Crustal evolution in Mars does not follow the formula for Earth

Artist's concept of the interior of Mars. NASA/JPL

Scientists at Cornell are proposing an alternative theory for Mars’ continental crust, which may not be Earth-like but instead they are proposing a new theory, crystalized magma welled up from inside the red planet. 

Data from NASA rover Curiosity’s drillings from three years ago, led to a publication by scientists where they describe the “granite-like” rock found by the rover, indicating a Martian continental crust similar to Earth. 

However, geology can be complicated. “To make continental crust you need to brew its ingredients for a very long time – millions and millions of years. The brewing process is complex, involving process of plate tectonics,” said Esteban Gazel, Cornell associate professor of earth and atmospheric sciences. 

Gazel and colleagues saw no indication the Martian crust was formed by plate tectonics or a true continental crust published in the work “Formation of Evolved Rocks at Gale Crater by Crystal Fractionation and Implications for Mars Crustal Composition,” on May 31 in the Journal of Geophysical Research: Planets. 

These investigators studied the continental crust hypothesis, simulating how magma forms igneous (volcanic) rocks, they used the thermodynamical software called MELTS. For starting composition data, the team used a Martian meteorite that fell to Earth and five Mars surface rocks. They realized that simple magma evolution would create a planetary crust through a process called fractional crystallization, since magma cools down and produces crystals, then changes in composition as new crystals form. 

Principios de la cristalización fraccionada en un magma. Durante el enfriamiento la composición de un magma va evolucionando porque, a partir de la masa fundida, cristalizan sucesivamente minerales diferentes. 1: cristaliza olivino; 2: cristalizan olivino y piroxeno; 3: cristalizan piroxeno y plagioclasa; 4: cristaliza plagioclasa. En el fondo de la cámara magmática se va formando un cúmulo de cristales. Wikipedia.

That was a simpler geologic recipe revealed at the area surrounding Gale Crater. The group found that the “granite-like” rocks near Gale Crater do not constitute continental crust, analogous to Earth crust. 

Gazel said that the magma evolutionary process is very common on Earth. “You can find it in Hawaii, Iceland or the Canary Islands. Volcanoes from these locations also produce magma that has high-silica content, but it does make it a continental crust. Although this magma has high amounts of silica, the magma lacks the remaining ingredients,” he explained. “This is just a natural process that happens in Earth’s volcanoes too, and it doesn’t necessarily make new continents.” 

As an analogy, Gazel explained that the granite used to make kitchen countertops is created through an accumulation of crystals in a magma chamber. “You cannot have kitchen countertops if, in previous geologic processes, magma does not cool down,” he said. “That process is called fractional crystallization, resulting in the compositions commonly found on Mars. Nevertheless, our study confirms the formation of Mars’ early magmas by activity similar to processes found in Hawaii today,” Gazel said. “There are gigantic upwellings of hot mantle material from deep regions in Mars.” 

Sources: Cornell Chronicle, Wikipedia,