Earth as a Planet Final

-What is known about Mars's seasonal cycle?

It has fall, winter, spring, and summer, but also aphelion and perihelion because it's orbit is more elliptical than earth's, these two seasons happen over the course of one martian year (about 2 earth years), has a 25 degree tilt

-What observation led to the discovery of Neptune?

Saw discrepancies in Uranus' orbit

-Venus is considered Earth's sister planet. In what ways are they similar? How are they different?

Similarities: mass (venus is only 20% smaller), densities, rocky, significant atmospheres, atmospheric pressures and temperatures, volcanoes; Differences: venus rotates clockwise (most planets rotate counter clockwise), one venus day is 117 earth days and one venus year is 2 venus days, venus is very hot and its air is almost entirely carbon dioxide

-What is Comparative Planetology?

Comparative planetary science or comparative planetology is a branch of space science and planetary science in which different natural processes and systems are studied by their effects and phenomena on and between multiple bodies.

-What does it mean for a planet to be in opposition?

A planet is in opposition when there is a straight line from the sun, to the earth, to the planet; apparent retrograde motion, visible almost all night - rising around sunset, culminating around midnight, and setting around sunrise, at the point in its orbit where it is roughly closest to Earth, making it appear larger and brighter, nearly completely sunlit; the planet shows a full phase, analogous to a full moon, at the place where the opposition effect increases the reflected light from bodies with unobscured rough surfaces

-What is a protoplanetary disk? Where does the material it contains come from?

A rotating disk of dust and gas, formed from a collapsed nebula cloud. As gravity pulls material in the collapsing cloud closer together, the center of the cloud gets more and more compressed and, in turn, gets hotter. This dense, hot core becomes the kernel of a new star. The disk around the star may eventually develop into orbiting celestial bodies such as planets and asteroids.

-In the absence of any other effects, what would the structure of the Moon have been following this cooling model?

Also, the moon does show seismic activity - "moonquakes" which suggests that the lunar core may be partially molten. The lunar crust, on the other hand, is much thicker in relation to the lunar radius than is earth's. This is the result of the rapid cooling one would expect for a small body.

-Why is Titan an interest for astrobiology, the study of the origin and distribution of life in the universe?

Among our solar system's more than 150 known moons, Titan is the only one with a substantial atmosphere. And of all the places in the solar system, Titan is the only place besides Earth known to have liquids in the form of rivers, lakes and seas on its surface.

-Can you describe the general stages of planetary growth from dust to fully formed planets?

As a disk spins, the material within it travels around the star in the same direction. Eventually, the material in the disk will begin to stick together, somewhat like household dust sticking together to form dust bunnies. As these small clumps orbit within the disk, they sweep up surrounding material, growing bigger and bigger. The modest gravity of boulder-sized and larger chunks starts to pull in dust and other clumps. The bigger these conglomerates become, the more material they attract, and the bigger they get. Soon, the beginnings of planets — "planetesimals," as they are called — are taking shape.

-How might tides have played a role in the origin of Saturn's rings?

As the planet coalesced during the birth of the solar system more than 4.5 billion years ago, the swirling disk of gas surrounding it included several moons about the size of Titan, Saturn's largest remaining satellite, which is about 50% larger than Earth's moon. But gravitational interactions with the gas caused the moons' orbits to shrink, and one by one the satellites entered death spirals and plunged into the planet. Before each moon collided, immense tidal forces produced by Saturn's gravity stretched and contracted it, stripping off much of its ice. Subsequent moons gravitationally captured this ice, but they were eventually stretched and contracted until they too shed their ice and plunged into Saturn. Today's ring system is the fossil remains of the last moon to fall prey to Saturn's immense gravity, Canup contends. This moon was basically a giant ice ball with a rocky center. After its ice-rich veneer was stripped away in large chunks, its rocky core disappeared beneath the saturnian clouds. The fragments of that final doomed moon, each originally between 1 and 50 kilometers across, formed an icy ring system as much as 1000 times as massive as today's rings. In the subsequent 4.5 billion years, innumerable collisions between these large chunks produced the much-smaller ring particles now orbiting Saturn. What little rocky material occurs in today's ring system probably is the debris of collisions between icy ring particles and asteroids and comets swept up by the planet's huge gravitational field, says Canup.

