The Sun, Moon, and Inner Solar System

Below are some features of the inner planets:

- All have rocky compositions and are also known as the terrestrial planets. - All have few or no moons. - None have ring systems—like the famous rings of Saturn. - They all have heavy metals, like iron and nickel, in their cores, while their mantles and crusts are made of lighter elements, such as silicon and oxygen. - All have impact craters from ancient meteorite bombardments. - All have tectonic surface features, such as rift valleys and volcanoes, though only Earth has current active geological activity.

Prominence Solar Flare Solar Wind Coronal Mass Ejection Sunlight Ultraviolet Radiation

- Prominence: An eruption of plasma, usually a loop shape Prominence is an eruption of plasma from the Sun and usually has a loop shape - Solar Flare: Violent explosion near a sunspot A violent explosion from the Sun is a solar flare. - Solar Wind: Streams of ener getic particles and radiation The solar wind is made of streams of energetic particles and radiation. - Coronal Mass Ejection: Huge balloon-shaped burst of plasma. A coronal mass ejection is a large and very powerful burst of plasma from the Sun's surface. - Sunlight: May travel to Earth as visible sunlight Sunlight travels at various energies, including visible sunlight. - Ultraviolet Radiation: Causes sunburn on Earth Sunburns are caused by ultraviolet radiation.

core radiative zone convection zone photosphere chromosphere corona sunspot granulation

- core: inner part of the Sun where nuclear fusion takes place Feedback: The core is the inner part of the Sun. - radiative zone: part of the Sun wh ere energy travels very slowly Feedback: Energy travels slowly through the radiative zone. - convection zone: zone marked by rising and sinking of heated material Feedback: The convection zone is marked by the rising and sinking of heated material. - photosphere: visible surface of the Sun Feedback: The photosphere is the visible surface of the Sun. - chromosphere: part of the Sun's atmo sphere directly above the photosphere Feedback: The chromosphere is part of the Sun's atmosphere and is just above the photosphere. - corona: outer part of the Sun's atmosphere; extends millions of kilometers into space Feedback: The corona is the outer part of the Sun's atmosphere. - sunspot: surface feature of the Sun marked by intense magnetic activity Feedback: A sunspot is a surface spot on the Sun and has intense magnetic activity. - granulation: surface feature of the Sun that arises from convection currents of plasma Feedback: Granulation arises from convection currents of plasma within the Sun.

Category 4: Mars 100 Why is Mars red? volcanic activity iron oxides in its soil red gases in its atmosphere 200 How many moons does Mars have? 0 2 3 300 The atmosphere of Mars is made of oxygen carbon dioxide water 400 The surface of Mars is covered with ancient and extinct volcanoes water frozen gas

13. 2 Feedback: Mars is the red planet because of iron oxide minerals in its soil. 14. 2 Feedback: Mars has two moons. 15. 2 Feedback: The atmosphere of Mars is made of carbon dioxide. 16. 1 Feedback: The surface of Mars is cove red with ancient and extinct volcanoes.

The Inner Solar System

The Sun is certainly the most visible object in the daytime sky. At night, the Moon takes over, as well as the stars, and several other objects. One of the brightest of these other objects in the night sky is Venus. While it twinkles like a star, it is really a planet. In this picture, Venus is the very bright object shining near the center of the image. Because Venus is close to Earth, and because it is surrounded by a thick layer of clouds that reflect sunlight, Venus looks especially bright to us. Along with Earth, Mercury, and Mars, Venus is part of the inner solar system.

What are the four states of matter? Which one do you think makes up the sun?

The four states of matter are solid, liquid, gas, and plasma. The Sun is made of plasma. Keep reading to learn more about plasma.

inner

The inner solar system also includes a belt of asteroids, which are small rocky objects that orbit the Sun, but are not large enough to count as planets.

Granulation

The photosphere has a look of granulation that comes from convection currents of plasma within the convection zone.

