Solar System Beginnings
This icy object is made mostly of ice, dust, and frozen gases and can form a glowing coma and tail near the Sun.
What is a comet?
Heat released when unstable atomic nuclei break down in early Earth materials is called this.
What is radioactive decay?
The leading explanation for the Moon’s formation says this type of body collided with early Earth.
What is a Mars-sized planetesimal?
Early photosynthetic organisms released this gas into oceans before it built up in the atmosphere.
What is oxygen?
In undisturbed sedimentary rock layers, this principle says the oldest layer is generally at the bottom.
What is the principle of superposition?
In the solar-nebula model, gas and dust first condensed; then particles collided and stuck together to form these small early bodies.
What are planetesimals?
As Earth gained mass, squeezing material inward raised its temperature through this process.
What is gravitational compression?
In the leading model, this material formed the Moon after the collision with early Earth.
What is debris ejected into orbit from the collision?
When oxygen reacted with dissolved iron in ancient seawater, it formed these layered rock deposits.
What are banded iron formations?
After one half-life, a sample that began with 100 grams of a radioactive parent isotope has this much parent material remaining.
What is 50 grams?
This process caused dust particles in the early solar system to grow as repeated collisions and gravity pulled material together.
What is accretion?
Collisions with planetesimals added both mass and thermal energy to proto-Earth through this process.
What is impact accretion?
Similar oxygen-isotope signatures in Moon rocks and Earth rocks provide evidence for this Moon-origin explanation.
What is the giant-impact hypothesis?
Before oxygen built up in the atmosphere, much of it was removed because it reacted with this dissolved substance in the oceans.
What is iron?
Radiometric dating works because radioactive isotopes decay at predictable rates known as these.
What are half-lives?
Put these stages in order: protoplanets, gas and dust condense, planetesimals, collisions and sticking.
What is gas and dust condense → collisions and sticking → planetesimals → protoplanets?
When early Earth partially melted, dense iron and nickel sank to form this internal layer.
What is the core?
The Moon has fewer volatile elements than Earth. This observation supports the idea that the Moon formed from hot material created by this event.
What is a giant impact/collision with early Earth?
Once oxygen accumulated in the atmosphere, this protective gas could form in the upper atmosphere.
What is ozone?
Radiometric dating determines age by measuring this relationship in a rock or mineral sample.
What is the ratio of parent isotopes to daughter products?
A student claims dust grains became planets because every grain underwent nuclear fusion. Identify the better explanation.
What is gravitational attraction and repeated collisions allowed particles to stick together and grow?
Name the three major processes that heated early Earth and helped lead to differentiation.
What are impact accretion, gravitational compression, and radioactive decay?
A student claims the capture hypothesis is the best explanation for the Moon’s formation. Give the strongest evidence from rock chemistry that challenges the claim.
What is that Moon rocks have chemical and isotopic similarities to Earth rocks?
Explain what banded iron formations reveal about the changing oxygen levels of ancient oceans and the atmosphere.
What is oxygen first reacted with dissolved iron in the oceans to form iron oxides/banded iron formations; after much of the iron had reacted, oxygen could begin accumulating in the atmosphere?
A 4.6-billion-year Earth history is represented on a timeline where 1 centimeter equals 100 million years. How long should the timeline be?
What is 46 centimeters?