-Why is Europa the focus of so much scientific interest?

Beneath the icy surface of Jupiter's moon Europa is perhaps the most promising place to look for present-day environments suitable for life.

-In what ways does Mercury look like the Moon? How is it different?

Both are generally gray, covered in craters, have no atmosphere and very thin exospheres. Mercury is larger and has a different composition with more colors, it's craters are mostly volcanic

-What are comets? In what ways are comets scientifically interesting objects to study?

Comet, a small body orbiting the Sun with a substantial fraction of its composition made up of volatile ices. * May be the oldest, most primitive bodies in the solar system preserving the earliest record of material from the nebula which formed the sun and the planets. * Bring volatile light elements to the planets, playing a role in forming oceans and atmospheres. * Are the most organic-rich bodies in the solar system providing ready-formed molecules possibly involved in the origin of life on Earth. * Impact the Earth and other planets at hypervelocities, causing major changes in climate and dramatically affecting the ecological balance, possibly including the extinction of the Dinosaurs. * Are the building blocks of planetary systems around other stars.

-Why is Enceladus such an interesting target for astrobiology? What has been observed that has been enticing to this study?

Has the highest potential of hosting life in the solar system outside of Earth. Despite its frigid temperatures, the moon hosts liquid water beneath its surface that appears to directly contact the rocky seafloor, making complex chemical reactions possible — such as those reactions that lead to life.

-Why did Percival Lowell look for Pluto?

He saw that Uranus and Neptune were displaced from their predicted positions, possibly by some object's gravitational pull, so he looked for Planet X

-Why do we say that the final stages of planet formation can be very violent?

Hundreds of these planetesimals are forming at the same time, and inevitably they meet up. If their paths cross at just the right time and they're moving fast enough relative to each other, SMASH! — they collide, sending debris everywhere. But if they slowly meander toward one other, gravity can gently draw them together. They form a union, merging into a larger object. If the participants are farther apart, they might not physically interact but their gravitational encounter can pull each body off course. These wayward objects start to cross other lanes of traffic, setting the stage for additional collisions and other meetings of the rocky kind.

-What property(ies) in the disk varies with distance from the sun? How does this impact the materials that are available to take part in planet formation?

In the inner part of the disk, most of the material at this point is rocky, as much of the original gas has likely been gobbled up and cleared out by the developing star. This leads to the formation of smaller, rocky planetesimals close to the star. In the outer part of the disk, though, more gas remains, as well as ices that haven't yet been vaporized by the growing star. This additional material allows planetesimals farther from the star to gather more material and evolve into giants of ice and gas.

-Why is Pluto no longer considered a planet?

It is small icy body that is part of the Kuiper Belt. A planet must be a celestial body that 1. orbits the sun, 2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round shape), 3. clears the neighborhood around its object ==> pluto did not satisfy #3.

-Why is Io the most geophysically active body in the Solar System? What types of geophysical evolution are observed?

Jupiter's moon Io is the most volcanically active world in the Solar System, with hundreds of volcanoes, some erupting lava fountains dozens of miles (or kilometers) high. Io is caught in a tug-of-war between Jupiter's massive gravity and the smaller but precisely timed pulls from two neighboring moons that orbit farther from Jupiter—Europa and Ganymede.

-Mercury's density revealed the planet was anomalous among the others in the Solar System in what way?

Mercury is the only planet which doesn't rotate exactly once every year - instead rotating three times for every two orbits of the Sun. This is because it is nearly tidally locked to the Sun. ?????????

-Why are meteorites of scientific interest? What kinds of meteorites exist and how are they of interest to us?