Category 5: Asteroids 100 Asteroids: are smaller than the planets orbit the Sun both of the above 200 The main asteroid belt is between Mars and Earth Mars and Jupiter Mercury and Venus 300 Asteroids are gaseous liquid rocky 400 The asteroids never made a planet because of the influence of Jupiter's gravity because they are too rocky because there was not enough time

17. 3 Feedback: Asteroids are smaller than planets and orbit the Sun. 18. 2 Feedback: The main asteroid belt is between Mars and Jupiter. 19. 3 Feedback: Asteroids are rocky. 20. 1 Feedback: The asteroids never made a planet bec ause of gravitational influences from Jupiter.

Category 2: Venus 100 Venus is the _____ planet from the Sun. first second third 200 Venus is very bright because it is close to Earth has a thick layer of clouds that reflect sunlight both of the above 300 The atmosphere of Venus is mostly oxygen carbon dioxide sulfur dioxide 400 Venus is the ____ planet because of _____. hottest; greenhouse gases in its atmosphere coldest; its lack of an atmosphere hottest; its small size

5. 2 Feedback: Venus is the second planet from the Sun. 6. 3 Feedback: Venus is bright to us on Earth because it is close to Earth and because of its thick clouds. 7. 2 Feedback: The atmosphere of Venus is mostly carbon dioxide, a powerful greenhouse gas. 8. 1 Feedback: Venus is the hottest planet because of its thick covering of greenhouse gases.

Category 3: Earth 100 Earth has more ___ than any other planet. sunlight mass oxygen 200 Early life altered Earth's atmosphere by adding oxygen removing sulfur removing toxic metals 300 Earth is the only inner planet that has surface features an atmosphere active geological activity 400 Earth is the ____ planet from the Sun. third second first

9. 3 Feedback: Earth has more oxygen in it s atmosphere than any other planet. 10. 1 Feedback: Early life altered Earth's atmosphere by adding oxygen to it. 11. 3 Feedback: Earth is the only inner planet t hat has current active geological activity. 12. 1 Feedback: Earth is the third planet from the Sun.

Coronal Mass Ejections

A coronal mass ejection (CME) occurs when huge, balloon-shaped bursts of plasma erupt out of the Sun. CME events are very powerful and can affect Earth by interfering with radio transmissions, disrupting power, and damaging satellites in orbit around Earth. They also cause strong light displays in the night sky, such as the Northern Lights, or Aurora Borealis.

3. What is a coronal mass ejection?

A coronal mass ejection is a very large burst of plasma from the Sun.

2. How does a solar flare form?

A solar flare is a violent explosion and release of energy near sunspots on the Sun. They release streams of highly energetic particles.

Prominence

A solar prominence is a large, bright feature that erupts from the surface of the Sun. It is made of relatively cool plasma and usually has a loop shape. Prominences can loop hundreds of thousands of miles into space and stick around for several months. They are anchored to the Sun's photosphere by magnetic activity and extend outward from the corona. In this picture, the prominence is the looped feature on the top right side of the Sun.

1. What are the main features of a solar prominence?

A solar prominence is a loop-shaped featur e that erupts from the surface of the Sun.

Characteristics

The Moon is Earth's only natural satellite. A satellite is a body that moves around a larger body in space. The Moon orbits Earth in the same way that Earth orbits the Sun. The Moon remains close to Earth because of the strength of Earth's gravity. The Moon is about 3,200 kilometers in diameter, about one-sixth the size of Earth. Therefore, gravity on the moon is only one-sixth as strong as it is on Earth. You could jump six times as high on the moon as you can on Earth. The moon makes one complete orbit around Earth every 27.3 days. The moon also rotates on its axis once every 27.3 days. Thus, the same side of the moon always faces Earth; from Earth we always see the same side of the moon. The side of the moon that faces Earth is called the near side. The other side of the moon is called the far side. The moon makes no light of its own; it only reflects light from the Sun.

The Corona

The corona is the outermost layer of the Sun. It is also considered part of its atmosphere. It has a temperature of two to five million degrees Celsius and it is hotter than the visible surface of the sun, or photosphere. The corona is a type of plasma that extends millions of kilometers into space.

The Photosphere

The photosphere is the visible surface of the Sun. This is the region of the Sun that emits sunlight. It is also one of the coolest layers of the Sun — only about 6700 degrees Celsius.

2. Describe the surface features of the Moon.

The Moon has no water, no atmosphere, and no life. It is covered by impact craters, low areas, called maria, and highlands, called terrae.

