“He shouldn't be there.” Planetoid Ryugu with a mineral surprise

Samples from Ryguu asteroids are tested in earthly laboratories. A mineral was discovered in one of the grains, which should not arise in conditions that – according to current knowledge – was experienced by the asteroid – informs the Japanese University of Hiroshima.

The Ryugu Planetoid was the target of the Japanese mission of the unmanned Hayabusa probe on December 6, 2020, samples taken from the asteroid reached the ground and from now on they are tested in laboratories.

Ryugu is a C -class planetoid, in which coal and coal compounds are characteristic (hence the name, from the determination of coal with the letter C in chemistry). It is known that this object is made of rocks similar to meteorites called carbon chondics, and more precisely – to their group marked as you. They contain large amounts of coal. It is known that extensive changes in the aquatic environment have undergone in the past.

Researchers from the University of Hiroshima discovered in the grain from Ryuga the occurrence of a mineral, which does not match the conditions for which the planetoid was exposed from the moment of its creation.

The mineral is called “Djerfisherite”, which refers to the name of prof. Daniel Jerome Fisher (1896-1988), an American mineralog. This mineral is iron sulfide and nickel containing potassium. Usually, environments such as in enstatite chondics are formed (a different group of meteorites than coal chondrites) and has never been reported in the coal -headed chondics, or during the research of other grains from Ryugu.

The presence of this mineral is therefore very surprising to scientists. “It's like finding tropical seeds in the ice cream of the Arctic. This indicates an unexpected local environment or long -distance transport at an early stage of the solar system” – explains prof. Masaaki Miyahara from the university in Hiroshima, the first author of the publication.

Finding such a mineral suggests that the matter of various stories of formation could mix in the early stages of the evolution of the Solar System. Alternatively, Ryugu itself could experience some specific local conditions that scientists are not known about. This is a challenge for the current assumption that Ryugu has a homogeneous structure and raises doubts about the complexity of the primary asteroids.

It is known that Ryugu is part of a larger object formed from 1.8 million to 2.9 million years after the beginnings of the Solar System. It is believed that the larger body came from further areas of the planetary system, in which water and carbon monoxide existed in the form of ice. Inside this object, the heat generated by radioactive breakdown caused ice to stop 3 million years after the formation of the body. The temperature probably did not exceed 50 degrees Celsius.

In turn, the parent bodies of Enstatite Meteorites, which contain the mineral in question, formed in the inner part of the planetary system. Calculations indicate that this mineral formed directly from high temperature gas. Hydrotermal synthesis experiments have shown that it can also be created through a reaction between potassium-free fluids and Fo-Ni sulfides (sulfur, iron and nickel compounds) at a temperature above 350 degrees Celsius.

Researchers proposed two hypotheses explaining the presence of a surprising mineral in the grain from Ryug. The first proposal is to reach a place from the outside when the formation of the native body of Ryugu asteroids. The second hypothesis is an inside of the object when the temperature increased above 350 degrees Celsius. Scientists are more inclined to the latter explanation.

Further research will be compared by other grains from Ryugu in the hope of solving the mystery of their origin.

The research results are described in an article that appeared in the journal “Meteoritics & Planetary Science”. (PAP)

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