The closest planet to Earth with a temperature above 450 degrees Celsius on the surface and a layer of clouds of sulfuric acid. In 2029, Russian scientists plan to send a research mission to Venus. This will be the first research in the history of modern Russia: the last domestic Vega 1 and Vega 2 probes were sent to Venus in 1984.
In the 20th century, the Soviet Union was leading the exploration of this planet – from 1961 to 1984, Soviet scientists sent 19 missions in which they received data on the atmosphere and the first photographs of the surface. How did these studies go, what do scientists know about Venus today, and what information do they plan to obtain in the next missions?
Venus
Extreme conditions
Venus is the hottest planet in the Solar system, the average temperature on the planet is 470 degrees Celsius. This is higher than the temperature at which lead, tin, and zinc melt. Even though Mercury is closer to the star by fifty million kilometers, the greenhouse effect created by the atmosphere of Venus warms up the surface of the planet more. Almost completely: 96 percent of the atmosphere consists of carbon dioxide, and an opaque layer of clouds of sulfuric acid also covers the planet from prying eyes, complicating its study from a distance.
A day on Venus lasts 243 Earth days. A year is 224.7 Earth days. I.e., the planet orbits around the Sun faster than around its axis. Moreover, the planet rotates from east to west: in the direction opposite to the direction of rotation of most planets, only Uranus rotates in the same direction as Venus. The size of the planet is as close as possible to the size of the Earth – its diameter is only 640 kilometers smaller.
The atmospheric pressure on the planet is almost 100 times greater than on the surface of the Earth. 92 atmospheres are equivalent to a kilometer in the ocean. Extreme temperature and pressure, an ultra-dense atmosphere of semi-liquid-semi-gaseous carbon dioxide, acid clouds, and rains complicate the work of space technology on the surface: none of the vehicles that successfully landed on Venus operated there for more than two hours.
19 missions
The smooth white disk, which can be seen almost immediately after sunset and shortly before dawn, intrigued people back in the Middle Ages. Galileo Galilei observed the planet at the beginning of the 17th century. Mikhail Lomonosov discovered the planet’s atmosphere in 1761 by observing through a telescope with smoked glass how it passes along the line between the Earth and the Sun. “Before the Venus ingress, when its front side approached the solar edge […] a bulge set up which progressively became more pronounced as Venus came to leave the Sun […] for the bulge formed close to the solar disc edge at the time of Venus emergence, the refraction of solar rays should be responsible,” the scientist wrote in his diary.
Basic data about the planet was obtained only in the second half of the 20th century when probes began to be sent to Venus. Scientists of the Soviet Union carried out 19 successful launches of research vehicles, which with varying success brought this or that information.
On February 12, 1961, the Venera 1 station went into space. It was the first spacecraft created to explore other planets. For the first time, the technique of orientation along the three axes of the spacecraft by the Sun and the star Canopus was used, and a parabolic antenna was used to transmit telemetry information. However, data on Venus could not be obtained from the station: a week after the launch, when the device was 2 million kilometers away from Earth, contact was lost. Venera 1 passed about one hundred thousand kilometers from the planet and entered a heliocentric orbit.
And so the Soviet Union lost the primacy in obtaining data about Venus: in December 1962, the American probe Mariner 2 successfully transmitted the first information. In particular, the theory about the extremely hot atmosphere of the planet was confirmed, it turned out that Venus has no magnetic field, and the rotation speed of the planet around its axis was measured.
Zond 1, Venera 2, and Venera 3, the spacecraft that were sent to study the planet in 1964 and 1965, transmitted scientific data about outer space and near-planetary space and helped obtain information valuable for solving the problems of ultra-long-distance communication and interplanetary flights. But the control systems that failed before reaching Venus did not allow the probes to transmit data about the planet itself. A descent vehicle was installed at the Venera 3 station – a ninety-centimeter sphere in which a metal globe of the Earth and the pennant of the Soviet Union were placed. This sphere became the first spacecraft to reach the surface of another planet.
Venus 4 was crushed by the pressure at an altitude of 28 kilometers. Before the launch of the probe, scientists assumed that the pressure on the planet could reach 10 atmospheres. The descent module was made with a double margin of safety – 20 atmospheres, which was not enough to work in extreme conditions at a Venusian pressure of 92 atmospheres. Even though the already faulty station reached the surface, the most important data on the temperature, pressure, density and chemical composition of the atmosphere of Venus allowed adjusting the production of the following probes.
1970 Venera 7 made a soft landing on the surface of the planet. Venera 9 in 1975 transmitted the first black-and-white photographs. Venera 14 took a color panorama. Studies of the planet were regularly conducted until 1985, during which time scientists received data that are known today.
Expectations
Studies of Venus by Russian probes could be continued by the end of this decade when Venera-D will go to the planet. D stands for “dolgozhivushaya”(long-lasting) – it is planned that the new probe will work in extreme conditions on the planet’s surface much longer than its Soviet predecessors.
The website of the Venera-D project states that, despite past successes, the issues of the formation and evolution of Venus, its current state of climate are still unknown. To study it, it is necessary to study the isotopic composition of small components, including inert gases, the composition of the surface, the interaction of the atmosphere and the surface of the planet.
The study of Venus is interesting not only from the point of view of fundamental knowledge. Discoveries in the field of comparative planetology are possible: research helps to better understand the history of the formation and development of the planets of the Earth group, the evolution of their atmosphere. Such information can show possible ways of evolution of the Earth.
Based on open sources
Photo: miro3d / ru.123rf.com
