Mars has long intrigued humanity, prompting extensive scientific inquiry into its nature. A key question concerns the composition and characteristics of its core. Understanding what lies beneath Mars’s surface provides insights into its formation and evolution. The planet’s deep interior holds clues to its past, influencing its geological activity and atmospheric history.
The Presence of Mars’s Core
Mars, like Earth and other rocky planets, possesses a central core primarily made of iron. This internal layering results from planetary differentiation, where denser materials like iron sank to the center, while lighter silicates formed the mantle and crust. Scientists continue to study the core’s precise nature and properties.
Scientific Evidence for Mars’s Core
Scientists have gathered evidence for Mars’s core through various methods, with recent seismic data providing the most direct insights. NASA’s InSight lander, with its seismometer (SEIS), detected numerous “marsquakes,” which are seismic vibrations traveling through the planet’s interior. By analyzing how these seismic waves—P-waves (compressional) and S-waves (shear)—propagate, researchers deduce the properties of its internal layers. P-waves travel through both solid and liquid materials, while S-waves cannot pass through liquids.
Seismic waves traveling through Mars’s deep interior, including those that traversed the core, provided crucial data. For instance, two marsquakes in 2021, originating on the opposite side of the planet from InSight, allowed seismic waves to pass through the core. The absence of S-waves passing through the core provided strong evidence that the core is at least partially liquid. Other evidence includes observations of Mars’s gravitational pull, which reveals density variations, and weak, localized magnetic fields in its crust. These crustal magnetic fields are remnants of an ancient global magnetic field, indicating a core that was once active.
Composition and Structure of Mars’s Core
Mars’s core is primarily composed of iron, but it also contains lighter elements like sulfur, oxygen, carbon, and possibly hydrogen. The presence of these elements lowers the core’s density compared to a pure iron core. Recent analyses of InSight data suggest the Martian core is smaller and denser than earlier estimates, with a radius of approximately 1,650 to 1,700 kilometers, roughly half the radius of Mars itself.
Unlike Earth’s core, which has a solid inner core and a liquid outer core, Mars’s core is believed to be entirely or mostly liquid. This fully liquid state differentiates it from Earth’s more complex core structure. Recent studies indicate that Mars’s liquid metallic core may be surrounded by an insulating layer of molten silicates, about 150 kilometers thick. This layer, which Earth does not possess, acts like a “heating blanket” around the core, influencing its thermal evolution and cooling.
Implications of Mars’s Core
The characteristics of Mars’s core have implications for understanding the planet’s past and current state. The primarily liquid nature of the core, coupled with the insulating molten silicate layer, likely explains why Mars lacks a strong, global magnetic field today. Unlike Earth’s constantly convecting liquid outer core, which generates its protective magnetic field, the Martian core’s dynamics are different. The absence of effective convection within Mars’s core means it cannot sustain a global magnetic dynamo.
The lack of a strong global magnetic field had consequences for Mars’s atmosphere. Without this protective magnetosphere, the solar wind, a stream of charged particles from the Sun, stripped away Mars’s early atmosphere over billions of years. This atmospheric loss contributed to the planet’s transformation into the cold, arid world observed today, where liquid water cannot persist on its surface.
Understanding the core’s composition and state helps scientists piece together Mars’s geological history, its internal heat budget, and the factors that led to the loss of its past habitability.