Examining conditions within the Earth’s interior is crucial not only to give us a window back to Earth’s history but also to understand the current environment and its future. This study offers an explanation of carbon’s descent into the deep Earth. “The stability regions of carbonates are key to understanding the deep carbon cycle and the role of the deep Earth in the global carbon cycle.” says Leonid Dubrovinsky, from the University of Bayreuth. “The intense X-rays from the ESRF allow us to access the extreme conditions within the entire Earth’s mantle.” underlines Valerio Cerantola, lead author, former PhD student at the University of Bayreuth and now postdoctoral scientist at the ESRF.