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Astronomy - Planet Venus
Mass: 4.869 X 1024 kg (0.815 Earths)
Radius (equatorial): 6 052 km
Mean density: 5.25 g cm-3
Distance from Sun: 108 200 000 km
Rotational period: 243.02 days
Orbital period: 224.7 days
Escape velocity: 10.36 km s-1
Apparent magnitude: -4.4
Surface temperature: 482°C
Atmospheric composition: Carbon dioxide (96%),
nitrogen (3%), sulfur dioxide, argon, helium etc. (1%)
Number of satellites: none
Characteristics
Historically, Venus is well known as the morning star, or evening star. Named
after the Roman goddess of love and beauty its surface is veiled by thick clouds.
Beside the Sun and Moon, Venus is the brightest celestial object, shine with
steady bright white light. Its physical dimensions are rather similar to that of
Earth and is referred to as the Earth's sister planet. Venus rotates very slowly on
its axis once every 243 Earth days, longer than the duration it orbits the Sun,
every 225 days. It also rotates retrograde, or spin in the opposite direction of its
orbit round the Sun. In other words, if one stands on the Venusian surface the
Sun would seem to rise in the west and set in the east.
The relationship with the Earth as a twin sister ends when comparing surface
features between the two planets. In many respect the Earth would be how Venus
looks now if the former volcano activities are increased by hundreds of thousands
of times. Geologically speaking, Venus' surface is relatively young that seems to
have completely reconstructed 300 to 500 million years ago. Volcano activities,
deformation of the crust have shaped the surface. At least 85% of the Venusian
surface is covered with volcanic rock with huge lava flows flooded the plains. The
flows have also produced channels that extend for hundreds of kilometers. There
are at least 1000 volcanoes larger then 20 km and probably over a million more
that are over 1 km in diameter. However, there is no direct evidence that these
volvanos are still active.
Not surprisingly, its atmosphere is thick with carbon dioxide, probably as a result
of its past volcano activities and contains droplets of sulfuric acid. The atmosphere
essentially creates a run-away greenhouse effect that allows the Sun's heat in but
does not allow it to escape. This results in a temperature that is hotter
than Mercury. In addition, the surface pressure is 90 times that of Earth which is
why probes that landed on Venus only survived several hours before being
crushed by the tremendous pressure. The dense atmosphere also acts as a
protective cover against small meteorite impacts as no craters greater than 2 km
can be found on the surface.
Recent results from the Magellan spacecraft suggest that Venus’ crust is stronger
and thicker than had previously been thought. Venus has no satellites and no
intrinsic magnetic field, but the solar wind rushing by Venus creates a pseudofield around the planet.
3. Venus is actually the hottest planet in the Solar System
Even though Mercury is the closest planet to the Sun, Venus is the hottest planet in our Solar System.
Venus’s thick atmosphere traps the heat from the Sun, a kind of greenhouse effect, and retains it. Sulfuric
acid and carbon dioxide in the atmosphere are compounds that help trap the heat. The temperature on
Venus is about 465°C (870°F). Venus’s extreme temperatures and toxic atmosphere make it an unlikely
place for the existence of life.