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Molten Martian core could explain red planet''s magnetic quirks

Unraveling the Mysteries of Mars: New Evidence Points to a Fully Molten Core Beneath the Red Planet

In a groundbreaking revelation that reshapes our understanding of the Red Planet, scientists have uncovered compelling evidence suggesting that Mars possesses a completely molten core. This discovery, drawn from seismic data collected by NASA's InSight lander, challenges long-held assumptions about the internal structure of our neighboring world and offers fresh insights into why Mars evolved so differently from Earth. Far from being a dormant, solidified relic of the solar system's early days, Mars appears to harbor a dynamic, liquid heart that could explain its geological quirks, from its extinct volcanoes to its vanished magnetic field. As researchers delve deeper into this molten mystery, the implications extend beyond planetary science, touching on questions of habitability, magnetic protection, and the potential for life on other worlds.

The journey to this discovery began with the InSight mission, which touched down on Mars' Elysium Planitia region in November 2018. Equipped with a sensitive seismometer, the lander was designed to eavesdrop on the planet's internal rumblings—marsquakes that send seismic waves rippling through its layers. Over its operational lifespan, InSight detected hundreds of these quakes, providing a seismic portrait of Mars' interior. Initial analyses painted a picture of a planet with a relatively large core, but uncertainties lingered about its state—solid, liquid, or a mix? Now, a new study published in a leading scientific journal has refined these models, concluding that the Martian core is likely entirely molten, composed primarily of iron and lighter elements like sulfur.

To understand the significance, it's essential to contrast Mars with Earth. Our home planet boasts a layered core: a solid inner sphere of iron-nickel alloy surrounded by a liquid outer core. This churning liquid generates Earth's protective magnetic field through a dynamo effect, shielding the atmosphere from solar wind erosion and enabling life to thrive. Mars, however, tells a different story. Billions of years ago, it too had a global magnetic field, as evidenced by magnetized rocks in its southern hemisphere. But that field flickered out around 4 billion years ago, leaving the planet vulnerable to atmospheric stripping and rendering its surface a barren, radiation-blasted desert.

The new findings suggest that Mars' core never developed a solid inner component. Instead, it remains a seething ball of molten metal, perhaps due to the planet's smaller size and faster cooling rate. Without the temperature and pressure extremes needed to solidify the inner core, the dynamo weakened and eventually shut down. "This molten core model fits the seismic data like a glove," explains one of the lead researchers, a planetary geophysicist involved in the study. "It explains why Mars' magnetic field died young and why we see no evidence of ongoing tectonic activity today."

Diving into the details, the core is estimated to span about 1,800 kilometers in radius—roughly half the planet's total radius—making it proportionally larger than Earth's core relative to the planet's size. Seismic waves from distant marsquakes, including some triggered by meteor impacts, have been crucial in mapping this. P-waves (primary waves) and S-waves (secondary waves) travel at different speeds through solid and liquid materials. The absence of certain wave reflections at the core-mantle boundary, combined with the planet's overall density measurements from orbital data, points unequivocally to a liquid state. Moreover, the core's composition includes a significant fraction of lighter elements, which lower its melting point and keep it fluid even as the planet cools.

This revelation has profound implications for Mars' geological history. A fully molten core implies that heat transfer within the planet has been more efficient than previously thought, potentially fueling ancient volcanic activity. Olympus Mons, the solar system's tallest volcano, and the vast Tharsis bulge could be remnants of this internal vigor. Yet, without a solid inner core to sustain convection, the dynamo stalled, dooming Mars to magnetic silence. This loss allowed solar winds to strip away much of the atmosphere, turning a once-potentially habitable world into the arid expanse we see today.

But why does Mars differ so starkly from Earth? Size matters. Mars is only about half Earth's diameter, so it lost internal heat more rapidly after formation. Earth's larger mass retained heat longer, allowing for the complex core dynamics we enjoy. Additionally, Mars' core may have formed with more sulfur or other volatiles, keeping it molten. These differences highlight the delicate balance required for planetary habitability. "Mars serves as a cautionary tale," notes a co-author of the study. "It shows how small variations in a planet's makeup can lead to vastly different evolutionary paths."

The findings also tie into ongoing debates about Mars' water history. A molten core could have influenced mantle convection, driving hydrothermal systems that might have supported microbial life in the planet's wetter past. While InSight's data doesn't directly detect water, it complements evidence from rovers like Perseverance, which has found signs of ancient lakes and rivers in Jezero Crater. If Mars once had oceans, a dynamic core might have cycled nutrients and heat, creating niches for life.

Looking ahead, this discovery fuels excitement for future missions. The upcoming Mars Sample Return mission, a joint NASA-ESA effort, aims to bring back rocks that could reveal more about the planet's interior through isotopic analysis. Seismic networks proposed for future landers could provide even finer-grained data, potentially confirming the core's fluidity and mapping its boundaries more precisely. Moreover, understanding Mars' core enhances our models for exoplanets. As telescopes like the James Webb Space Telescope hunt for Earth-like worlds, knowing how cores influence magnetic fields and atmospheres will help identify truly habitable candidates.

Yet, challenges remain. InSight's seismometer went silent in late 2022 due to dust accumulation on its solar panels, limiting the dataset. Some scientists caution that alternative models—perhaps a partially solid core—could still fit the data with tweaks. "We're dealing with indirect measurements from a single location," admits a skeptic in the field. "More data from diverse sites would solidify these conclusions." Nonetheless, the consensus is shifting toward a fully liquid core, prompting revisions in textbooks and simulations.

In the broader context of solar system exploration, this molten core underscores Mars' allure as a natural laboratory. It's not just a dead world but one with a hidden vitality, a reminder that even in stillness, planets pulse with ancient energies. As we prepare for human footsteps on Martian soil—perhaps by the 2030s under NASA's Artemis program or private ventures like SpaceX's Starship—this knowledge will inform everything from resource utilization to radiation shielding. Imagine drilling into the regolith, tapping geothermal heat from a world that's still warm at heart.

Ultimately, peering into Mars' molten core is like reading the diary of a planet that once dreamed of life. It whispers secrets of formation, evolution, and demise, urging us to cherish Earth's fragile protections. As research continues, each seismic echo from the Red Planet brings us closer to answering the age-old question: Why did Mars falter while Earth flourished? In this cosmic tale, the molten core is not just a scientific fact—it's a key to unlocking the mysteries of our place in the universe.

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Read the Full Phys.org Article at:
[ https://phys.org/news/2025-04-molten-martian-core-red-planet.html ]