Scientists have discovered the mineral djerfisherite in previously unexplored samples from the asteroid Ryugu, which was previously thought to be impossible to find there. This is evidence that the formation of celestial rocks did not occur as previously thought, and that they were formed from mixed material.
New study of Ryugu samples
Previously unexamined samples from the asteroid Ryugu contain a mineral that should not be there. These conclusions were made by scientists from Hiroshima University, who published the results of their new research. They wanted to find out how terrestrial conditions affect them, and during microscopic studies they discovered something unexpected.
We are talking about djerfisherite — a potassium-containing iron-nickel sulfide. This mineral has been found in meteorites before, but not with the same composition as in Ryugu. It needs an alkaline environment to form, but the rocks that make up Ryugu are acidic.
This leads researchers to question how it could have ended up in number 15 grain, where it was found. This calls into question existing theories about the formation of asteroids. It is quite possible that at some stage in their existence, they underwent mixing of material that formed in different parts of the protoplanetary disk.
The origins of Ryugu
It is believed that Ryugu broke away from a much larger parent body. It, in turn, formed between 1.8 and 2.9 million years after the emergence of the Solar System in its outer part, where water and gases were in a frozen state.
About 3 million years ago, the decay of radioactive elements heated Ryugu to 50°C, causing volatile substances to melt and partially evaporate, giving it its modern appearance. At the same time, djerfisherite was forming in those chondrites that were originally closer to the Sun.
Previously, it was generally believed that this mineral could only be formed directly from superheated gas. However, experiments on hydrothermal synthesis have shown that djerfisherite can also be formed as a result of reactions between potassium-containing liquids and Fe-Ni sulfides at temperatures above 350°C.
It is believed that these two types of chondrites did not mix. However, after new research on Ryugu, it became necessary to determine at what stage material from the inner part of the Solar System entered the bodies that formed in colder regions.
There are two possibilities here. First, it may have ended up in Ryugu from some external source, the more likely scenario. However, we should not rule out the second possibility, that the radioactive decay processes were more intense and the asteroid material was able to heat up to the required 350°C. Isotopic studies of grains will be able to resolve these disputes.
According to phys.org
