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We have lots of questions about the Mars lander InSight's seismometers, and I remember reading that they have detected microseisms from wind blowing over InSight's solar panels and the surface of Mars itself.

Question: But have any seismic events associated with the planet's interior been detected yet? Are there any estimates of how frequently these might be expected?

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  • $\begingroup$ Ah, I was going to upload a picture from my magazine, but the current answer has that picture! Hooray. $\endgroup$ – Magic Octopus Urn Sep 5 at 14:26
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    $\begingroup$ Confirmed in the news media, 2019-10-03: Mars lander captures symphony of sounds on planet's surface $\endgroup$ – Fred Oct 3 at 9:13
  • $\begingroup$ @Fred thanks for keeping an eye on this! I added an answer with some of that here as well. $\endgroup$ – uhoh Oct 3 at 9:17
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It sure looks like it. At least wind has been ruled out as the cause of this recording:

NASA's InSight Detects First Likely 'Quake' on Mars

NASA's Mars InSight lander has measured and recorded for the first time ever a likely "marsquake."

The faint seismic signal, detected by the lander's Seismic Experiment for Interior Structure (SEIS) instrument, was recorded on April 6, (2019) the lander's 128th Martian day, or sol. This is the first recorded trembling that appears to have come from inside the planet, as opposed to being caused by forces above the surface, such as wind. Scientists still are examining the data to determine the exact cause of the signal.

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  • $\begingroup$ Thanks for the speedy answer! Feel free to roll back the edit or edit further. I wasn't sure what "eight months before those references" means though. $\endgroup$ – uhoh Sep 4 at 2:52
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From Gizmodo's Now You Can Listen to Marsquakes:

After landing on Mars last year, the InSight probe deposited a sensitive seismometer called the the Seismic Experiment for Interior Structure (SEIS) on the Martian surface. After first recording a strange, possible Marsquake this past April, the experiment has now counted at least 21 quakes among 100 vibrational signals. Here are two of those Marsquakes:

These quakes were recorded on Martian day 173 and 235, and equate to magnitudes of 3.7 and 3.3, respectively. You’re not listening to the vibrations directly: the readings were of vibrations below audible frequencies. Instead, it’s vibrational data processed and sped up so you can hear it, according to a press release.

Initial vibrational signals were ambiguous as to their cause, according to a previous NASA press release, and it was unclear what caused the initial Marsquake. Newer quakes have been closer to the kinds of quakes that scientists expected to hear from the planet, with lower frequencies. Scientists have learned to pick these quakes out from other sources of vibrations such as the wind and even the lander moving.

From NASA's NASA's InSight 'Hears' Peculiar Sounds on Mars

Put on headphones to listen to two of the more representative quakes SEIS has detected. These occurred on May 22, 2019 (the 173rd Martian day, or sol, of the mission) and July 25, 2019 (Sol 235). Far below the human range of hearing, these sonifications from SEIS had to be speeded up and slightly processed to be audible through headphones. Both were recorded by the "very broad band sensors" on SEIS, which are more sensitive at lower frequencies than its short period sensors.

The Sol 173 quake is about a magnitude 3.7; the Sol 235 quake is about a magnitude 3.3.

Same two Sound Cloud links?

Each quake is a subtle rumble. The Sol 235 quake becomes particularly bass-heavy toward the end of the event. Both suggest that the Martian crust is like a mix of the Earth's crust and the Moon's. Cracks in Earth's crust seal over time as water fills them with new minerals. This enables sound waves to continue uninterrupted as they pass through old fractures. Drier crusts like the Moon's remain fractured after impacts, scattering sound waves for tens of minutes rather than allowing them to travel in a straight line. Mars, with its cratered surface, is slightly more Moon-like, with seismic waves ringing for a minute or so, whereas quakes on Earth can come and go in seconds.

and later:

Mechanical Sounds and Wind Gusts

SEIS has no trouble identifying quiet quakes, but its sensitive ear means scientists have lots of other noises to filter out. Over time, the team has learned to recognize the different sounds. And while some are trickier than others to spot, they all have made InSight's presence on Mars feel more real to those working with the spacecraft.

[...] Evening is also when peculiar sounds that the InSight team has nicknamed "dinks and donks" become more prevalent. The team knows they're coming from delicate parts within the seismometer expanding and contracting against one another and thinks heat loss may be the factor, similar to how a car engine "ticks" after it's turned off and begins cooling.

You can hear a number of these dinks and donks in this next set of sounds, recorded just after sundown on July 16, 2019 (Sol 226). Listen carefully and you can also pick out an eerie whistling that the team thinks may be caused by interference in the seismometer's electronics.

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