The wind from the dusty station on Mars piled Martian regolith onto InSight’s solar panels. The rumbling of the wind against the small egg-shaped shield protecting the mission’s delicate seismometer drowned out the low-magnitude tremors normally felt on Mars. In the midst of this, NASA scientists thought the InSight spacecraft might have detected its last marsquake before the mission came to an end.
Then, on May 4, InSight’s 1,222nd day on Mars, the spacecraft detected a magnitude 5.0 earthquake, by far the most powerful earthquake ever detected on Earth. As Mark Panning, project scientist at InSight, says inverse“We were approaching a time when the dust storm would possibly end our mission, and we weren’t seeing small events anymore, so it was possible that we didn’t see any more events, and then Mars decided to show and gave us a big event that was so big. that no matter how noisy Mars was.”
WHAT’S NEW – While the Apollo missions left a set of seismographs on the Moon that operated until 1977, InSight is the first Martian mission to carry seismic equipment. Prior to the probe’s arrival in 2018, knowledge of Mars’ interior was “very coarse”, according to Panning, based on mapping the planet’s gravity, with “large error bars in each estimate”. As Mars is smaller than Earth, its interior has cooled more and there is no evidence so far of plate tectonics; the researchers expected the Red Planet to be relatively peaceful.
According to Anna Horleston, a seismologist at the University of Bristol and co-leader of the Marsquake Service’s frontline team, they expected to see a type of seismic activity on Mars like the activity found in the middle of Earth’s continental plates known as intraplate seismicity. which is driven by the cooling of rocks deep within the planet.
Prior to August of last year, the only earthquakes detected by the spacecraft in its first two years were small by Earth standards, below magnitude 3.7 — a level you can experience as a vibration of light within five miles of the epicenter. . In August and September, the spacecraft detected a pair of magnitude 4.2 and 4.1 earthquakes — which, as the earthquake’s magnitude is measured logarithmically, were three times greater than any previously measured earthquake.
At magnitude 5.0, the latest quake was six times stronger than anything ever seen on another planet and released nearly 16 times more energy. Panning and Horleston note that this is the most powerful marsquake InSight expected the module to detect over the course of its mission.
WHY DOES IT MATTER – Although InSight’s seismometer, the Seismic Experiment for Interior Structures (or SEIS), is shielded from turbulence by its heat and wind shield, the surface of Mars is a noisy place. Specifically, dust storms from the planet shake the shield, while sudden winds can cause ground-level pressure changes that shake the probe itself. All this noise makes it difficult to sort out data on how seismic energy is reflected in the core and crust of Mars.
In addition, Horleston [notes], while the Earth is full of cobwebs with thousands of carefully guarded seismic stations, there is only one seismometer on the entire planet, which makes the distinction between signal and noise even more challenging. The team had to develop analysis tools specifically to separate signals from weaker tectonic events from those from storms that pass overhead.
But this event was much stronger and clearer than any previous event. “It’s a beautiful seismic record,” says Panning, “and we’re going to do a lot of science with it.” Having a much larger event will make it much easier to confirm and improve the team’s methods of separating seismic data from the ambient noise of Mars’ atmosphere.
Panning says that, in turn, will make it possible to go back and find smaller signals in the first 1,200 days of InSight’s seismic recording.
WHAT IS THE NEXT- The same dust storms that make it difficult for InSight’s seismographs to detect smaller marsquakes are bringing other difficulties for the spacecraft. InSight went into safe mode shortly after recording the earthquake. The accumulation of dust on the panels combined with the decrease in solar energy reaching the surface means that the InSight team is now planning a reduced amount of time using the SEIS instrument in the future.
Panning notes that while the exact timing is determined by Mars, the accumulation of dust will soon reach a point where it won’t have enough power to operate its science instruments – unless something happens to blow dust off the panels, which rovers do. previous Spirit and Opportunity were lucky to happen.
At that time, the lander will enter an extremely low power mode. But the team will continue to listen to the communication while waiting for the solar panels to disappear.
But just as – as Panning puts it – InSight was about to “move into the Martian sunset”, the planet gave an energetic farewell.