After it was proven that it was possible to send satellites to orbit the Earth, the Americans and Russians increased their efforts to study the other inner planets in the solar system, Mariner spacecraft made familiarization tours of all three bodies: Venus, Mercury and Earth
Mariner 1
The first research spacecraft in the Mariner spacecraft series was launched on July 22, 1962 towards the planet Venus. The goal was to reach Venus in 139 days when it travels a distance of 350 million km. The launcher was Atlas Aegina B, the weight of the spacecraft was 202 kg and the intention was to measure the atmosphere, clouds, magnetic field and more of Venus. 290 seconds after launch, the launcher and spacecraft were destroyed for security reasons. A malfunction in the guidance mechanism caused the launcher to deviate from its course in the 212th second after launch. The space engineers waited a few seconds in the hope that the launcher would automatically correct its course. When all efforts failed the launcher exploded. The spacecraft is similar to the Ranger spacecraft. Its length is 3.04 meters and its width is 1.52 meters. A tubular center is attached to the hexagonal base. Attached to the base are two solar racks and a dish-like antenna.
Mariner 2
Mariner 2 was launched on August 27, 1962 and arrived at Venus on December 14. The spaceship's distance from it was 34,835 km. Its weight is 202 kg, including 18 kg of the weight of the devices. The spacecraft's instruments surveyed Venus three times. The spacecraft was launched by the Atlas Agena B launcher. Its structure is identical to Mariner 1.
From the data provided by the spacecraft it became clear that the surface of Venus has a temperature of 483 degrees, higher than expected. The cloud cover which is 22.5 km thick moves at an altitude of 67.5 - 90 km above the ground. At the base of the cloud cover there is a temperature of 104 degrees. In the center it is 34 degrees below zero and in the upper part 28 degrees below zero. There are no noticeable temperature differences on the surface of the star, so the atmosphere cyclically transfers large amounts of heat from its day side to the dark side and consequently causes the formation of hot winds that scorch the surface of the star. No openings were discovered in the cloud cover near the southern end, at the end of the transit flight. In this area the temperature is 10 degrees lower than its surroundings. There is no water vapor in the atmosphere. Venus does not have a strong magnetic field and radiation bands and it rotates around its axis once every 243 Earth days.
The spacecraft instruments revealed important details:
1. Solar winds consisting of ionized gases frequently erupt from the Sun's turbulent face.
2. The degree of density, speed and temperature of such a wind depends on changes in the actions of the sun, especially during the formation of solar flares.
3. The solar wind creates interstellar magnetic fields, which disrupt the Earth's magnetic field.
4. Weak magnetic fields (relative to Earth's) are almost always found in interstellar space.
5. The amount of cosmic radiation in the space between the Earth and Venus and its intensity is uniform.
6. It is possible to have reliable radio transmissions between the Earth and spacecraft in interstellar space.
7. Micro meteoroids are not as numerous in interstellar space as there are around the Earth.
Mariner 5
On July 14, 1967, Mariner 5 was launched towards Venus and on October 19, it reached it. The weight of the spacecraft is 245 kg and it was launched by the Atlas Agena D launcher. Originally, this spacecraft was supposed to replace Mariner 4. The spacecraft was supposed to fly towards the Sun and towards Mars and its destination was changed. The new target was Venus. Mariner 5 traveled 349 km. After passing by Venus, it entered orbit around the Sun. The sun shelves have been replaced with smaller shelves. The spaceship was covered with a heat shield and its instruments were more sophisticated than those of the previous spaceships.
Mariner 5 measured Venus while passing 4,000 km from it. The measurements were indirect. They measured the way in which the atmosphere of Venus affected radio waves that were 10 cm long that were transmitted through it. As the spacecraft approached Venus its gravity affected it and diverted it from its path, so that it passed behind it. The spacecraft's radio signals had to pass through increasingly dense layers of the atmosphere and eventually disappeared altogether. Additional measurements were taken when the spacecraft returned and appeared on the other side of the planet. The results of the indirect measurements are not exactly the same as the direct measurements made by the Russian spacecraft Venera 4. The reason for these discrepancies is not clear.
The spacecraft discovered a certain magnetic activity in the vicinity of Venus whose strength is between 0 and 1/300 that of the Earth. The atmospheric pressure is 4 or 5 times greater than the one measured by Vanra 4. The temperature of the ground is 267 degrees. An ionized ionosphere was discovered in the upper layers of the atmosphere. After the spacecraft finished the transit near Venus, it continued to transmit the results of measurements made in space up to a distance of 87 million km from the Sun.
Mariner 10
As mentioned, Mariner 10 on its flight to Mercury passed by Venus in order to take advantage of its gravity to accelerate its speed. During this transit she measured Venus and these are the results of the measurements:
1. Ultraviolet photographs showed that the clouds surround the star in the form of symmetrical rings, in different shades and parallel to the star's equator and similar to Jupiter's cloud rings. It was suggested that the presence of the rings indicates the existence of a spiral system of forces from the equator to the poles within the atmosphere. The clouds appear as alternating dark and light areas. It was estimated that they had a connection to the clouds surrounding Venus once for 4-5 days.
2. Venus has heavy and bright clouds.
3. The thick layer of the clouds moves at a speed 60 times higher than the axial speed of Venus.
4. The poles of the star are surrounded by bright rings, most of which are colored.
5. In the area of the equator, a large eye-shaped opening opens in the cloud cover. This opening was probably created due to the influence of the sun's heat moving around Venus.
6. In the surface of the clouds surrounding Venus there are no temperature differences between the equator and the poles. It is possible that the heat is transferred from the equator to the poles and that the ultraviolet spots show the movement of this heat.
7. The hydrogen on the planet originates more from the Sun than from Venus itself. It is possible that all the hydrogen that was once on Venus escaped into space, and that the planet never had oceans.
8. They noticed that Venus has helium, oxygen and carbon. Argon and neon may also have been in the past.
9. A thin haze was discovered at an altitude of 25 km above the clouds.
Venus has been hypothesized to have three layers of clouds. The upper layer is at an altitude of 60 km above the surface. Mariner 10's radio signals penetrated up to an altitude of 45 km from the ground. The way radio waves propagate in the cloud cover allows for a better understanding of this cloud layer.
Mariner 10 transmitted 3,500 high quality photographs. The spacecraft examined the interplay between the solar wind and Venus and discovered a long trail of charged particles behind the star in the opposite direction to the sun. Because Venus has no magnetic field, the spacecraft's instruments could detect the trail. Since the atmosphere is compressed, the solar wind acts directly on it and creates an ionosphere, which in turn creates a shock arc.
