InSight has detected seismic motion on the Red Planet since early 2019. Their data showed crust thickness and core size.
Scientists say they can now describe the inner rocky structure of Mars in huge numbers.
The data was obtained from the InSight spacecraft, which has been detecting seismic motions on the Red Planet since early 2019.
The mission led by the US space agency, NASA, revealed that the average thickness of the Martian crust is between 24 and 72 kilometers – slightly thinner than expected.
But the main discovery was the size of the planet’s core – its 1,830 km radius is the highest of previous estimates.
This is the first time that scientists have been able to directly map the inner layers of a planet (not counting the Earth). This was also done on the Moon, but Mars (total radius: 3,390 km) was at a much larger scale.
Having this information allows researchers to better understand the formation and evolution of different planetary bodies.
Insight arrives at these findings in the same way that seismologists study the Earth’s interior—tracking for signs of earthquakes.
These events release waves of energy. Changes in the course and speed of the waves reveal the nature of the rocky material they pass through.
The seismograph system installed by NASA’s probe detected hundreds of tremors, some of which were discovered in the past two years that had the right characteristics to “imagine” the interior of Mars.
The instrumentation team, led by France and the United Kingdom, determined that the hard outer part, the crust, of Mars is 20 kilometers or 39 kilometers thick just below the probe (depending on which sublayer is present).
Extrapolating the data to known surface geology for the rest of the planet, this indicates an average thickness of between 24 km and 72 km. For comparison purposes, the average thickness of the Earth’s crust is 15-20 km. Only in such a continental area as the Himalayas it can reach 70 km.
However, the really interesting number indicates the essence. Signals from “harmful waves” resonating in this metallic element indicate that it begins about halfway below the surface, at a depth of about 1,560 km – and that it is in a liquid state.
Most previous estimates predicted a smaller core.
The InSight probe was launched in 2018, and landed on Mars in November of the same year.
Photo: NASA/JPL-Caltech/Lockheed Martin
The mission team says that two impressive results stem from the new direct observations.
The first is that the known mass and moment of inertia of Mars indicate that the core is much less dense than previously thought, and that the iron-nickel alloy that dominates its composition must be significantly enriched with lighter elements such as sulfur.
The second finding concerns the layer between the core and the crust – the mantle, which is thinner than initially thought.
Again, based on the known size of Mars, this mantle is unlikely to reach the pressures at which the mineral bridgemanite becomes stable.
On Earth, this hard mineral covers the core, slowing down convection and heat loss. Early on Mars, its absence would have resulted in rapid cooling.
This initially allowed for strong convection in the metal core and a dynamo effect that resulted in the generation of a global magnetic field. But this, of course, is now disabled. Today, no global magnetic field can be detected on this planet.
If it was there, it would provide some protection to protect its surface from the harmful radiation that is constantly emitted from space and makes the world very inhospitable.
The surface of Mars is cold and dry, as well as bombarded with radiation.
Photo: NASa/JPL-Caltech/Asu/Msss
Tom Pike, a professor at Imperial College London, UK, is one of the leading researchers of the Insight seismograph system.
“We’ve been able, for the first time, to look inside another planet using seismology, and what we’ve seen on Mars is that we have a core that’s bigger and lighter than we expected. That says a little bit about how the planet evolved from geological time,” he told BBC News.
San Cottar of the University of Cambridge in the UK, who is not part of the mission team, called Insight’s findings an “achievement”, given the difficulty of studying small earthquakes that occur on Mars.
Its magnitude never exceeds 4 degrees, which humans will notice only several kilometers from the epicenter. “Martemotos is very, very weak,” he explains.
“It’s more challenging than doing seismology on Earth. The mission scientists also had to develop ways to work with just one seismometer represented by the InSight spacecraft. With this data it’s really impressive.”
