Mass of Mercury
| Value | 3.3011e23 kg |
| Status | Measured: ± 7.30e+18 kg (0.000022 relative) |
| Source | NASA planetary fact sheet; GM from MESSENGER tracking divided by CODATA 2022 G |
| Categories | Astronomicalsolar-systemplanets |
| microgram | 3.3011000e+32 μg |
| milligram | 3.3011000e+29 mg |
| gram | 3.3011000e+26 g |
| kilogram | 3.3011000e+23 kg |
| metric tonne | 3.3011000e+20 t |
| ounce | 1.1644288e+25 oz |
| pound | 7.2776797e+23 lb |
| stone | 5.1983427e+22 st |
| US short ton | 3.6388399e+20 ton |
| grain | 5.0943758e+27 gr |
| unified atomic mass unit (dalton) | 1.9879689e+50 u |
Learning zone
Mercury is barely a third of Earth's radius but its uncompressed density is the highest in the solar system: an iron core makes up roughly 85 per cent of the radius, leaving a rocky shell a few hundred kilometres thick. Something stripped away most of the original mantle — a giant impact and vaporisation by the young Sun are the leading candidates — and MESSENGER's measurement of surprisingly volatile-rich surface chemistry complicated both stories.
The planet's orbit made history twice. Its perihelion advances 43 arcseconds per century faster than Newtonian gravity allows, an anomaly that led Le Verrier to postulate a planet Vulcan in 1859 and that Einstein explained exactly with general relativity in 1915 — the theory's first empirical triumph.