The Venus Express spacecraft - interim summary

For over two years the Venus Express spacecraft has been circling Venus and studying the composition of the atmosphere, the clouds and more. Summary of the findings so far

introduction

On November 5.11.2005, 2, the European Space Agency launched a spacecraft to the planet Venus. It was the fourth time (after the Huygens that landed on Titan, the Mars Express that was put into orbit around Mars and the Bagel 153 that tried to land on it) within the framework of Europe's activities in space that a spacecraft is launched towards a planet in the solar system. This spacecraft is mainly based on equipment and instruments developed for its Mars Express spacecraft and it relies on the work teams that were used to develop the Mars spacecraft, all with the aim of saving costs. This international cooperation also included Russia since Europe does not have powerful launchers to launch spacecraft destined for the planets. After a journey of 11.4.2006 days, the spacecraft reached its destination on 250. It entered orbit around the planet and after a series of maneuvers it was placed in an orbit whose extreme points are 400-65,000 km and 24 km. A highly elliptical orbit that allows for very wide views of the atmosphere of Venus in the remote parts. One lap lasts XNUMX hours.

spacecraft instruments

There are 7 research instruments in the spacecraft and they are:

1. Space plasma analyzer and energetic atoms - ASPERA

   Analyzer of Space and Energetic Atoms
   This device is designed to test the interaction between the solar wind and the star's atmosphere by measuring the flux of particles from the atmosphere of Venus as well as particles from the solar wind. In addition, they examine how molecules and ions escape from the atmosphere.

2. Magnetometer - MAG

   Venus Express Magnetometer
   Venus has no magnetic field of its own at all. The field surrounding it is a product of the interaction between the solar wind and the atmosphere. The magnetometer examines this process and enables a better understanding of its effects on the atmosphere such as the escape of the ions from the atmosphere.

3. Planetary Feria Spectrometer - PFS

   Planetary Fourier Spectrometer
   This device measures the temperatures at altitudes between 55-100 km with very high resolutions. It measures the composition of the atmosphere as well as the ground temperatures, which makes it possible to look for volcanic sources.

4. Atmospheric spectrometer in ultraviolet and infrared

   SPICAV/SOIR and Infrared Atmospheric Spectrometer
   This device analyzes the atmosphere. It tries to find small amounts of water vapor that are estimated to be in the atmosphere. The device looks for sulfur compounds and oxygen molecules and will determine the density and temperature of the atmosphere at altitudes between 80-100 km.

5. An experiment in radio science - VeRa

   Venus Radio Science Experiment
   The device analyzes the powerful connection between the spacecraft and the Earth to study the common conditions in the atmosphere. The researchers use this to study the density, temperature and atmospheric pressure at altitudes between 35-40 km up to a height of 100 km from the ground. The hardness, the electrical properties of the soil and the conditions of the solar wind in the inner part of the solar system are also examined.

6. Spectroscopic mapping in ultraviolet, visible light and infrared VIRTIS

   Ultraviolet/Visible/Near-Infrared mapping Spectrometer
   This device makes it possible to examine the composition of the atmosphere from the ground up to an altitude of 40 km. It monitors clouds in ultraviolet and infrared and examines the dynamics of the atmosphere at different altitudes.

7. VMC surveillance camera

   Venus Monitoring Camera
   A wide-angle, multi-channel camera that can photograph the star in the near infrared, ultraviolet and visible light. The camera can take global photographs, measure the dynamics of the clouds and photograph the ground. It also helps in identifying phenomena visible in other devices.

In order to achieve maximum utilization of the equipment on the spacecraft, two significant measures were taken which are considered a landmark in the exploration of planets. One means is a wise use of the orbit of the spacecraft around Venus and a second means is to take advantage of the passage of the American Messenger spacecraft near the planet on its way to Mercury.

One of the most interesting phenomena in the atmosphere of Venus is a binocular vortex that is permanently located above the south pole. In order to provide an explanation for this phenomenon, those responsible for the VIRTIS instrument decided to start the research journey above the south pole (1). The observation is initially focused on the target while taking advantage of the aphiga point. This point allows the device to focus on the object of observation over time within the frame of the field of view. From this distance it is possible to make optimal use of the multi-channel spectral capability of the VIRTIS device.

