NCERT Solutions Curiosity Chapter 13 .2 What Do the Planets of Our Solar System Look Like? — In-text Questions
Book page 21313 Updated on2026-09-05
Q1.
Venus, the second planet from the Sun has the highest average temperature and is the hottest planet. Why is this so?
Answer
Because of its atmosphere, not its distance. Venus's air is almost entirely carbon dioxide, and carbon dioxide does not let heat escape.
Follow the energy in three steps:
Sunlight passes through the atmosphere and warms the surface of the planet.
The warmed surface gives off its own radiation, back towards space.
Carbon dioxide in the thick atmosphere absorbs that outgoing radiation instead of letting it through. The heat stays in.
This is the greenhouse effect. On Venus it is so strong that the planet reaches about 450 °C — hotter than Mercury, even though Mercury is closer to the Sun and receives more sunlight.
The greenhouse effect. Sunlight gets in easily; the heat the surface radiates back does not get out easily.
Why it happens: A planet's temperature is set by the balance between the energy it receives and the energy it loses. Distance decides how much comes in; the atmosphere decides how much can get out. Venus receives less than Mercury but loses far less, so it settles at a much higher temperature.
Did you know? The same effect on Earth is mild, and we depend on it — without it the Earth would lose its heat to space and become too cold for liquid water. The problem today is not the greenhouse effect itself but the extra carbon dioxide we add by burning fossil fuels.