Mercury and Venus

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Mercury and Venus are the innermost of the eight planets in the Solar System. It is also the smallest, and its orbit has the highest eccentricity of the eight. It orbits the Sun once in about 88 Earth days, completing three Mercury orbitrotations about its axis for every two orbits. Mercury has the smallest axial tilt of the Solar System planets. The perihelion of Mercury’s orbit precesses around the Sun at an excess of 43 arcseconds per century beyond what is predicted by Newtonian mechanics, a phenomenon that was explained in the 20th century by Albert Einstein’s General Theory of Relativity. Mercury, being an inferior planet, appears as a morning star and an evening star, but is much more difficult to see than the other inferior planet, Venus. At its brightest, Mercury is technically a very bright object when viewed from Earth, but it is not easily seen in practice because of its proximity in the sky to the Sun.

Physical characteristics
Equatorial diameter 4,879.4 km
Superficial area 7,5 × 107 km²
Mass 3,302×1023 kg
Average density 5,43 g/cm³
Superficial gravity 2,78 m/s²
Period of rotation 58d 15,5088h
Axial inclination
Albedo 0,10-0,12
Speed of escape 4,25 km/s
Average Temp. superf.: Day 623 K
Average Temp. superf.: Night 103 K
Skin temperature
min. average max.
90 K 440 K 700 K



The second planet from the Sun, orbiting it every 224.7 Earth days. Venus is Earth’s closest neighbor in the solar system and the brightest object in the sky after the Sun and the Moon. The planet is named after the Roman Venus orbitgoddess of love and beauty. The planet is a little smaller than Earth, and is similar to Earth inside. We can’t see the surface of Venus from Earth, because it is covered with thick clouds. The atmosphere of Venus is made up mainly of carbon dioxide, and thick clouds of sulfuric acid completely cover the planet. The atmosphere traps the small amount of energy from the sun that does reach the surface along with the heat the planet itself releases. This greenhouse effect has made the surface and lower atmosphere of Venus one of the hottest places in the solar system! Why should Venus and not the Earth have a hot and thick atmosphere? Some scientists call it the Goldilocks phenomenon. Venus is one of the terrestrial planets with solid, rocky surfaces inhabiting the inner part of our solar system. The surface of Venus is a very desolate, barren place. Nonetheless, efforts were made to study the planet by several Soviet Venera spacecraft. These spacecraft were able to take pictures, as well as sample rocks and take other various measurements. The transit of Venus comes in pairs about once every century, with the previous one occurring in 2004. The next one will not take place until 2117.

Physical characteristics
Equatorial diameter 12,100 km
Mass 0.815 Earth
Average density 5,25 g/cm³
Superficial gravity 0.88 Earth
Speed of escape 4,25 km/s
Average Temp. superf.: Day 477 ºC
Average Temp. superf.: Night -33 ºC
Atmosphere CO2

sources: NASA, WikiPedia