The BRICS TimesA breakthrough study confirms the presence of a solid inner core on Mars — the first time such a discovery has been made on a planet beyond Earth.
Image credit: Vadim Sadovski
In a landmark discovery, Chinese researchers working alongside international collaborators have, for the first time, identified a solid inner core inside Mars with an estimated radius of nearly 600 kilometers. This breakthrough offers vital insights into the planet’s deep interior and provides key evidence to understand the evolution of Mars’ once-active magnetic field.Among all the terrestrial planets in our solar system, Mars has long been regarded as Earth’s closest analog in terms of environment, making it an essential subject for probing planetary interiors and their evolutionary processes. It has also been a central focus for interplanetary exploration. Yet, examining the hidden structures deep within planets remains an immense challenge. For comparison, even Earth — the planet scientists know best — posed difficulties: researchers first hypothesized the presence of its solid inner core based on seismic wave behavior in 1936, but it took another fifty years before the discovery could be confirmed with certainty.Unraveling Mars’ inner structure has proven even more daunting. Although thousands of marsquakes have been detected in recent years, weak signals combined with interference and background noise have limited scientists’ ability to study its deeper layers.The new findings were achieved by a research group led by Sun Daoyuan and Mao Zhu of the University of Science and Technology of China in Anhui Province, working together with an international expert. Using seismic data recorded by NASA’s InSight lander, the team applied advanced array analysis techniques to 23 marsquake events with relatively strong signals. This allowed them to extract the seismic phases that traveled directly through Mars’ interior and detect features within its core.Published on Wednesday in the journal Nature, the study revealed that Mars possesses a distinctly layered core structure. The planet hosts a liquid outer core and a deeper solid inner core characterized by faster seismic wave speeds. Their measurements indicate the radius of Mars’ inner core is approximately 600 kilometers, which equates to nearly one-fifth of the planet’s total radius. When scaled proportionally to Earth’s size, Mars’ inner and outer core structure is remarkably similar to Earth’s.Further analysis of marsquake data revealed a roughly 30 percent increase in seismic wave velocity and a 7 percent density difference between the outer liquid core and the solid inner core. These results enabled the researchers to model the potential composition of Mars’ innermost region. Unlike a core made solely of iron and nickel, Mars’ inner core appears to include lighter elements: between 12 and 16 percent sulfur, 6.7 to 9 percent oxygen, and up to 3.8 percent carbon.The presence of such light elements is significant, as it provides important clues to the history of Mars’ magnetic field — from its early active state to its present-day inactivity. At the same time, it helps lay the groundwork for comparing the evolutionary differences between Earth and other rocky planets in the solar system.This is the first confirmed detection of a solid inner core in any planet other than Earth, demonstrating that Mars also experienced core-mantle differentiation similar to Earth’s geological history. Beyond Mars itself, the innovative seismological techniques employed in this research could serve as a valuable reference for future deep-space missions, including lunar exploration, where similar methods may be used to investigate planetary interiors.”The authors have done a detailed job of using multiple working lines of evidence for their phase detection analysis. Martian seismology is notably tough, so congratulations to the authors for doing such a thorough and careful job,” the journal’s reviewer commented.
