The Chang’e-5 mission, China’s pioneering project that returned to Earth with lunar samples for the first time since 1976, has provided scientists with invaluable insights into the moon’s geological history.
By delivering 1.73 kilograms of regolith from the vast lunar plain known as Oceanus Procellarum, the mission has opened up new avenues for understanding the moon’s surface and its formation processes.
The lunar regolith, which includes a mixture of rocks, dust, and a new mineral named Changesite-(Y), offers a unique glimpse into the moon’s past.
Researchers from the Chinese Academy of Sciences have embarked on a detailed study, comparing the composition of these samples to those from other lunar and Martian missions.
Their findings, published in the journal Matter and Radiation at Extremes, shed light on the transformative effects of celestial impacts on the moon’s surface.
Celestial objects, such as asteroids and comets, collide with the moon at high velocities, creating shock waves that alter the mineral composition and structure of the lunar regolith through a process known as impact metamorphism.
This process is characterized by a rapid change in temperature and pressure, leading to the formation of high-pressure minerals like stishovite and seifertite. These minerals, though chemically identical to quartz, possess different crystalline structures due to the intense conditions under which they form.
Interestingly, despite the abundance of impact craters on the lunar surface, high-pressure minerals are rare in lunar samples.
This rarity is attributed to the instability of these minerals at high temperatures, which likely causes them to undergo a retrograde process, reverting to more stable forms.
However, the CE-5 samples contain both stishovite and seifertite within a single silica fragment, a combination that suggests these minerals formed under conditions of varying pressure and temperature, challenging our understanding of the mineral transformation processes on the lunar surface.
The discovery of Changesite-(Y), a new mineral with distinct physical characteristics, further enriches the scientific value of the CE-5 samples.
This phosphate mineral, with its colorless, transparent columnar crystals, adds to the moon’s mineralogical diversity and provides clues to the conditions present during its formation.
By analyzing the peak pressures and durations of the impacts that created these minerals, researchers have been able to estimate the size of the crater resulting from the collision, offering insights into the dynamics of lunar impacts.
Additionally, the identification of specific impact craters as the source of the distant ejecta found in the CE-5 regolith points to the Aristarchus crater as a likely origin for the silica fragment containing stishovite and seifertite.
The Chang’e-5 mission’s success not only marks a significant achievement in space exploration but also enhances our understanding of the moon’s geological history.
Through the analysis of lunar samples, scientists can unravel the complex processes that have shaped the lunar surface over billions of years, shedding light on the broader dynamics of celestial bodies in our solar system.
The research findings can be found in Matter and Radiation at Extremes.
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