Mars Temperature Factors
The atmosphere of Mars is primarily composed of carbon dioxide ($\text{CO}_2$), a known greenhouse gas. Generally, a thicker atmosphere rich in greenhouse gases leads to higher surface temperatures due to the greenhouse effect, trapping heat. However, Mars's surface temperature is significantly lower than Earth's. We need to identify the main reason for this difference.
Evaluating Temperature Determinants
- Greenhouse Gas Effect: While Mars has $\text{CO}_2$, its overall atmospheric density is much lower than Earth's, limiting the greenhouse effect's intensity compared to what might be expected. Option 1 is incorrect because $\text{CO}_2$ is a greenhouse gas.
- Atmospheric Composition: The absence of ozone (Option 2) primarily affects UV radiation levels, not the overall surface temperature regulation to this extent.
- Geological Activity: Volcanic activity (Option 3) influences atmospheric composition over time but isn't the direct cause for Mars's current lower temperature compared to Earth.
- Orbital Distance: Mars orbits the Sun at a greater average distance than Earth.
Impact of Orbital Distance
Mars's larger orbit places it farther from the Sun. This greater distance results in Mars receiving substantially less solar radiation (sunlight) compared to Earth. The amount of solar energy received is a primary factor determining a planet's average surface temperature.
Therefore, despite having a $\text{CO}_2$ atmosphere, the reduced solar energy input due to Mars's larger orbit is the main reason its surface temperature is less than that of Earth.
Important Questions from Planetary Bodies
- The correct sequence of planets in order of increasing surface temperature is:
- Consider two planets A and B with radii $2r$ and $r$, respectively. Let their distances from the Sun be $d$ and $2d$, respectively. The solar constants for A ($F_{\text{SA}}$) and B ($F_{\text{SB}}$) are related by
- Consider two planets 'A' and 'B' with the following characteristics. The relationship between $T_1$ and $T_2$ is
Distance from the Sun Radius of the planet Incident Solar flux density Equivalent temperature Planet A $d_1$ $r_1$ $F_1$ $T_1$ Planet B $d_2 = 4d_1$ $r_2 = 2r_1$ $F_2$ $T_2$ - Venus is closer to the Sun than Earth, and therefore solar energy incident on Venus is higher than that on Earth. However, the effective radiating temperature of Venus is lower than that of the Earth, because
A planet of radius $r$ has a core of radius $r_c$ and a mantle. It has no crust. Its mean density is $\rho$ and the density of its core is $\rho_c$. What is the density of the mantle?
