Surface Gravity of Mars

Thirty-eight per cent of a g is the number that shapes Mars exploration. It is gentle enough that Ingenuity could fly a helicopter in an atmosphere less than one per cent as dense as Earth's, and it lets terrain features grow tall — Olympus Mons reaches 22 km partly because weak gravity and a stationary crust let a volcano pile up over hundreds of millions of years.

It is also the reason entry, descent and landing is so hard: the atmosphere is thick enough to require a heat shield but far too thin to stop a spacecraft, so every mission needs some combination of parachutes, retro-rockets and, for the heaviest rovers, a sky crane. What 3.71 m/s² does to human physiology over years is one of the open questions of crewed Mars planning — we have data on 1 g and on zero, and none in between.