Mercury Fact Sheet


Mercury

Mercury/Earth Comparison


Bulk parameters

   
   Mercury   
 
   Earth   
Ratio
(Mercury/Earth)
Mass (1024 kg) 0.33011 5.9724 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 5514 0.984
Surface gravity (eq.) (m/s2) 3.70 9.80 0.378
Surface acceleration (eq.) (m/s2) 3.70 9.78 0.378
Escape velocity (km/s) 4.3 11.2 0.384
GM (x 106 km3/s2) 0.022032 0.39860 0.0553
Bond albedo 0.068 0.306 0.222
Visual geometric albedo 0.142 0.367 0.387
Visual magnitude V(1,0) -0.42 -3.86 -
Solar irradiance (W/m2) 9082.7 1361.0 6.674
Black-body temperature (K) 439.6 254.0 1.731
Topographic range (km) 7 20 0.350
Moment of inertia (I/MR2) 0.35 0.3308 1.058
J2 (x 10-6) 50.3 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) 47.36 29.78 1.590
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) 0.034 23.44 0.001
Inclination of equator (deg) 0.034 23.44 0.001

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 Elements (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: 281.010 - 0.033T
Declination    :  61.414 - 0.005T
Reference Date : 12:00 UT 1 Jan 2000 (JD 2451545.0)
T = Julian centuries from reference date 

Mercury Magnetosphere

MESSENGER Model 2010
Dipole field strength: 0.002 Gauss-Rh3
Dipole tilt to rotational axis: 0.0 degrees
Dipole Offset: 0.17 Rh 
Surface (1 Rh) field strength: 0.0025 - 0.007 Gauss

Rh denotes Mercurian model radius, here defined to be 2,440 km


Mercury Atmosphere (Exosphere)

Surface pressure: <~5 x 10-15 bar (0.005 picobar)  
Average temperature: 440 K (167 C) (590-725 K, sunward side)
Total mass of atmosphere: <~10000 kg

Atmospheric composition (Column abundances in 106 per cm2):
Sodium 12,000-200,000; Magnesium 100,000; Oxygen <40,000; Hydrogen 5000, Potassium 800-1300, 
Calcium 300-1000; Iron <300; Aluminum 15; and
possible trace amounts of Argon (Ar), Carbon Dioxide (CO2), 
Water (H2O), Nitrogen (N2), Xenon (Xe), Krypton (Kr), 
Neon (Ne), Helium (He) 

(The atmosphere of Mercury is a surface bounded exosphere, essentially a vacuum. 
Values for some species can vary with local time or location, these are given as ranges.)

Notes on the factsheets - definitions of parameters, units, notes on sub- and superscripts, etc.

Planetary Fact Table - metric units
Planetary Fact Table - U.S. units
Planetary Fact Table - Earth ratio


Mercury Home Page
Directory to other Planetary Fact Sheets

NASA
Author/Curator:
Dr. David R. Williams, dave.williams@nasa.gov
NSSDCA, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771
+1-301-286-1258


NASA Official: Ed Grayzeck, edwin.j.grayzeck@nasa.gov
Last Updated: 13 July 2016, DRW