In the early Solar System, dust grains, including ice, accreted to form planetesimals, and subsequent collisions and coalescing of planetesimals resulted in the formation of large planets.
The unblemished dust no longer exists in its unique structure in the present Solar System. Yet, its subordinates are found in small bodies that have not developed into planets: comets and asteroids.
Recently, a team of scientists from Japan, China, and the U.K. has discovered ice fossils on the surface of a meteorite. The Acfer 094 meteorite was found in the Algerian mountains back in 1990—since that time, it has undergone intense scrutiny due to its age—it has been dated back to approximately 4.6 billion years ago, which makes it a primitive meteorite.
The 82-gram meteorite is believed to harbor evidence of the primitive solar system and may, therefore, be able to provide scientists with clues about how planets and other celestial bodies formed.
For the study, synchrotron radiation-based X-ray computed nanotomography was used to study the meteorite. During the study, they found evidence of extremely tiny pores of 10 microns across.
According to them, these tiny pores are fossilized ice crystals—or more correctly, small indentations on the surface of the meteorite that once contained ice crystals. The pores were left behind when the meteorite crossed the snow line—a virtual sphere surrounding the sun that marks the boundary where heat from the sun melts ice on meteorites.
Scientists also reported the evidence of mineral formation in the pores. This might be the result of interactions between water and materials in the rock that make up the meteorite.
Scientists noted, “There could not have been enough water in the pores to produce the amounts of minerals they found. There had to have been more ice. This is a sign that the parent body (they believe the meteorite was once part of a larger object) was heterogeneous.”
“Also, as a parent body crossed the snow line, surface ice would have melted and dissipated. And this would have resulted in higher water or ice content in the core than the outer layers. Such a finding is important, they claim because it could lead to a better understanding of how the water here on Earth arrived. Their findings suggest it had to have come from farther out in the solar system than has been thought.”