The Inner Planets — Reading Comprehension

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Grades

Standards

MS-ESS1-2
MS-ESS1-3

About This Reader

This comprehensive science passage for grades 6-8 explores the inner (terrestrial) planets of our solar system—Mercury, Venus, Earth, and Mars—aligned to NGSS standards MS-ESS1-2 and MS-ESS1-3. Students will learn about the observable features and underlying mechanisms that make each planet unique, such as their rocky composition, atmospheric differences, and distance from the Sun. The passage explains how interactions between planetary atmospheres, magnetic fields, tectonics, and solar energy have led to dramatically different environments, from Mercury's barren surface to Venus's runaway greenhouse effect and Earth's life-supporting conditions in the Goldilocks zone. Real-world connections include planetary evolution, climate science, and the search for extraterrestrial life. Accompanying activities include a glossary, quiz, writing prompts, graphic organizers, and both English and Spanish versions (including audio integration). This resource builds science literacy and critical thinking skills while deepening understanding of planetary systems.

CONTENT PREVIEW

Terrestrial planets make up the inner part of our solar system. Mercury, Venus, Earth, and Mars are called terrestrial because they have solid, rocky surfaces. These planets are relatively small and orbit close to the Sun. Scientists study the differences and similarities among these planets to understand why only Earth supports life.

Rocky Worlds and Their Features

The four inner planets share a rocky composition but show unique characteristics. Mercury is the smallest planet and has almost no atmosphere. Its surface is covered in craters, and temperatures swing from 430°C (day) to -180°C (night) because there is no atmosphere to trap heat. Venus is similar in size to Earth but has a thick carbon dioxide atmosphere. This causes a runaway greenhouse effect, making Venus the hottest planet, with surface temperatures around 465°C. Earth is unique—it has liquid water, an oxygen-rich atmosphere, and supports a wide diversity of life. Mars has a thin atmosphere, mostly carbon dioxide, and evidence of past water in rivers and lakes. Mars has two small moons and surface temperatures that rarely rise above freezing.

Why Are the Inner Planets So Different?

Although the inner planets formed from similar materials, their environments evolved differently. Mercury’s small size and proximity to the Sun caused it to lose its atmosphere quickly. Venus, although farther from the Sun than Mercury, trapped heat due to its dense carbon dioxide atmosphere, leading to extremely high temperatures. Earth orbits in the Goldilocks zone, where conditions are just right for liquid water. Earth’s magnetic field protects its atmosphere from solar wind. Plate tectonics recycle materials and help regulate climate. Mars, being smaller and farther from the Sun, lost much of its atmosphere over time, but signs like dried riverbeds show it once had liquid water.

Earth’s Uniqueness and Broader Implications

Earth stands out among the inner planets because of its ability to support life. The combination of its distance from the Sun, active plate tectonics, and protective magnetic field allow water to remain stable and temperatures to stay moderate. Scientists use what they learn about the inner planets to search for potentially habitable worlds elsewhere. Comparing their evolution helps us understand how planets change and what conditions are necessary for life.

In summary, the inner planets demonstrate how factors like atmosphere, size, distance from the Sun, and planetary processes interact to create very different worlds. These comparisons deepen our understanding of planetary systems and guide future exploration.

Interesting Fact:
Venus rotates so slowly that a day on Venus (one full rotation) is longer than its year (one orbit around the Sun)!

Which planets are called terrestrial planets?

Mercury, Venus, Earth, and MarsJupiter, Saturn, Uranus, and NeptuneEarth, Mars, Jupiter, and SaturnVenus, Earth, Neptune, and Pluto

What is unique about Venus's atmosphere?

It is made mostly of nitrogenIt has a thick layer of carbon dioxide causing extreme heatIt has lots of oxygen and water vaporIt is very thin and almost gone

What causes Mercury to have such high and low temperatures?

It rotates very slowlyIt has a thick atmosphereIt has almost no atmosphere to trap heatIt is very far from the Sun

Which word in the passage means 'the region where conditions are just right for liquid water'?

Greenhouse effectTerrestrial zoneGoldilocks zoneSolar region

What is the role of Earth's magnetic field?

It creates earthquakesIt protects the atmosphere from solar windIt makes the planet rotate fasterIt heats the surface

Why is Earth able to support life while the other inner planets cannot?

Earth is the largest planetEarth has the most cratersEarth is in the Goldilocks zone with water, a magnetic field, and plate tectonicsEarth is farthest from the Sun

Why did Mars lose most of its atmosphere over time?

It is the hottest planetIt is too close to the SunIt is small and far from the Sun, so it couldn't keep a thick atmosphereIt has too many moons

Which of the following is true about the inner planets?

They all have thick atmospheresThey are all made of gasThey are close to the Sun and have rocky surfacesThey all have many large moons

Venus is the hottest planet in our solar system. (True/False)

TrueFalse

Earth is the only inner planet with evidence of past water. (True/False)

TrueFalse