The graph below plots the escape velocity of each planet along the vertical axis and its surface temperature along the horizontal. The lines plotted in the figure are the average speeds of gas particles as a function of temperature for various gases. Which of the planets or satellite plotted in this diagram is least able to hold an atmosphere?

A) Mars
B) the Moon
C) Mercury
D) Venus
E) Earth

Question

The graph below plots the escape velocity of each planet along the vertical axis and its surface temperature along the horizontal. The lines plotted in the figure are the average speeds of gas particles as a function of temperature for various gases. Which of the planets or satellite plotted in this diagram is least able to hold an atmosphere?
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A) Mars 
B) the Moon 
C) Mercury 
D) Venus 
E) Earth

Quizplus · Accepted Answer

The escape velocity of a planet indicates the minimum speed that a gas particle must have in order to leave the planet's gravitational field. The ability of a planet to hold an atmosphere depends on its escape velocity, which should be greater than the average speed of gas particles at its surface temperature. From the graph, we can see that the Moon has the lowest escape velocity of all the planets and satellites plotted. Additionally, the average speed of gas particles for all gases increases rapidly with temperature at the Moon's surface temperature, indicating that it would be difficult for the Moon to hold onto any significant atmosphere.

The Graph Below Plots the Escape Velocity of Each Planet