Origins of an Ending

FOR SEVERAL YEARS, KS Sajinkumar, along with a team of researchers, would travel to a remote location—the village of Luna in Gujarat’s Kutch district—looking for evidence of a meteor strike. A large circular depression in that area, nearly two kilometres in diameter when mea­sured, had long been rumoured to be a crater formed by a meteor strike, but such a shape could be explained by other factors like the crater of a volcano. “It was reported in a paper [a scientific journal] in 2006. But the researcher didn’t give any evidence [of a meteor strike]. He said there were some melt rocks [which are formed during meteor impacts] there, but he didn’t do any analysis on them,” he says.

Sajinkumar, an assistant professor in the Department of Geol­ogy at the University of Kerala, along with other geologists, began investigating the area from 2015 onwards, but because it is now marshy and often filled with water, their progress would often be impeded. “The first time we went, we couldn’t enter the area because it was full of water. The second time, we were able to reach up to the crater, but we couldn’t enter it, although we did pick up samples around it,” he says. In 2022, they were able to finally enter the crater and pick up several samples. Their findings, published in the journal Planetary and Space Science in December last year, confirm that a meteor had struck Luna. When Sajinkumar and his colleagues dated the layer of soil just below the ejecta layer (the layer formed by materials that get flung nearby when a me­teor strikes a location), they found that it was about 6,900 years old, which implies that the meteor must have struck sometime after this period. Sajinkumar and his colleagues have now dated the ejecta layer itself, which would provide a more precise date, and found that it is about 4,000 years old. They are yet to publish their findings.

For geologists, the discovery of a meteor strike by itself is big news. Only about 210 impact craters, according to Sajinkumar, have been discovered in the world so far, the one in Luna being the fourth such discovery in India. With a date of about 4,000 years, it is also, according to Sajinkumar, the youngest meteor impact so far found on Earth, and potentially a record of the only major me­teor to have struck since human beings appeared on the planet.

This date of 4,000 years, and the location of the site, also invites another tantalising query. This area is known to have thrown up remnants of the Indus Valley Civilisation (IVC) in the past, and Dholavira, one of the largest IVC sites, is only a few hours drive away. A meteor strike dated to about 2000 BCE here would land it bang in the midst of IVC’s mature phase.

What could a strike by a meteor, that according to Sajinkumar measured between 100 and 200 metres in diameter and which created a crater nearly 2km wide, mean for IVC? “The meteor that struck Mexico and led to the extinction of dinosaurs was about 10km in diameter. It took 20 years for the dust to settle after that impact, which means there was no photosynthesis for 20 years. There were tsunamis, forest fires. The impact was huge,” Sajinku­mar says. “This meteor [that struck Luna] was smaller. But this place is a thorny bush area. So trees can burn very fast. It is also a geo­logically active area with faultlines running through it. The Bhuj earthquake [of 2001] did take place here. So it [the meteor strike] could have triggered earthquakes, fires, and the whole area would have been covered by dust for weeks. These are to be expected.”

IVC is said to have gone into decline from 1900 BCE. For de­cades now, people have argued why this happened, offering reasons from the invasion of a large military force, the so-called Aryans, the likelihood of diseases and rupture in trade relations with other civilisations, to climate change. Could a meteor strike have something to do with it?

MOST PUBLICATIONS THAT reported the findings of this paper have suggested so. One newspaper asked if a ‘Mete­orite Ended Indus Valley Civilisation?’ Another said, we were looking at the possibility of a “human civilization possibly being wiped out by a meteorite”.

The researchers themselves do not think so. “It might have affected this region and there may have been deaths too. But IVC was huge. It might have caused a migration of people from this location to another area. But it could not have led to the demise of the civilisation,” Sajinkumar says.

