Venus Varied Altitudes.

The Planet Venus, its rotation is slowing down and makes this a fascinating calculation. Liquid oxygen return alpine sample. European Probe Venus Express 2006-2014 shows shape shifting in its polar vortices. Venus Express also showed winds in excess of 200 mph as its cool side like burning embers.
This discovered a surprisingly new cold region high in the planet's atmosphere. Where conditions may be frigid enough for carbon dioxide to freeze out as ice or snow. This is  although the planet's surface is like a red hot furnace, conditions are very different at an altitude of 125 km, where Venus Express revealed a very frigid layer with a temperature of around -175°C. The unexpected cold layer is far chillier than any part of Earth's atmosphere, despite Venus being much closer to the Sun. As on Earth, solar ultraviolet radiation removes electrons from the atoms and molecules in the upper atmosphere, creating a region of electrically charged gas known as the ionosphere. This ionised layer interacts with the solar wind and the magnetic field carried by the solar wind. During the continuous battle with the solar wind, the ionosphere is able to slow and divert the flow of particles around the planet, creating an elongated magnetotail, shaped rather like a tadpole or wind sock, on the lee side of the planet. Until now, magnetic reconnection was not generally thought to occur near non-magnetised planets, so scientists were surprised.

Venus Express detected the reconnection events. This reconnection splits the magnetotail, causing most of the plasma (electrically charged particles) in the tail to be ejected into space. It also forms a plasmoid structure which heads towards Venus and channels some of the energy of the solar wind into the night-side atmosphere. As a result, the magnetic reconnection causes plasma circulation at Venus, similar to what happens in Earth's magnetotail. The discovery was made possible by the near-polar orbit of Venus Express, which is ideal for instruments such as the magnetometer and low-energy particle detector to observe the solar wind – ionosphere –magnetotail interaction. Previous missions, such as Pioneer Venus, have either been in different orbits or been active at different periods of solar activity, so they were not able to detect the reconnection events. The discovery was made by studying light from the Sun as it passed through the atmosphere, revealing the concentration of carbon dioxide gas molecules at various altitudes along the terminator – the dividing line between the day and night sides of the planet. Armed with information about the concentration of carbon dioxide and data on atmospheric pressure at each height, scientists could then calculate the corresponding temperatures.

Since the temperature at some heights dips below the freezing temperature of carbon dioxide, the main constituent of the atmosphere, carbon dioxide ice might be able to form there – possibly forming clouds of ice or snow particles. The data also show that the cold layer above the terminator is sandwiched between two comparatively warm layers. The temperature profiles on the hot day side and cool night side at altitudes above 120 km are extremely different, so the terminator is affected by conditions on both sides. The night side may be playing a greater role at one altitude and the day side might be playing a larger role at other altitudes. Analyser of Space Plasma and Energetic Atoms (ASPERA) instrument discovered a rapid loss of hydrogen and oxygen from the night side. This depletion occurs because water molecules in its upper atmosphere are split by incoming ultraviolet radiation from the Sun. This process creates two hydrogen atoms and one oxygen atom for each dissociated molecule. The solar wind is a stream of charged particles from the Sun – then strikes the upper atmosphere and carries the hydrogen and oxygen atoms into space. Unlike Earth, Venus does not generate a magnetic field which can protect its atmosphere from the solar wind.

Venus Express has measured the rate of this escape and confirmed that roughly twice as much hydrogen as oxygen is escaping, confirmation that water (H 2 O) is the source of these escaping ions. It has also shown that a heavy form of hydrogen, called deuterium, is progressively enriched in the upper regions of Venus's atmosphere because the heavier gas finds it less easy to escape the planet's gravitational grip. This situation is unique to Venus, since the temperature profile along the terminator in the atmospheres of Earth or Mars is very different. This is one of the major discoveries made by Venus Express during the last eight years. The ozone layer in Earth's stratosphere is well known, and traces of ozone (O 3 ) were detected more than 40. years ago in the atmosphere of Mars, but until the arrival of Venus Express, no one knew whether Venus had a comparable atmospheric layer.Using observations made with the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) instrument, scientists were able to detect the presence of a tenuous layer of ozone gas in its atmosphere.

The ozone was detected by means of stellar occultations – analysing light from distant stars as it passed through different layers of the atmosphere. The method relies on the availability of stars in the line of sight, meaning that it yields an uneven coverage of the planet and is limited to the night side. According to the new data, ozone is located at varying altitudes in the Venusian atmosphere, between 90 and 120 km – compared with 15-50 km on Earth – and is always confined to a rather thin layer, measuring 5 to 10 km across. The ozone layer on Venus is also very tenuous – up to 1000 times less dense than that on Earth. One surprise was the absence of ozone at the anti-solar point, where molecular oxygen is highly concentrated. Other studies based on Venus Express observations showed that sunlight illuminating the day side of the planet splits carbon dioxide molecules, liberating oxygen atoms. These are then carried to the anti-solar point, on the night side, by a strong wind which flows from the hot day side to the cooler night side.

Oxygen atoms transported to the anti-solar point give rise to molecular oxygen, so some production of ozone was also expected. However, none was found. The lack of ozone detected there can be explained if the molecules are destroyed by chlorine-based compounds, which are funnelled to the anti-solar point by the same mechanism that carries the oxygen there. The chlorine-catalysed destruction of ozone at Venus' anti-solar point may be caused by reactions very similar to those responsible for the Antarctic 'ozone hole' on Earth, highlighting the similarity of atmospheric processes on these two planets.This is one of the major discoveries made. Several planets in the Solar System, including Earth, have been found to possess hurricane-like vortices, where clouds and winds rotate rapidly around the poles. Some of these take on strange shapes, such as the hexagonal structure on Saturn, but none of them are as variable or unstable as the southern polar vortex on Venus.

The existence of the polar vortices on Venus has been known for many years, but high-resolution infrared measurements obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on Venus Express have revealed that the southern vortex is far more complex than previously believed. The southern polar vortex on Venus. The new observations show that the centre of the vortex has a highly variable shape and internal structure, and its morphology is constantly changing on timescales of less than 24 hours, as a result of differential rotation. This fast-moving feature is all the more surprising since its centre of rotation is offset from the geographical South Pole. The images show that the core of the dynamic southern vortex can take almost any shape, so although it often looks like an 'S' or figure 8, it may become completely irregular, or even chaotic, in appearance. These rapid shape changes indicate complex weather patterns, which are strongly influenced by the fact that the centre of the vortex does not coincide with the geographical pole.

Images from the Venus Monitoring Camera and from the VIRTIS instrument show that the speeds of the zonal winds change with latitude, so that the vortex is continually being pulled and stretched. Although the mean zonal wind is retrograde (blowing from east to west), its speed decreases toward the pole. The centre of rotation drifts right around the pole over a period of 5-10 Earth days. Its average displacement from the South Pole is about three degrees of latitude, or several hundred kilometres. Although its highly elliptical orbit means that Venus Express flies too close to the planet's North Pole for detailed imaging, it is likely that both vortices have similar structures and behave in a similar way. This is one of the major discoveries made by Venus Express during the last eight years. Venus is a rarity among planets as it's a world that does not generate a magnetic field internally. However, Venus does have an elongated magnetotail on its night side. Furthermore, Venus Express has discovered evidence for magnetic reconnection – the process responsible for the Northern Lights on Earth – in Venus' magnetotail. Although Venus has no magnetosphere to deflect the charged particles of the solar wind (electrons and protons) as they stream past the planet, it is partially protected from erosion of the outer atmosphere by an induced magnetic field arising from the interaction of the solar wind and the planet's ionosphere