According to the Giant Impact Hypothesis, how did the moon form?
The Moon formed approximately 4.5 billion years ago when a Mars-sized impactor struck the young Earth. The impact blasted mantle material from both bodies into orbit and formed a ring around the Earth, which eventually condensed to create the Moon.
What evidence in the rock record supports the link between the K-T impact and the Chicxulub Crater?
Elevated levels of iridium (rare on Earth but common in meteorites) & shocked quartz (formed only under extreme pressure of an impact)
What geological evidence identifies the K-T impact as a significant event in Earth’s history?
The K-T impact is marked in the rock record by iridium levels 10 to 100 times higher than typical Earth levels, as well as the presence of impact-derived materials like shocked quartz and tektite spherules.
Why is the Hadean Eon described as the “hellish” era of Earth’s history?
Named after the Greek word for “hell,” the Hadean Eon (4.56–4 Gya) was characterized by frequent volcanic eruptions and heavy impacts. It represents the earliest stage of Earth’s history, and conditions were so extreme that no rocks from this period have survived to the present day.
Which time period is characterized by the highest frequency of impacts in Earth’s history?
Early Bombardment
Why is it unlikely that Earth acquired its water during its initial accretion phase?
Earth formed inside the “water ice snow line” where temperatures were high enough that water existed only as a gas. Because Earth was not massive enough to accrete large amounts of gas, it is more likely that water was delivered later by ice-rich small bodies from the outer solar system. Also, at Earth’s orbital location, rock & metal would have been in solid form while water would have been in gaseous form.
Earth acquired water after formation.
There were lots of impacts in the early solar system. Isotopic analyses show that most of Earth’s water was delivered by small bodies that originated in the outer regions of the asteroid belt, but comets likely contributed as well.
What was the “Great Oxidation Event,” and which eon did it occur in?
The Great Oxidation Event occurred during the Proterozoic Eon, approximately 2.4 to 2 billion years ago. During this time, atmospheric oxygen levels rose dramatically due to the emergence and activity of oxygenic photosynthesis.
Why does the presence of Zircons dating back to 4.4 Gya suggest the Hadean Earth might have been ‘calm’ at times?
They provide evidence for the existence of early oceans & continents
In the context of geological time, the ‘Precambrian’ refers to what percentage of Earth’s total history?
88% (Hadean, Archean, Proterozoic)
What is the primary chemical difference between Earth’s secondary atmosphere and its current atmosphere?
The secondary atmosphere was dominated by carbon dioxide and lacked free oxygen. It formed via volcanic outgassing of gases trapped in the Earth’s interior.
Why does the ‘Gow Crater’ in Saskatchewan appear much less defined than the ‘Meteor Crater’ in Arizona, despite being larger?
It is significantly older & has been subject to more erosion
Based on Kepler’s Second Law, how does a planet’s orbital speed change relative to its distance from the Sun?
Kepler’s Second Law establishes that a line connecting a planet to the Sun sweeps out equal areas in equal time intervals. This implies that a planet must move faster when it is closer to the Sun (covering more orbital distance to sweep the area) and slower when it is further away.
Explain the fundamental difference between Kepler’s work and Newton’s work regarding planetary motion.
Kepler’s Laws are descriptive, determining “how” planets move based on observational data. Newton’s Laws provided the physical explanation or the “why” behind that motion by introducing the concepts of inertia, force, and gravity.
What is Newton’s First Law (law of Inertia)?
An object at rest will remain at rest and an object in motion will remain in motion in a straight line at a constant speed unless acted upon by an external force
What is Newton’s Second Law?
The net force acting on an object is proportional to an object’s mass & its resultant acceleration
What is Newton’s Third Law?
For every action there is an equal and opposite reaction
What is Newton’s Law of Universal Gravitation?
Objects attract each other with a force that is directionally proportional to the product of their masses & inversely proportional to the square of the distance between them
What is Kepler’s First Law?
A planet orbits the Sun in an ellipse, with the Sun at one focus of the ellipse
What specific detail of lunar composition supports the Giant Impact Hypothesis?
What are other observations?
It resembles Earth’s mantle.
others:
- moon is receding from Earth
- moon is in a “regular” orbit
- moon is massive compared to Earth
- moon was completely molten roughly 4.5 Ga ago
What were the two primary components of Earth’s atmosphere during the Archean Eon?
Nitrogen & CO2
Mercury has an extremely tenuous atmosphere known as what?
An exosphere
During the formation of a solar system, why does a collapsing molecular cloud flatten into a spinning disk?
Due to the conservation of angular momentum. As the cloud collapses and its radius decreases, it must spin faster to conserve angular momentum, naturally flattening into a disk shape.
Define “periastron” and “apoastron” in the context of orbital velocity.
Planets move most quickly when they are near the periastron (the point closest to the star). Conversely, they move most slowly when they are near the apoastron (the point farthest from the star).
What is the semimajor axis of an ellipse?
Half of the long side of the ellipse