In the next two hundred years after IVC’s decline began in 1900 BCE, several of its famous cities lay abandoned. The debates around what could have caused this sudden decline began not long after people first realised that a civilisation of such nature had existed. Many have believed it could have been the result of a bloody invasion by another group of people, the so-called Ary­ans. One of its famous proponents, the British archaeologist Mor­timer Wheeler, who thought such an invasion might represent the arrival of Indo-Aryan speaking people, once famously wrote “Indra stands accused”. However, no evidence of war has ever been discovered, and most now view this theory as myth. Oth­ers have claimed that the rivers IVC depended on either changed their course, dried up or got flooded, but this theory too has its critics. Some have wondered if it wasn’t the disruption in trade networks that was behind it all. IVC people were known to trade majorly with other groups like those in Mesopotamia, which was undergoing political problems. But many feel this theory places too much weight on the importance of foreign trade, which was probably negligible to the survival of IVC as a whole. Some have wondered if the culprit wasn’t the spread of diseases. Some re­searchers, examining human remains, have found evidence of malaria and cholera, and found that the people were increasingly suffering from infectious diseases. But it is unclear why diseases would have such an impact, when they must have been around even during the heyday of the civilisation.

One theory that has had the most purchase is that IVC declined because of climate change. And increasingly, in recent years, this has begun to look like the most credible cause. Several recent studies, for instance, find a reduction in monsoon rainfall. A 2014 paper by Yama Dixit, et al in Geology, where they carried out isotope analysis of lake sediment cores adjacent to IVC settle­ments in Haryana, found that there was around a 200-year-long failure of monsoons about 4,100 years ago.

Earlier this year, the journal Communications Earth & Environ­ment published a study that identified three protracted droughts within a period of about two centuries—each lasting between 25 and 90 years—about 4,200 years ago. The researchers learnt this by examining growth layers in a stalagmite (a kind of rock formation that rises from the floor of a cave) collected from a cave near Pithor­agarh in Uttarakhand. This period coincides with what is known as the 4.2-kiloyear event, which led to a long-term drought, one of the most severe climatic events in that epoch, and is theorised to have led to the collapse of the Akkadian Empire in Mesopotamia, Egypt’s Old Kingdom and the Liangzhu culture in the lower Yang­tze River area. At IVC, farmers and traders would have been able to adjust to a long drought, but such a severe dry spell that stretches from 25 to 90 years would have had far-reaching implications.

“There are two important aspects of these droughts,” Alena Giesche, the study’s lead author who conducted the research as part of her doctorate programme at Cambridge’s Department of Earth Sciences, says. “First, the periods of drought (25 years and longer) are long enough to affect multiple generations of people, which would lead to long-term adaptations to drier conditions, and possibly the movement of people to zones of higher overall rainfall. This outcome is supported by rural sites in areas of higher annual rainfall in the east that get settled during the Late Harappan Phase. Second, the droughts span both the summer and winter rainfall seasons, which affects both the summer (kharif) and winter (rabi) cropping seasons and compounds stresses on the food supply.”

According to her, cities with dense populations are vulnerable to such fluctuations in food supply, particularly when shortages outlast stored supplies for several seasons in a row. “In this case, a rural lifestyle may be more flexible and adaptable, but you may lose the advances and complexities of urban centres,” she says.

Could it be that IVC did not collapse suddenly, as is often popu­larly believed, but got transformed over a period of time, with people leaving the cities as their crop patterns changed in the face of drought, from large-grained cereals like wheat and bar­ley to drought-resistant species of small millets and rice, which was probably recently introduced from China? A 2016 paper published in Nature (by Anindya Sarkar, et al) argues that once crop patterns shifted, most cities lost their purposes and were abandoned. “Because these later crops [millets and rice] gener­ally have much lower yield, the organized large storage system of mature Harappan period was abandoned giving rise to smaller more individual household based crop processing and storage system and could act as catalyst for the de-urbanisation of the Harappan civilisation rather than an abrupt collapse,” they write.

Back in Luna, Sajinkumar is hopeful that he might be able to convince government authorities to establish a crater research centre at the location. “It is a very important site. This [meteor­ite] has landed in a marshy terrain. So there is a possibility of the meteorite itself being buried inside the crater. So we want to do some drilling,” he says. “Also, this is the only one impact [crater] which might have affected human civilisation. So this isn’t just important geologically. It is also important from an archaeologi­cal, anthropological, and sociological perspective.”

End of Indus Valley CivilisationKS Sajinkumarmeteor strike at Lunanew researchsatellite images