So far, everything indicated that our neighboring planet Mars has a completely liquid core. But seismic data from the NASA-Landesonde Mars Insight now draw a different picture. With the help of new analysis methods, researchers have discovered some abnormalities in the waves of Marsquakes recorded by the probe. They indicate a structural border and density differences within the Mars of Mars. This suggests that the red planet has a solid inner core – similar to the earth. This inner core of Mars is around 1200 kilometers in size and accounts for around 18 percent of the Marsradius. The seismic data also allow initial conclusions to be drawn about the composition of the inner core. Accordingly, the inner mars of Mars can contain more lighter elements such as sulfur, oxygen and carbon than the inner core of the earth. This could explain his density and crystallization under the conditions of the interior of the Mars, as the planetary researchers report.
Although Mars is our neighboring planet, many questions about his inner structure were unclear for a long time: is he also a smaller brother of the earth in terms of its inner life? Or is his inner layer different from that of our planet? First answers delivered the landing of the NASA probe Mars Insight on the red planet in November 2018. She brought a seismometer to Mars, which in the following four years recorded the seismic data of more than 1,300 Marsquakes. From the term and shape of these waves, planetary researchers were able to gain valuable information on the nature, density and temperature of the interior of the Mars. Among other things, the data revealed that the Mars crust is thicker than the earthly, but the Marsmantel lacked a correspondence to the lower mantle. At the core coat limit there is also probably a thin layer of liquid silicate rock. The core of Mars is around 1800 kilometers tall and significantly lighter and less dense than the Earth core. However, the biggest difference: According to the first evaluations, the Mars has no fixed, crystallized inner core, it is predominantly liquid – so the state of research so far.
Fast waves and an additional reflection
In order to check this assumption more precisely, researchers around Huixing BI from the University of Hefei in China have once again subjected the seismic data from Mars Insight to a more precise analysis. To do this, they evaluated the primary waves of 23 low -frequency Marsquakes, which had passed the deep interior of the planet before they arrived at the Seismometer of the Mars probe. The team used a method for its analysis of the terms and amplitudes, the so -called seismic array analysis, which is normally used to combine the data of several measuring stations. Because there was only one measuring station on Mars with Mars Insight, BI and his colleagues convert these analyzes so that they were able to compare the characteristics of the different quakes in the form of so -called vespectrums. It showed that the quake waves reflected on the opposite border of the Mars nuclei met around 50 to 200 seconds earlier than for a liquid core at the Marssonde seismometer.
“This significantly earlier arrival of the PKKP waves indicates faster terms in the center of the core,” explains the team. According to their calculations, the seismic waves crossed the central part of the Marshes around 0.25 kilometers per second faster than its outer areas. “Such a steep speed gradient is difficult to reach with a purely liquid core,” write BI and his colleagues. They also identified some quake waves that had apparently been thrown back from a structural border inside the Marsh. Such a PKIKP phase is considered an indicator of the existence of an inner solid core, at the border of which the seismic waves are reflected. “This was previously demonstrated by the earth and the moon,” explain the researchers. In the PKIKP waves of the Marsdats, you therefore see a strong indication of the existence of a solid inner core, even with the red planet. This is supported by amplitude comparisons of the seismic waves, which allow conclusions to be drawn about the density of the passed material. “In order to explain the observed amplitude differences between PKKP and PKIKP waves, a density jump of around seven percent would be suitable at the inner kernel limit,” the team writes.
More light elements in the core
Together, the analyzes suggest that Mars could have a solid inner core, unlike previously. This should have a radius of around 613 kilometers. As BI and his colleagues explain, this corresponds to around 18 percent of the total radius of Mars. The solid inner core of Mars has thus proportional a size of the size of the earth that makes around 19 percent of the earth’s radius. If this is confirmed, Mars would be a smaller twin brother on earth, at least in terms of its core.
Both planets therefore have a metallic, crystallized inner core, which is surrounded by a liquid outer core. The new analyzes also provide the first indications of what the Interior of the Mars is made of. “Our calculations indicated that a pure iron nickel inner nickel core cannot explain the observed characteristics,” write BI and his team. Instead, the inside of the Mars must contain a relatively large proportion of light elements to cause the density jump and crystallization. By comparing with geodynamic models, the team determined that the inside of the Mars should contain around 12 to 16 percent by weight sulfur, 6.7 to 9 percent oxygen and around 3.8 percent carbon. Iron and oxygen could then form iron oxide (FEO), which stirries in the interior of the Mars, as the researchers explain.
“This discovery provides an important indication of the understanding of the thermal and chemical state of Mars”, state BI and his colleagues. “In addition, the connection between the development of the inner core and the development of the Marsian magnetic field could provide new insights into the dynamo effects on various planets.” Unlike the earth, Mars no longer has a global magnetic field. So far, planetary researchers suspected that this is related to the lack of a solid inner core. Because the earthly magnetic dynamo is powered by the interaction of the liquid iron flowing around the solid iron core in the outer core. However, according to BI and his team, the failure of the magnetic dynamos on Mars can also be explained by interior core. They assume that the distribution of lighter elements in the core areas, the type of crystallization and the pace of cooling the interior of the Mars play a role. In order to understand the development of the interior of the Mars and the effects on the magnetic field of the planet, further studies are now necessary.
Source: Huixing BI (University of Hefei, China) et al., Nature, DOI: 10.1038/S41586-025-09361-9
