23.1 Exploring the Solar System Concepts

Discuss the role of planetesimals in the formation of planets.

• Planetesimals collide and stick together to form larger bodies, eventually becoming planets.

• Planetesimals provide the heat necessary for planet formation.

• Planetesimals are remnants of planets that failed to form.

• Planetesimals orbit planets and contribute to their gravitational pull.

Answer explanation

Planetesimals are crucial in planet formation as they collide and stick together, gradually building larger bodies that eventually become planets. This process is fundamental to the growth of planetary systems.

What is the primary difference between a planetesimal and a protoplanet?

• A planetesimal is larger than a protoplanet.

• A protoplanet has cleared its orbit of other debris, while a planetesimal has not.

• A planetesimal is composed of gas, while a protoplanet is composed of rock.

• A protoplanet is a fully formed planet, while a planetesimal is not.

Answer explanation

The primary difference is that a protoplanet has cleared its orbit of debris, indicating it is more developed, while a planetesimal has not yet done so, making it a smaller, less evolved body in the formation process.

Which of the following processes is essential for the formation of a protoplanetary disk?

• Collapse of a nebula under its own gravity.

• Cooling of the universe.

• Absorption of a nebula by a black hole.

• Expansion of a star.

Answer explanation

The formation of a protoplanetary disk is primarily driven by the collapse of a nebula under its own gravity, which leads to the accumulation of material and the creation of a rotating disk around a forming star.

Why are terrestrial planets generally smaller than Jovian planets?

• Terrestrial planets have stronger magnetic fields that limit growth.

• Terrestrial planets have more moons, which limits their size.

• Terrestrial planets formed closer to the Sun where there was less material.

• Terrestrial planets are made of lighter materials.

Answer explanation

Terrestrial planets are smaller because they formed closer to the Sun, where there was less material available for their growth compared to the larger Jovian planets that formed further out in the solar system.

What is a nebula primarily composed of?

• Solid rock and metal.

• Ice and dust.

• Gas and dust.

• Liquid water and gas.

Answer explanation

A nebula is primarily composed of gas and dust, which are the building blocks for stars and planets. The other options, such as solid rock and metal, do not accurately represent the composition of a nebula.

Evaluate the impact of Jovian planets on the stability of the solar system.

• Jovian planets destabilize the solar system by attracting comets and asteroids.

• Jovian planets stabilize the solar system by their gravitational influence, which helps to clear debris.

• Jovian planets have no impact on the stability of the solar system.

• Jovian planets destabilize the solar system by causing other planets to change orbits.

Answer explanation

Jovian planets, due to their massive size and strong gravitational fields, help stabilize the solar system by attracting and clearing out debris such as comets and asteroids, reducing potential collisions with inner planets.

Which of the following is NOT a characteristic of Jovian planets?

• They have thick atmospheres.

• They are located closer to the Sun than terrestrial planets.

• They have ring systems.

• They are larger than terrestrial planets.

Answer explanation

Jovian planets are located farther from the Sun than terrestrial planets. They have thick atmospheres, ring systems, and are larger than terrestrial planets, making the second option the only incorrect characteristic.

What characteristic is common among all terrestrial planets?

• They have ring systems.

• They are larger than Jovian planets.

• They are primarily composed of rock and metal.

• They have thick atmospheres.

Answer explanation

All terrestrial planets, including Earth, Mars, Venus, and Mercury, are primarily composed of rock and metal, distinguishing them from gas giants, which are mostly made of gases and have thick atmospheres.

How do planetesimals contribute to the diversity of planetary compositions in the solar system?

• Planetesimals are all composed of the same materials, leading to uniform planetary compositions.

• Planetesimals vary in composition, leading to diverse planetary compositions as they combine to form planets.

• Planetesimals only contribute to the formation of gas giants.

• Planetesimals do not contribute to planetary compositions.

Answer explanation

Planetesimals vary in composition, containing different materials like metals, ices, and silicates. As they collide and merge to form planets, this diversity leads to the varied compositions observed in the solar system's planets.

Which of the following is a characteristic feature of Jovian planets?

• They have a solid surface.

• They are primarily composed of gases and ices.

• They are smaller than terrestrial planets.

• They have no moons.

Answer explanation

Jovian planets, such as Jupiter and Saturn, are primarily composed of gases and ices, distinguishing them from terrestrial planets, which have solid surfaces. This characteristic is key to their classification.