InSight Data Helped Find Out The Thickness Of The Martian Crust And Mantle
Planetologists have determined the thickness of the crust and mantle of Mars, as well as calculate the diameter of its core, thanks to data from the Mars InSight spacecraft, according to the scientific journal Geophysical Research Letters.
"Such data will help us understand how Mars originated and how the planets as a whole are formed. The thickness of the crust and mantle of Mars in the past was calculated using theoretical models, and InSight gave us the first opportunity to test and improve them, " said one of the authors of the study, Professor Alan Levander of Rice University in Houston (USA).
The InSight lander is a joint project of NASA, the German aerospace center (DLR), and the French national center for scientific research. It landed on the surface of Mars in December 2018. Its main tasks are to search for traces of marsquakes and study the internal structure of the red planet. His scientific work began in February last year when German and American scientists completed the installation of the SEIS seismograph and began to deploy the HP3 drilling rig.
The first task InSight was decided in the first six months after planting: he has recorded more than 170 marsquakes. Some of them were formed at great depth and were powerful enough to pass through the entire thickness of the Martian interior. This was used by scientists to study the structure of Mars and determine the size of its core.
On Earth, as Levander and his colleague Sizhuan Deng write, such measurements are usually carried out based on data from several seismic stations located in different parts of the planet. On Mars, however, planetologists have only one seismometer, so they have developed an alternative method for analyzing signals from SEIS.
Secrets of the bowels of Mars
In particular, scientists tried to identify in the collected information those periodic changes in the properties of seismic noise that are associated with the onset of day and night, as well as other recurring phenomena. Besides, planetologists have identified a kind of "reflection" of these noises from different layers inside the bowels of Mars. Such fluctuations are random in themselves, but if they occur periodically, then you can extract information about the surfaces from which they are reflected.
Based on these considerations, Dan and Levander analyzed the entire SEIS data set. They identified three sets of signals associated with specific layers in the interior of Mars, which are located at depths of 35, 1110-1170 and 1520-1600 km from the surface of the planet.
The first of them is an analog of the Earth's surface of Mohorovich. This line separates the mantle rocks from the crust rocks. The second is a conditional boundary between the lower and upper part of the mantle of Mars. It is dominated by two different types of rocks – olivine and the product of its transformation under the influence of high temperature and pressure-wadsleyite. It passes seismic waves much faster than olivine, which is reflected in the seismic signals that were recorded by SEIS.
In turn, at a depth of 1520-1600 km, according to scientists, there is a border between the lower mantle of Mars and the surface of its liquid core. This means that its radius is from 1730 to 1840 km. This is comparable to the results of some past theoretical assessments of how the interior of the red planet is arranged.
Subsequent observations, the researchers' hope, will show whether there is solid metalcore in the core of Mars. Knowing this is important to understand whether the red planet had a strong magnetic field in the past, as well as to find out why it disappeared.