The use of a 3 micron wavelength in the infrared thermal range allows simultaneous observation of both the day and night side of the star and viewing to different depths of the atmosphere. The result, the ability to build a three-dimensional model of the atmosphere. For example, a combination of wavelengths of 3.8 and 1.7 microns makes it possible to observe the top of the clouds at an altitude of 65 km. The 1.7 micron wave makes it possible to observe the part of the atmosphere below the clouds on the night side. The morphological changes of the vortex can be clearly observed throughout 8 hours of continuous observation. and compare with a subsequent observation. Cross-referencing the information from many observations while integrating them into models Computerized fluid dynamics allows for the construction of an up-to-date atmospheric model of Venus. Since the spacecraft finished the original work program in the summer of 2007, it has begun a work program that was prepared before the end date of the program. that were not included in the master plan.

Another means used by the researchers is taking advantage of a rare opportunity that fell into their hands, using the measurements of another spacecraft. This refers to the American Messenger spacecraft which used the gravity of Venus to reach Mercury. The Messenger spacecraft performed this transit flight on June 5.6.2007, 338. At the time of the transit, the Messenger's distance from Venus was 165 km on the opposite side to that of the Venus Express. The Messenger was on its night side and its position relative to the ground at this point was E°12.25- S°35,000. The Venus Express was then over the horizon almost above The South Pole is 2 km from the star. Both spacecraft observed Venus at the same time (90). One of the instructive examples of this type of observation is the utilization of previous information that the researchers had from previous flights and national observations. Given the speed of local winds that depend on their height above the ground and latitude, it is possible to track a given group of clouds at any point in time. The researchers chose a cloud that moves west at a rate of 12° (degrees of longitude) every day, which could be observed by Venus Express and which would also be shown by MESSENGER 12 hours later when it was at its minimum distance from Venus. This cloud could be viewed again by the Venus Express spacecraft 24 hours later after the messenger passed, this time on the night side of the planet. That is, the researchers were given the opportunity to follow a particular cloud for 40 hours. This move allowed Venus Express to observe the cloud located 45-50 km from the ground and the messenger to observe it when it was at a distance of 75-630 km above the ground. Altogether, the messenger transmitted XNUMX photographs from Venus.

Atmospheric

Based on the findings of previous spacecraft that measured the star, a model was built according to which this planet is similar to the Earth, with its formation there was a large amount of water. Water and water vapor are inherently a heat-trapping greenhouse gas (2). The evaporation process is accelerated to the point where all the water becomes a thick atmosphere of water vapor and these are broken down into their components by the ultraviolet radiation coming from the sun into oxygen and hydrogen. Chemical reactions with minerals in the rocks turn the oxygen into CO3 and the hydrogen escapes into space. The measurements made by the Venus Express confirm a model It. The comparison of the residual hydrogen with deuterium (an isotope of hydrogen) showed that the escape rate of the latter from the star is slower. It turned out that the ratio of hydrogen / deuterium is 2 times greater than that on Earth. This finding is consistent with measurements from previous observations. What was surprising is that the concentration of deuterium in the upper atmosphere is 150 times higher than that of the land

The ultraviolet radiation also breaks down the CO2 molecules in the upper atmosphere into oxygen and CO. The Venus Express observed an airglow of 2O in the upper atmosphere and the presence of CO at the top of the clouds. The molecular oxygen glow was discovered on the night side of the star. This warning has been observed in previous terrestrial and spacecraft observations that have reached Venus. The warning occurs when the oxygen atoms bond together and form a molecule of 2O that emits light. The accepted assumption is that at high altitude on the light side, the strong flow of ultraviolet radiation coming from the sun breaks the CO2 molecules and releases the oxygen atoms that are transported by the movement of the atmosphere towards the night side. Here these atoms descend to lower layers of the atmosphere, where they recombine and form the 2O. In this process, they release light at a wavelength that allows it to be distinguished by spacecraft surrounding it and from Earth. This type of observation is of utmost importance. It is possible to use the careful distribution of the CO2 clouds to better understand how the lower layers of the atmosphere move and behave. The chemistry of the atmosphere can be monitored. Calculating the speed at which atoms connect to molecules will allow in the future to understand mechanisms that support this connection and to learn from it about the connection of other chemical components in the atmosphere. In addition, this observation will allow a better understanding of energy exchanges between the mesosphere (the middle atmosphere at the upper limit where it is located the warning with the thermosphere) and a higher layer that is directly affected by the sun.

