“Summers with Meteorites”

My Research Experience at PRL, Ahmedabad

Siddharth Rajpriye
Sep 6, 2018 · 9 min read
Fast…. Make a Wish!

If you are not from a first world country, chances are you might have seen shooting stars during your childhood days, when power cuts used to happen. For most of Indians, this is true. During peak summer season, power cuts used to be normal phenomenon and it was not uncommon to sleep at terrace under the night sky. During such times, it was quite common to see streaks of light known as “Shooting Stars”. And being a child you must have definitely asked for few wishes to come true.

These supposedly wish fulfillers, “Shooting Star”, is actually a Misnomer! They have nothing to do with stars. They are extraterrestrial rock fragments which just happened to intercept the earth’s orbit and enter the atmosphere. They ablate as they pass through the atmosphere due to air resistance and this is why a streak of light is seen. If they are big enough, they reach the earth’s surface and are named as Meteorites. If they melt on the way, no solid mass reaches the surface, and only a visual phenomena is observed. This is called Meteor or a Shooting Star. At certain times of year, you are likely to see a great number of meteors in the night sky. These events are called meteor showers and they occur when the Earth passes through the trail of debris left by a comet as it orbits the Sun.

KEDtalks with Dr. Meenakshi Wadhwa: Visitors from another World

And needless to say, these meteors have fascinated a large chunk of population and intrigued them to go beyond their daily chores into a world far away from earth. And fortunately I happen to be one of those. And somehow I ended up studying Geology at IIT Roorkee. In my 3rd year of study, I opted for an elective course “Planetary Geosciences”. If you are still reading this, you might have guessed the reason why. For once in 3 years, I really got interested in Geology. I took another elective “Applied Geochemistry”, which opened the doors for studying meteoritics in future.


Physical Research Laboratory was founded in 1947 by Dr. Vikram Sarabhai

Internship season was approaching and I had applied at Physical Research Laboratory, Ahmedabad which happens to be the premiere institute for Space and Planetary Sciences in India. Luckily I got the project as per my interest. I was supposed to study an Indian meteorite and unravel the mysteries of universe during my summer vacations.

Meteorites are named after the places where they fall or are found. For example the meteorite which I was working on was named “Mahadevpur Meteorite”, since it fell at Mahadevpur (27°40′N, 95°47′E), Arunachal Pradesh, India.

We study meteorites for a variety of reasons. Meteorites are a window into the early evolution of planets and other bodies in our Solar System. Much of what we know about the origin of the Earth and the other planets is due to meteorites. Their ages, bulk composition and formational history can tell us much about the history of the Earth. Currently, space exploration is prohibitively expensive for resource prospecting, so studying the meteorites that could represent future potential resource reservoirs is the most practical method for establishing a knowledge base.

Let me explain the timeline or the workflow of how studies on meteorites are done (As I experienced firsthand).

Allende meteorite is the largest carbonaceous chondrite ever found on Earth. The fireball was witnessed at 01:05 on February 8, 1969, falling over the Mexican state of Chihuahua.

Firstly we need a meteorite. There are no sophisticated meteorite tracking mechanism in India. And finding any new meteorite is purely based on luck and location. Most meteorite falls are recovered on the basis of eyewitness accounts of the fireball or the impact of the object on the ground, or both. Therefore, despite the fact that meteorites fall with virtually equal probability everywhere on Earth, verified meteorite falls tend to be concentrated in areas with high human population densities such as Europe, Japan, and northern India.

In India the Geological Survey of India (GSI) is the custodian of all meteorite falls/finds in the country. Meteorite samples for scientific research can in principle be obtained from the official custodian to carry out scientific studies.

An immediate objective, when a new meteorite has been identified, is to classify it properly for further detailed studies. The classification of meteorites has evolved over the decades to give us information about their formation environment (nearer or farther from Sun), thermal and aqueous processing and/or melting and chemical differentiation of its parent body (asteroid), based on studies of their chemical, petrological and isotopic systematic. This classification allows us to select the proper meteorite sample that is pertinent to the specific aspect under investigation. Despite this detailed knowledge base, we still keep finding ‘first of its kind’ meteorites, making each meteorite fall a very interesting object for detailed study.


Meteorites have traditionally been divided into three broad categories: Stony meteorites that are rocks, mainly composed of silicate minerals; Iron meteorites that are largely composed of metallic iron-nickel; and Stony-Iron meteorites that contain metallic and rocky material. Modern classification schemes divide meteorites into groups according to their structure, chemical and isotopic composition and mineralogy.

