Mars Planet Layers Revealed

By monitoring seismic waves that were transmitted through Mars’ interior, scientists discovered a layer of molten rock surrounding its liquid metal core – thus challenging current theories about its structure and evolution.

This new discovery could help scientists gain a greater understanding of how Mars formed, evolved and lost its capacity for life over time. Furthermore, it could shed light on how Mars may have obtained its current barren surface.

The Core

Mars resembles other differentiated terrestrial planets in that it features a metal alloy core surrounded by silicate mantle and crust layers, similar to Earth. These distinct layers may have resulted from an early global magma ocean stage4,5 when heavy iron gravitationally separated from lighter silicates to form its core6,7,8. Existing observations and models indicated that Mars, like Earth, contains a core composed primarily of iron and nickel with some light elements such as sulfur, carbon, oxygen, and hydrogen also present. Samuel and his colleagues found this assumption counterintuitive, since most chondritic meteorites that comprise Mars’ core-forming solids have low densities relative to their total mass, making it unlikely for large quantities of light elements to sink to its core2,3,4.

Instead, they suggested that Earth had a much smaller and denser core surrounded by an outer shell composed of molten silicate. To test this theory, scientists turned to seismic waves produced by marsquakes; when rock moves underground it produces P and S waves which reveal its inner structure through boundaries that remain hidden beneath its surface. Marsquakes produce these same P/S waves but at lower frequencies than Earth’s; seismometers on board spacecraft are required in order to detect them.

Through careful examination of P and S wave data, the team determined that Mars has a liquid layer of molten silicate approximately 93 miles thick that surrounds its liquid iron core – supporting their theory that instead of being rich with light elements like oxygen or sulfur, its core contains 9-14% lighter materials.

Additionally, the team discovered that the mantle beneath our planet is more viscous than previously assumed. This mantle may behave more like a lava lamp than a molten bath in terms of heating distribution; slowly conducting heat from below into our surface layers for thermal lithosphere formation9,10.

Science magazine published on July 22 a study led by Amir Khan of ETH Zurich using marsquake data to confirm that Mars has an interior thermal break extending between 250 to 370 miles down. At this depth, its crust and mantle conduct heat as a single stable shell known as the lithosphere; beyond this point it becomes more like fluid with convecting waves moving downward like an oil lamp.

The Mantle

As Mars formed from dust and larger meteorite debris orbiting the Sun, its layers gradually separated to become three distinct areas: crust, mantle and core. Scientists have been trying to gain an understanding of this process known as differentiation which took place on Mars.

As part of their ongoing effort, two separate scientific teams have used seismic data from NASA InSight lander to discover that an unimaginable layer of partially molten silicate rock lies astride the metal core on Mars – necessitating an overhaul of existing theories regarding its internal structure, geological history and evolutionary development.

Henri Samuel, a geodynamicist from Paris Institute of Planetary Physics and Paris Cite University in France, joined the InSight mission team prior to its launch in 2017. His work centers on understanding how terrestrial planets such as Earth and Mars formed, evolved, and their current states. Samuel had conducted extensive studies of Mars from both geodynamical and geological viewpoints and noted that existing models of its interior assumed that its present-day mantle is homogenous.

But he recognized that in order to understand Mars’s thickness and composition, researchers needed to study how seismic waves traveled through its interior – with InSight’s seismometer providing the ideal way of doing this by recording how fast seismic waves travel within its confines.

Scientists analyzing data from InSight discovered a distinct variation in the speed at which seismic waves traveled through various areas of Mars’ interior, which they interpret as evidence for a molten mantle layer.

Their findings support theories that early Mars was once covered by an ocean of magma that crystallized into an abundant silicate layer rich in iron and radioactive elements at its core, leading to its current barren state and impacting both thermal evolution and cooling trajectory of planet. Furthermore, this layer could have had a great effect on generation/weakening of Mars’ magnetic field; understanding their role is integral for understanding planetary science according to Lekic.

The Crust

Science had only ever had an estimate of Mars’ crust thickness until recently. Thanks to analyses from NASA’s InSight lander’s seismic data collection, scientists now have tangible constraints on this thickness based on analysis of seismic data alone and gravity and topography data as well. They’ve utilized all this data along with gravity measurements and topographic maps from spacecraft missions that satisfy seismic constraints to build global crustal thickness models that satisfy these seismic constraints.

These models demonstrate that Mars’ molten silicate layer is much thinner than previously believed and suggest it may be hidden underneath by more complex structures composed of mafic rock-forming minerals, like olivine and pyroxene that form basalt, the dark volcanic rock that constitutes most of Mars’ crust. Furthermore, this molten silicate layer attenuates seismic waves well, making it an attractive candidate to hold clues for other ongoing mysteries about the planet like how its dense mantle deforms in response to Phobos orbit.

Knowledge of how planetary layers form is critical in understanding its history and evolution over time; especially how its crust develops is crucial to understanding whether or not its surface can support life.

Before, it was thought that Mars’ crust formed after cooling of an ocean of magma on Earth. However, the new study indicates this might not necessarily be the case; magma may have melted and crystallized while still moving through Mars’ mantle layer to produce molten silicate layers that thermally emitted heat and drove early plate tectonic processes on Mars.

Researchers are continuing their investigation of Mars’s layers, particularly how its mantle and core interact. According to their latest research, their latest estimates for its core have revealed it as denser and smaller than earlier estimates; its structure being enclosed by low density liquid silicates instead of being encased by dense rock layers like Earth. Furthermore, iron found within Mars’s core was more likely mixed with nickel than chromium–an indicator that suggests it may have formed during an earlier stage in solar system’s creation–perhaps when still just a swirling nebula!

The Surface

Scientists understand a great deal about Mars’ history, such as that it has had periods of wetness and volcanic activity in its past. Additionally, its tilt on its axis changes over time leading to various climates on its surface – some areas where water once flowed cratered but others smooth regions where once flowed water.

Mars resembles Venus in that its surface is divided between older, heavily cratered highlands and younger lowland plains; like these planets, most of Mars is covered by an icy layer.

Mars’ atmosphere contains water vapor and carbon dioxide, along with plenty of minerals such as iron and magnesium. Furthermore, due to rusting (oxidization of minerals in rock), it has taken on an orange hue due to oxidization processes oxidizing rock layers in space.

Mars may not be as active today than Earth, but there still exist some tectonic shifts and volcanic activity on its surface. Furthermore, recently a rover on Mars detected signs of water in its soil indicating it once had liquid water on its surface.

The surface of our planet contains many canyons that were likely formed through wind erosion or lava flows, with some dry and eroded while others filled with water-ice snow. Scientists speculate these remnants date back to earlier epochs when our world was warmer and wetter than it is now.

One significant discovery during the Noachian period was boron’s discovery as a mineral used for producing sugars that make RNA, thus expanding our understanding of life on Mars.

2021 saw another piece of the puzzle fall into place when researchers analyzed data from a meteorite that struck Mars and produced seismic waves picked up and mapped by Insight’s seismometer. Researchers soon realized that Mars’ underlying structures are much more complicated than they imagined – for example, their assumptions regarding how solidly attenuating their molten mantle beneath its crust and over its liquid metal core should have been.

Scientists also discovered that Mars’ crust is thinner than previously assumed; their study, published in Science, suggests it has two or three sub-layers. This explains why certain areas have more craters than others.