Below an altitude of 70 km, small amounts of water vapor and gaseous SO2 are found in the atmosphere. These are usually buried in the cloud layer that blocks viewing of the star in visible light. If these molecules are raised slightly above the top of the clouds, they are exposed to the sun's ultraviolet radiation, which also breaks them down and their behavior It is more reactive. These parts reconnect while creating a haze ( 4 ). This haze is not visible In visible light, but in ultraviolet light. In an observation made in July 2007, the development of a bright haze was seen in the South Pole. For several days this haze became brighter and then dimmed, moving towards equatorial latitudes and back towards the pole. As quickly as it appears, it disappears in the process of these episodes, the brightness at southern latitudes quickly intensifies by 1/3 and disappears just as quickly. This is during the crystallization of the sulfuric acid particles. An obvious question is what is the source of the SO2? Based on what is known from the Earth, it has been hypothesized that the origin of this gas is volcanic activity. It is possible that there was massive volcanic activity on the surface of the planet 10 million years ago. Instead of sinking to the ground and creating different chemical reactions with it, like on Earth, it remains in the air because it takes a long time to reach the ground.

The spacecraft discovered for the first time molecules of hydroxyls (OH) in the atmosphere. These molecules were discovered in the upper atmosphere 100 km above the ground (5). On Earth these molecules purify the atmosphere of impurities and on Mars they probably stabilize the CO2 by preventing it from turning into CO. It is possible that they make the Martian soil sterile for life Microbial. The amount of hydroxyls in the atmosphere of Venus changes rapidly in volumes of 50% in short periods of time. These changes were observed in the time intervals of a spacecraft orbiting Venus. The reason for this may be changes in the amount of ozone in the atmosphere. Ozone is a strong absorber of ultraviolet radiation from the sun.

The structure of the atmosphere - new discoveries

It has been known for years that the atmosphere of Venus has many clouds and that the atmosphere itself is very dynamic. The Venus Express added another layer to the structure of the atmosphere. And this is thanks to new discoveries. The planet has a thick layer of sulfuric acid clouds located at an altitude of 40-60 km above the ground. Above it is the mesosphere, which is demarcated at heights between 60-100 km and serves as a transition zone between low-velocity winds and high-velocity winds (6). At an altitude between 90-120 km a layer of warm air was discovered on the night side. At this altitude it is usually cold. The temperatures are so low that the researchers gave the place the name Cryosphere. The measured temperatures showed that at an altitude of 100 km the temperatures range between 70-30°C ° XNUMX. At this height you find a light haze made of particles of sulfuric acid and water. This area changes rapidly and sometimes it is visible Bright. The spacecraft's instruments measured the amount of light absorbed in the atmosphere at different wavelengths, which made it possible to identify chemicals and temperatures in the different layers of the atmosphere. It turned out that a process of thermal inversion takes place in the atmosphere. on the night side. The warming of the atmosphere on the night side occurs when lumps of gas sink into the dense atmosphere. The increase in air pressure "squeezes the pockets" and raises the temperature.

In high latitudes near the South Pole there is a dark and cold strip (cold collar) and what characterizes it is that the temperature of the clouds in it is lower than the temperature around it. A similar structure is also found in the North Pole (7).

polar vortexes

Venus has two hurricane-like eddies at the poles. The hurricane of the South Pole was discovered in 1974 by Mariner 10 and it turned out to be 2000 km in diameter and in its center an eye similar to that found in terrestrial hurricanes was observed. A similar phenomenon was discovered at the North Pole in 1979 by Pioneer Venus. Venus Express discovered New things about the southern vortex. It turned out that the vortex has two eyes in its center and the name it received is the Polar Dipole. This double eye is not found in the vortex above the North Pole. The discovery of this phenomenon raised two questions.

It has long been known that very strong winds blow on Venus. They circle the star in 4 days in a westerly direction. These winds are defined as super rotation winds. This movement is done simultaneously with the recycling of the air in the atmosphere. It is possible that these winds have an effect on the formation of the vortices above the poles. The discovery of this phenomenon led to the discovery of another phenomenon, a band of cold air around the vortex. It may be a product of upward air movement (8). The southern vortex moves counterclockwise and the northern vortex moves clockwise. It also became clear that the southern vortex rapidly changes its shape in time frames of hours. In June 2006 the vortex resembled an hourglass, similar to the vortex observed in the North Pole by the Venus Pioneer. The day before on 26.2.07 the double eye was seen in the center of the vortex similar to what was seen before. In the observation on 25.2 the vortex is almost circular. In other observations, the center of the vortex is elliptical. A combination of the images in a video shows what it is about the nature of the vortex. It is very complex, different gases within it move in different directions and at different heights. The dynamics itself is reminiscent of earthly eddies, including those observed in the centers of hurricanes. According to one explanation, atmospheric gases heated by the sun at the equator rise upwards and from there move towards the poles. They contract and sink with their movement towards the poles and are deflected to the side due to its axial movement. An infrared observation showed that the center of the vortex is very bright, which indicates that many atmospheric gases are moving down, creating a depression at the top of the clouds and making the entire area warmer (9).

