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Quakes on Mars as seen by InSight

Martian quake map as seen by InSight

After completing its first full Martian year on the surface of the Red Planet, the scientists for the lander InSight today gave a report [pdf] of their results at this year’s annual 52nd Lunar and Planetary Science Conference, normally held in Texas but being done virtually this year out of terror of the coronavirus.

All told the lander’s seismometer has, as of just a few days ago, detected just over 500 quakes. The map to the right, showing the most distinct quakes and their locations, was adapted from a different presentation [pdf] at the conference. The numbers indicate the sols after landing when these quakes were detected.

This is essentially the region on Mars that I call volcano country. Some of the lava flood plains here are the youngest on Mars. To the east just beyond the edge of the map is the Tharsis Bulge, which holds Olympus Mons and the string of three giant volcanoes to its east. South of Cereberus Fossae but north of the yellow-colored cratered highlands is the vast Medusae Fossae Formation, the largest volcanic ash deposit on Mars.

The quakes suggest they are occurring as large blocks shift along faults, creating fissures and cracks that geologists call grabens. The long fissures of Cereberus Fossae are considered an example of grabens, so this activity suggests that shifting is still going on in the region.

In addition to outlining the location of the detected volcanoes, the presentation today summarized these other discoveries made by InSight about Mars’ interior structure:

  • The crust of Mars has likely two or three layers either 12 or 24 miles thick, with a total thickness no more than 45 miles. This is much thinner than most scientists had expected.
  • The mantle layer below the crust is estimated at about 250 to 375 miles thick, with a temperature between 1,600 to 1,700 degrees Kelvin. While quite hot, this is a cooler mantle than expected.
  • The core of Mars is somewhere between 1,100 to 1,300 miles in diameter, with a outer layer made of liquid. These results are at the high end of pre-mission expectations.

As already admitted, it was noted that the heat sensor experiment will not be able to provide the interior temperature of Mars, as its digging mole was unable to dig into the ground the 9 to 15 feet planned.

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  • Chris

    I’m not a seismologist but I would think triangulation (3 dimensional) is one of the fundamental tools required to start to understand anything going on on a sphere. As such I would have expected a requirement of all future probes to be a Mars-quake sensor. This would of course would start slow but with every new probe a new point would be established. After enough the math and other analysis can help provide the answers – or at least good guesses.

  • Chris: Your idea has merit, but it is likely not practical. A close look at the technical requirements needed to make this seismometer sensitive enough to provide worthwhile data, outlined in today’s talk, makes it clear that the cost to produce a similar instrument on all other landers would likely conflict too much with their other purposes.

  • Chris

    Ok. If not practical- then not prectical

  • Alex Andrite

    OK, nice to attempt to figure out the martian interior structures and stuff. I get it. (almost)
    How does all of this translate into me shaking on the ground if I where there ?
    I know the shake, and following shake/shudders, of Loma Prieta quake of ’89 – M6.9. I was on my commute – S.J. > Santa Cruz at that time.

    What does the current Mars InSight info tell me in that regard ?
    Beside that their are no commuter lanes on Mars.

  • Max

    Chris, I agree.
    A small detachable independent seismograph/ weather station with its own roll out solar panel should be sent with every lander. The descent rocket that lowers the lander could have this package attached to it? It has enough weight to be an excellent base if they landed it, instead of crash it.

    Didn’t we discuss dropping such probes, that collect heat measurements and seismic activity, “from space” so they can impell themselves at desired locations? A ribbon of flexible solar panel can keep the metal stake vertical until impact. Or maybe they should use feathers like an arrow and just protect the solar panel/broadcast instruments inside the hollow tube for protection and perform extraction after impact.

    Sensitive equipment like temperature, barometer, fish eye lenses, communication capabilities can fit in a wrist watch. A small light unit in a helium mylar balloon with a solar panel top could drift around mars for years collecting data. In fact, the parachute, If it’s double layered, could be filled with helium after detachment, for this purpose. (I wonder if they filled it before detachment if it would have enough “lift” to slow the descent more effectively?)
    It would not take much volume from the helium tank, because of the low atmospheric pressure. The canister and the ascent/descend pump would last for year’s before the tank was empty and could be dropped like ballast.

  • David Telford

    Amazing what they can do with seismology. Maybe not every lander, but I wonder if they’d get a serious improvement with just one more seismometer?

    But these numbers don’t add up: crust at 45 miles, mantle at 375 miles and core of 1300 miles diameter. All packed together you get “2 ( 45 + 375 ) + 1300” = 1720 miles across, coming up short of the real Mars at 4212 miles. My guess, the mantle is considerably thicker at about 1400 miles thick.

  • mrsizer

    But, but, but they told me there would be no maths! Good catch, David.

    Is there another component that gets what’s leftover? That is, are crust, mantle, and core the only three layers? I see “inner” and “outer” broken out of “core” in some places.

  • David Telford: I suspect what Bob reports as mantle thickness is more precisely “upper mantle”. So your missing layer is “lower mantle”.

    As they acquire more data, they will come up with a more exact model for Mars interior structure. Of course it would really help if we had more stations, and maybe people there to maintain and operate them :-)

    But then you’d have WAY more human-created seismic noise!

  • Luke

    Huh. I thought we’d believed that Mars lacked magnetosphere from its core being frozen.

    So much for simple explanations, I guess.

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