The mass of Mars is 11 percent of Earth's mass, while its radius is half of Earth's radius. What do these figures suggest for the density of Mars?

Question

Quizplus · Accepted Answer

Density is mass divided by volume. Given Mars has 11% of Earth's mass and a radius half of Earth's, its volume is 1/8th of Earth's (since volume scales with the cube of the radius). Therefore, Mars has a higher mass-to-volume ratio than 1/8 (11% > 1/8), but because its mass is significantly less proportionally compared to its volume reduction, its density is less than Earth's.

The Mass of Mars Is 11 Percent of Earth's Mass