Why are we unable to get a clear view of the surface of Venus, as we have so successfully done with the surface of Mars?

Venus is often referred to as Earth’s sister planet, but its atmosphere is drastically different. The atmosphere is incredibly thick and dense, mainly composed of carbon dioxide (about 96.5%). The remaining atmosphere consists of nitrogen and traces of other gases. Additionally, Venus' atmosphere contains thick clouds of sulfuric acid, making it extremely impenetrable. This thick atmosphere not only blocks visible light but also reflects and scatters sunlight.
One of the main reasons we can't get a clear view of Venus' surface is due to this dense atmosphere. Optical instruments like telescopes, which rely on visible light, struggle to penetrate these opaque cloud layers. Essentially, the atmosphere acts as a shield, preventing us from seeing the surface directly.

The surface of Venus is incredibly hot, with temperatures reaching up to 467 degrees Celsius. This extreme heat is primarily due to a runaway greenhouse effect. The high concentration of carbon dioxide traps heat in the atmosphere, making Venus the hottest planet in our solar system, even hotter than Mercury which is closer to the Sun.
Such high temperatures contribute to the thick clouds and also make the atmospheric conditions even more hostile. The surface is so extreme that any spacecraft attempting to land on Venus would likely be destroyed quickly. The temperatures also further complicate any efforts to map or observe the surface directly, as most instruments can't withstand the heat for long periods.

Due to the impenetrable nature of Venus' atmosphere, scientists have had to find alternative ways to study its surface. One effective method is radar mapping. Unlike optical telescopes, radar systems use radio waves that can penetrate through the clouds and dense atmosphere.
The Magellan spacecraft is a notable example that used radar mapping to reveal detailed information about Venus' surface. By emitting radio waves and measuring the time it takes for them to bounce back, scientists can construct images and gather data about the planet's topography. This technique has allowed us to explore Venus' geological features, such as mountains, valleys, and volcanic activity, without having to endure the extreme surface conditions directly.

The greenhouse effect on Venus is a classic example of a runaway scenario that has led to extraordinarily high surface temperatures. The process begins with sunlight entering the atmosphere and being absorbed by the surface.
However, the heat is trapped by the thick carbon dioxide-rich atmosphere, which prevents it from escaping back into space. This trapped heat increases the overall planetary temperature, leading to an even more dense and reflective cloud cover composed mainly of sulfuric acid.
The extreme greenhouse effect on Venus serves as a stark reminder of the potential effects of atmospheric composition on planetary conditions. Unlike Earth, where the greenhouse effect is moderate and helps regulate temperature, Venus’ greenhouse effect is so intense that it creates a hostile and uninhabitable environment.