While we have yet to discover any life on Mars, the planet is far from calm. In the depths, seismic waves of the geologically active Red Planet were discovered.
The first dataset from NASA's Mars InSight probe gave us the first direct evidence of Marsquakes. This puts the planetary profile of seismic activity somewhere between the Earth (high) and the Moon (low).
A series of articles detailing the new InSight results have just appeared in a special issue of Nature.
“This is the first mission to focus on direct geophysical measurements of any planet other than Earth, and it gave us our first real understanding of Mars' internal structure and geological processes,” says geologist Nicholas Schmerr of the University of Maryland.
“This data helps us understand how the planet works, its level of seismicity, how active it is and where it is active.”
InSight, a lander designed to tell us more about what's inside Mars, felt its first tremors last April with the Seismic Inner Structure Experiment Instrument (SEIS).
On Mars, the first shock was not strong enough to measure it. But over 235 Martian days, the device recorded 174 quakes. Of these, 150 were high-frequency tremors similar to those recorded by Apollo's experiments on the moon.
The remaining 24, however, were low frequency earthquakes. This is really interesting because while planetary geologists believe that Mars was once tectonically active, it is generally believed that the planet is now quite quiet.
“The other 24 are predominantly low-frequency, and their spectral shapes follow the same scaling laws as earthquakes and lunar quakes, which leads us to conclude that they are of tectonic origin,” the team wrote in the article summarizing.
'The characteristics of these spectra are consistent with expectations for distant tectonic events.'
In addition, the way waves propagate through the crust can be used to track earthquakes back to their source. Three out of 24 earthquakes were strong enough to attempt this.
The team was able to trace two of these three earthquakes in the Cerberus Fossey region, where a series of fractures caused by faults that split the crust can be found. Evidence suggests that it has been tectonically and volcanically active in recent times, that is, over the past 10 million years.
But that's not all. InSight is not only equipped with seismic instruments, but also measures the atmosphere and the surrounding geology of the landing site.
We know from orbiters that atmospheric gravity waves – ripples in fluids such as gases and liquids – can occur on Mars. In an article on the Martian atmosphere, InSight provided a catalog of the various types of such waves in the Martian atmosphere.
And they found infrasound in the Martian atmosphere too.
“From these measurements, we discovered Martian infrasound and an unexpected similarity between atmospheric turbulence on Earth and Mars,” the researchers write. “We anticipate that InSight observations of the Martian atmosphere will be key to predictive capabilities and further exploration.”
In another article, a team of researchers studied the planet's magnetic field at the InSight landing site. Mars has been found to have a fairly weak magnetic field, which is believed to contribute to its inhospitable nature.
But the results show that Mars was not always like this.
“We find the field is ten times stronger than satellite models predict,” the researchers write. “We find magnetized rocks below the surface, within ~ 150 km of the landing site.”
Taken together, the results show that Mars was once a very different place. And, of course, they could help inform crewed missions to the planet – not just telling us what to expect, but where to look to find more clues to Mars' secrets.
Meanwhile, the InSight mission is slated for yet another Earth year … so we must learn more about what lies beneath the mysterious red surface.
The work was published in a special issue of the journal Nature. You can find them here, here, here, here, here and here.
Sources: Photo: ESA / DLR / FU Berlin
