Astronomy Semester 2 Module 2: Inner Planets
How many moons does Earth have?
1; The Moon
How many moons does Mars have?
2, Phobos and Deimos.
How long is Venus's year?
224.7 days; It takes 224.7 Earth days to complete one orbit around the Sun and 243 Earth days to rotate once around its axis.
How far is Earth from the sun?
93 million miles (150km) and it is the third closest planet from the sun
What is a Planetary System?
A planetary system is a system of objects in space that orbit a star. Our solar system is a planetary system that includes the Sun, the planets, and many other smaller objects.
Is Mercury volcanically active?
Although Mercury was once volcanically active, all activity has now stopped, and there is no tectonic activity on the planet.
what's an example of an extrasolar system?
An example of an extrasolar system is the Upsilon Andromeda system. The star Upsilon Andromeda has at least three planets that were discovered by measuring the apparent magnitude of the star. This system is located in the constellation Andromeda.
Satellite
An object that orbits, or revolves around, another.
What do astronomers believe about the start of the formation of the solar system?
Astronomers believe that the solar system began forming from the great explosion of the Big Bang, approximately 3.7 billion years ago. The Big Bang created a gigantic cloud of dust and gas called the solar nebula. This cloud contained several times the mass of the Sun that condensed and collapsed into a dense, flat, spinning disk with an extremely hot center. It is thought that the hot central part of the disk gradually became the Sun, while the planets and all other objects in the solar system formed from the remaining material.
how big is Mercury?
At 4,875 kilometers (3,029 miles) in diameter, Mercury is the smallest planet in our solar system.
How many seasons does Mercury have? why? And what is a consequence?
Because Mercury's axis of rotation is almost completely vertical, the planet has no seasons. This vertical axial arrangement also causes the poles of Mercury to never receive sunlight, causing them to remain permanently cold.
How long is a day on Mercury?
Because of Mercury's slow rotation, a day on Mercury is almost 59 Earth days long. Therefore, Mercury's period of rotation is almost 59 Earth days long.
Venus's Internal Structure
Because of Venus's similarities in size and density with Earth, astronomers believe that the planet has an internal structure similar to that of Earth's, with a core, mantle, and crust. The core of Venus is thought to consist mainly of solid iron and nickel, with an outer core of molten iron and nickel. The mantel is composed of rock, and the crust is made of silicate.
Why is Mars called the Red Planet
Because of its rust-red color, Mars is also known as the Red Planet, but it is officially named after the Roman god of war.
Mar's Atmosphere
Because of its thinner atmosphere and greater distance from the Sun, Mars is a cool planet. Midsummer temperatures recorded by the Mars Pathfinder range from 8° to 177°F (-13° to 77°C). Martian air is so thin that the air pressure on the surface of Mars is about the same as it is about 30 kms (18 miles) above Earth's surface. The air pressure is so low that any liquid water would quickly boil away. The only water found on the surface of Mars is in the form of ice.
Lesson 1: Gravity and Motion in Space
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Lesson 2: Meet mercury
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Lesson 3: Visiting Venus
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Lesson 4: Home, Sweet Home (Earth)
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Lesson 5: The Red Planet (Mars)
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The Exosphere
Beyond the Thermosphere and officially outer space
Venus's Size and Density
Earth and Venus are almost identical in size, but Venus is slightly smaller with a diameter of 12,104 kms (7,521 miles); it is also less massive and less dense than Earth.
Earth's Atmosphere
Earth is surrounded by the atmosphere, a layer of gases many hundreds of kilometers thick. The atmosphere is thought to have been created partly from gases released by ancient volcanoes; however, its oxygen content, so vital to the survival of most life forms, was created mostly by plants through the process of photosynthesis. Our atmosphere is mostly nitrogen gas with some oxygen gas. Nitrogen and oxygen make up 99 percent of dry air by volume. Argon gas makes up 0.9 percent of the atmosphere, and the remaining percent is composed of other trace gases. Scientists have classified our atmosphere into four major different layers: The Troposphere, The Stratosphere, The Mesosphere, and The Thermosphere.
Earth's Motion
Earth revolves around the Sun once approximately every 365 days and spins on its axis in a counter-clockwise prograde rotation once about every 24 hours.