Many researchers think that the double eye vortex is formed when warm air in the equatorial regions rises into the atmosphere and moves forward while descending towards the pole. Here it starts to cool and move in spiral movements and thus creates the vortex. The vortex powerfully drives the dynamics of the clouds at all altitudes. It has an important role in the balance of the atmosphere. The Venus Express has revealed new details about a swirling region called the
Sub-solar (the zenith). which is on the day side and changes rapidly with the axial movement of the star. This is where Venus receives the most heat from the Sun. This place is extremely important for the dynamics of the atmosphere (10).

The observational penetration capability of the spacecraft in the South Pole is up to a height of 45-50 km. Weighing all the findings including this figure raises the possibility that the vortex cannot reach the lower atmosphere due to its high density including the ground of the star.

Clouds and fog

The photographs of Venus in visible light clearly show that it is covered by a thick mantle of clouds, which does not allow observation of these wavelengths on the surface of the star and that apparently the layer of clouds is almost static. Switching to observation in ultraviolet changes the picture completely. It turns out that the cloud layer is very complex, dynamic in nature and the atmosphere in large parts of it is extremely turbulent. We observed a sequence of cyclical "wave" patterns that were created as a result of local heat and pressure changes due to tidal forces acting on the star which were also noticed in these observations.

Spots were seen at the top of the clouds that were defined as "ultraviolet radiation absorbers". This name was given to them because they absorb half of the ultraviolet radiation coming from the sun. What causes this is not clear. Due to their high absorption power, they are of utmost importance in understanding the heat and radiation balance of the entire planet and the dynamics of the atmosphere. A night observation of the middle and lower layers of the atmosphere and the latitudes between S ° 90 - S ° 20 shows that the clouds are pushed by the winds. It has been known for a long time that the thickness of the cloud layer is 20 km and that it reaches a height of 65 km above the ground Measurements using the stellar occultation technique on the night side of the star show that the top of the clouds can reach up to to a height of 90 km in the form of an opaque haze and from there it continues as a more transparent layer up to a height of 105 km. The fact that the haze can reach such a high altitude surprised the researchers. At an altitude of 20 km, it is already possible to notice drops of sulfuric acid (11). In a photo taken on 12.4.06 in infrared at a wavelength of 1.7 microns, spiral clouds were noticed at an altitude of 55 km (12).

In a photograph taken on 23.9.06 at a wavelength of 1.7 microns, you can see an area near the South Pole with a bright and very large spot. In this place the cloud is thin. Such places are similar to large holes that allow heat radiation from under the clouds to rise up and are very large in relation to the environment (7). The clouds move quickly and regularly change their shape even though these are repeating shapes. They also change their position in short and long time spans, which makes the meteorology of the star complicated. very. One of the observed clouds is 2000 km long and 500 km wide. Usually the clouds are elongated due to the high speed of the winds up to 360 km/h (13). From photographs taken during 2007 it became clear that at the equator the clouds have a bubble shape. Normal and dashed. With the movements of the super rotation winds their speed reaches higher than 400 km/h At higher latitudes they integrate within the eddy form (14).

As for the haze itself, it may be the product of condensation of water into ice crystals on the night side, although the amount of water on Venus is extremely small. If they concentrated all the water vapor in the atmosphere and wrapped it around the surface of the star, their total height would not be more than 3 cm. Today they are in the upper layers of the atmosphere (11).

lightning

One of the questions that has accompanied researchers for years is whether there is lightning in the atmosphere of Venus. The mechanism that creates lightning on Earth requires the presence of water ice particles, the amount of which in the atmosphere of Venus is too small for this purpose. There were those who, following the findings of the Pioneer Venus spacecraft, hypothesized that in the atmosphere of Venus there are large particles of an unknown chemical composition capable of making this possible (15). The measurements of the Venus Express revealed bursts of radio waves known as whistlers, which on Earth are created by lightning (3). It turned out that there are indeed lightnings on Venus, although their origin is different from that of the lightnings on Earth. The confirmation of this comes from observations made by the Venus Express when it was in its perigee. These observations were conducted for several days when the spacecraft was in the segment of the orbit closest to the ground. Each observation of this type lasted two minutes. It turned out that the origin of the lightning is in clouds made of sulfuric acids. The importance of this discovery is knowing Because electrical breakdowns are related to the chemistry of the atmosphere by the fact that it breaks molecules into several parts that can then connect in unexpected ways (16).

