Which of the following is the least dense planet among all planets?

Appeared in: RML 2023

Explanation

Saturn has the lowest density of all planets in the solar system, with an average density of approximately 0.687 g/cm³.
This density is famously less than that of water (1.0 g/cm³), which means Saturn would theoretically float in a sufficiently large body of water.
As a gas giant, Saturn is composed mainly of hydrogen and helium, which are the two lightest elements, contributing to its very low overall density.

Option A: Earth is the densest planet in the solar system, with a density of about 5.51 g/cm³. This is due to its composition of rock and a large, heavy metallic core.
Option B: Uranus is an ice giant and is the second least dense planet in the solar system (about 1.27 g/cm³). However, Saturn's density is significantly lower.
Option C: Jupiter is the largest planet in the solar system, but it is denser than Saturn, with an average density of about 1.33 g/cm³.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Planetary Density Comparison as background academic context rather than a clinical decision trigger.
This question tests general knowledge, a component of many competitive examinations, which assesses a candidate's overall awareness and analytical skills.
Understanding basic scientific principles like density helps in classifying celestial bodies. Planets are broadly categorized into terrestrial (rocky, dense) and Jovian (gaseous/icy, less dense) types.
What if? If the question asked for the planet with the most moons, the answer would also be Saturn (as of recent discoveries), highlighting that each planet has unique characteristics.

How to Approach the Question

First, identify the key concept in the question: 'least dense planet'.
Recall or deduce the general classification of the planets provided. Earth is a rocky, terrestrial planet, while Jupiter, Saturn, and Uranus are gas or ice giants.
Apply the general principle that terrestrial planets are significantly denser than gas/ice giants. This immediately eliminates Earth as a potential answer.
Among the remaining gas and ice giants, access the specific knowledge that Saturn is famously the only planet in our solar system with an average density less than water.
This unique fact makes Saturn the least dense planet overall.
Conclude by selecting Saturn as the correct answer.

Concept Tested & Keywords

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