Glass with embedded metal and sulfides (GEMS) are tiny spheroids in

cosmic dust Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...

particles with bulk compositions that are approximately

chondritic A chondrite is a stony (non-Metallicity, metallic) meteorite that has not been modified, by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the ea ...

. They form the building blocks of anhydrous interplanetary dust particles (IDPs) in general, and ''cometary'' IDPs, in particular. Their compositions,

mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the proce ...

and

petrography Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The classi ...

appear to have been shaped by exposure to ionizing radiation. Since the exposure occurred prior to the

accretion Accretion may refer to: Science * Accretion (astrophysics), the formation of planets and other bodies by collection of material through gravity * Accretion (meteorology), the process by which water vapor in clouds forms water droplets around nuc ...

of cometary IDPs, and therefore

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or Coma (cometary), coma, and sometimes also a Comet ta ...

s themselves, GEMS are likely either

solar nebula The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened int ...

or presolar interstellar grains. The properties of GEMS (size, shape, mineralogy) bear a strong resemblance to those of interstellar silicate grains as inferred from astronomical observations.Bradley and Ireland, 1996

References

Footnotes

Planetary science Solar System Meteoroids Glass compositions Glass in nature {{glass-stub