Nature India | Indigenus

Building blocks of life from space

Narendra Bhandari, a planetary scientist formerly with the Indian Space Research Organisation, recollects the time when he fortuitously became part of a meteorite detective team.

Narendra Bhandari with a meteorite fragment.

We spend crores of rupees trying to go to the Moon and other planets and bring back rocks. But nature is bountiful, even lugging space debris to our door step free of cost.

I regaled in one such gift a few summers back.

Just before sunrise at 5.15 a.m. on 6 June 2016, a rock of extraordinary type fell from the skies in the farm of Bishan Mehta of the Mukundpura village. The sound woke up the whole village, located in the outskirts of the pink city of Jaipur in Rajasthan.

I was driving down from Ahmedabad to Udaipur in Rajasthan when I heard about the meteorite fall on radio. I called Rajendra Prasad Tripathi, my friend who had recently retired from Jai NarainVyas University, Jodhpur and had settled in Jaipur. Tripathi immediately went to the site and surveyed the small foot-deep pit that the meteorite had created. To his dismay, the Geological Survey of India had swiftly collected all the pieces of the 2.5 kg meteorite. Not one to give up, Tripathi went home to fetch a kitchen sieve and filtered the sand from the bottom of the pit. He found two small pitch black chips, easily distinguishable as meteorite pieces owing to their colour.

Within a day, three of us – Tripathi, Ambesh Dixit of Indian Institute of Technology Jodhpur and I – measured the pieces using Mossbauer spectroscopy- to be sure the rocks were a rare type of carbon-containing meteorite, somewhat similar to the famous rock that fell at Murchison, in Australia, in 1969. About 2.5 per cent carbon content made this black, fragile, coal-like rock a scientific treasure.

A fragment of the Mukundpura rock , about 3 cm x 2 cm. The greyish surface on the left is due to heating in the Earth’s atmosphere. Dark black colour of the interior suggests presence of carbon, which contains organic molecules including amino acids, the building blocks of life. Mineral grains appear white.

Anil Shukla

When we analysed the minerals and chemical composition, it became clearer that this was going to be an important rock to study. Soon, we embarked on a detailed study with N.G. Rudraswami and colleagues at the National Institute of Oceanography, Goa, and found several amino acids in it. Amino acids, the chemical molecules from which biomolecules can be formed, are the building blocks of life.

We found evidence of water activity on various silicate minerals indicating the presence of abundant water on the asteroid where this rock had been lying for most of its life time, till it was kicked off by another space rock to come to Earth. Isotopes of carbon and nitrogen confirmed its extraterrestrial origin from the interstellar space.

M. S. Kalpana at the National Geophysical Research Institute, Hyderabad soon joined the effort, bringing a different set of expertise and technically sophisticated machines to complete the description of the extraterrestrial rocks. The team work paid off and using many techniques of mass spectrometry and gas chromatography, we were able to identify over 40 organic molecules of polyatomic aliphatic and aromatic hydrocarbons, including some fatty acids, and naphthalene.

These molecules are formed in the interstellar clouds from which our sun and planets were made 4.5 billion years ago. It is surprising that these organic molecules, easily destroyed at high temperature, survived the chaotic and complex processes in the severe environment that resulted in the formation of the Earth. Obviously the rock had not gone through much heating, may be it stayed below 100 degrees Celsius on the asteroid harbouring water, which saved the organic molecules, albeit with some alteration.

Hundreds of meteorites fall on the Earth every year, but what we received were among the rarest of rare rocks – only five such have fallen in India, the last one about 75 years ago. The Mukundpura rocks are now kept at Geological Survey of India museum in Kolkata.

These messengers from space packed with valuable information can tell us how life appeared on the earth. Together, we found over 15 heavenly rocks of different types in the past 30 years, many of which are described in my book Falling Stones and the Secrets of the Universe.

Strange rocks, like the ones that fell at Piplia Kalan and Lohawat in Rajasthan, tell different stories of their origin from different asteroids and their journeys to Earth. They increase our horizon of knowledge on space and fetch us extraordinary material for laboratory studies. These rocks tell us fascinating storiess of how it all began — the formation of the Sun, Earth, planets and life.

(Narendra Bhandari can be reached at nnbhandari@yahoo.com.)

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