Origin of the Earth's atmosphere and hydrosphere

Question 1

What is the Earth’s atmosphere primarily composed of today?

Answer 1

Nitrogen and oxygen

Question 2

Why didn’t Earth retain its primary atmosphere (from the solar nebula)?

Answer 2

Solar wind and high temperatures stripped it away

Question 3

What was the major source of Earth’s secondary atmosphere?

Answer 3

Outgassing from magma and impacts

Question 4

When did liquid water (rain) first appear on Earth?

Answer 4

Once temperatures dropped below 100 °C

Question 5

What process removed CO₂ from the atmosphere and led to the collapse of the early greenhouse effect?

Answer 5

Reaction with hot rocks and carbonate formation

Question 6

Which minerals or rocks provide evidence for the presence of liquid water over 4 billion years ago?

Answer 6

Jack Hills zircons

Question 7

What do banded iron formations (BIFs) indicate about Earth’s history?

Answer 7

That oxygen began accumulating in the oceans

Question 8

What role did cyanobacteria play in Earth’s evolution?

Answer 8

They released oxygen through photosynthesis

Question 9

How did nitrogen become abundant in Earth’s atmosphere?

Answer 9

It was degassed from oxidized mantle materials