According to modern classification scheme, meteorite are often divided into following broad categories

  1. Chondrites — These are meteorites that have not been modified due to melting or differentiation of the parent body. They are named for the millimeter sized droplets of quenched silicate melts, known as Chondrules, that are particularly abundant in these meteorites. They are further divided into 3 categories
  • Carbonaceous — They are characterized by the presence of carbon compounds, including amino acids. They are thought to have been formed the farthest from the sun of any of the chondrites as they have the highest proportion of volatile compounds. Another of their main characteristics is the presence of water or of minerals that have been altered by the presence of water.
  • Ordinary — Ordinary chondrites are by far the most common type of meteorite to fall to Earth: about 80% of all meteorites are ordinary chondrites.
  • Enstatite — A rare form of meteorite thought to comprise only about 2% of the chondrites that fall to Earth. They are among the most chemically reduced rocks known. This suggests that they were formed in an area that lacked oxygen.
Modern Classification Scheme of Meteorites (Weisberg et al.)

CI chondrites are notable because their chemical compositions closely resemble that of the solar photosphere, neglecting the hydrogen and helium. They have the most “primitive” compositions of any meteorites and are used as a standard for assessing the degree of chemical fractionation experienced by materials formed throughout the solar system.

2. Achondrites — An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to plutonic rocks and has been differentiated and reprocessed due to melting and recrystallization.

3. Primitive Achondrites — They are called primitive because they are achondrites that have retained much of their original chondritic properties.

Chondrites consist of 4 major components Chondrules, Fe-Ni Metal, Refractory Inclusions and Fine Grained Matrix.

Chondrules are spherical grains found in chondrites. Chondrules form as molten or partially molten droplets in space before being accreted to their parent asteroids and are one of the oldest solid materials within the Solar System. Most chondrules are composed primarily of the silicate minerals Olivine [(Mg, Fe)2SiO4] and Pyroxene [ XY(Si, Al)2O6 where X represents Ca, Na, Fe(II) or Mg and Y represents Cr, Al, Fe(III) and Mg].

My first week was spent in reading and browsing journals and research papers. In the second week, My guide Dr. Dwijesh Ray gave me a meteorite sample. The sample was about the size of fingernail. Initially I had to classify the sample on the basis of its mineral chemistry. Since the meteorite samples are quite rare, non destructive mode of analysis is preferred. Non-destructive testing (NDT) is a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage.

Scanning Electron Microscope

SEM (Scanning Electron Microprobe) and EPMA (Electron Probe Micro Analyser) are the most widely used analytical tools for nondestructive analysis. They both use a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens. The signals that derive from electron-sample interactions reveal information about the sample including external morphology (texture), chemical composition, and crystalline structure and orientation of materials making up the sample.

Firstly I had to prepare thick section of the meteorite sample to be analysed using these analytical tools. Thick sections are basically cylindrical shaped with a diameter of about 1 inch made of solidified epoxy resin and contain the meteorite sample. After thick section preparation, Polishing (To expose the top surface) and Coating (Samples intended for electron microscopy are electrically non conductive. Bombarding them with electrons would lead to overcharges that may inhibit image formation. So a conductive coating is applied to those samples) is done. Now our meteorite sample is ready for revealing untold secrets of the universe.

To get an overall view of the sample, I took a number of images using SEM at 45x magnification. The complete surface area of sample was covered in around 30 images. Then using Adobe Photoshop, all the images were merged into one mosaic, showing the complete surface of sample.

Overall view of the Meteorite Sample at 45x

After mosaic completion, a number of high magnification (100–500x) images of all the distinguishable chondrules, metal areas and other areas of interest present in the sample were taken. Elemental compositions were determined using SEM-EDX at specific points in a number of chondrules, metallic areas and other areas of interest.

Elemental compositions were determined at around 200 locations in the sample. From the SEM images, I identified different mineral phases and micro texture of different chondrules in meteorite sample. Using the elemental composition I did petrologic classification and characterization of meteorite. I also estimated the equilibration temperature based on Two-Pyroxene Thermometry and studied the evolution of thermal history of the parent body of meteorite. This was all I could achieve in two months. Other studies to be done includes-

  • Cosmic Ray Exposure Determination
  • Shock Metamorphism Study
  • Thermal/Aqueous Alteration History

Work Culture at PRL

Known as the cradle of Space Sciences in India, the Physical Research Laboratory was founded on 11 November 1947 by Dr. Vikram Sarabhai. It is supported mainly by Department of Space, Government of India. This research laboratory has ongoing research programmes in astronomy and astrophysics, atmospheric sciences and aeronomy, Earth sciences, Solar System studies and theoretical physics. It manages the Udaipur Solar Observatory and is located in Ahmedabad.

A team of scientists at PRL recently discovered a distant exoplanet six times bigger than Earth and revolving around a Sun-like star about 600 light years away. Link

If you are interested in one of the broad disciplines being pursued at PRL, it is one of the best places in India to pursue Ph.D. The work culture here gives you the freedom to pursue your research without hassle, laboratories are well equipped, the mentors are capable and internationally reputed.

This place has given me some of the best memories of my life!

Siddharth Rajpriye

Written by

Geology Undergrad at IIT Roorkee

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