Venus I. Bulk properties: density = 5.245 gm/cm³ ; radius = 6051.5; moment of inertia (unknown but assumed similar to Earth). The bulk density and radius are both slightly lower than Earth. The corrections for compression and thermal structure on density are not well known, but a small bulk density difference from Earth, if confirmed, may be significant for composition.

II. Rotation and figure: rotation 245 days retrograde. Small equatorial bulge exceeds that expected for formation at its current rotation rate.

III. Gravity field: good correlation with surface features and long wavelength equal potential surface, suggesting a thicker lithosphere than Earth or creep in mantle slower than Earth so isostasy is not obeyed as well.

IV. Composition and interior structure: Little is known, but its similarity to the Earth in radius and bulk density suggests a similar radial structure. Expected compositional differences from Earth would be slight enrichtment relative to Earth in refractories, depletion of water in crust and mantle, lack of a solid phase of iron in its core.

V. Thermal structure and tectonic activity: High surface temperature (700 deg K) suggests a thin lithosphere of only 40 km. This seems to contradict the results for lithospheric thickness inferred from gravity, which would suggest a lithosphere in excess of 300 to 400 km thickness. No evidence of plate subduction. Compressional features near the poles and possible spreading centers and tensional features in equatorial region. Age of surface everywhere less than 800 m.y. Last major tectonic episode possible 200-300 m.y. An episodic tectonism has been proposed. Hot-spot like tectonism with no organized plates is observed.

VI. Magnetic field: weak or no measureable magnetic field. The surface temperature is near the Curie temperature of silicate rocks, and no measurable remanent magnetization is possible. The rotation rate, although small, is sufficient for a dipole field.Although a liquid molten iron core is likely by analogy to Earth, the P-T regime of the Venusian core may be completely in the field of solid iron. Thus, it is currently not possible for a solid inner core to be progressively forming by gravitative differentiation, which is the most favored mechanism for the Earth's dynamo.

VII. Atmosphere: primarily CO2; 90 bar pressure at surface.

VIII. Surface features include compressional and tensional faulting, volcanism, cratering including collapse features and spider-like normal faults radiating from center of some craters. Lava flows and no large craters found. Extensive surface mapping was made possible by Magellan radar imaging. Click here for images from Magellan and an explorer's guide .