Chapter 7: Problem 26
Why were the four giant planets able to collect massive gaseous atmospheres, whereas the terrestrial planets could not? Explain the source of the secondary atmospheres surrounding the terrestrial planets.
Short Answer
Expert verified
Giant planets could collect massive gaseous atmospheres because they formed beyond the frost line and had stronger gravity. Terrestrial planets developed secondary atmospheres from volcanic outgassing and impacts.
Step by step solution
01
Understanding Planet Formation
The giant planets and terrestrial planets formed in different regions of the solar nebula. Giant planets formed beyond the frost line where temperatures were low enough for volatile compounds like water, ammonia, and methane to condense into solid ice grains. This helped them accumulate mass quickly.
02
Accumulation of Mass
The presence of ice in addition to rock and metal allowed giant planets to gather more material, forming larger cores. Their substantial cores could attract and retain hydrogen and helium gas from the solar nebula due to their stronger gravitational pull.
03
Location and Composition Differences
Terrestrial planets formed closer to the Sun where it was too warm for ices to condense, leading them to form mainly from rock and metal. These planets remained smaller and could not attract significant gaseous envelopes due to their relatively weaker gravity.
04
Secondary Atmospheres
The secondary atmospheres of terrestrial planets arose from volcanic outgassing and impacts of volatile-rich objects such as comets and asteroids. These processes released gases like carbon dioxide, water vapor, and nitrogen into the planets' atmospheres.
05
Summary
In summary, the giant planets' ability to collect massive gaseous atmospheres was a result of their formation location beyond the frost line, enabling them to gather large cores and capture gases. Terrestrial planets, forming closer to the Sun with higher temperatures, remained smaller and developed secondary atmospheres from geologic and impact processes.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
giant planets
Giant planets, such as Jupiter and Saturn, formed in the outer regions of the solar nebula. This area is beyond what is known as the **frost line**, where the temperatures are low enough for gases like water vapor, methane, and ammonia to freeze into solid ice grains.
These ice grains combined with metal and rock to form massive planet cores. The substantial core mass of these planets enabled them to attract and retain hydrogen and helium—light gases that were abundant in the solar nebula.
Because of their strong gravity, giant planets were able to maintain thick gaseous atmospheres, making them distinct from their terrestrial counterparts. Here are the reasons summarized:
These ice grains combined with metal and rock to form massive planet cores. The substantial core mass of these planets enabled them to attract and retain hydrogen and helium—light gases that were abundant in the solar nebula.
Because of their strong gravity, giant planets were able to maintain thick gaseous atmospheres, making them distinct from their terrestrial counterparts. Here are the reasons summarized:
- Location: Beyond the frost line
- Temperature: Low enough to condense volatile compounds
- Core Formation: Inclusion of ice, rock, and metal
- Gravitational Pull: Strong enough to attract and retain gases
terrestrial planets
Terrestrial planets, including Earth and Mars, formed much closer to the Sun. This closer proximity meant higher temperatures in their region of the solar nebula, preventing icy compounds from condensing. As a result, terrestrial planets primarily formed from rock and metal.
The absence of ices made it difficult for these planets to amass large cores, resulting in smaller planets compared to the giant ones.
Due to their smaller sizes and weaker gravitational pull, terrestrial planets could not maintain significant amounts of hydrogen and helium from the solar nebula, leading them to lack thick gaseous atmospheres. Instead, they have thin atmospheres composed of what scientists call secondary atmospheres.
The absence of ices made it difficult for these planets to amass large cores, resulting in smaller planets compared to the giant ones.
Due to their smaller sizes and weaker gravitational pull, terrestrial planets could not maintain significant amounts of hydrogen and helium from the solar nebula, leading them to lack thick gaseous atmospheres. Instead, they have thin atmospheres composed of what scientists call secondary atmospheres.
- Location: Closer to the Sun
- Temperature: Too warm for ices to condense
- Core Composition: Mainly rock and metal
- Gravitational Pull: Not strong enough to hold substantial gaseous envelopes
solar nebula
The solar nebula is the swirling cloud of gas and dust from which our solar system formed. It consisted primarily of hydrogen and helium, along with small amounts of heavier elements and compounds.
Over time, particles within the nebula collided and stuck together, forming planetesimals. These small bodies served as the building blocks for planets. The position within the solar nebula greatly influenced the characteristics of the resulting planets.
For example, the giant planets formed in the cooler outer regions where ices could condense, while terrestrial planets formed in the warmer inner regions where they were limited to rock and metal. This temperature gradient led to the significant differences between these two types of planets. Reasons to understand:
Over time, particles within the nebula collided and stuck together, forming planetesimals. These small bodies served as the building blocks for planets. The position within the solar nebula greatly influenced the characteristics of the resulting planets.
For example, the giant planets formed in the cooler outer regions where ices could condense, while terrestrial planets formed in the warmer inner regions where they were limited to rock and metal. This temperature gradient led to the significant differences between these two types of planets. Reasons to understand:
- Main Composition: Hydrogen, helium, and minor heavier elements
- Formation of Planetesimals: Building blocks of our planets
- Temperature Gradient: Dictates the composition of resulting planets
secondary atmospheres
Unlike giant planets, terrestrial planets have what are called secondary atmospheres. These atmospheres are not remnants of the solar nebula but instead formed through other processes after the planets had formed.
Secondary atmospheres arise from **volcanic outgassing** and impacts of volatile-rich objects such as comets and asteroids. Volcanic activity releases gases trapped inside the planet, like carbon dioxide, water vapor, and nitrogen, into the atmosphere.
Similarly, when comets and asteroids strike a planet, they can deliver volatile compounds that contribute to the atmosphere.
The combination of these processes over time leads to the development of an atmosphere that can be significantly different from the primary atmospheres captured by giant planets.
Secondary atmospheres arise from **volcanic outgassing** and impacts of volatile-rich objects such as comets and asteroids. Volcanic activity releases gases trapped inside the planet, like carbon dioxide, water vapor, and nitrogen, into the atmosphere.
Similarly, when comets and asteroids strike a planet, they can deliver volatile compounds that contribute to the atmosphere.
The combination of these processes over time leads to the development of an atmosphere that can be significantly different from the primary atmospheres captured by giant planets.
- Volcanic Outgassing: Releases gases from inside the planet
- Impact Delivery: Comets and asteroids bring volatiles
- Components: Common gases include carbon dioxide, water vapor, and nitrogen