Oldest solid material discovered on Earth: 7 billion-year-old meteorite grains

The researchers analyzed a piece of meteorite that fell in Australia fifty years ago and came to the conclusion that part of the object that originated the meteorite was formed over a period between 5 and 7 billion years.

This dating makes this object the oldest solid material ever found on Earth and one of the most interesting studies worked on by Philipp Heck, a researcher at the Field Museum and professor at the University of Chicago and author of a study that appeared on PNAS.

The researchers have specifically analyzed the particles of material contained in the Murchison meteorite called “presolar grains”. Some of these particles seem to have formed even before the birth of the Sun. They are “real stardust”, as Heck himself explains, since they are particles expelled from the same stars after their death and then trapped for billions of years in other space bodies, as a comet can be.

Being small and very rare, they are also very difficult to find. They are so rare that they have only been found in 5% of meteorites that have fallen to Earth and they are so small that 100 units of presolar grains could cover space from the dot to the end of this sentence.

The Murchison meteorite fell near Murchison, Australia in 1969. The researchers first isolated the prehalarial grains from the meteorite and then started the dating process based on the isotopes produced by cosmic rays on the same grains discovering that some of them refer to a period of 7 billion years ago during which there seems to have been a boom in star formation in the Milky Way.

This is in contrast to the theory that the star formation rate in our galaxy has been relatively constant over time. And that’s one of the key findings of the study, as Heck himself explains.