In the first measurement of the nucleus of another planet, seismography carried out over several Martian years has revealed that the liquid metal nucleus is softer than expected, more like a tune from Mars than a rod from Mars.
While the newly arrived Perseverance rover has been garnering much of the Mars-related attention, a trio of recently published papers that measured the depth and composition of the Red Planet’s iron-nickel crust, mantle, and core, conducted in 2018 NASA’s InSight lander seeks to steal the limelight.
Using the same techniques in Earth seismography, geoplanetary scientists analyzed data obtained from InSight’s extremely sensitive seismometer to measure a series of “marsquakes.” The data they recovered helps paint a picture of the progression of Mars from a planet that once had plenty of liquid water and a stable atmosphere thanks to its magnetic field, to a world of cold temperatures and rust.
There were challenges, and in what National Geographic described as a great analytical feat, it is worth mentioning what needed to be overcome.
- On Earth, seismography is performed with thousands of instruments placed in different areas. InSight has one.
- With no plate tectonics to speak of, earthquakes on Mars are extremely weak and humans would hardly notice the strongest ever recorded, even if they were within a few kilometers of the epicenter.
- Given the lack of additional instruments and the weakness of tremors, the seismometer in InSight needed to be extremely sensitive, so that it would also pick up wind readings, as well as crackle from minute molecular changes in the lander’s metal as it went. gets hot and cold every Martian day.
- The most seismically active region of Mars was half a planet from the lander, and the planet’s core blocked any readings that might have reached InSight.
A big soft
Through all of this, the team managed to obtain dimensions of the planet’s core, upper mantle, and Martian crust, all with an accuracy of a few kilometers.
“As a seismologist, you probably have one chance in your life to find a core for a planet,” says InSight member Simon Stähler, a seismologist at the research university ETH Zurich, in an interview with National Geographic.
Its main resources were P waves and S waves, the same two types of tremors that scientists measure on Earth and on the Moon. P waves move a bit like the wind in water, pushing things down, while S waves vibrate and move from side to side, dislodging particles as they move.
These two waves move through different types of matter, giving a kind of “length and height” level of granularity. P waves can move through solids, liquids, and gases, while S waves can only move through solids. Because P waves can pass through a solid mantle into a liquid core, measuring your readings in a sonar-like way gives you an idea of the depth of the core, while measuring the return velocity of the S wave gives you a depth. in which the nucleus begins, since it cannot pass through the liquid and returns attached to the surface.
By measuring a set of P waves, S waves, and then a weaker delayed S wave a few hundred seconds later, the team determined that the Martian core is about 1,830 kilometers wide, slightly larger than anticipated. This means that, unlike Earth, which has an upper mantle and a lower mantle, Mars has only one, roughly 500 kilometers deep.
“We infer an average core density of 5.7 to 6.3 grams per cubic centimeter, which requires a substantial complement of dissolved light elements in the iron-nickel core,” write the authors, who published a paper on each layer. planetaria in the magazine. Science.
Estimated to contain carbon, oxygen, hydrogen and sulfur, this softer-than-expected core and the single-layered lithosphere could shed light on the creation and disappearance of the Martian magnetosphere that took place 3.7 billion years ago.
With a smaller lithosphere and a more porous core, the convection currents would have created the potential for rapid cooling of the interior that National Geographic Hypothesis as the genesis of the Martian magnetosphere.
The loss of the magnetosphere would have caused the original Martian atmosphere to dissipate, so understanding what planetary components could have led to that is key to understanding why Mars lost all of its water and became a cold, rusty desert.
Finally, by detailed mapping of the Martian crust, consisting of two or three layers at a depth of between 24 and 72 kilometers, the team found that radioactive elements that produce heat were between 13 and 21 times more abundant than elsewhere, which could help form a theory of work on why Martian volcanoes appear. where they do it on a planet that doesn’t have plate tectonic forces that would normally create them.
The Red Planet is revealing its secrets to us, forming a case study of planetary geosciences in conditions totally different from those of Earth and expanding our capacities to understand the most interesting celestial bodies: the planets.
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