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<h3>Notes on the Fact Sheets</h3>
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<h5>Bulk Parameters</h5>
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<b>Mass (10<sup>24</sup> kg)</b>: Mass of the body in 10^24 kilograms
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<b>Volume (10<sup>10</sup> km<sup>3</sup>)</b>: Volume of the body in 10^10 km^3
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<b>Equatorial radius (km)</b>: Radius of the body at the equator in kilometers
<b>Polar radius (km)</b>: Radius of the body at the poles in kilometers
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<b>Volumetric mean radius (km)</b>: Radius of a sphere with the same volume as the body.
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<b>Core radius (km)</b>: Radius of the planet core in kilometers
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<b>Ellipticity</b>: The ratio (equatorial - polar radius)/(equatorial radius) also called the flattening (dimensionless).
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<b>Mean density (kg/m<sup>3</sup>)</b>: Average density of the body (mass/volume) in kilograms/(meter^3).
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<b>Surface gravity (m/s<sup>2</sup>)</b>: Gravitational acceleration at the surface of the body or the 1 bar level in meters/(second^2)
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<b>Escape velocity (km/s)</b>: Initial velocity required to escape the body's gravitational pull in kilometers/second
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<b>GM (x 10<sup>6</sup> km<sup>3</sup>/s<sup>2</sup>)</b>: Gravitational constant times the mass of the body in 10^6 kilometers^3/seconds^2.
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<b>Visual geometric albedo</b>: The ratio of the body's brightness at a phase angle of zero to the brightness of a perfectly diffusing disk with the same position and apparent size, dimensionless.
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<b>Bond albedo</b>: The fraction of incident solar radiation reflected back into space without absorption, dimensionless. Also called planetary albedo.
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<b>Visual magnitude V(1,0)</b>: The visual magnitude of the body if it were one AU (1.496 x 10^8  kilometers) from the Earth at a phase angle of zero, dimensionless.
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<b>Solar irradiance (W/m<sup>2</sup>)</b>: Solar energy on the body in Watts/(meter^2)
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<b>Black-body temperature (K)</b>: Equivalent black body temperature is the surface temperature the body would have if it were in radiative equilibrium and had no atmosphere, but the same albedo, in degrees Kelvin.
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<b>Topographic range (km)</b>: Difference in elevation between the highest and lowest points on the planet's surface, in kilometers.
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<b>Moment of inertia (I/MR<sup>2</sup>)</b>: The moment of inertia of the body expressed asthe rotational inertia divided by the body's (mass x radius^2).  A hollow spherical shell has a moment of inertia of 2/3, a homogeneous sphere 0.4
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<b>J<sub>2</sub> (x 10<sup>-6</sup>)</b>: The ratio of the difference in the moments of inertia to the mass of the body times the radius^2, (C-A)/(M R^2), x 10^-6, dimensionless
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<h5>Orbital parameters</h5> 
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<b>Semimajor axis (10<sup>6</sup> km)</b>: Mean distance from the Sun in 10^6 kilometers
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<b>Sidereal orbit period (days)</b>: The time it takes the body to make one revolution about the Sun relative to the fixed stars in days.
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<b>Tropical orbit period (days)</b>: The time for the body to make one revolution about the Sun from equinox to equinox in days. For Earth, this equals exactly 1 year.
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<b>Synodic period (days)</b>: The time interval between similar configurations in the orbit (e.g. opposition) of the body and Earth, in days.
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<b>Perihelion (10<sup>6</sup> km)</b>: The point in a body's orbit closest to the Sun, in 10^6 kilometers.
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<b>Aphelion (10<sup>6</sup> km)</b>: The point in a body's orbit furthest from the Sun, in 10^6 kilometers.
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<b>Mean orbital velocity (km/s)</b>: The average speed of the body in orbit, in kilometers/second.
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<b>Orbit inclination (deg)</b>: The inclination of the orbit to the ecliptic, in degrees
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<b>Orbit eccentricity</b>: A measure of the circularity of the orbit, equal to (perihelion - aphelion distance)/(2 x semi-major axis). For a circular orbit, eccentricity = 0. Dimensionless.
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<b>Sidereal rotation period (hrs)</b>: The time for one rotation of the body on its axis relative to the fixed stars, in hours.
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<b>Obliquity to orbit (deg)</b>: The tilt of the body's equator relative to the body's orbital plane, in degrees.
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<h5>Atmospheres</h5>
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<b>Surface Pressure</b>:  Atmospheric pressure at the surface, in bars, millibars (mb = 10^-3 bar), or picobars (10^-12 bar).
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<b>Surface Density</b>:  Atmospheric density at the surface in kilograms/meters^3.
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<b>Scale height</b>:  The height interval in which the atmospheric pressure changes by a factor of e = 2.7183
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<b>Average temperature</b>:  Mean temperature of the body over the entire surface in degrees Kelvin.
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<b>Diurnal temperature range</b>: Temperature range over an average day in degrees Kelvin.
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<b>Wind speeds</b>:  Near surface wind speeds in meters/second
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<b>Atmospheric composition</b>:  Relative composition by volume of gasses in the atmosphere.
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<b>Mean molecular weight</b>:  Average molecular weight of the atmospheric constituents in grams/mole. 
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<b>Atmospheric composition (by volume)</b>: Relative volume of constituents in the atmosphere, by percentage or ppm (parts per million).
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<h5>Related Definitions</h5>
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<b>Bar</b> - A measure of pressure or stress.  1 bar = 10^5 Pascal (Pa) = 10^5 kg m^-1 s^-2
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<b>Ecliptic</b> - An imaginary plane defined by the Earth's orbit.
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<b>Equinox</b> - The point in a body's orbit when the sub-solar point is exactly on the equator.
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<b>Gravitational Constant</b> - Relates gravitational force to mass, = 6.6726 x 10^-11 meters^3 kilograms^-1 seconds^-2 
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<b>Opposition</b> - An orbital configuration in which two bodies are on exact opposite sides of the Sun
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<b>Phase Angle</b> - The angle between the Earth and Sun as seen from the body.
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