüstite, kirschsteinite, ulvöspinel, hercynite, and fayalite. The whole rock analysis denotes PGE enrichment, with notably higher average concentrations of Ru (19.02 ppb), Rh (5.68 ppb), Pd (8.64 ppb), Os (6.03 ppb), Ir (10.63 ppb) and Pt (18.31 ppb). The target is not exposed at Luna, owing to the overlying thick sequence of Quaternary sediments. The mineralogical and geochemical signatures points to an impact into a target, which is rich in clay with elevated calcium and silica (sand/silt) content. Geochemical data suggests an iron or stony-iron meteorite as the potential projectile at Luna. The silt layer containing plant remnants, underlying the strewn layer, yielded a radiocarbon age of 6905 years, making Luna the biggest crater to result from an iron bolide within the last 10,000 years. . . .
In this study, we introduce the Luna structure (23°42′16″ N; 69°15′35′E) with 1.5–1.8 km diameter, as a potential hypervelocity impact crater. The structure remains submerged (and inaccessible) for a greater part of the year owing to its presence in the low-lying Banni Plains of the Kutch Basin of western India. Interestingly, the Luna region was one amongst the several settlements linked to the ancient Harappan Civilization (7000-1900 BP). . . . We present strong petrographic, mineralogical, and geochemical evidence to confirm the impact origin of Luna structure, along with an age estimate. 
K.S. Sajinkumar, et al., "The Luna structure, India: A probable impact crater formed by an iron bolide" 240 Planetary and Space Science 105826 (January 2024).


Darayvus said...

Nice maps, but better would be one map with both the crater and the Mehrgahr site on the same map.

andrew said...

True, but beyond my cartographic ability.