A team of scientists found how gypsum, an economically important material, forms and in the process, discovered new ways to interpret water availability on Mars. Gypsum is one of the materials that both Earth and the red planet contain.

Chemically known as calcium sulfate dihydrate, gypsum is used widely as the commercial construction material Plaster of Paris. Despite its importance to people on Earth, there is little knowledge on how gypsum grows from ions in solutions.

In the study published in the journal Nature Communications, a team of geochemists showed that gypsum forms through a complex process involving four steps. The process itself will help scientists develop an efficient means to make plaster.

In the past, the formation of gypsum, which comes from concentrated aqueous solutions of calcium sulfate, was believed to be just a single process. To show the complex process of how this material forms, the scientists examined the process using in situ and time resolved synchrotron-based X-ray scattering at the Diamond Light Source facility in the United Kingdom.

They were able to identify each of the four steps of the process, stressing that the first few moments in the reaction chain are important since they will shape the final properties of gypsum. During the first step, several small elongated particles form "bricks" that collect, arrange and assemble on their own in the final stages, eventually forming gypsum crystals.

Gypsum mainly contains calcium, water and sulfur bound to oxygen. The scientists believe that knowing the breakdown of each step in the formation of gypsum can help in understanding the presence of hydrological matter on the surface of Mars and perhaps on other planets.

"Our results allow for a quantitative understanding of how natural calcium sulfate deposits may form on Earth and how a terrestrially unstable phase-like bassanite can persist at low-water activities currently dominating the surface of Mars," the researchers concluded.

Gypsum is considered non-toxic to humans and the environment. It is an abundant mineral on Earth and is known to have been used since the ancient Egyptian period. Most of the gypsum in North America is used to manufacture gypsum board, plasters and other products.

Photo: Quinn Dombrowski | Flickr