[Fathom Zero]

I'm lost here. Not that that should be a surprise to anyone.

That's true. I'm wondering about the penetration, though. Of course it'll be distorted through our atmosphere and that of any other object, but I'm wondering how effective they are at penetrating certain layers of elements. It'd surely possible to get a reading of a layer, then adjust for that layer so that you can read the next one. But I'm really wondering if there would be a way to take one efficient reading some day that passes through the entirety of an object, say Mars, and provide info about the composition down to the core. How did it come into being? Was it spawned like any other planet or did other objects collide and form this object over time? How old is the core? We can tell a lot of this already by inference.

I'm just musing about how easy it will be one day, to even have a handheld meter that would provide us that information.

This is assuming humanity doesn't fall to some catastrophe before then. Space travel would likely be commonplace, so charting the universe would probably be very important. Our Solar System would be old hat at that point and we wouldn't need to look at minute changes in blurry photographs to show that there is water flowing on the surface of a planet.