New Insights Refine How Martian Meteorites Formed in Space
Recent findings from the California Institute of Technology suggest that earlier estimates of the forces that hurled Martian rocks into space were too high. Scientists now have a clearer picture of the pressure conditions during the ejection events that sent Martian material toward Earth.
Researchers have identified 266 meteorites on Earth that originated on Mars. These rocks were carved free by extreme, high-energy processes during the impacts that transported other meteorites. For many years, the prevailing view held that these rocks were formed under huge pressures, produced by colossal impacts.
In the study led by Hu Jinping and collaborators, the team sought to determine the precise conditions that caused Martian stones to be expelled into space. A key component of Martian rocks is the mineral plagioclase. When subjected to intense pressure, such as from a major impact, plagioclase can transform into maskelynite, a glassy phase. Thus, the presence and proportion of maskelynite in a sample serve as a direct indicator of the impact pressure experienced during formation.
To replicate the ejection process, the researchers used a specialized launcher capable of propelling plagioclase fragments at speeds exceeding Mach 5. Earlier experiments indicated that plagioclase converts to maskelynite at pressures around 30 gigapascals (GPa), equating to roughly 300,000 times Earth’s sea-level atmospheric pressure. It also corresponds to the pressure a diver might encounter at depths near 3 kilometers.
However, the latest experiments show that the transition to maskelynite occurs at about 20 GPa. This new figure aligns with pressure estimates derived from analyses of other Martian minerals found in meteorites, reinforcing a revised understanding of the energetic conditions during meteorite ejection.
The authors hope that this refined pressure benchmark will enable scientists to more accurately reconstruct the events that created individual meteorites and, in turn, identify the corresponding impact craters on Mars that produced them.
In a related line of inquiry, some scientists have noted a broader curiosity about brain activity in dying individuals, a field that continues to evolve as new observations emerge (attribution: Caltech study team and cited researchers).