Though Mars has no tectonic plates,the first marsquakes were detectedwithin months of the probe landing.
These may result from vibrations resulting from meteorites hitting the surface or from processes inside the planet.
Planets grow by accumulating material (accretion) early in the life of a solar system.
Until now, how much of Mars each of these layers occupied was unknown.
40% off TNW Conference!
Instead, to estimate its size, we used seismic waves (created by marsquakes).
Shear waves travel from a marsquake and reflect off the iron-nickel core.
Careful seismic processing by seismologists from around the world revealed signals from six marsquakes relatively close to the probe.
This may help us understand why there is no planet-wide magnetic field on Mars today, unlike on Earth.
Layers and layers
A planets crust comprises a tiny fraction of its mass.
This suggested the possible average Martian crust thickness is between 24km to 72km.
This means we can rule out earlier estimates of up to about 100km.
To sample different depths of the mantle we can use both direct and reflected seismic waves.
Direct P- or S-waves dive deep into the mantle and then return to the surface.
By comparing the data and the models, they found that Marss lithosphere is between 400km and 600km thick.
