Mars Reveals a Surprising Molten Rock Layer

A recent meteorite impact on Mars has led to groundbreaking discoveries about the planet’s interior, challenging previous assumptions and offering new insights into its formation and evolution.

Key Takeaways:

  • A meteorite impact in September 2021 has reshaped our understanding of Mars’s interior.
  • Seismic energy analysis post-impact revealed a molten rock layer surrounding Mars’s liquid-metal core.
  • This discovery indicates that the Martian core is smaller than previously believed.
  • The findings shed light on the red planet’s formation and billions of years of evolution.
  • NASA’s InSight mission played a crucial role in these discoveries.

A Deep Dive into Mars’s Core

In a remarkable turn of events, a meteorite that struck Mars in September 2021 has provided scientists with invaluable data about the planet’s inner structure. By analyzing the seismic energy that resonated through Mars after the impact, researchers identified a layer of molten rock enveloping the planet’s liquid-metal core. This revelation, discussed in two recent papers in Nature, suggests that Mars’s core is more compact than previously estimated. It also addresses long-standing questions about the planet’s formation and its evolution over billions of years.

NASA’s InSight Mission: A Game-Changer

The pivotal data comes from NASA’s InSight mission, which positioned a seismometer on Mars’s surface. From 2018 to 2022, this instrument detected numerous ‘marsquakes’ that shook the planet. Seismic waves, whether from quakes or impacts, can vary in speed based on the materials they traverse. This allows seismologists to infer a planet’s internal structure. On Earth, earthquake data has revealed our planet’s layers, including the crust, mantle, and core. Understanding if other planets have similar layers is crucial for grasping their geological history and potential habitability.

In July 2021, based on 11 marsquake observations, researchers believed Mars’s liquid core had a radius of approximately 1,830 kilometers. This measurement was larger than anticipated and implied the core had a high concentration of light elements like sulfur mixed with iron.

However, the September 2021 meteorite impact provided a breakthrough. The impact occurred on the opposite side of Mars from the InSight lander, allowing the probe to detect seismic energy traversing the Martian core. This data led Henri Samuel, a geophysicist, to propose the existence of a molten rock layer surrounding Mars’s core. The seismic energy’s path revealed that the previously assumed boundary between the liquid core and solid mantle was, in fact, the juncture of the molten rock layer and the mantle. Samuel suggests the actual core lies beneath this molten layer and has a radius of only 1,650 kilometers.

Solving the Martian Puzzle

The revised core size aligns better with laboratory and theoretical estimates, eliminating the need for high concentrations of light elements. The presence of a second liquid layer within Mars also corresponds with other evidence, such as Mars’s gravitational interaction with its moon, Phobos.

Simon Stähler, a seismologist, acknowledges the new findings, emphasizing that the previously identified boundary was indeed between liquid and solid layers, but it marked the top of the molten rock layer rather than the liquid-metal core.

Unique Layering of Mars

Another study, independent of Samuel’s, concurs with the presence of a molten rock layer around Mars’s core but estimates the core’s radius to be 1,675 kilometers. This research analyzed seismic waves from the same meteorite impact and simulated the properties of molten elements under Martian core conditions. Amir Khan, a geophysicist, notes the unique “liquid-liquid layering” on Mars, a phenomenon not observed on Earth.

The molten rock layer might be a remnant of a magma ocean that once enveloped Mars. As this magma cooled and solidified, it would have left a deep layer of radioactive elements that continue to release heat, keeping the rock molten at the mantle’s base.

With the InSight lander now out of commission, further significant revisions to Mars’s core size seem unlikely in the near future. However, revisiting past mission data might uncover more details about the red planet’s interior.

Source: Nature