Earths Structure
Earth's rotation causes its equator to bulge out by about 22 kms (13 miles) compared with the poles. Like the other terrestrial planets, Earth contains a core, mantle, and crust; however, we know that the core is divided into two distinct parts, the inner and outer core. The inner core is composed of solid iron and nickel metal, and the outer core is made of molten iron and nickel metal. The mantle is solid silicate rock, and the crust is solid and rocky. The Earth's crust consists of many different types of rocks and minerals but is mostly composed of silicates.
What are some of the things that gravity is responsible for?
Gravity is responsible for many occurrences within our solar system. Without gravity, the Moon would not orbit Earth, and Earth and other planets would not orbit the Sun. The spherical shape of Earth and other planets is due to gravity. As planets form, particles in space collide and stick together randomly; however, as the mass of the forming object increases, the force of gravity becomes stronger, making the planets the spherical shape we know today. Gravity is also the force that keeps us firmly planted on Earth and not floating off into space. Even though the speed of rotation at Earth's equator is slightly over 1,609 kilometers per hour (1,000 miles per hour), we do not physically feel the effect of Earth's rotation. Because our planet is extremely large when compared with us as individuals, its gravitational attraction holds us firmly on the ground.
The Stratosphere
If you've ever ridden in a jet plane, you've probably entered the stratosphere, the second-lowest layer of Earth's atmosphere.
Venus's Surface
Impact craters are considered prolific (or present in large numbers or quantities; plentiful) on Venus; however, when compared to our Moon and Mercury, there are very few. Astronomers believe that there were once more craters, but lava flows from past volcanic activity have smoothed out the surface of the planet.
Mercury's Surface
Impact craters blanket Mercury's surface. They range in size from small, bowl-shaped craters to a basin that is a quarter of the diameter of the planet. Multi-ring basins, caused by large meteorite impacts, are present on the surface. Steep cliff-like north and south ridges stretch over Mercury's surface and are believed to have been caused by early tectonic activity and tidal forces. These ridges stretch up almost 3 kms (2 miles) high and are over 500 kms (310 miles) long.
The Mesosphere
It takes a rocket to enter the mesosphere, which is also the layer where most meteors burn up as they enter our atmosphere. This is also the coldest layer of our atmosphere.
How many layers does Mercury have?
Like Earth, Mercury has three distinct layers: a core, mantle, and crust. Mercury's core is composed of iron and is believed to be completely solid; however, some scientists think that there may be a thin liquid layer of molten iron surrounding the core. The mantle, or middle layer of the planet, is made of rocky silicate and is also believed to be solid. Mercury's crust is made of silicate rock, specifically the silicate material anorthosite.
Earth's Surface Features
Like other planets, Earth's surface has encountered thousands of meteorite impacts over its history, but because Earth's surface is so dynamic, the evidence of most of these impacts has been masked by erosion and deposition of soil. Earth is a dynamic place. Tectonic plates, huge slabs of lithosphere or crust, float on top of a layer of liquid magma found above the Earth's solid mantle. The plates interact by colliding with one another to create volcanoes, mountains, and ridges. Tectonic plates can also separate, causing rifts, or slide past one another causing earthquakes
Mar's Structure
Like the other terrestrial planets, Mars has a core, mantle, and crust. Astronomers believe that the core is small and composed of solid iron metal. The mantle is made of silicate rock, and the crust is composed of rock. Even though liquid water cannot exist on Mars's surface today, evidence strongly suggests that it existed there in the past. Mars has surface features that might have resulted from deposition of sediment in a lake. This finding means that Mars might have been warmer and might have had a thicker atmosphere in the past.
Mar's Volcanic History
Mars has a rich volcanic history. Unlike Earth, where volcanoes exist in many places, Mars has only two large volcanic systems. The largest volcanic system, the Tharsis region, stretches thousands of kilometers across the planet. The largest mountain in the solar system, Olympus Mons, is an extinct shield volcano similar to Mauna Kea on the island of Hawaii on Earth. Mars not only is smaller and cooler than Earth, but it also has a slightly different chemical composition. This composition may have kept the Martian crust from moving around as Earth's crust does on tectonic plates. As a result, the volcanoes kept building up in the same spots on Mars. Images and data sent back by probes, such as the Sojourner rover, are helping to explain Mars' mysterious past.
