Surface Gravity of Mercury
| Value | 3.7 m/s² |
| Status | Measured: ± 0.01 m/s² (0.0027 relative) |
| Source | NASA NSSDC Planetary Fact Sheet, Mercury (mean surface gravity) |
| Categories | Astronomicalsolar-systemplanets |
| microgal | 370,000,000 μGal |
| milligal | 370,000 mGal |
| millimeter per second squared | 3,700 mm/s² |
| centimeter per second squared | 370 cm/s² |
| gal | 370 Gal |
| inch per second squared | 145.66929 in/s² |
| kilometer per hour per second | 13.32 km/h/s |
| foot per second squared | 12.139108 ft/s² |
| mile per hour per second | 8.2766643 mph/s |
| meter per second squared | 3.7 m/s² |
| standard gravity | 0.377295 g |
Learning zone
Mercury and Mars pull with nearly identical force at their surfaces — 3.70 against 3.71 m/s² — even though Mars has almost twice Mercury's diameter and three times its surface area. The coincidence is density: surface gravity scales as density times radius, and Mercury's huge iron core makes it the second densest planet after Earth, compensating for its small size almost exactly. A visitor could not tell the two worlds apart on a bathroom scale.
That 38 per cent of Earth gravity shapes everything about the surface. It is strong enough to have pulled the planet into a near-perfect sphere, yet the gravity field mapped by MESSENGER's radio tracking is lumpy at fine scales, recording the dense volcanic fills of the great impact basins. The field also confirmed a liquid outer core layer, from the way the planet's rotation librates as it orbits.