Vrftsjtryk

I had a friend whose summer job, a long long time ago, was to travel around an unsuspecting rural area, lay a heavy steel plate on the ground, and whack the plate with a sledge hammer. Apparently he also had some kind of seismometer or accelerometer nearby. This was apparently a cheap and dirty way to get some idea of the soil and rock below the surface.

This was on Earth, not Mars.

The question InSight and active pinging of Mars asks about generating artificial seismic events on Mars for InSight's seismometers to listen to. @DrSheldon's answer mentions that this is not part of the plan; that InSight is expected to return meaningful data without this.

It doesn't mean that it wouldn't benefit from it though.

What kinds of schemes might a frugal and/or clever space agency use to generate seismic events that would be meaningful and useful for InSight measurements of Mars?

I can imagine two classes, one to help verify nothing is wrong, so something local perhaps, and the other far enough away to give geological or even planetary information.

The traditional method (as used in the Apollo project) was to crash used SIVB stages into the Moon.

Let's examine what's already on InSight:

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  A seismometer (SEIS). It's so sensitive that it is expected to be able to sense windstorms, dust devils, and the tidal forces of Mars' moon. To isolate the sensors from motions of the main body of InSight, SEIS is in its own pod that will be placed a few feet away by a robotic arm, and attached by an umbilical.

  
  
  

  The sensors can be recorded during the "impact" of this placement process, and there is a small chance that something useful could be learned from the results.

  
  


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  A burrowing temperature probe (HP³). It will be placed by the robotic arm, and then dig with an impact hammer up to 5 meters depth. The head of the "mole" is attached with a cable that has temperature sensors along its length.

  
  
  

  The vibrations caused by dropping the mole, as well as its digging, could possibly help the seismometer map out the nearby subsurface geology.

  
  



• An X-band radio (RISE). This transmitter and transponder will work with antennas in the Deep Space Network to locate the position (within 2 cm) and velocity of Mars. It doesn't seem to have any moving components to create a seismic "ping".




• The aforementioned arm. This could be manipulated to "thump" the surface around the lander.




• Other sensors include pressure, temperature, wind direction and speed, and magnetic field. There is a laser retroreflector on the deck, a color stereo camera on the arm, and a color panoramic camera below the deck. I don't see how any of these could be used to create a seismic "ping".




• Finally, the usual spacecraft components: landing legs, solar panels, computer, antennas, etc.

Therefore, the spacecraft itself has a limited capability to produce some seismic "pings", which might reveal the nearby subsurface geology. The most revealing observations will be by passive seismology and the other instruments.

To address the problem with martian atmosphere - maybe an impactor with high explosives could be better. Something like Tallboy bomb.

I think energy of the impact will not be higher than from a meteorite impact. Probably even much less. But intended impact have some big advantage - we know where and when exactly it happened. It can be very useful for calibration of seismic velocities model of Mars.

The main problem is cost, of course. The impactor should be specially designed. Stuff like old satellites or rocket stages is not dense enough and not stiff enough to impact martian surface with enough energy after encounter with the atmosphere. The impactor mission would cost at least 100-200 mln $ including launch.