Mercury/Earth Comparison
Bulk Parameters
| MERCURY | EARTH | RATIO (MERCURY/EARTH) | |
| Mass (1024kg) | 0.3302 | 5.9736 | 0.0553 |
| Volume (1010 km3) | 6.083 | 108.321 | 0.0562 |
| Equatorial radius (km) | 2439.7 | 6378.1 | 0.383 |
| Polar radius (km) | 2439.7 | 6356.8 | 0.384 |
| Volumetric mean radius (km) | 2439.7 | 6371.0 | 0.383 |
| Ellipticity (Flattening) | 0.0000 | 0.00335 | 0.000 |
| Mean density (kg/m3) | 5427 | 5515 | 0.984 |
| Surface gravity (eq.) (m/s2) | 3.70 | 9.78 | 0.378 |
| Escape velocity (km/s) | 4.3 | 11.2 | 0.384 |
| GM (x 106 km3/s2) | 0.02203 | 0.3986 | 0.0553 |
| Bond albedo | 0.119 | 0.306 | 0.389 |
| Visual geometric albedo | 0.106 | 0.367 | 0.289 |
| Visual magnitude V(1,0) | -0.42 | -3.86 | - |
| Solar irradiance (W/m2) | 9126.6 | 1367.6 | 6.673 |
| Black-body temperature (K) | 442.5 | 254.3 | 1.740 |
| Moment of inertia (I/MR2) | 0.33 | 0.3308 | 0.998 |
| J2 (x 10-6) | 60 | 1082.63 | 0.055 |
| Number of natural satellites | 0 | 1 | |
| Planetary ring system | No | No |
Orbital Parameters
| MERCURY | EARTH | RATIO (MERCURY/EARTH) | |
| Semimajor axis (106 km) | 57.91 | 149.60 | 0.387 |
| Sidereal orbit period (days) | 87.969 | 365.256 | 0.241 |
| Tropical orbit period (days) | 87.968 | 365.242 | 0.241 |
| Perihelion (106 km) | 46.00 | 147.09 | 0.313 |
| Aphelion (106 km) | 69.82 | 152.10 | 0.459 |
| Synodic period (days) | 115.88 | - | - |
| Mean orbital velocity (km/s) | 47.87 | 29.78 | 1.607 |
| Max. orbital velocity (km/s) | 58.98 | 30.29 | 1.947 |
| Min. orbital velocity (km/s) | 38.86 | 29.29 | 1.327 |
| Orbit inclination (deg) | 7.00 | 0.00 | - |
| Orbit eccentricity | 0.2056 | 0.0167 | 12.311 |
| Sidereal rotation period (hrs) | 1407.6 | 23.9345 | 58.785 |
| Length of day (hrs) | 4222.6 | 24.0000 | 175.942 |
| Obliquity to orbit (deg) | 0.01 | 23.45 | 0.0004 |
Mercury Observational Parameters
| Discoverer | Unknown |
| Discovery Date | Prehistoric |
| Distance from Earth | |
| Minimum (106 km) | 77.3 |
| Maximum (106 km) | 221.9 |
| Apparent diameter from Earth | |
| Maximum (seconds of arc) | 13 |
| Minimum (seconds of arc) | 4.5 |
| Maximum visual magnitude | -1.9 |
| Mean values at inferior conjunction with Earth | |
| Distance from Earth (106 km) | 91.70 |
| Apparent diameter (seconds of arc) | 11.0 |
Mercury Mean Orbital Elemens (J2000)
| Semimajor axis (AU) | 0.38709893 |
| Orbital eccentricity | 0.20563069 |
| Orbital inclination (deg) | 7.00487 |
| Longitude of ascending node (deg) | 48.33167 |
| Longitude of perihelion (deg) | 77.45645 |
| Mean Longitude (deg) | 252.25084 |
North Pole of Rotation
| Right Ascension | 281.01 - 0.003T |
| Declination | 61.45 - 0.005T |
| Reference Date | 12:00 UT 1 Jan 2000 (JD 2451545.0) |
| T = Julian centuries from reference date |
Mercurian Magnetosphere
| Dipole field strength | 0.0033 gauss-Rh3 |
| Dipole tilt to rotational axis | 169 degrees |
| Longitude of tilt | 85 degrees (from Mercury I flyby) |
| 115 degrees (from Mercury III flyby) | |
| Note: Rh denotes Mercurian radii, 2,439 km |
Mercury Atmosphere
| Surface pressure | ~10-15 bar (0.001 picobar) |
| Average temperature | 440 K (167 C) (590-725 K, sunward side) |
| Total mass of atmosphere | ~1000 kg |
| Atmospheric composition | 42% Oxygen (O2), 29% Sodium (Na), |
| 22% Hydrogen (H2), 6% Helium (He), 0.5% Potassium (K), | |
| possible trace amounts of Argon (Ar), Carbon Dioxide (CO2), | |
| Water (H2O), Nitrogen (N2), Xenon (Xe), Krypton (Kr), Neon (Ne) | |
| (The atmosphere of Mercury is essentially a vacuum. | |
| Compositional values are not well constrained, values from "Mercury", | |
| Vilas, Chapman, and Matthews, eds., University of Arizona Press, 1988) |
