A new study could significantly advance astronomers’ understanding of the Red Planets’ geological past and the processes that shaped its surface. Researchers involved in the multi-university study discovered evidence of a heterogeneous mantle and crustal structure that formed during Mars’ early days. The findings suggest that Mars went through a period of intense volcanic activity that contributed to the planet’s unique geology.
Martian meteorites, rocks ejected from the surface of Mars that have landed on Earth, serve as vital records of Mars’ geological history. Among these meteorites, two types, nakhlites and chassignites, are particularly important. Nakhlites are basaltic rocks rich in the mineral augite, while chassignites are primarily comprised of olivine. These meteorites are believed to have formed from the same magmatic system on Mars, providing a unique window into the planet’s past.
“Martian meteorites are the only physical materials we have available from Mars,” lead author and Scripps Institution of Oceanography geologist James Day said. “They enable us to make precise and accurate measurements and then quantify processes that occurred within Mars and close to the Martian surface. They provide direct information on Mars’ composition that can ground truth mission science, like the ongoing Perseverance rover operations taking place there.”
The researchers analyzed highly siderophile elements (chemical elements that preferentially associate with metallic iron) and osmium isotopes in these meteorites to understand their origins and the processes they underwent. Their findings suggest that nakhlites and chassignites formed from a common volcanic system, which experienced various geological processes over billions of years.
The study confirms that nakhlites and chassignites originated from the same magmatic source, meaning they crystallized from the same molten rock. This indicates a layered structure in Mars’ interior, comprising an ancient, enriched basaltic crust and a depleted mantle.
Some nakhlites show signs of incorporating older, altered basaltic crust during their formation. This crust differs from other ancient Martian crustal materials represented by meteorites like Allan Hills 84001 or Northwest Africa 7034/7533. The altered crust contained elements incorporated into the nakhlites as they crystallized.
“With the existing collection of Martian meteorites, all of which are volcanic in origin, we are able to better understand the internal structure of Mars,” Day said.
The data suggest a complex, layered structure within Mars. It includes an ancient basaltic crust formed from magma ocean cumulates rich in trace elements, a mantle that has undergone chemical alteration, and a deep mantle layer that lost some original elements through volcanic processes.
These findings have profound implications for understanding Mars’ geological evolution.
“What’s remarkable is that Mars’ volcanism has incredible similarities, but also differences, to Earth,” Day said. “On the one hand, nakhlites and chassignites formed in similar ways to recent volcanism in places like Oahu in Hawaii. There, newly formed volcanoes press down on the mantle generating tectonic forces that produce further volcanism.”
However, Mars’ reservoirs are extremely ancient, separating shortly after the Red Planet formed.
“On Earth, plate tectonics has helped to mix reservoirs back together over time,” Day said. “In this sense, Mars provides an important link between what the early Earth may have looked like from how it looks today.”
The interaction between the crust and mantle layers through processes like volcanic activity played a crucial role in shaping Mars’ surface and geological features.
This study emphasizes the importance of Martian meteorites in uncovering the planet’s history. Continued analysis of these meteorites will remain essential as astronomers await samples returned directly from Mars by future missions. Understanding the interaction between Mars’ crust and mantle teaches scientists about the Red Planet and offers comparative insights into how planets like Earth evolved geologically.
The findings appeared in the journal Science Advances.
