The space agency’s InSight lander detected the sound shortly after it touched down on Mars in November 2018. The robot was using a seismometer tool to measure so-called “marsquakes” when it picked up the background “hum” of the Red Planet, NASA says. The lander also registered more than 400 quakes, confirming that Mars has plenty of seismic activity.
The humming sound is thought to be a combination of wind above and geological movement below the Martian surface, although the exact cause remains a mystery.
The so-called “hum” falls largely outside the range of human hearing, meaning future human visitors to Mars likely won’t be able to hear the Red Planet’s “song.”
The planet is also basically shivering with earthquakes as it gets colder, InSight’s readings show.
Researchers published their findings in multiple Nature-branded journals on Monday.
“We have discovered Martian infrasound and unexpected similarities between atmospheric turbulence on Earth and Mars,” they wrote in one of the studies.
Infrasound is noise that falls below the range that’s audible to conscious humans. The phenomenon has long been a topic of mystery, fascination and suspicion on Earth, where it’s been blamed as the invisible culprit for many maladies. However, the science around its actual effects remains fuzzy.
Some humans have reported infrasound as a “hum” that torments them at the edge of hearing. The sound has been reported more frequently around certain technologies and in particular areas, such as Windsor, Ont., although its exact cause has not been pinpointed.
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Researchers have also previously identified a “hum” to the planet Earth, much like the one they’ve now detected on Mars.
The Martian hum is one of several fresh mysteries that InSight researchers look forward to delving into in the future.
“It’s just such a relief to finally be able to stand up and shout, ‘Look at all this great stuff we’re seeing,'” Bruce Banerdt, the principal InSight investigator, told National Geographic.
InSight has been taking its readings from a small crater called the Elysium Planitia, which is located on a volcanic plane that’s often ravaged by wind and dust storms.
Researchers also gathered a trove of data about the Martian region’s seismic activity and magnetic field, which proved to be 10 times stronger than initially expected.
The lander recorded 174 so-called “marsquakes” over its first 10 months on the Red Planet, the papers say. Twenty-four of them were moderately powerful with magnitudes around 3-4, while the rest were smaller and of uncertain origin. The vast majority of the quakes would not have posed a threat to humans on the surface, researchers said in a press conference.
The quakes are being caused by Mars contracting as it cools down, Banerdt told reporters on Monday. However, it’s not exactly clear what’s triggering individual quakes.
“As the planet cools, it contracts, and then the brittle outer layers have to fracture in order to sort of maintain themselves on the surface,” Banerdt told reporters. “That’s the long-term source of stresses.”
Banerdt’s InSight colleague, Suzanne Smrekar, also hinted at another mystery that might still be waiting below the Martian surface.
“This area still has activity at depth, perhaps including hot magma,” she told reporters.
In other words, Mars is singing a song we can’t quite hear — and it might be hiding lava that we just can’t see.
— With files from The Associated Press and Reuters