Rank the top best scientists of all time. Of all time. [so far]

[Anomalocaris]

Tectonic activity is indicative of an object with a functioning geomagnetic dynamo. You know, the thing that keeps us alive from being blasted into oblivion by a bombardment the sun's light matter.

So actually, plate tectonics work anywhere.

Also, plate tectonics explain any terrestrial planet with a geodynamo must have a molten core, as the core depends on the (incredibly slow) convection of the continental plates.

This is from what I've learned in astrophysics.

No, plate tectonics is not indicative of dynamo, and dynamo doesn't happen everywhere.

First of all, let's separate tectonics from plate tectonics. Tectonics is any process which changes the structural geology of a planet or moon. Plate tectonics is a particular style of tectonics involving large scale horizontal movements of segment of crust of a planet driven by convection of the planet's mantle. Tectonics happens on every large body with a solid surface. Plate tectonics is so far as we know for certain unique to the earth.

Second, plate tectonics is not directly related to geomagnetic dynamo. Instead plate tectonics is related to a thin, lubricated planetary crust and an active global system of mantle convection powered by a hot core. Geomagnetic dynamo involves the differential rotation of liquid and solid layers within the planet's hot core. A planet with a hot core capable of powering mantle convection that drives active plate tectonics need not have differential rotation within that core to power a geomagnetic dynamo. For example, Venus rotates very slowly and probably as a result has no differential rotation in its core. In any case it has no detectable geomagnetic dynamo and no global magnetosphere. But its core is thought to still be just as hot as earth's core and hot enough to power comparable mantle convention. Venus has no plate tectonics, but that probably has to do with its lack of ocean to lubricate subduction zones rather than lack of convection or thin crust. Instead Venus may have a style of intermittent catastrophic volcanic tectonics where the crust remains appearently stable for hundreds of million of years, then completely break up and sink into the mantle, leaving the planet with a completely new surface made of exposed mantle material in a short amount of time.

Mercury, on the other hand, probably has differential rotation in its hot core to power a geomegnetic dynamo since it has a global magnetosphere. But its uncertain whether it still has mantle convection. In any case its planetary crust is thick and exhibit no evidence of plate tectonics. There is tectonics on Mercury to be sure, as evidenced by a global system of thrust faults, but no plate tectonics as would have been evidenced by spreading centers and subduction zones.