Which planet do scientists think had a “runaway” greenhouse effect, leading to extreme present atmospheric temperatures?

The planet that scientists believe experienced a "runaway" greenhouse effect, leading to extreme present atmospheric temperatures, is Venus.

Here are the steps that explain why:

1. Venus is the second planet from the sun and is similar in size and structure to Earth.

2. However, Venus has a very thick atmosphere, which is mainly composed of carbon dioxide with clouds of sulfuric acid, unlike Earth's nitrogen and oxygen-rich atmosphere.

3. This thick atmosphere traps the sun's heat, causing what is known as a greenhouse effect.

4. Scientists believe that Venus once had a moderate climate and possibly even liquid water on its surface.

5. However, if the water evaporated due to increasing temperatures, it would have released more carbon dioxide into the atmosphere, further strengthening the greenhouse effect.

6. This process could have continued, with the increasing heat causing more water to evaporate and releasing more carbon dioxide, leading to a "runaway" greenhouse effect.

7. This runaway greenhouse effect has resulted in Venus having the hottest surface of any planet in our solar system, with an average temperature of 467 degrees Celsius (872 degrees Fahrenheit).

8. Therefore, scientists believe that Venus is an example of a planet that has experienced a "runaway" greenhouse effect.

Scientists believe that Venus experienced a "runaway" greenhouse effect, which has led to its extremely high present atmospheric temperatures. Here's a step-by-step explanation:

1. Initial Conditions: Venus likely had conditions similar to Earth in its early history, with the potential for liquid water on its surface.

2. Solar Radiation: Being closer to the Sun, Venus received more solar radiation than Earth, which increased surface temperatures.

3. Evaporation of Water: The increased temperatures caused any surface water to evaporate, adding water vapor to the atmosphere.

4. Greenhouse Effect: Water vapor is a potent greenhouse gas. As more water vapor entered the atmosphere, it trapped more heat, further increasing temperatures.

5. Positive Feedback Loop: The rising temperatures caused more water to evaporate, which in turn trapped more heat, creating a positive feedback loop.

6. Loss of Water: Eventually, the water vapor in the upper atmosphere was broken down by solar radiation, and hydrogen escaped into space, leading to a loss of water.

7. Carbon Dioxide Dominance: With the loss of water, carbon dioxide became the dominant component of the atmosphere, further enhancing the greenhouse effect.

8. Extreme Temperatures: This runaway greenhouse effect resulted in the extremely high surface temperatures observed on Venus today, making it the hottest planet in the solar system.