Mar's Surface Features
Mars has two polar icecaps made of both frozen water and frozen carbon dioxide. However, the polar icecaps do not have enough water to create a thick atmosphere or rivers. Looking closely at the walls of some Martian craters, scientists have found that the debris around the craters looks as if it were made by the flow of mud rather than by dry soil. In this case, where might some of the lost Martian water have gone? Many astronomers believe that the lost water is frozen beneath Mars' soil.
Mars location and Distance from the Sun
Mars is the outermost of the four inner terrestrial planets. It is also 142 million miles away from the Sun
Mar's Motion
Mars orbits elliptically around the Sun, and the distance from one side of its revolution to the other varies greatly, causing a large difference in temperature on different parts of the planet. The tilt of Mars's axis is similar to that of Earth's, and, like Earth, the planet experiences changes in seasons at the north and south poles. Mars' axial tilt can fluctuate because of the force of Jupiter's gravitational pull. These fluctuations have caused changes in climate. For example, when Mars is heavily tilted, the poles are more exposed to the Sun, causing water and ice to heat up and vaporize around the colder, lower latitudes. If the tilt is decreased, water and ice become concentrated at the colder poles.
What is the closest planet to the sun?
Mercury
Mercury's Atmosphere
Mercury has a very thin and temporary atmosphere because the mass of the planet is too small for an atmosphere to continuously stay around the planet. Because the planet is so close to the Sun and daytime temperatures are so extremely high, any gaseous elements surrounding the planet quickly fly off into space. In 1974, the Mariner 10 spacecraft analyzed the composition of the atmosphere and found it to contain traces of oxygen, helium, hydrogen, sodium, potassium, and calcium.
Whats unique about Mercurys orbit?
Mercury has one of the most unique orbits of all planets. Even though it is only about 46 million kms (26 million miles) away from the Sun, Mercury's farthest orbit from the Sun reaches approximately 70 million kms (43 million miles).
What resource does Mercury have in abundance?
Mercury is the richest in iron metal.
The planets arranged in orbits of increasing distance from the Sun
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
How do astronomers know so much about Mars?
Much of astronomers' knowledge of Mars has come from information gathered by spacecraft. Viking 1 and Viking 2 landed on Mars in 1976, while the Mars Pathfinder landed there in 1997.
Does Mercury have moons?
No
What caused the solar nebula to collapse and what came of it?
No one knows for sure what caused the solar nebula to begin to collapse. Astronomers, however, are certain that gravity overcame these forces and collapsed the cloud, causing it to rotate and spiral exponentially. As the disk began to spin, the central region became hotter and denser, and the only solid materials that could survive these forces were rocky and metallic. These small solids gradually condensed further to become planetesimals , which are small bodies of rock in space, up to several kilometers in diameter, from which planets are created. Eventually these planetesimals formed into the rocky inner planets of Mercury, Venus, Earth, and Mars. In the outer, cooler regions of the disk, planetesimals formed into different types of rocks and frozen materials such as water, ammonia, and methane. These materials eventually became the planets Jupiter, Saturn, Uranus, and Neptune.
How many moons does Venus have?
None
Venus's Atmosphere and Temperatures
Of all the inner terrestrial planets, Venus has the densest atmosphere. Venus' atmosphere has 90 times the pressure of Earth's atmosphere. The air on Venus is mostly composed of carbon dioxide but also contains some of the most destructive acids known, including sulfuric acid. The carbon dioxide traps thermal energy from the sunlight in a process called the greenhouse effect. This greenhouse effect causes Venus' surface temperature to be extremely high. At 867°F (464°C), Venus has the hottest surface of any other planet in the solar system. Although the equator of Venus receives more solar energy than its polar regions, surface temperatures throughout the planet fluctuate by only a few degrees.
The Thermosphere
Once you hit the thermosphere, temperatures actually increase as this layer absorbs most of the Sun's radiation. This is also the layer where you would find the International Space Station. Beyond this you would find the exosphere, officially entering outer space!
what are planets outside of our solar system called and where did they come from?
Planets outside of our solar system are called extrasolar planets, and astronomers believe that they first came from the distortion of the proplyd disks.
