Comparing Earth and Rocky Planets

Comparing Earth and Rocky Planets

Middle School

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Learning Objectives

• Describe the conditions a planet needs to support life and be considered habitable.

• Explain how Earth and Mars are systems of interacting spheres.

• Compare landforms on Earth and Mars to understand the geologic processes that shaped them.

• Use claims, evidence, and reasoning to evaluate different geological findings.

Key Vocabulary

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Habitable

Capable of supporting life, believed to require liquid water and an energy source.

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Rocky Planet

A planet, like Earth or Mars, composed primarily of silicate rocks or metals.

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System

A set of interacting parts, such as a planet's geosphere, atmosphere, and hydrosphere.

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Geologic Process

A natural event that changes the structure of a planet's surface.

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Landform

A natural feature of a solid planetary body, such as a mountain or canyon.

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Channel

A landform that is a long, narrow groove, which could be formed by flowing liquid.

Key Vocabulary

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Claim

A statement or conclusion that answers a question, which needs to be supported by evidence.

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Evidence

Scientific data that is collected to support or reject a specific claim you have made.

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Reasoning

The process of explaining how a piece of evidence supports a specific claim.

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Gravity

The force of attraction between two objects that increases with mass and decreases with distance.

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What Makes a Planet Habitable?

• A planet needs liquid water and a stable energy source, like a star.

• The 'habitable zone' is the perfect distance from a star for liquid water.

• Planets too close are too hot, and those too far are too cold.

• Mars is on the outer edge, so its potential for life is studied.

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Multiple Choice

What are the two most important things a planet needs to support life?

• Liquid water and a stable energy source

• A rocky surface and a large moon

• A thick atmosphere and many volcanoes

• A strong magnetic field and deep oceans

Multiple Choice

What is the significance of the 'habitable zone'?

• It is the area in space with the most stars.

• It is the region where planets are safe from asteroids.

• It is the specific distance from a star where a planet can have liquid water.

• It is the name for any planet that has life on it.

Multiple Choice

A newly discovered planet is found to be much closer to its star than the habitable zone. What is the most likely conclusion about this planet's conditions?

• The planet is likely too hot for liquid water to exist.

• The planet is likely too cold for liquid water to exist.

• The planet has the perfect conditions for life.

• The planet receives very little energy from its star.

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Planets as Systems

• A rocky planet is a complex system of interacting parts called 'spheres'.

• Earth's spheres are the geosphere (rock), hydrosphere (water), atmosphere (air), and biosphere (life).

• These spheres constantly interact, like a river carving a canyon in rock.

• Mars has a geosphere and thin atmosphere but a mostly frozen hydrosphere.

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Multiple Choice

What makes a rocky planet like Earth considered a 'system'?

• It is made of several interacting parts called spheres.

• It is a large, round object that orbits a star.

• It has a solid surface made mostly of rock.

• It has at least one moon orbiting it.

Multiple Choice

The example of a river carving a canyon shows an interaction between which two spheres?

• The atmosphere and the biosphere

• The hydrosphere and the geosphere

• The geosphere and the biosphere

• The atmosphere and the hydrosphere

Multiple Choice

Based on the descriptions provided, what is the most significant difference between the interactions on Mars and Earth?

• The thin atmosphere prevents any interaction with the surface.

• The frozen hydrosphere cannot interact with the geosphere.

• The absence of a biosphere means interactions involving life are missing.

• The geosphere on Mars is too different from Earth's to allow interactions.

Gravity and the Solar System

• Gravity is the force that pulls objects with mass toward each other.

• Its strength depends on the mass and distance between the objects.

• This force keeps planets in stable orbits around the Sun.

Multiple Choice

What is gravity?

• The force that pulls objects with mass toward each other

• The force that pushes objects with mass away from each other

• The energy an object has due to its motion

• The magnetic pull between a planet and its moon

Multiple Choice

What is the relationship between the mass of objects and the force of gravity between them?

• The greater the mass of the objects, the stronger the gravitational force

• The greater the mass of the objects, the weaker the gravitational force

• The distance between objects is the only factor that affects gravity

• The mass of an object has no effect on its gravitational force

Multiple Choice

Based on the principles of gravity, what would most likely happen to the planets if the Sun's mass increased?

• The planets' orbits would be pulled closer to the Sun

• The planets would drift further away from the Sun

• The planets' orbits would not be affected by the Sun's mass

• The planets would stop orbiting and move in a straight line

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Geologic Processes: Shaping Surfaces

Slow Processes

• These natural processes gradually change a planet's surface over very long periods of time.

• Examples include the weathering of rock by wind or the erosion of a coastline by waves.

• These changes can take thousands or even millions of years to become noticeable on the landscape.

Catastrophic Events

• Catastrophic events are processes that happen very quickly and cause dramatic changes to the surface.