Spirits

When the 4 Pioneer Venus probes penetrated the planet's atmosphere in 1978, it became clear that the wind speed is very high, 360 km/h. These speeds allow them to circle the planet once every 5-7 days (Earthly). This is the super rotation. From an hour As Venus Express began to make its measurements, it became clear that these high-speed winds at the equator are in a constant "struggle" with various types of eddies. local and thus create complex forms of clouds. Another type of local wind is a product of a strong flux of solar radiation that hits the day side of the star. This flux heats the atmosphere and creates convection cells. Masses of hot air rise up and create local vortices and winds No flux of radiation from the sun, but the shape of the clouds and the dynamics of the winds are for some reason similar to those operating on the day side Is there any mechanism responsible for the equatorial vortices on both sides of the star.

The Alpha Regio region located near the equator is characterized by a very complex relief, it rises to a height of 4 km and its ridges and valleys face different directions. Is there any connection between the topography and the local atmospheric vortices? (14). Comparison between photographs taken on the day side of the star and those made on the night side allowed the researchers to follow clouds for several months. As a result, new things were discovered regarding the spirits The speed. Between the equator and the middle latitudes, constant winds blow from east to west, and their speed depending on the height decreases from 370 km/h to 180 km/h. From the middle latitudes towards the pole, their speed drops to zero in the polar region where a large vortex forms. Between the lines The movement is weak - 15 km/h. The speed of the super rotation winds is not constant over time. It turned out that there are Fluctuations in speed. For the first time a "solar thermal tide" was observed. These tides are an effect in the high latitudes. The relative movement of the sun on the clouds and the intensity of the heat affecting them makes the super rotation winds stronger at sunset than at sunrise (17).

Until September 2008, the researchers tracked 625 clouds at a height of 66 km, 662 clouds at a height of 61 km and 932 clouds at a height of 45-47 km both on the day side and on the night side. These trackings gave several additional indications regarding the winds. Between the latitudes S °55 -S °50 the wind speed varies from 370 km/h at an altitude of 66 km to 210 km/h at a height of 45-47 km. At latitude 65 ° the hurricane-like vortex becomes dominant. The clouds at different heights are pushed by winds whose speed is uniform regardless of height and the speed drops to zero in the center of the vortex.

It turned out that the speed of the zonal winds that blow parallel to the latitude depends on the local time. The difference in the heat of the sun that reaches the star in the morning and in the evening, the so-called solar tide effect, largely affects the dynamics of the atmosphere, causing the winds to blow stronger in the evening. In general, the winds regain their speed every 5 days (18).

Measuring temperatures in the atmosphere

The day side is warmer than the night side at both low and high altitudes. Since the sun's energy is absorbed by the clouds on the day side, the temperature increases by 40 - 30 C from the south pole towards the equator up to a height of 60 km, which means that the clouds absorb more of the sun's heat at the equator than at the poles. On the night side, in contrast Therefore, the temperature is more or less constant up to an altitude of 60 km. There appears to be a heat gap between day and night at the equator reaching up to 40 C ° up to an altitude of 55 km. The cold band, a heat cascade surrounding the two poles is clearly visible on both the day and night sides between latitudes S°-S° 80 at an altitude of 60 km. This strip reaches up to latitude S °63 during the night (40).

Measurements made in August 2006 over the Themis Regio and Phoebe Regio regions in the Southern Hemisphere revealed differences of 30° between the low and high regions. These measurements confirmed findings of radar observations from previous flights. Themis Regio is located at S °37- E °270 and has had strong volcanic activity at least in the past. As on Earth the mountain tops are colder. The temperature on the ground is C°477 and on the mountain tops C °447 (19).

