With high-pressure experiments at DESY's X-ray light source PETRA III and other facilities, a research team around Leonid Dubrovinsky from the University of Bayreuth has solved a long standing riddle in the analysis of meteorites from Moon and Mars. The study, published in the journal Nature Communications, can explain why different versions of silica can coexist in meteorites, although they normally require vastly different conditions to form. The results also mean that previous assessments of conditions at which meteorites have been formed have to be carefully re-considered.
With high-pressure experiments at DESY's X-ray light source PETRA III and other facilities, a research team around Leonid Dubrovinsky from the University of Bayreuth has solved a long standing riddle in the analysis of meteorites from Moon and Mars. The study, published in the journal Nature Communications, can explain why different versions of silica can coexist in meteorites, although they normally require vastly different conditions to form. The results also mean that previous assessments of conditions at which meteorites have been formed have to be carefully re-considered.
The scientists investigated a silicon dioxide (SiO2) mineral that is called cristobalite. „This mineral is of particular interest when studying planetary samples, such as meteorites, because this is the predominant silica mineral in extra-terrestrial materials,“ explains first author Ana ?ernok from Bayerisches Geoinstitut (BGI) at University Bayreuth, who is now based at the Open University in the UK. „Cristobalite has the same chemical composition as quartz, but the structure is significantly different,“ adds co-author Razvan Caracas from CNRS, ENS de Lyon.
Different from ubiquitous quartz, cristobalite is relatively rare on Earth's surface, as it only forms at very high temperatures under special conditions. But it is quite common in meteorites from Moon and Mars. Ejected by asteroid impacts from the surface of Moon or Mars, these rocks finally fell to Earth.
Surprisingly, researchers have also found the silica mineral seifertite together with cristobalite in Martian and lunar meteorites. Seifertite was first synthesised by Dubrovinsky and colleagues 20 years ago and needs extremely high pressures to form. “Finding cristobalite and seifertite in the same grain of meteorite material is enigmatic, as they form under vastly different pressures and temperatures,” underlines Dubrovinsky. “Triggered by this curious observation, the behaviour of cristobalite at high-pressures has been examined by numerous experimental and theoretical studies for more than two decades, but the puzzle could not be solved.”
Read more at Deutsches Elektronen-Synchrotron DESY
Image: A fresh impact crater on Mars, as imaged by the HiRISE camera on board NASA's Mars Reconnaissance Orbiter. (Credit: NASA/JPL/University of Arizona)