• These rapid events include volcanic eruptions, major earthquakes, or large meteor impacts on a planet’s surface.

• Unlike slow processes, these events can completely reshape a landscape in just minutes or hours.

Multiple Choice

What is the primary difference used to categorize the geologic processes of weathering and volcanic eruptions?

• The speed at which they cause changes to a surface.

• The types of planets where they can be found.

• The time of year when the changes are most active.

• The size of the landforms that are created.

Multiple Choice

Which of these describes a landscape being shaped by a slow geologic process?

• A major earthquake creating a large crack in the ground.

• A coastline gradually changing shape over thousands of years.

• A volcano erupting and covering a field with lava in one day.

• A large meteor striking a planet and forming a crater.

Multiple Choice

A planetary scientist observes satellite images of a planet taken one week apart. The new image shows a mountain's peak is completely gone, a change that occurred in just a few hours. What conclusion can be drawn from this evidence?

• The landscape was most likely shaped by a catastrophic event.

• The landscape was definitely shaped by the weathering of rock.

• The changes must have been caused by coastal erosion from waves.

• The changes seen are temporary and will reverse next season.

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Comparing Landforms on Earth and Mars

Earth's Rivers

• We understand the geologic processes that form the various landforms on our home planet.

• Rivers on our planet often wind and twist, a process known as meandering.

• At their mouths, rivers often form large, fan-shaped deposits of sediment called deltas.

Mars' Channels

• By comparing landforms, scientists can infer how Martian features were formed in the past.

• Mars has many ancient channels that meander and merge, looking very similar to Earth's rivers.

• Fan-shaped deposits, much like river deltas on Earth, are also found on Mars.

Multiple Choice

What is the main reason scientists study Martian landforms by comparing them to landforms on Earth?

• To infer how features on Mars may have been formed.

• To find the exact location of ancient rivers on Earth.

• To understand the geologic processes currently happening on Mars.

• To prove that all planets have the same types of landforms.

Multiple Choice

Based on the shared characteristics of landforms, what is one important similarity between Earth's rivers and the ancient channels on Mars?

• Both are currently filled with flowing water.

• Both are located near large, active volcanoes.

• Both show evidence of meandering, or winding and twisting paths.

• Both form straight, narrow lines across the surface.

Multiple Choice

The discovery of meandering channels and fan-shaped deposits on Mars provides the strongest evidence for which conclusion?

• That the sediment on Mars is identical to the sediment on Earth.

• That a liquid, similar to Earth's rivers, likely flowed on Mars in the past.

• That Mars and Earth have always had very similar climates.

• That life must have existed on Mars to create the channels.

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Scientific Argumentation: Claim, Evidence, Reasoning

• A claim is a concluding statement that answers a question.

• ​Evidence is the scientific data that provides support for the claim.

• Reasoning connects the evidence to the claim and explains why it matters.

• For example, a channel on Mars is evidence to claim it was formed by water.

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Multiple Choice

In the context of scientific argumentation, what is a claim?

• A concluding statement that answers a question.

• The scientific data used as support.

• A question that begins an investigation.

• The process of collecting data.

Multiple Choice

What is the relationship between evidence, claim, and reasoning in a scientific argument?

• Reasoning explains how the evidence supports the claim.

• Evidence is the concluding statement in an argument.

• A claim is the data collected during an experiment.

• Reasoning is another word for the original question.

Multiple Choice

A scientist states that a channel on Mars (evidence) was formed by water (claim). To complete the argument, the scientist must now explain why channels are typically formed by water. Which part of the scientific argument does this explanation represent?

• The reasoning, because it explains the link between the data and the conclusion.

• The claim, because it is the final answer.

• The evidence, because it is the scientific data.

• The observation, because it is what the scientist first saw.

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Common Misconceptions

Misconception	Correction
Mars is red because it's hot.	Its red color comes from iron oxide (rust). Mars is actually very cold.
All changes on a planet's surface are violent and fast.	Many changes are slow, like erosion carving canyons over millions of years.
Mars has no gravity.	Mars has gravity, but its pull is weaker than Earth’s.
A scientific claim is just a guess.	A claim is based on observations and needs evidence for support.

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Summary

• A planet is habitable if it has liquid water and an energy source.

• Rocky planets like Earth and Mars are complex systems of interacting spheres.

• Gravity is the force that holds the solar system together.

• A planet's surface is shaped by slow geologic processes and rapid catastrophic events.

• By comparing landforms, scientists can infer how they were formed.

• Scientists use claims, evidence, and reasoning to construct logical arguments.

Poll

On a scale of 1-4, how confident are you about your understanding of the geology of Mars after this review?

• 1 (Not confident at all)

• 2 (A little confident)

• 3 (Mostly confident)

• 4 (Very confident)