What is Cosmic Dust?

Dust particles are found almost everywhere, in the air we breathe, in the river banks, deserts and the upper atmosphere. On the other hand, dust signatures are found in almost every corner of the visible Universe. Furthermore, these dust particles which are found in outer space are, in general, termed "Cosmic Dust".

Scanning electron microscope image of a porous interplanetary dust particle. The authors of this figure are Donald E. Brownlee, University of Washington, Seattle, and Elmar Jessberger, Institut für Planetologie, Münster, Germany. This file is licensed under Creative Commons Attribution 2.5 License: https://creativecommons.org/licenses/by/2.5/ See the (Jessberger chapter in Grün, E., Gustafson, B.A.S., Dermott, S.F., Fechtig, H. (Eds.) Interplanetary Dust book for more details on this kind of dust particle. References E. K. Jessberger, T. Stephan, D. Rost, P. Arndt, M. Maetz, F. J. Stadermann, D. E. Brownlee, J. P. Bradley, G. Kurat (2001). Properties of Interplanetary Dust: Information from Collected Samples, in Grün, E., Gustafson, B.A.S., Dermott, S.F., Fechtig, H. (Eds.) Interplanetary Dust, pp. 253–294, Springer-Verlag.

Cosmic dust can be categorized according to its sources, such as interplanetary Dust (IDP), interstellar Dust, circum-planetary Dust, protoplanetary Dust, Dust in debris disks and intergalactic dust. The IDPs can be further categorized into comet dust and asteroid dust.

The physics of dust plays a crucial role in the overall understanding of the formation and evolution of stars and galaxies. The Solar System's cosmic dust, i.e., the IDPs, come from comets and asteroids. Scientists believe that the origin of cosmic dust can be traced back to collisions that happened during the Big Bang to the formations of different galaxies and Solar Systems, including our own.

By studying cosmic dust present in different regions of space, scientists can travel back in time and understand how the matter was formed, ultimately leading to life on Earth. Recent studies of planet formation indicate that dust grains are the main building blocks of rocky planets and planetary satellites (Moons). Small dust grains coagulate to form larger particles (aggregates/clusters of smaller grains) which, under gravity, go through more collisions and eventually form larger planetesimals.

The studies related to IDPs collected from Antarctic Ice and Earth's stratosphere reveal different physical properties of cosmic dust in our Solar System. For example, cosmic dust particles are found to possess fractal assemblage of smaller sub-micron or nanometer size grains. Spectroscopic studies of material composition present in the collected samples of IDPs reveal the presence of magnesium iron-rich Silicate minerals, organics, and traces of other minerals. On the other hand, observed extinction, absorption, and spectral energy distribution of different star-forming regions and star clusters reveal the presence of silicates, graphite and PAHs. Both amorphous and crystalline silicate minerals are formed under extreme pressure and temperature. Thus, silicate dust in our Solar System and interstellar space provides a glimpse of the violent past, having extreme temperatures and pressure that led to the formation of cosmic dust.