The video discusses two main theories of how Earth and Mars formed. The recent theory suggests planets formed by accreting millimeter-sized rocks from the outer solar system. However, a new study supports the classical model, which involves collisions between moon to Mars-sized planetary embryos. The study analyzed meteorites from Mars, comparing isotopes with those from Earth and other meteorites, concluding that only 4% of Earth and Mars material came from the outer solar system. The study also suggests Jupiter's early formation may have limited Earth's size by blocking incoming material.

What does the more recent theory suggest about the formation of terrestrial planets?

• They were formed by the gravitational pull of the sun.

• They were formed by the fusion of gas clouds.

• They formed by collisions between large planetary embryos.

• They formed by accreting millimeter-sized rocks.

According to the new study, what percentage of Earth and Mars is made up of materials from the outer solar system?

• 10%

• 25%

• 50%

• 4%

What did scientists analyze to support the classical model of planetary formation?

• Asteroids from the asteroid belt

• Comet tails

• Meteorites from Mars

• Gas clouds around the sun

Which isotopes were compared in the study to draw conclusions about planetary formation?

• Iron, nickel, and cobalt

• Titanium, zirconium, and molybdenum

• Carbon, nitrogen, and oxygen

• Helium, neon, and argon

How might Jupiter's early formation have affected the size of Earth?

• By blocking incoming material from fusing with planetary embryos

• By causing Earth to spin faster

• By increasing the amount of material available for Earth's formation

• By altering Earth's orbit around the sun