Solar System Final- 3
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- Which of the following planets may have STARTED forming (not necessarily finished) before CAIs (Calcium Aluminum rich Inclusions found in Meteorites) formed?
- Saturn.
- Where in the solar system would you expect to find the largest and most massive planetary embryos shortly before the any of them started accreting hydrogen and Helium from the nebula gases?
- In the Jupiter/Saturn region in which the low dust number density was still sufficient to allow growth to embryo size before the T-Tauri winds cleared the nebula.
- Which planet in the solar system uniquely has the right mass to be a surviving planet embryo when we take into account its distance from the sun.
- Mars.
- Which of the planet systems below would be the most likely if the Sun had reached its T-Tauri stage earlier than it did?
- Hundreds of smaller planets between the Sun and Mars with ice giants but no gas giants beyond.
- How do we know that the Solar system formed 4.6 billion years ago?
- From radioactive Rubidium decay to Strontium dating of meteorites.
- What age(s) can be determined directly from radioactive dating of meteorites?
- The elapsed time from formation of radioactive nuclides to the time chemical bonds formed in the solids. The time since chemical bonds formed in the solids (to the present).
- Which of the following environmental conditions affects the rate of radioactive decay of for example Rubidium to Strontium?
- No environmental factor affects to decay rate.
- Do we know if CAIs (Calcium Aluminum rich Inclusions found in some Meteorites) formed before other surviving rocky matter formed in the solar system?
- Yes, if other minerals formed first they would have bound up the oxygen needed to form the chemicals found in CAIs.
- What minerals now found in the solar system are the oldest?
- Radioactive dating shows that some minerals that survived in the outer parts of the solar system are older than CAIs but those minerals are believed to have formed in supernovae outflows, not in the solar system.
- How do we know when the hydrogen and helium dominated nebula gas was cleared from the solar system?
- Radioactive dating of chondrules (inclusions in some meteorites) show that the tem- perature in the nebula determined from chondrule mineralogy varied with time until the cycles suddenly stopped. This evidently marks the age when the nebula gas dissipated.
- What is the importance of finding how large the most energetic collision to have occurred in the solar system were?
- Post embryo planetary growth suggested by present planet masses is refuted if we do not find evidence for collusions between bodies that are larger than planetesimals.
- What of the following features are evidence for collisions among planetary embryos?
- Retrograde spin of the planet Venus.Densities of Mercury, Venus and Earth exceed 4 g/cm3.Uranus’s spin axis tilts 98 degrees, so that the axis lies almost in the orbital plane.The very existence of the Earth’s moon.The density of the moon and depletion of volatiles.
- What is the mare on the Moon?
- The mare are basalt plains.
- What is the significance of finding basalt (approximately 3 g/cm3 density) surface minerals (rocks) on the Moon (who’s bulk density is approximately 3 g/cm3)?
- The Moon does not have a significant metal core.Metals are depleted compared to the levels we may expect for a body accreted similarly as a planet since the density of surface rocks is nearly as high as the bulk density.The Moon does not have extensive low density materials like water ice because if it were there it would be on the surface.
- Which of the following MUST happen if two bodies formed far apart in the solar nebula are to be trapped in orbit about one another and become a planet / satellite pair?
- Energy must be dissipated somehow, often through collision(s) or through the pres- ence of a third body.
- Before two massive bodies collide their mutual gravitational attraction causes the bodies to \"fall toward one another\" and increase their velocities at the moment of impact. How does this affect collisions?
- The impact speed being at least equal to their escape velocity, Collisions between massive bodies has a minimum energy (an energy it equals or exceeds).When the bodies are sufficiently massive their collision always results in the bodies breaking apart before they reassemble.
- Which of the following best describes what happens as more an more material accretes onto a planet?
- The planet dimensions increase at first but for each material there is a maximum size beyond which the planet gets smaller if more material is added.
- Where was most of the material now found in giant gas planets like Jupiter made?
- In the Big Bang
- Only one body in the solar system has the right combination of distance from the sun, mass, density, and spin to be an embryo. Which body is that?
- Mars.
- What do comets and asteroids have in common?
- Both types of bodies are surviving planetesimals grown through accretion and neither reached the embryo state.
- Why do we expect a magma (rock) ocean layer resulting in the formation of continents only on the surface of a sufficiently large planetesimal?
- Impactors gain velocity as they are attracted by gravity. This results in sufficiently violent impacts to melt the surface layer which then freezes back over between impacts.
- What is meant by differentiation of a celestial body?
- Metals separate from rocks of lower density and find their way to the core while the rocks form a mantle.
- What do the size of crystals in meteorites primarily tell us about the conditions where the meteoroid material formed?
- The cooling rate or how long it took the material to cool and solidify into crystals.
- We did see that a meteorite from asteroid Vesta has little bubbles inside. What do these bubbles tell us about the conditions where the meteoroid material solidified?
- The meteoroid material moved from higher pressure to lower pressure as it solidified which is indicative of a volcanic eruption.
- What evidence do we have that planets cool down as they accrete and after some time differentiate and heat up in the interior?
- Valles Marineris on Mars which looks like and is a big crack on the surface of the planet.