Tau.Neutrino said:
Minitremors detected on Mars for first time
THE WOODLANDS, TEXAS—After months of delicate maneuvering, NASA’s InSight lander has finished placing its hypersensitive seismometer on the surface of Mars. The instrument is designed to solve mysteries about the planet’s interior by detecting the booming thunder of “marsquakes.” But just a few weeks into its run, the car-size lander has already heard something else: the minute tremors that continually rock our red neighbor. If marsquakes are the drum solo, these microseisms, as they’re known, are the bass line.
more…
> On Earth, microseisms are ubiquitous, caused largely by the sloshing of the ocean by storms and tides. Mars, despite the dreams of science fiction writers, has no present-day oceans. Instead, this newly discovered noise is likely caused by low-frequency pressure waves from atmospheric winds that rattle the surface, inducing shallow, longer-period waves in the surface, called Rayleigh waves.
Oh good, these were expected. I know Rayleigh waves.
> The microseisms are an important indicator that the lander’s seismometer is working as hoped. In recent decades, seismologists have begun to see microseisms on Earth as not just a nuisance, but as a valuable tool for understanding features in the subsurface
Yes, and yes. I wonder if there’s a technical article about using Rayleigh waves to probe Earth’s subsurface crust. I’m not sure how to look for one, this article from 2008 is starting to get close to the right topic and is interesting in its own way. Background Love and Rayleigh waves simultaneously generated at the Pacific Ocean floors
> deployment still took a month longer than planned, thanks to two delicate tasks. First, scientists had to carefully tweak the electric tether connecting the seismometer to the lander, in order to reduce noise coming off the lander. Then, they had to place a wind and heat shield over the instrument.
First I’ve heard about reducing noise from the lander. The wind and heat shield was part of the original plan.
> InSight has spent much of its time troubleshooting for its second instrument, a heat probe designed to burrow up to 5 meters below the surface. The robotic arm placed that instrument in mid-February. But soon after the probe began to hammer itself into the surface, its 40-centimeter-long “mole” got stuck on a rock or some other blockage just 30 centimeters down. Now, mission scientists have put the hammering on hold as they wait for the agencies’ engineers to evaluate their options. That will continue for several more weeks
Oh dear. At least with a depth of only 0.3 metres (1 foot) they do still have options. Deeper would be harder to extricate.
NASA’s record as regards subsurface sampling is not good. At least two Apollo missions had great difficulty in extracting a core sample from the Moon. On Apollo 11 they failed completely. On Apollo 15 either one or both astronauts suffered long term injury from trying to extract the core, and once extracted they were unable to break it into more than three pieces. The Russians managed better. I don’t know what would happen to the seismometer when there is hammering from the heat probe nearby, not good I suspect.
> first marsquake, not seeing one yet
Three sources of the bigger Marsquakes. 1. Impact from meteorites.
These would be expected to occur in clusters, or would they? So far as I know, Mars passes through the stream of meteors known as the Taurids but not the Perseids. There may be other meteor showers on Mars. I’m ignorant about whether all of these would burn up in the atmosphere or not. There would be other meteor showers.
2. Landslides on the surface. These have been observed from space. They’d be seasonal, occurring more often in times of greatest thawing, but I don’t know whether than means spring or midsummer.
3. Tectonic quakes from deeper. I see that again my ignorance is showing. There is no plate tectonics. I’m of the opinion that Mars is solid throughout, but that’s still uncertain. A solid core and mantle would reduce tectonic quakes to nearly nothing, but would it still allow faulting at say up to a km deep? If so, that would be a major coup for the mission. Again, these could occur in clusters.