Sounds a bit like a rockfall to me, perhaps nearby? The slow buildup and slower subsidence of the sound intuitively fits what I would expect for a rockfall, and also we know there are rockfalls on the surface of Mars. It would be neat if that could be corroborated with surface evidence of a rockfall (I think a few have even been captured by satellite!)
Impulsive quakes on Earth have a characteristic waveform which this does not match: The arrival of a compression wave, followed by a larger shear wave. That waveform wouldn't be much different on another planet, since the shape of the waveform arises from the mechanical properties of rock. If it were not a rockfall, it would have to correspond more to a seismic tremor, which happens more slowly-- I know less about those and I am curious how this matches up.
Having multiple stations would really help to narrow down what the source of sounds like this could be.
This is recorded from vibrations in rock, not in air. There is some sound in the very thin Martian atmosphere, and there is plenty of sound in the Martian crust.
The article states definitively that Mars does not have tectonic plates. This is news to me because hitherto I thought there is no evidence either way.
This omnipresent seismic noise is also a big challenge for building terrestrial gravitational wave detectors like LIGO. Even though the noise is "only" a bunch micrometers of movement, they had to deploy multiple levels of noise suppression to be able to measure gravitational waves: https://youtu.be/j4gE-hSQm68?t=1380
Interesting, I didn't know that quakes could still occur without tectonic activity. The explanation makes sense, but I had just never thought about it.
Impulsive quakes on Earth have a characteristic waveform which this does not match: The arrival of a compression wave, followed by a larger shear wave. That waveform wouldn't be much different on another planet, since the shape of the waveform arises from the mechanical properties of rock. If it were not a rockfall, it would have to correspond more to a seismic tremor, which happens more slowly-- I know less about those and I am curious how this matches up.
Having multiple stations would really help to narrow down what the source of sounds like this could be.