Meteorites are left-overs from the formation of the solar system. While Earth rock has been reprocessed by geological forces over many eons, most meteorites have never experienced any reprocessing and are just as they were when the solar system was formed. By examining a meteorite, we are looking at the chemical composition of the solar system as it was being born. A few meteorites come to us from the Moon or other planets, such as Mars. When you are holding a piece of martian meteorite in your hand, you are holding an actual real piece of the red planet. By studying these kinds of meteorites, we learn about the geology and atmospheres of other planets at long ago times, when the meteorite was chipped off the planet. 3 types of meteorites: 1. IRON, almost completely made of metal, cores of asteroids that melted early in their history, During the decay of radioactive elements in the early history of the solar system, many asteroids melted and the iron they contained, being dense, sank to the centre to form a metallic core, Sometimes they have an iron core and concentric layers, surrounded by a silicate mantle and crust, This type of structure is very similar to terrestrial planets (Mercury, Venus, Mars and Earth), which also have metallic cores. Iron meteorites can tell us a great deal about how the metallic cores of planets formed 2. STONY, most beautiful, two types: pallasites and mesosiderites, pallasites are thought to be samples of the boundaries between a metal core and the silicate, olivine-rich mantle around it. If this is the case, they could tell us a lot about the formation of Earth and other terrestrial planets, mesosiderites form when debris from a collision between two asteroids is mixed together. In the crash, molten metal mixes together with solid fragments of silicate rocks. Mesosiderites can therefore both record the history of both meteorites and reveal a snapshot of the conditions required for asteroids to melt and form iron cores. 3. STONY-IRON, the majority of meteorites, two types: chondrites (some of the oldest materials in the solar system) and achondrites (including meteorites from asteroids, Mars and the Moon).

-Why is Planet IX hypothesized to exist? What evidence would support or refute this hypothesis?

Orbits of small icy objects are being effected by the gravitational force of something, perhaps a 9th planet. as-yet-undiscovered planet should be about four times the size of Earth and 10 times its mass. That would make it similar to super-Earth exoplanets found orbiting other stars. And that would be interesting, since many super-Earths have now been discovered, although there were none to be seen in our own solar system. But maybe there is one after all, so far from the sun that it has remained hidden.

-What evidence is there to support liquid water was present on the surface of Mars?

Streaks of salt deposits lining the rocks, also remnants of liquid water lake under south polar ice cap, water on mars would greatly increase the chance of microbes and make it easier for astronauts

-How did impacts affect the surface of the moon? What was their role in forming Maria?

The earth would look the same as the moon if it did not have an atmosphere, liquid water, and tectonic plates. Moon's craters are impact craters. The Moon has no atmosphere, so even the tiniest bit of high-speed dust can hit the surface and cause a crater to form. On Earth, erosion due to water and wind eventually erases the craters caused by impacts of objects large enough to hit the ground.

-What is Oumuamua? Why are people talking about it?

The first interstellar object to be seen passing through the solar system. It sped up on its way out of the solar system. We do not know where it came from or how long it had been here. Some thought it could be an alien probe.

-The moon is believed to have formed hot, with everything in it melted. This led to different mineral groups forming: olivine/pyroxene and then feldspars. As the moon cooled, how and why did these mineral groups separate from one another?

The moon was formed when a Mars-sized body known as "Theia" collided with Earth and vaporized chunks of Earth were thrown in to space and came together because of gravity. This is why it is less dense than the Earth, it was made up of crust elements. ?????????????

-What does it mean that bodies orbit in resonances? What effect does a resonance have? Why?

Two planets orbital periods are related by a ratio of small integers; Orbital resonances greatly enhance the mutual gravitational influence of the bodies, i.e. their ability to alter or constrain each other's orbits. In most cases, this results in an unstable interaction, in which the bodies exchange momentum and shift orbits until the resonance no longer exists. Under some circumstances, a resonant system can be stable and self-correcting, so that the bodies remain in resonance.

-While asteroids are predominantly found in the Main Asteroid Belt, where else can they be found?

