This is how NASA detected a march march for the very first time

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Image of Mars surface taken by ESA Mars Express spacecraft

Mars does not have plate tectonics like the Earth. Instead, its earthquakes are generated by the movement of magma deep within its surface, the slow cooling of the planet and the shock waves created by tiny meteorites pounding the planet.

Despite all this activity, it took two months of listening to the NASA InSight probe before detecting the first rumblings of the red planet. On April 6, the probe seismometer recorded what was later confirmed as the first March earthquake detected by human instruments.

But measuring the rumblings of a planet that – closer to us – remains at nearly 34 million kilometers, requires an almost unimaginable amount of patience. Twice a day, a team in Switzerland receives seismic data from the InSight probe, where it performs a first analysis.

For Renee Weber, a global scientist with Mars InSight's seismology team, this involved checking her e-mail obsessively at the start of the day, hoping that a signal would be detected overnight. "Even before I get up in the morning, every day I pick up my phone and look at my email as follows:" Maybe it will be the day! Are we going to have this earthquake? Is it going to be now? And now? ", She says.

She was not alone in her anticipation. "It was very tempting when [the probe landed] and potentially see [a signal] every day, "says Tom Pike, an engineer at Imperial College London, who led the team that designed and built the silicon sensors for the British part of the seismometer. "Then, weeks passed and we did not see any, then more weeks – more than one hundred soils (Martian days) on the planet and more than two months since their deployment, before we saw a signal clear."

Fifty years after the seismometers placed by the astronauts during the Apollo missions detected the first moonstrokes, and forty years after the Viking lander's seismometers were disappointed by the wind, they were too strong to detect earthquakes on Mars, the InSight detector actively detects the weakest vibrations on another world. .

The team was made aware of these signals a few hours after their first detection, but spent a few weeks analyzing the results before releasing the data on April 23, shortly before InSight's principal investigator, Bruce Banerdt. , announcing the results on stage at a meeting of the Seismological Society of America. in Seattle. "This is just the beginning of seismology on Mars," says Philippe Lognonné, a member of the Mars InSight team at the Paris Institute of Earth Physics and a veteran of missions exploring the seismic activity of Mars.

The signal has also been recorded in audio form. This is the first time we hear the inner workings of Mars. In one Clip posted on Nasa's Twitter accountyou can hear the bottom swirl of the Martian wind blending into a growing racket – the sound of a marsquake. The strong acceleration at the end of the clip, which has been multiplied by 60, corresponds to the sound of the LG maneuvering his camera to sweep the sky.

This long, slow accumulation is similar to lunar earthquake recordings and may be related to the fact that Mars' surface is so exposed to meteorite attacks because of its weak atmosphere. Over the course of billions of years, meteorite impacts have shattered the upper surface of Mars. "It moves like a cracked mirror producing a whole wave of vibrations," says Pike. This broad crack wave may be the seismic signature of broken dry rocks, in contrast to the more consistent movement of intact and wet surface rocks on Earth.

However, understanding the cause of the earthquake will take longer and compare with other seismic events. "We do not know yet about a source – it could be an impact, it could come from the planet itself – but anything causes vibrations inside the planet Says Pike.

"It's essential to determine the noise and the signal by monitoring the background for a prolonged period of time," says Weber, explaining that the team needs to determine if the probe detects wind, weather, and weather conditions. robotic movements. instead of detecting the actual seismic signals.

Mars InSight has the most responsive portable seismometer ever designed. When the spacecraft was in Colorado for testing, it detected wave shock in the Atlantic and Pacific Oceans. And when Pike was testing sensors at Oxford, he noticed very distinct signals occurring every Sunday at the same time. After a little analysis, he was able to locate one of the signals to a nearby church with a steeple.

The seismometer did not capture the sound of the bells, but the vibration of the spire of the church. "The bell tower looks like a big stick in the ground coming and going," he says. "It's a very beautiful seismic source."

After identifying the first church, Pike was able to locate about a dozen additional churches, calling to confirm their ring schedule and even identify when muted bells were being used for commemoration services one morning. "We were spying on the activity of each ringer during the tests," he says. "They were worried. The Oxford Bellringers Association has indeed looked into the matter. "

But on Mars, nothing is as familiar as a church steeple. Each new seismic signal will have to be searched for clues as to its source. "We are just starting to ask questions such as," What is it? " It looks weird. It was not what we expected, "says Weber.

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