A study from the University of Cape Town’s (UCT) Department of Geological Sciences that used Martian meteorite to understand the volcanic process on Mars has been published in the journal Nature Communications Earth and Environment.
Martian meteorite are rare rocks from Mars that have landed on Earth, ejected by large impacts and surviving atmospheric entry, serving as our primary physical samples of Mars for study.
Findings reveal that Mars contains long-lived geochemical reservoirs in its mantle, producing chemically distinct magmas – closed-system behaviour – but that its volcanic systems are also dynamic and capable of open-system mixing and assimilating crustal material during magma ascent to surface.
The study formed part of Dr Chad Peel’s PhD thesis. Supervised by Dr Geoffrey Howarth, an associate professor attached to the Kimberlite research group (KRG) and the Terrestrial and Planetary Petrology (TAPP) research group at the Department of Geological Sciences, the study sought to answer some fundamental questions about the composition of the deep interior of Mars.
“Our study used a group of martian meteorites called shergottites to understand how volcanic systems on Mars formed and evolved, and what they reveal about the planet’s deep interior,” says Peel, the lead author. “These meteorites originate from volcanic eruptions on Mars that were later blasted off the planet’s surface during impact events and into space before eventually landing on Earth.”
Scientists have long recognised that shergottites fall into “depleted”, “intermediate”, and “enriched” groups based on their geochemical compositions. However, it has been unclear whether these geochemical differences reflect distinct mantle sources inside Mars or mixing with crustal material as magmas rose to the surface.
To address this, researchers measured rare earth elements inside the very first crystals that formed from martian magmas, olivine, and in trapped melt pockets within those crystals. These inclusions act as snapshots of the original magma before any later modification.
“Our results show that Mars contains long-lived geochemical reservoirs in its mantle, producing chemically distinct magmas but that its volcanic systems are also dynamic and capable of open-system mixing and assimilating crustal material during magma ascent to surface,” says Peel.
Interest in how planetary interiors work
Peel says he has always been fascinated by how planetary interiors work.
“I was drawn to this topic because martian meteorites represent the only physical samples we have of Mars, making them an incredibly precious scientific resource. This project gave me the unique opportunity to use these samples to address one of the most fundamental and big-picture questions in planetary science, what is the composition of the martian mantle and how has it evolved?,” he says.
“Our main goal was to determine why martian volcanic rocks have such diverse geochemical compositions. Do these differences reflect variations in the martian mantle, or do they result from mixing and assimilation as magmas rise through the crust?
“By analysing the trace-element chemistry of the earliest-formed minerals, we wanted to directly test whether martian magmas behaved as closed or open systems. We hoped to build a clearer picture of the origin and evolution of martian magmas and the dynamics of the planet’s interior.”
Insights into the composition of Mars’ mantle
This research provides important insight into the composition of Mars’ mantle, helping refine models of how the planet formed and how it cooled over time.
“It enhances our understanding of the evolution of martian volcanoes, revealing whether magmas rose directly from the mantle or interacted with the crust during ascent. Ultimately, our research contributes to a more accurate and complete understanding of Mars’ geological history and interior evolution,” says Peel.
He adds that the study captured a rare “before and after” record inside a single martian meteorite, known as LAR 12011.
“This meteorite preserves both an original depleted magma and a later enriched magma trapped inside olivine crystals, providing direct evidence of open-system processes such as magma mixing or crustal assimilation occurring on Mars.
“Such processes have long been suggested but have never been observed so clearly in these meteorites.”
Peel says the work highlights the importance of pristine sample curation, as terrestrial alteration can obscure the original martian chemical signatures in some meteorites.