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Q16 (CDS-I/2012) Geography › World Physical Geography › Solar system bodies Answer Verified

Lack of atmosphere around the Moon is due to—

Result
Your answer: —  ·  Correct: A
Explanation

The lack of a substantial atmosphere on the Moon is primarily due to its low gravitational attraction and the resulting low escape velocity. The Moon's escape velocity is approximately 2.38 km/s, which is significantly lower than Earth's 11.2 km/s. Because the Moon has low mass and gravity, gas molecules—especially lighter ones like hydrogen and helium—can easily achieve the kinetic energy required to reach this escape velocity [1]. When the root mean square (RMS) velocity of gas molecules exceeds the escape velocity of a celestial body, those molecules escape into space rather than being retained as an atmosphere. On the Moon, even at moderate temperatures, the thermal speed of gas molecules is high enough relative to the weak gravitational pull that the gases are 'stripped' away over time, leaving only a negligible exosphere [1].

Sources

  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Atmospheric Escape > p. 280
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