Venus: The Planet of Scorching Heat
Venus is the second planet of the Solar System and is the most similar to Earth in size and mass, often leading to its designation as Earth’s “sister planet.” Despite these similarities, the planets exhibit radically different surface conditions. Venus is enveloped by a thick layer of sulfuric acid clouds, and due to an extreme greenhouse effect, it maintains the highest surface temperatures of any planet in the solar system.
Key Parameters of Venus
| Parameter | Value |
|---|---|
| Diameter | 12,104 km |
| Mass | 4.8675 x 10^24 kg (approx. 0.815 Earth masses) |
| Mean Distance from the Sun | approx. 108.2 million km (0.72 AU) |
| Orbital Period | 224.7 days |
| Rotational Period (Retrograde, Sidereal) | 243 days |
| Surface Temperature | Average +462 °C |
| Atmosphere | Dense, CO2 (approx. 96.5 %), 92 bar surface pressure |
| Number of Moons | 0 |
| Gravity Field | 8.87 m/s² (approx. 90 % of Earth’s gravity) |
| Albedo | 0.77 (Highest of all planets) |
Atmosphere and Extreme Greenhouse Effect
Venus has the densest atmosphere of all terrestrial planets. It is composed of approximately 96.5 % Carbon Dioxide. This atmosphere generates a surface pressure over 90 times greater than that on Earth – comparable to the pressure about 900 meters below the surface of the ocean.
The dominant CO2 content is responsible for a runaway greenhouse effect. It almost completely absorbs the infrared radiation emitted from the Venusian surface, resulting in a constant surface temperature of +462 °C, hot enough to melt lead. This temperature remains nearly uniform across both the day and night sides.
Surface and Geology
The surface of Venus is characterized by extensive, relatively young volcanic plains. Despite the intense heat, evidence for active plate tectonics, modeled after Earth, is not conclusively observed.
- Volcanism: The surface features thousands of volcanoes, including massive shield volcanoes like Maat Mons. It is hypothesized that periodic, massive volcanic resurfacing events completely renew the planet’s surface over geologically short timescales.
- Impact Craters: Craters are distributed relatively uniformly, but small craters are scarce. This is because smaller meteorites burn up in the dense atmosphere before reaching the ground.
- Unique Features: Notable unique structures include Coronae (large, circular or oval features caused by the upwelling of magma from the mantle) and Arachnoids (spider web-like fracture patterns).
Retrograde Rotation
Venus rotates retrograde (clockwise) compared to most other planets, meaning it spins in the opposite direction to its orbit around the Sun. This extremely slow rotation takes 243 Earth days.
Interestingly, the solar day (sunrise to sunrise) on Venus is shorter, at 116.75 Earth days, than its sidereal rotational period. On Venus, the Sun rises in the west and sets in the east.
Magnetic Field and Internal Structure
Unlike Earth, Venus does not possess a global, intrinsic magnetic field. This is thought to be due to its extremely slow rotation, which fails to drive a dynamo effect in its core.
The internal structure is believed to be similar to Earth’s, consisting of an iron core, a mantle, and a crust. However, the solar wind interacts directly with the upper atmosphere, leading to a significant loss of atmospheric gases to space.
Space Missions
Exploration of Venus is highly challenging due to the extreme surface pressure and temperature.
- Venera Program (USSR): Probes Venera 7 through 14 achieved the first successful landings, although longevity was limited to mere hours due to the conditions.
- Magellan (NASA): Used radar mapping from 1990 to 1994 to map nearly the entire surface, providing detailed topographic data.
- Akatsuki (JAXA): A Japanese orbiter that has been studying the upper atmosphere and dynamic cloud structures since 2015.
- Planned Missions: NASA’s DAVINCI+ and VERITAS missions, alongside ESA’s EnVision mission, are scheduled for the late 2020s and early 2030s, aiming to study the atmosphere, geology, and internal structure in greater detail.