Explain why the terrestrial planets have meager atmospheres compared to the Jovian planets.
The correct answer and explanation is :
The terrestrial planets (Mercury, Venus, Earth, and Mars) have meager atmospheres compared to the Jovian planets (Jupiter, Saturn, Uranus, and Neptune) due to their lower masses, weaker gravity, proximity to the Sun, and differences in atmospheric composition.
Explanation:
One of the primary reasons terrestrial planets have thin atmospheres is their lower mass and weaker gravitational pull. Atmospheres are held by gravity, and since terrestrial planets are much smaller than the Jovian planets, their gravity is insufficient to retain lighter gases like hydrogen and helium. In contrast, Jovian planets have massive gravitational fields that effectively trap vast amounts of these light gases, forming thick atmospheres.
Another key factor is their proximity to the Sun. Terrestrial planets are located closer to the Sun, which means they experience higher temperatures. The increased heat provides gas molecules with more kinetic energy, allowing lighter gases to reach escape velocity and leave the planet’s atmosphere over time. This is especially evident on Mercury, which has almost no atmosphere due to its weak gravity and extreme temperatures.
Additionally, the composition of terrestrial planets differs from that of Jovian planets. Terrestrial planets formed primarily from heavier elements like iron, silicon, and oxygen, while Jovian planets accumulated large amounts of hydrogen and helium during their formation. The difference in composition is a result of the solar nebula theory, which suggests that the early solar system had a temperature gradient, preventing lighter gases from condensing close to the Sun.
Furthermore, terrestrial planets lack the strong magnetospheres of Jovian planets, making them more vulnerable to solar wind, which can strip away atmospheric gases over time. Without significant protection, the atmospheres of smaller planets erode, leading to thinner atmospheres compared to the thick, extensive gas envelopes of the Jovian giants.