Missons to Mars
Several missions to Mars have been launched to gain a better understanding of the Martian world. The Mars Express Orbiter, launched by European astronomers in 2003, was designed to help astronomers determine the composition of the Martian atmosphere and climate. Also, NASA's Twin Rovers, Spirit and Opportunity, have been roaming around the surface of Mars gathering information since 2004. These two were joined by the larger rover, Curiosity, in 2012. While these missions have not resulted in meeting any Martians, they do show that the conditions for life might have existed thousands of years ago. There are additional missions scheduled by NASA for the year 2020. Mars is also being observed from the sky, thanks to the Mars Reconnaissance Orbiter, which has now completed 50,000 trips around the planet and provided images that document 99.1 percent of the surface of Mars. Not only do these missions help us better know our neighboring planet, they may help scientists prepare for human exploration on Mars.
The Discovery of the planets in our solar system and times
Up until the 17th century, the universe was thought to have only eight bodies. These bodies included the planets Earth, Mercury, Venus, Mars, Jupiter, Saturn, the Sun, and Earth's Moon. Because these bodies are the only ones that can be seen from Earth with the naked eye, they were the only observable planets until the invention of the telescope. After the telescope was invented in the 17th century, more discoveries were made, and by the end of the 17th century, nine more large bodies were discovered. These newly discovered bodies were the moons of Jupiter and Saturn. By the 18th century, the planet Uranus, along with two of its moons and two more of Saturn's moons, were discovered, and at the end of the 19th century, Neptune, as well as moons of several other planets, were also discovered. Finally, in the 20th century, a ninth body in our solar system, Pluto, was discovered.
How many volcanos does Venus have?
Venus has hundreds of volcanoes, from large, shallow shield volcanoes to dome volcanoes. Approximately 85 percent of Venus' surface is composed of low-lying volcanic plains with large amounts of flowing lava.
Venus's Orbit?
Venus's orbit is the least elliptical of all the planets in our solar system as it revolves around the Sun in an almost perfectly circular path.
Earth's Development of Life
Water is perhaps the most dominant feature of Earth's surface and is the most important factor in determining the development of life on Earth. The water in the oceans on Earth can hold a lot of heat energy, enabling the planet to sustain a stable and comfortable temperature for life. Earth is warm enough to keep most of its water from freezing, but unlike Venus, Earth is cool enough to keep its water from boiling and evaporating away. Liquid water is the vital part of the chemical processes that living things depend upon for survival. The abundance of surface water in the oceans, lakes, atmosphere, and polar icecaps is a key factor in the development of life on Earth.
Does Venus have volcanic activity?
Yes; Between 1990 and 1992, the Magellan spacecraft mapped the surface of Venus by using radar waves. The radar waves traveled through the clouds and bounced off the planet's surface. Data gathered from these radar waves showed that Venus, like Earth, has volcanic activity. Astronomers believe that although volcanic activity has greatly slowed in the last few million years, there are still active volcanoes on the planet. Although Venus's highest mountains and largest volcanoes are comparable in size with Earth's, overall Venus's features have less variation in altitude.
Gravity
a universal force of attraction between objects; the amount of gravity is proportional to the distance between and difference in mass between two objects. The force of gravity attracts all objects toward each other. The farther away an object is, the weaker its gravitation pull, and the more mass an object has, the stronger its gravitational pull.
When was the first telescope used to study planet and stars created?
it wasn't until the 17th century that Galileo first used a telescope to study planets and stars;
How long is a year on Mercury?
its year is only 88 Earth days long. As you have also previously learned, a year is the time a planet takes to revolve around the Sun once. The time that an object takes to revolve around the Sun once is the object's period of revolution. Every 88 Earth days, or 1.5 Mercurian days, Mercury revolves around the Sun once.
How much would you weigh on Mercury?
on Mercury you would weigh only 38 percent of what you weigh on Earth. The weight you have on Earth is due to surface gravity, which is generally less on less massive planets.
What does Mercury, Venus, and Mars represent to the Romans? What about Earth?
