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Bulk Parameters, Orbital Parameters,
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| Mercury
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| Bulk Parameters | Mercury | Earth | Ratio (Mercury/Earth) |
| Mass (1024 kg) | 0.3302 | 5.9736 | 0.0553 |
| Volume (1010 km3) | 6.085 | 108.321 | 0.0562 |
| Equatorial Radius (km) | 2440 | 6378 | 0.383 |
| Polar radius (km) | 2440 | 6356 | 0.384 |
| Volumetric mean radius (km) | 2440 | 6371 | 0.383 |
| Ellipticity | 0.0000 | 0.0034 | 0.000 |
| Mean density (kg/m3) | 5427 | 5520 | 0.983 |
| 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 | 0.056 | 0.385 | 0.145 |
| Visual geometric albedo | 0.11 | 0.367 | 0.300 |
| Visual magnitude V (1,0) | -0.42 | -3.86 | - |
| Solar irradiance (W/m2) | 9214 | 1380 | 6.677 |
| Black-body temperature (K) | 442.5 | 247.3 | 2.531 |
| Moment of inertia (I/MR2) | 0.33 | 0.3308 | 0.998 |
| J2 (x 10-6) | 60. | 1082.63 | 0.055 |
| Orbital Parameters | Mercury | Earth | Ratio (Mercury/Earth) |
| Semimajor axis (106 km) | 57.9 | 149.6 | 0.387 |
| Sidereal orbit period (days) | 87.969 | 365.256 | 0.241 |
| Tropical orbit period (days) | 87.968 | 356.242 | 0.241 |
| Perihelion (106 km) | 46.0 | 147.1 | 0.313 |
| Aphelion (106 km) | 69.8 | 152.1 | 0.459 |
| Synodic period (days) | 115.88 | - | - |
| Mean orbital velocity (km/s) | 47.87 | 29.79 | 1.607 |
| Orbital inclination (deg) | 7.00 | 0.00 | - |
| Orbit eccentricity | 0.2056 | 0.0167 | 12.311 |
| Sidereal rotation period (hrs) | 1407.6 | 23.9345 | 58.785 |
| Obliquity to orbit (deg) | ~0.1 | 23.45 | 0.004 |
| Observational Parameters | |||
| Discoverer: | Unknown | ||
| Discovery Date: | Prehistoric | ||
| Apparent diameter from Earth | Maximum | 13. | |
| (seconds of arc): | Minimum | 4.5 | |
| Distance from Earth | Maximum | 221.9 | |
| (106 km): | Minimum | 77.3 | |
| Apparent magnitude near opposition: | -1.9 | ||
| Mean Orbital Elements (J200) | |||
| Semimajor axis (A.U.) | 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 | ||
| Mercurian Magnetosphere | |||
| Dipole field strength | 0.0033 gauss-Rh3 | Rh: denotes Mercurian radii (2,439 km) | |
| Dipole tilt to rotational axis | 169 degrees | ||
| Longitude of tilt (deg) | 285 (from Mercury I flyby) | 115 (from Mercury III flyby) | |
| Mercury Atmosphere | |||
| Surface Pressure | ~10-15 bar | (0.001 picobar) | |
| Average temperature | 440 K | (590-725 K, sunward side) | |
| Atmospheric Composition: | 42% Oxygen (O2) | 29% Sodium (Na) | 22% Hydrogen (H2) |
| 6% Helium (He) | 0.5% Potassium | ||
| Trace amounts of: | Argon (Ar) | Carbon Dioxide (CO2) | Water (H2O) |
| Nitrogen (N2) | Xenon (Xe) | Krypton (Kr) | |
| Neon (Ne) | (Compositional values not well constrained, values from "Mercury," Vilas, Chapman and Matthews, eds., University of Arizona Press, 1988) | ||
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Fact sheet source from NSSDC/NASA |