This article was automatically translated from the original Turkish version.
Sun system’s second planet, Venus, is often referred to as “Earth’s twin” due to its similar size and mass to Earth. However, it differs from Earth to a remarkable degree in terms of surface conditions and atmospheric structure.
Venus orbits the Sun at an average distance of 0.72 astronomical units (AU) in a nearly circular path. This proximity results in significantly greater solar radiation reaching the planet’s surface compared to Earth. Venus’s orbital period is approximately 225 Earth days. Interestingly, both Mercury like and Venus rotate very slowly on their axes, and this rotation is in the opposite direction to that of most other planets in the Solar System (retrograde rotation). A Venusian day is approximately 243 Earth days long, which is longer than its orbital period. This duration results in a solar day on Venus—the time from one sunrise to the next—being approximately 117 Earth days. This unusual retrograde rotation profoundly affects the planet’s atmospheric circulation and surface temperature distribution.
The most distinctive feature separating Venus from other terrestrial planets is its extremely dense atmosphere, composed primarily of carbon dioxide (%96.5). Nitrogen (%3.5) and trace amounts of other gases (sulfur dioxide, water vapor, etc.) also play significant roles.
Surface pressure is about 92 times that of Earth’s, equivalent to the pressure found at a depth of approximately 900 meters in Earth’s oceans. This thick carbon dioxide atmosphere produces the strongest greenhouse effect in the Solar System. Sunlight reaches the surface of Venus, but the heat radiated back from the surface is trapped by the dense carbon dioxide. As a result, the average surface temperature reaches an extreme value of approximately 464°C. This temperature is high enough to melt lead and renders the planet completely inhospitable to known forms of life.
Venus’s atmosphere also contains thick, persistent cloud layers. These clouds are primarily composed of sulfuric acid droplets and prevent direct optical observation of the planet’s surface through telescopes. These clouds contribute to the planet’s high albedo by reflecting a significant portion of incoming solar radiation back into space, while simultaneously enhancing the greenhouse effect and contributing to extreme surface heating. Strong winds are observed in the atmosphere.
In particular, in the upper atmosphere, winds known as “superrotation” blow at speeds far exceeding the planet’s own rotation rate. The origin and mechanism of these winds have not yet been fully understood and remain an active area of research.
Due to its dense cloud cover, direct optical observation of Venus’s surface through telescopes has been impossible. Detailed information about the planet’s surface has been obtained through spacecraft equipped with radar imaging techniques, such as the Magellan mission.
Radar images reveal that Venus’s surface is relatively young and bears clear signs of volcanic activity. The surface features numerous volcanic mountains, long lava flows, and extensive lava plains (planitia). The number of impact craters is lower than on Earth and Moon, suggesting that the surface is geologically active and continuously reshaped by volcanism and other processes.
The surface of Venus also contains unique structures called “coronae.” These are large circular or oval regions characterized by fractures and ridges, formed by volcanic and tectonic activity. Additionally, continent-scale high plateaus such as Ishtar Terra and Aphrodite Terra are prominent surface features. Ishtar Terra is roughly the size of Earth’s Australia continent, while Aphrodite Terra is approximately the size of South America.
Whether active plate tectonics like those on Earth exist on Venus remains an open question. However, some studies suggest that tectonic deformations and volcanism on the surface may be linked to mantle convection.
There are no direct seismic data available on Venus’s internal structure. However, based on fundamental parameters such as its mass, density, and size, it is believed to have an internal structure similar to Earth’s.
Accordingly, Venus is expected to have a core composed of iron-nickel alloy, a silicate mantle, and a thin crust. However, it is striking that Venus lacks a significant global magnetic field.
Earth’s magnetic field is generated by a dynamo effect resulting from convective motion in its molten iron core. Venus’s slow rotation rate may prevent such a dynamo mechanism from operating effectively. The absence of a magnetic field leaves Venus’s atmosphere exposed to direct interaction with the solar wind, which may have contributed to atmospheric loss over time.
Therefore, the solar wind interacts directly with Venus’s upper atmosphere and can induce a weak magnetosphere in the ionosphere.
Venus has been known since ancient times due to its brightness. However, detailed study of its surface became possible only with the advent of the space age. The Soviet Union’s Venera program sent the first spacecraft to land on Venus’s surface and provided the first images and data from the surface. These landings revealed the extreme challenges posed by the planet’s hot, high-pressure environment. NASA’s Magellan mission (1990–1994) produced a high-resolution radar map of nearly the entire planet, offering unparalleled insights into surface morphology.
Today, data collected by various spacecraft and place-based telescope observations continue to provide new information about Venus. Future missions will focus on objectives such as detailed atmospheric analysis, surface chemical composition, and improved understanding of geological activity.
Although Venus shares physical characteristics with Earth, its dense carbon dioxide atmosphere, extreme surface temperature, and unique surface features make it a fascinating and hostile member of the Solar System. Data from Past and ongoing space missions have provided significant insights into the planet’s atmospheric dynamics, surface geology, and internal structure. However, many questions remain unresolved, including the origin of superrotation, the existence of plate tectonics, and the absence of a magnetic field. Detailed study of Venus is critical to deepening our understanding of terrestrial planet evolution, the greenhouse effect, and the limits of habitability.
Orbital and Rotation Characteristics
Dense Atmosphere and Greenhouse Effect
Surface Morphology and Geology
Internal Structure and Magnetic Field
Exploration and Observations
Conclusion