Part Two – Venus
In this second part of a series of nine articles we look at the planet Venus.
Throughout this series, I would like to give a huge H/T to NASA. www.nasa.gov. I have used other sources as well, such as www.space.com and www.earthsky.org which is a great site for showing you where to look.
Venus is often named as Earth’s twin because both worlds share a similar size, surface composition and have an atmosphere with a complex weather system.
The figure on the right compares Venus and Earth spacecraft images. The surface of Venus is shown in orange as radar images while the atmosphere is reproduced on near true colours as it would be seen by the human eye. The upper clouds are brightest in the blue and ultraviolet wavelengths making Venus a white-blue colour planet. Both planets have almost the same size and density and Venus is only 30% closer to the Sun than Earth. Both share an interesting geological evolution with old volcanoes in Venus and some of them could still be active. One of the biggest mysteries of Venus is why its surface is so young on geological time-scales. It is interesting to remark that there is almost no water on Venus’ atmosphere.
Venus is a dim world of intense heat and volcanic activity. Similar in structure and size to Earth, Venus’ thick, toxic atmosphere traps heat in a runaway ‘greenhouse effect.’ The scorched world has temperatures hot enough to melt lead. Glimpses below the clouds reveal volcanoes and deformed mountains. Venus spins slowly in the opposite direction of most planets.
Distance from the sun: About 67 million miles, about 3/4 as far as the Earth is from the sun.
Year: About 225 Earth days.
Day: About 243 Earth days.
Average diameter: About 7,500 miles, almost as large as Earth.
General surface temperature: 864 degrees Fahrenheit. (462 degrees c)
Atmosphere: Carbon dioxide, nitrogen.
Whereas Earth rotates in about 24 hours Venus rotates in the contrary sense (retrograde rotation) in 243 days. The orbital period of Venus is 225 days so that a Venus year takes less than a full day. The combination of these two periods results in the Sun appearing from the West and disappearing over the East with a day-night cycle of 117 days.
The atmosphere of Venus is 90 times more dense than that on Earth and it is made of 96.5% of CO2 and a 3% of nitrogen. This means that both planets have the same amount of Nitrogen on their atmospheres. Surprisingly the CO2 on Earth is stored on calcite type rocks and if we would convert the CO2 on these rocks into atmospheric CO2 it would amount to the same amount of CO2 that there is on Venus’ atmosphere. Not that I think we would want to, global warming and all that!
Because of the denser atmosphere and the chemical composition Venus experiences an immense green-house effect that raises the temperature over the surface to more than 470ºC
Clouds are common on Earth but they cover completely Venus’ atmosphere. They are made of sulphuric acid droplets at 50-70 km above the surface and at temperatures comparable to Earth’s surface temperatures. They are extremely reflective making Venus the most reflecting body in the Solar System.
The first successful mission to Venus was by Mariner 2 which did a Flyby on the 14th December 1962. It has been orbited by several spacecraft since then, from NASA and the Soviet Union. Currently the only artificial satellite in orbit around Venus is the Japanese Akatsuki space probe.
Where to find it:
Check the above link regularly to see where planets and stars can currently be seen. Sadly not visible due to the suns glare this month. Will become visible again next February, but only for a short while before the sun rises.
© Phil the test manager 2018