Research Focus

Why meteorites: 

Meteorites are leftovers from the formation of the solar system. While geological forces have reprocessed Earth's materials over many eons, most meteorites have never experienced any reprocessing and are just as they were when the solar system was formed. By examining a meteorite, we are looking at the chemical composition of the solar system as it was being born.

A few meteorites come to us from the Moon or other planets, such as Mars. When holding a piece of Martian meteorite in your hand, you are holding an actual real piece of the red planet. By studying these kinds of meteorites, we learn about the geology and atmospheres of other planets at long-ago times, when the meteorite was chipped off the planet. (Source)

How do we get meteorites:

Impact events have been one of the most crucial and fundamental cosmic processes that have played an important role in the shaping and evolution of the planetary surface and interior. Such impact events on planets and asteroids are also responsible for the delivery of meteorites on the Earth’s surface. Meteorites are broken pieces of the asteroids or some planet (e.g., if it is from Mars, we call it a Martian meteorite) that got dislodged from the asteroid’s surface when two asteroids or an asteroid and a planet collide with each other (Figure 1). These broken pieces are later get sucked in by the Earth’s gravity and fall on the Earth’s surface as meteorites.

A journey from outer space to the Earth’s interior:

What can a piece of rock from space known as a meteorite can tell us about the processes in the deep interior of the Earth? Let us begin with some background discussion on the composition of planets and asteroids. The so-called ‘inner planets’ (Mercury, Venus, Earth, and Mars) in our solar system are made up of a similar kind of rocky material. However, further processes occurring due to the large size of the planets, like the melting of interior parts of these planets and subsequent gravity-driven separation of high-density materials from low-density material have modified the original composition. Nevertheless, the original composition is still preserved in the asteroid belt located between Mars and Jupiter. The asteroids are smaller chunks of rock, as compared to the planets, that did not combine and lithify to form a larger planet. Therefore, due to their smaller size, their composition remained the same without any modifications.

These collisions result in the formation of a wave called a ‘shock wave’. The main property of these waves is that they deform the rock and immensely increase the pressure known as ‘shock pressure’ (Figure 2). Furthermore, such collisions give rise to the formation of numerous fractures in the asteroid body. During the collision, the friction produced as the surface of these fractures moves past each other, causes temperature spikes and subsequent melting. Therefore, these fractures become localized zones of high-pressure and high-temperature and are called ‘shock-melt veins’ (Figure 2). These high-pressure and high-temperature conditions are similar to the condition prevailing at depths of ~400-700 km on Earth. The fact that the direct samples from such depths on Earth are not available, makes the meteorite samples that have experienced high-pressure and high-temperature of tremendous interest to planetary scientists. Thus, the mineralogical and compositional similarities between the Earth and asteroids allow researchers to probe the depths of the Earth by studying such meteorites.

What do I look for:

Although the whole sample of an extraterrestrial rock is of tremendous interest to me, I specifically look for the so-called 'shock-melt veins'. Numerous high-pressure polymorphs of olivine, pyroxene, and feldspar occur exclusively in and around these shock-melt veins. I seek these high-pressure polymorphs and attempt to constrain their pressure-temperature-time (P-T-t) history (shock conditions) and decipher their mode of transformation.