- Jonathan Amos
- BBC Science Correspondent
Image source,NASA
Since the beginning of 2019, InSight has detected more than 700 vibrations on Mars.
Scientists say they have some absolute data to describe the internal rock structure of Mars. The data comes from the InSight probe, which has been sensing vibrations on Mars since the beginning of 2019.
NASA led the mission, which showed that the average thickness of the Martian crust is between 24 kilometers and 72 kilometers, which is thinner than previously expected.
But the key discovery is the size of the core of Mars, with a radius of 1830 kilometers, which is at the top of previous estimates.
This is the first time that the scientific community has succeeded in directly mapping the internal layered structure of planets other than the Earth. Scientists have done similar things on the moon before, but the scale of Mars (total radius: 3390 kilometers) is much larger.
With this information, researchers can better understand the formation and evolution of different planetary bodies.
“Insight” uses the same way that seismologists study the stratification of the earth’s interior, namely by tracking vibration signals to achieve results.
These vibrations release energy waves, and changes in the path and speed of the energy waves will reveal the nature of the rock material that it passes through.
The seismograph system deployed by the NASA probe has observed hundreds of vibrations. In the past two years, a small number of vibrations have just the right characteristics that can be regarded as internal imaging of Mars.
The instrument team led by France and the United Kingdom determined that the hard outer crust of Mars is 20 kilometers or 39 kilometers thick directly below the probe (depending on the precise layering at the location). Combined with the known surface geology of other parts of Mars, it can be inferred that the average thickness is between 24 kilometers and 72 kilometers. In contrast, the average thickness of the earth’s crust is 15-20 kilometers. Only in continental areas like the Himalayas can it reach 70 kilometers.
But the really interesting numbers are about the core of the earth. The signal bounced from the “Martian Shock” to the instrument showed that it was in a liquid state from the surface of Mars all the way to a position of about 1,560 kilometers. Most previous estimates believe that the core of Mars is relatively small.
Image source,NASA
The InSight probe was launched to Mars in 2018 and landed in November of the same year.
The task team said that there are two interesting results from the new direct observations.
First, the known mass and moment of inertia of Mars mean that the density of the Martian core will be much smaller than previously predicted, and the dominant component of Mars, iron-nickel alloys, must be rich in lighter elements such as sulfur.
The second result is related to the layer between the core and the crust: the mantle. This layer is now thinner than previously assumed and seems to be different from the earth. This layer is composed of stones without major gradation.
According to the known size of Mars, this mantle pole height is unlikely to reach the pressure that stabilizes the mineral Richmanite.
On the earth, this hard mineral covers the center of the earth, slowing down convection and heat loss. Therefore, in the early stage of Mars formation, the absence of such minerals led to a rapid cooling of the temperature.
Initially this would allow the strong convection of the metal core and the generator effect that drives the global magnetic field. But this of course no longer exists. Today, the global magnetic field cannot be detected on this planet.
If it exists, it will provide some shielding to protect its surface from the destructive radiation that continues to fall from space, which makes the world extremely uninhabitable.
Image source,NASA
The surface of Mars is cold, dry, and radiant.
Professor Tom Pike of Imperial College London is one of the main researchers of the seismograph system of InSight. He told the BBC: “For the first time we can use seismology to observe the interior of another planet. What we see on Mars is that we have a larger and lighter core than expected. This does tell us a lot about the planet’s geological period. Information on the evolution.”
Dr. Sanne Cottaar from the University of Cambridge was not on the task force. She described the “Insight” result as a feat because it is very difficult to study the tiny vibrations that occur on Mars. They have never exceeded level 4, and humans will only notice them within a few kilometers of the epicenter.
She said: “Martian earthquakes are very, very weak. This is much more challenging than doing seismology on Earth. Mission scientists also had to develop a seismograph that the InSight detector can use. So see these data, and It is very encouraging to be able to use these data to observe the internal structure of Mars.”