Strategic Communications and Marketing News Bureau

Iron ‘snow’ helps maintain Mercury’s magnetic field, scientists say

Jie "Jackie" Li, a professor of geology, and graduate student Bin Chen have concluded that deep inside the planet Mercury, iron "snow" forms and falls toward the center of the planet, much like snowflakes form in Earth's atmosphere and fall to the ground. The movement of this iron snow could be responsible for Mercury's mysterious magnetic field.

Jie “Jackie” Li, a professor of geology, and graduate student Bin Chen have concluded that deep inside the planet Mercury, iron “snow” forms and falls toward the center of the planet, much like snowflakes form in Earth’s atmosphere and fall to the ground. The movement of this iron snow could be responsible for Mercury’s mysterious magnetic field.

CHAMPAIGN, Ill. – New scientific evidence suggests that deep inside the planet Mercury, iron “snow” forms and falls toward the center of the planet, much like snowflakes form in Earth’s atmosphere and fall to the ground.

The movement of this iron snow could be responsible for Mercury’s mysterious magnetic field, say researchers from the University of Illinois and Case Western Reserve University. In a paper published in the April issue of the journal Geophysical Research Letters, the scientists describe laboratory measurements and models that mimic conditions believed to exist within Mercury’s core.

“Mercury’s snowing core opens up new scenarios where convection may originate and generate global magnetic fields,” said U. of I. geology professor Jie “Jackie” Li. “Our findings have direct implications for understanding the nature and evolution of Mercury’s core, and those of other planets and moons.”

Mercury is the innermost planet in our solar system and, other than Earth, the only terrestrial planet that possesses a global magnetic field. Discovered in the 1970s by NASA’s Mariner 10 spacecraft, Mercury’s magnetic field is about 100 times weaker than Earth’s. Most models cannot account for such a weak magnetic field.

Made mostly of iron, Mercury’s core is also thought to contain sulfur, which lowers the melting point of iron and plays an important role in producing the planet’s magnetic field.

“Recent Earth-based radar measurements of Mercury’s rotation revealed a slight rocking motion that implied the planet’s core is at least partially molten,” said Illinois graduate student Bin Chen, the paper’s lead author. “But, in the absence of seismological data from the planet, we know very little about its core.”

To better understand the physical state of Mercury’s core, the researchers used a multi-anvil apparatus to study the melting behavior of an iron-sulfur mixture at high pressures and high temperatures.

In each experiment, an iron-sulfur sample was compressed to a specific pressure and heated to a specific temperature. The sample was then quenched, cut in two, and analyzed with a scanning electron microscope and an electron probe microanalyzer.

“Rapid quenching preserves the sample’s texture, which reveals the separation of the solid and liquid phases, and the sulfur content in each phase,” Chen said. “Based on our experimental results, we can infer what is going on in Mercury’s core.”

As the molten, iron-sulfur mixture in the outer core slowly cools, iron atoms condense into cubic “flakes” that fall toward the planet’s center, Chen said. As the iron snow sinks and the lighter, sulfur-rich liquid rises, convection currents are created that power the dynamo and produce the planet’s weak magnetic field.

Mercury’s core is most likely precipitating iron snow in two distinct zones, the researchers report. This double-snow state may be unique among the terrestrial planets and terrestrial-like moons in our solar system.

“Our findings provide a new context into which forthcoming observational data from NASA’s MESSENGER spacecraft can be placed,” Li said. “We can now connect the physical state of our innermost planet with the formation and evolution of terrestrial planets in general.”

With Li and Chen, Case Western Reserve University planetary geodynamics professor Steven A. Hauck II was a co-author of the paper.

The work was funded by the National Science Foundation.

 

Editor’s note: To reach Jie Li, call 217-333-7008; e-mail: jackieli@illinois.edu.

To reach Bin Chen, call 217-244-8479; e-mail: binchen2@illinois.edu.

Read Next

Health and medicine Dr. Timothy Fan, left, sits in a consulting room with the pet owner. Between them stands the dog, who is looking off toward Fan.

How are veterinarians advancing cancer research in dogs, people?

CHAMPAIGN, Ill. — People are beginning to realize that dogs share a lot more with humans than just their homes and habits. Some spontaneously occurring cancers in dogs are genetically very similar to those in people and respond to treatment in similar ways. This means inventive new treatments in dogs, when effective, may also be […]

Honors From left, individuals awarded the 2025 Campus Awards for Excellence in Public Engagement are Antoinette Burton, director of the Humanities Research Institute; Ariana Mizan, undergraduate student in strategy, innovation and entrepreneurship; Lee Ragsdale, the reentry resource program director for the Education Justice Project; and Ananya Yammanuru, a graduate student in computer science. Photos provided.

Awards recognize excellence in public engagement

The 2025 Campus Awards for Excellence in Public Engagement were recently awarded to faculty, staff and community members who address critical societal issues.

Uncategorized Portrait of the researchers standing outside in front of a grove of trees.

Study links influenza A viral infection to microbiome, brain gene expression changes

CHAMPAIGN, Ill. — In a study of newborn piglets, infection with influenza A was associated with disruptions in the piglets’ nasal and gut microbiomes and with potentially detrimental changes in gene activity in the hippocampus, a brain structure that plays a central role in learning and memory. Maternal vaccination against the virus during pregnancy appeared […]

Strategic Communications and Marketing News Bureau

507 E. Green St
MC-426
Champaign, IL 61820

Email: stratcom@illinois.edu

Phone (217) 333-5010