The Romans worshipped Mercury as the god of communication, mercantilism, thievery, and trickery. His Greek equivalent was Hermes, the "messenger" of the Gods. Born out of sea-foam, Venus (based in part on the Greek goddess Aphrodite) was the goddess of beauty, love, and sex. She (and her planet!) represent femininity and fertility, and many science fiction writers imagine Venusian aliens as belonging to all-women societies. In many ways, Mars (adapted from the Greek god Ares) was the counterpart to Venus for the Romans, representing war and masculinity. Many contemporary songwriters lament that "men are from Mars, and women are from Venus," as if these two genders were alien species to each other. The word "earth" comes from an Old English noun, eorðe, that has a similar form in all the "Germanic" languages (which include English, German, Dutch, Danish, Afrikaans, and Yiddish) but which doesn't refer to any mythological figures. However, other terms that could refer to our planet Earth include Gaia (the ancient Greek personification of Earth and mother of all life) and Terra (the Roman equivalent to Gaia). Or you could just call us "Sol III," the third rock from the Sun!
What are the six steps of the solar system formation?
The formation of the solar system can be divided into six different steps. First, the solar nebula formed, starting out as a huge cloud of cold gas and dust, many times larger than our present solar system. From the start, the solar nebula was most likely spinning very slowly and began to gradually increase in speed. Next, the protosun was formed. Under the influence of gravity, matter in the solar nebula condensed into a dense central region, called the protosun, and a less dense outer ring, called a protoplanetary disk, also known as a polyplyd. As the material in the solar nebula contracted, the cloud began to spin faster and faster and flattened the matter into a disk shape, reminiscent of a Frisbee. In the third phase of solar system formation, rings and planetesimals were formed as instabilities in the rotating disk caused regions in it to condense into rings. Very small objects made of rocks and ice formed in these rings through accretion. Recall that accretion is the gradual accumulation of matter by an astronomical body in space due to gravity. Next, rocky planets formed as the planetesimals attracted each other by gravity and formed planets. Closer to the protosun, where it was very hot, only rock material and metals could withstand the high temperatures. This is the reason that the inner planets are composed mainly of rocky material and metals. In the fifth phase of solar system formation, the gas giants, or outer planets, were formed. These planets are composed of large amounts of gas surrounded by small amounts of rock and ice. Finally, the remaining debris, leftovers of the formation of the solar system, created the comets, meteorites, and asteroids that remain in our solar system.
The Troposphere
The layer closest to Earth, where all weather occurs.
Why do astronomers believe that Mercury is very rich in the metal Iron?
The planet Mercury is extremely dense, leading astronomers to believe that this planet is very rich in the metal iron.
What is interesting about the surface environment of Mercury?
The surface environment is extremely harsh because the high temperatures make it difficult for the planet to acquire a shielding atmosphere. The temperatures on Mercury fluctuate to the extreme, with temperatures reaching up to 806°F (430°C) during the day and plummeting down to -292°F (-180°C) at night. Needless to say, it is highly unlikely that any organism would be able to sustain life on Mercury.
What does the word planet mean in greek?
The word planet means wanderer in Greek.
What developments allowed astronomers to learn more and more about our solar system?
This is due to advances in technology such as telescopes and satellites, rovers that search the surface of a planet, probes that are dropped onto a surface and send information back, and some that will even return samples to Earth.
(Earths temperature) Earth formed at just the right distance from the Sun to sustain a comfortable temperature for life. Our planet's average surface temperature is 59°F (15°C). True or False?
True
(Venus Day) The years are shorter but the days on Venus are much longer. If you wanted to catch the sunrise and sunset on Venus, you would need to be there for 117 Earth days. This is because the planet rotates in the opposite direction of its orbit around the Sun. So, while the years are short, the days are long. True or False?
True
(Venus Magnitude) Venus is one of the brightest planets as seen from Earth and is only surpassed in brightness by the Sun and the Moon. You can see Venus without a telescope in the early evening or early morning sky. True of False?
True
(Venus's Sunset) the Sun rises in the west and sets in the east, opposite of the way that the Sun rises in the east and sets in the west on Earth. If a planet, like Venus, spins in a clockwise direction, the planet is said to have retrograde rotation. Retrograde rotation is the clockwise spin of a planet as seen from about the planet's north pole True or False?
True
Compared to the other rocky planets Mercury in metals and poor in heat-producing, radioactive elements. True or False?
True
