Recent studies indicate that the heart of the Red Planet developed significantly faster than that of Earth, due to the penetration of molten sulfides of iron and nickel through solid rock formations.
Planets are composed of layers, similar to a cosmic onion: the outer layer is the crust, followed by the mantle, then the solid outer core, and the liquid inner core, which can generate a global magnetic field through its rotation.
Researchers refer to this layering process as “differentiation,” signifying the separation of elements based on their density: heavier elements like iron and nickel gravitate towards the center, while lighter elements, such as silicates, remain in the outer parts. It was previously believed that differentiation occurs only when a planet’s interior is molten, heated by the radioactive decay of isotopes like aluminum-26 or iron-56. This was thought to account for the formation of Earth’s core, a process that spanned over a billion years.
What Process Led to the Formation of Mars’ Core?
Nonetheless, Mars appears to deviate from this norm. Analysis of Martian meteorites revealed that the planet’s core came into existence merely a few million years after the Solar System’s inception, far more quickly than Earth’s core. This rapidity posed a challenge to traditional planetary formation models.
Currently, scientists at NASA’s Johnson Space Center, part of the Astromaterials Research and Exploration Science Division (ARES), believe they have uncovered the rationale. The key lies in Mars’ formation location, situated at the junction between the inner area of the protoplanetary disk (rich in dense elements) and the outer segment (abundant in lighter elements such as hydrogen and water). In this region, there was sufficient iron and nickel, together with oxygen and sulfur—a vital mix for their research.
The Aroma of Sulfur
Employing sulfate-rich rocks subjected to temperatures exceeding 1,020 °C (sufficient to melt sulfides, not silicates), the researchers examined how sulfide melts permeate cracks within solid rocks in laboratory conditions. Three-dimensional images produced via X-ray tomography clearly illustrated the movement of molten sulfides among minerals, congregating towards the center.
However, they required an external validation. The team sought chemical evidence of this identical process in meteorites, particularly in the uncommon category of oxidized meteorites. By partially melting synthetic sulfides infused with rare platinum group metals (such as iridium, osmium, palladium, platinum, and ruthenium), they succeeded in replicating chemical patterns analogous to those found in meteorites.
In order to identify these metals without destroying the specimens, researcher Jake Setera created a specialized laser ablation technique that enabled the detailed recognition of marks left by sulfur melt in solid rocks. The outcome: these rare metals function as chemical “fingerprints,” verifying that the molten sulfides can advance to the center and create a core even prior to the entire planet becoming molten, reports Space.com.
The framework proposed by the researchers may apply not only to Mars but also to all sizable bodies formed in the median section of the protoplanetary disk. Nevertheless, its implications for Mars could resolve one of the oldest enigmas concerning the Red Planet: the unusually quick formation of its core. Should this theory prove accurate, the core of the Red Planet is likely to contain significant amounts of sulfur, suggesting it may “smell” akin to rotten eggs.
This research was published in the journal <a href="https://www.nature.com/articles/s41467-025-58517-8"
