Perseverance captures a selfie of “Rochette,” the first rock successfully sampled by the rover on Mars.
While Earth boasts over 6,000 distinct minerals, Mars has only 161 minerals identified after more than 50 years of investigation, despite similarities in average chemical composition between the two planets.
A recent study suggests that this discrepancy arises from the limited pathways for mineral formation on Mars compared to Earth, as Mars lacks crucial factors for mineral formation: plate tectonics and life-forms.
The study found that Earth has 57 primary and secondary mechanisms for mineral formation, whereas Mars only has 20 identified modes of mineral formation.
In the early stages of both planet’s histories, minerals formed similarly. They crystallized from cooling magma and formed under high-pressure conditions caused by meteorite impacts. Tectonic and hydrothermal activities also contributed to the formation of numerous new minerals after the stabilization of crust and oceans on each planet. However, the mineralogical paths of Mars and Earth diverged.
Unlike Earth, Mars is geologically inactive today. Its smaller size allowed much of its internal energy generated by radioactive decay and primordial heat to dissipate into space, causing the cessation of currents of partially molten rock that drive plate tectonics on Earth.
Geologic sections of Earth and Mars showing the sub-surface layers and mineral composition.
Lacking plate tectonics, Mars does not have the necessary pressure and temperature conditions for the formation of many metamorphic minerals such as kyanite and garnet. Plate tectonics also play a vital role in creating new chemical combinations and minerals via continuous mixing of elements.
Geological evidence suggests that Mars had water approximately 3.6 billion years ago. However, due to the weak gravitational pull and lack of a dense atmosphere, most of the water evaporated over time or is now frozen underground.
In contrast, although conditions for life may have existed on Mars during its early days, Earth’s biodiversity has steadily increased over time.
Lead author of the study, Robert Hazen, explains, “One-third of Earth’s minerals could not have formed without biology.” Minerals such as apatite and calcite, found in the shells and bones of various organisms, were created due to microbial activity, which also resulted in the formation of 2,000 oxide minerals when microbes produced an oxygen-rich atmosphere over 2 billion years ago.
Even today, animals contribute to the diversity of minerals on Earth. For example, the mineral spheniscidite forms when penguin urine reacts with clay minerals beneath a rookery on Elephant Island in the British Antarctic Territory. Additionally, a survey conducted in 2017 uncovered 600 new minerals derived from recent human activities.
The study, titled “On the Diversity and Formation Modes of Martian Minerals,” was published in the Journal of Geophysical Research: Planets (2023). Additional material was provided by Rachel Fritts for the American Geophysical Union.