Up to a height of 65 km, the higher you go, the temperature drops. Above this height, there is a thermal inversion area. A series of warmings and coolings within the height range associated with the top of the clouds. This series of inversions is delimited by two boundary lines, upper and lower are well defined. below 65 km and above 70 km where a cooling trend is observed. the distance between these two boundary lines 3 times greater in the polar latitudes than in the space between the equator and the middle latitudes. The low inversion is felt in the polar latitudes with the increase in altitude towards lower latitudes. Although in general the temperature is more or less isothermal in the height space of 5.2 km, the series of inversions requires a subtle thermal structure at the top of the clouds. Similar inversion patterns were observed by the Pioneer spacecraft Venus, but were more prominent in polar latitudes than those observed by the Venus Express (20).

magnetic field

Unlike the Earth, Venus does not have its own magnetic field, so there is nothing to protect the atmosphere from the influence of the solar wind. As a result, this wind acts directly on the upper atmosphere. This interaction causes the atmosphere to lose gases in the form of ionized particles mainly of hydrogen, oxygen and helium. The oxygen and hydrogen ions are very important because they are the components of water. From all the observations made so far, it is clear that the water molecules are the most significant contributors of hydrogen in the upper atmosphere. The solar wind breaks the water molecules into charged particles, plasma, which escape into space.

The solar wind "oversees" every aspect of Venus's plasmatic environment. The magnetic field carried by the solar wind accumulates above the upper atmosphere and forms a mantle of weak magnetic field around the star and prevents the solar wind from penetrating the atmosphere. This field covers the day side of the star and continues to hug the shape of the star on its night side. The configuration of the night side magnetic field contributes to the acceleration The plasma and the result is a loss of the atmosphere (21).

Sources

1."Venus Express infrared camera goes filming" 8.5.07
http://www.spacedaily.com/Venus_Express_Infrared_Camera_Goes_Filming_999.html

2."Venusian rendezvous results: chapter one. 16.7.07
http://www.spacedaily.com/reports/Venusian_Rendevouz_Results_Chapter_One_999.html

3. Chang. K.-"New findings underscore an Earth-Venus kinship" 29.11.07
http://nytimes.com/2007/11/29/science/space/29venus_html?ref-ace&paperwanted=print

4. "The light and dark of Venus" 22.2.08
http://www.spacedaily.com/The_Light_And_Dark_Of_Venus_999.html

5. "Key molecule found in Venus atmosphere" 16.5.08
http://www.spacedaily.com/Key_Molecule_Found_In_Venus_Atmosphere_ 999.html

6. "The unexpected temperature profile of Venus's atmosphere" 28.11.07
http://www.esa.int/SPECIALS/Venus_Express/SEM5A373R8F_3.html

7. "Venus Express marks one year in orbit" 10.11.06
http://www.spacedaily.com/Venus_Express_Marks_One_Year_In_Orbit_999.html

8.” Venus Express spies double vortex” 28.6.06
http://www.spacedaily.com/reports/Venus_Express_Spies_Double_Vortex_999.html

9. "The puzzling eye of a Hurricane on Venus" 14.3.08
http://www.spacedaily.com/reports/The_Puzzling_Eye_Of_A_Hurricane_On_Venus_999.html

10. "The restless atmosphere of Venus" 28.11.07
http://www.esa.int/SPECIALS/Venus_Express/SEM2F373R8F_2.html

11. "Flying over the cloudy world - Science updates from Venus Express" 12.7.06
http://www.esa.int/SPECIALS/Venus_Express/SEM9A3XAIPE_2.html

12. "Unexpected detail in first Venus south pole images" 15.4.06
http://www.spaceflightnow.com/n0604/16venussouthpole

13.” Complex meteorology at Venus” 13.10.06
http://www.esa.int/SPECIALS/Venus_Express/SEM65OV74TE_2.html

14 "European Spacecraft tracing turbulence at Venus" 3.4.07
http://www.spaceflightnow.com/news/n0704/03venus

15. "Planet-C Venus climate Orbiter Mission of Japan"
http://www.stp.isas.jaxa.jp/venus/top_english.html

16."Earth like lighting on Venus. European space probe confirms. 29.1.07
http://www.sciencedaily.com/releases/2007/11/071128155513.htm

17. "Measuring the winds of Venus" 4.9.08
http://www.spacedaily.com/reports/Measuring_The_Winds_Of_Venus_999.html

18. How windy is it on Venus? Venus Express answers” ​​18.9.08
http://www.esa.int/esaMI/Venus_Express/SEMZ6Q4KKF_0.html

19.” Hot stuff on Venus! Venus Express sees right down to the hell hot surface" 14.12.06
http://www.esa.int/SPECIALS/Venus_Express/SEM4KXPJNVE_2.html

20. Patzold M. et al-"The structure of Venus middle atmosphere" Nature 29.11.07 p.657-660

21. "Caught in the wind from the Sun" 28.11.07