Bio A1.1.7 Extraplanetary origin of water on Earth and reasons for its retention

(HL only)

"What role did asteroids play in the origin of water on Earth?"

"Asteroids delivered water to Earth during the early solar system by carrying water locked within hydrated minerals."

"What is the solar nebula hypothesis?"

"The solar nebula hypothesis suggests that water was part of the dust and gas in the solar nebula from which Earth formed."

"Why is Earth's size significant for retaining water?"

"Earth's size provides a gravitational advantage

"What is the comet hypothesis regarding the origin of water on Earth?"

"The comet hypothesis suggests that water-rich comets collided with Earth

"What is Earth's gravitational advantage?"

"Earth's size allows it to maintain a strong gravitational pull

"What is the challenge to the comet hypothesis?"

"Not all comets have isotopic ratios consistent with Earth's water."

"What is the icy grains hypothesis?"

"The icy grains hypothesis proposes that icy grains in interstellar space were incorporated into the planetesimals that formed Earth."

"What evidence supports the asteroid hypothesis?"

"Isotopic ratios of water in carbonaceous chondrite meteorites closely match Earth's oceans."

"Why do scientists look for planets in the Goldilocks Zone when searching for life?"

"Liquid water is essential for life

"How does Earth's magnetic field contribute to water retention?"

"Earth's magnetic field shields the atmosphere from solar winds

"What role did volcanic activity play in the solar nebula hypothesis?"

"In the solar nebula hypothesis

"How does Earth's atmosphere affect water retention?"

"A protective atmosphere helps prevent water molecules from escaping into space

"What is the deuterium to hydrogen ratio?"

"The deuterium to hydrogen ratio is an isotopic measure used to compare the water composition of comets

"Why is being in the Goldilocks Zone not enough for retaining water?"

"Without sufficient gravity or a protective atmosphere

"What happens to water molecules on smaller planets like Mars?"

"On smaller planets with weaker gravity

"What is one reason Mars lost its water?"

"Mars' smaller size and weaker gravity allowed much of its atmosphere and water to escape into space."

"What is the asteroid hypothesis?"

"The asteroid hypothesis posits that water was delivered by carbonaceous chondrite asteroids during the late heavy bombardment period."

"What is the significance of isotopic analysis in the context of water origin?"

"Isotopic analysis helps determine the source of Earth's water by comparing the deuterium to hydrogen ratios in comets and meteorites."