Two sets of asteroids, called Trojan asteroids, share Jupiter's 12-year orbit around the Sun. One clump of Trojan asteroids stays 60 degrees ahead of Jupiter and the other clump stays 60 degrees behind. There are also many renegade asteroids that have highly elongated or unusual orbits, some coming very close to Earth and other planets.

-What is the Greenhouse Effect? What does it mean in regards to temperatures on the planet? What is a benefit it has for us on Earth?

Warms temperatures on the planet, keeps us warm so it sustains life

-When comets make their way to the inner solar system, they begin to warm. What happens then? How are comets then seen and oriented as they move along their orbits around the Sun?

When a comet comes close to the Sun, the ices sublimate (go directly from the solid to the gas phase) and form, along with entrained dust particles, a bright outflowing atmosphere around the comet nucleus known as a coma. As dust and gas in the coma flow freely into space, the comet forms two tails, one composed of ionized molecules and radicals and one of dust.

-What is the Doppler effect? What does it allow us to infer about an object at a distance? How was it used to evaluate the structure of Saturn's rings?

When wave energy like sound or radio waves travels from two objects, the wavelength can seem to be changed if one or both of them are moving. This is called the Doppler effect. The Doppler effect causes the received frequency of a source (how it is perceived when it gets to its destination) to differ from the sent frequency if there is motion that is increasing or decreasing the distance between the source and the receiver. This effect is readily observable as variation in the pitch of sound between a moving source and a stationary observer. Imagine the sound a race car makes as it rushes by, whining high pitched and then suddenly lower. Vrrrm-VROOM. The high pitched whine is caused by the sound waves being compacted as the car approaches you, the lower pitched VROOM comes after it passes you and is speeding away. The waves are spread out. When the distance between the source and receiver of electromagnetic waves remains constant, the frequency waves is the same in both places. When the distance between the source and receiver of electromagnetic waves is increasing, the frequency of the received wave forms is lower than the frequency of the source wave form. When the distance is decreasing, the frequency of the received wave form will be higher than the source wave form. Besides sound and radio waves, the Doppler effect also affects the light emitted by other bodies in space. If a body in space is "blue shifted," its light waves are compacted and it is coming towards us. If it is "red shifted" the light waves are spread apart, and it is traveling away from us. All other stars we have detected are "red shifted," which is one piece of evidence for the theory that the universe is constantly expanding, perhaps from a "big bang."

-Why did the first spacecraft to Venus fail to see the surface?

You cannot see through it's atmosphere, opaque clouds made of sulfuric acid make optical Earth-based and orbital observation of the surface impossible, information about the topography has been obtained exclusively by radar imaging

-Why is it difficult to understand how liquid water could have been present on Mars?

atmospheric pressures are too low

-What is Venus's atmosphere largely made of? How do we know? What else do we know about the atmosphere?

composed primarily of carbon dioxide (some nitrogen) and is much denser and hotter than that of Earth, venus does not have a magnetic field ionosphere separates the atmosphere from outer space and the solar wind. This ionised layer excludes the solar magnetic field, giving Venus a distinct magnetic environment. This is considered Venus's induced magnetosphere

Chemical variations among planets in our Solar System

small, rocky planets close to the star, and ice-containing planets further away, is due in part to higher temperatures were found in the inner solar nebula, transitioning to colder in the outer

-What are two ways we determined the dates of the Maria and Highlands? How did this play a role in helping us establish how the Highlands/Maria formed

the maria are younger than the highlands, because they have fewer craters. Radioactive dating can determine age of rocks???, the oldest material from the surface of the Moon is almost as old as the Solar System to be. This is more than a billion years older than the oldest Earth rocks that have been found because the Earth's surface is geologically active?????? The dark material filling the Maria is actually dark, solidified lava from earlier periods of Lunar volcanism. Both the Maria and the Highlands exhibit large craters that are the result of meteor impacts. 4. These rocks are around 400 million years old, and were laid down in the Devonian period. The Highlands are generally mountainous and are bisected by the Great Glen Fault.

Advection

the movement of hot material from one region to the other

-Why do we think of Mars being of interest in terms of life beyond Earth?

water