A1.1 HL The Origin of Earth’s Water
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Why is water essential for life?
It is a medium for chemical reactions
How did much of Earth’s water likely arrive?
From collisions with icy asteroids/planetesimals.
What ratio is used to study water’s origin?
Deuterium/hydrogen (D/H) ratio.
Why are comets unlikely as main water sources?
They have higher D/H ratios.
Which objects match Earth’s D/H ratio?
Carbonaceous chondrite asteroids.
How much water may comets have added?
~10%.
Why is Earth’s gravity important for water?
Prevents water from escaping into space.
Why couldn’t Earth have had liquid water at first?
Too hot after formation, water would vaporize.
What zone allows liquid water on Earth’s surface?
The habitable “Goldilocks zone.”
In what phases does water exist on Earth?
Solid, liquid, and gas (all three).
Where else in the solar system is liquid water suspected?
Europa, Ganymede, and Enceladus
Why are hydrothermal vents important for life?
Provide energy and minerals to support reactions.
hich moons may have more water than Earth?
Europa and Ganymede.
What covers oceans on icy moons?
Thick ice sheets.