Surface

The Moon has no water, no atmosphere, and therefore, no life. The footprints left there by astronauts will most likely remain unchanged for thousands of years, because there is no wind, rain, or living thing to disturb them. The lunar landscape is covered by large valleys, mountains, and craters caused by the impacts of meteorites that crashed into the Moon from space. The craters are bowl-shaped holes on the Moon's surface. Because the Moon has no water, wind, or weather, the craters remain unchanged, unlike features on Earth's landscape.

Surface Features of the Sun

The Sun is a mighty, active star that we rely on each day. The following game will help you check your understanding of terms related to the Sun's surface features.

Sun

The Sun is a sphere, but unlike Earth and the Moon, it is not solid. Most atoms in the Sun exist as plasma, or a fourth state of matter made up of superheated gas with an electrical charge. In the Sun, these gases consist almost entirely of the elements, hydrogen and helium. Because the Sun is not solid, it does not have a defined outer boundary. It does, however, have a definite internal structure. The Sun has several identifiable layers. Click each number in the image to learn about them.

Recall how the solar system formed from a planetary nebula. Where did most of the mass in the solar system end up?

Most of the mass ended up in the center, which is the part that became our Sun. Even with their enormous combined mass, all of the planets account for only 0.02 percent of the total mass of the solar system. The remaining 99.8 percent of mass in the solar system comes from just the Sun alone.

Solar Flares and Solar Wind

Near the magnetic areas around sunspots, there are sometimes solar flares, which are violent explosions that release huge amounts of energy. They release streams of highly energetic particles that make up the solar wind. The solar wind can be dangerous to spacecraft and astronauts because it sends out large amounts of radiation, which can harm the human body.

Earth's Moon

Of the inner planets, only Earth and Mars have moons. Earth's moon is the only other object in the solar system we Earthlings have visited. Its features have fascinated humans for thousands of years. Click through each tab to learn more about the Moon.

The Sun, Moon, and Inner Solar System: Introduction

On July 20, 1969, hundreds of millions of people all over the world excitedly sat in front of their televisions and witnessed something that had never happened before in the history of the world. On that day, two American astronauts, named Neil Armstrong and Edwin "Buzz" Aldrin, landed the Eagle on the surface of the Moon. Neil Armstrong was the commander of the mission. He was the first human to ever step foot on the Moon. Besides Earth, human hands had never touched another object in space. Even today, the Moon remains the only other body in space that humans have visited Between 1969 and 1972, six piloted spaceships were sent to land on the Moon. They are often referred to as lunar expeditions, the word lunar meaning "related to the Moon." On some missions, the astronauts brought back soil and rock samples from the Moon. Once back on Earth, the samples were studied to help scientists learn about the Moon's surface features. No astronauts have visited the Moon since 1972, but in 2010, United States President Barack Obama called for new missions to parts of the inner solar system, including asteroids and even the planet Mars. Maybe you can be one of the astronauts to return to the Moon or one of the first to visit Mars!

The Sun

Our Sun is a main sequence star that provides light and heat and supports almost all life on Earth. It is the center of the solar system and, by far, the largest object in our solar system.

The Radiative Zone

Outside the core is the radiative zone , which has a temperature of about 3.8 million degrees Celsius. The energy released in the core travels extremely slowly through the radiative zone. This is because photons (particles of light) can only travel a few millimeters before they hit another particle in the Sun. They are absorbed and then released again. Thus, it can take a photon as long as 50 million years to travel all the way through the radiative zone.

1. Explain how the Moon probably formed

Scientists believe that the Moon was formed about 4.5 billion years ago. While we are not completely sure of the details of how the Moon formed, the current hypothesis is that the moon formed when Earth was about 70 million years old. Unde r this hypothesis, an object from space, called Theia, collided with Earth and sent trillions of tons of magma and rock into Earth's orbit. Eventually, gravity pulled all of this material together to form the moon. This idea of how the Moon may have formed is called the giant impact hypothesis

Formation

Scientists believe that the Moon was formed about 4.5 billion years ago. While we are not completely sure of the details of how the Moon formed, the current hypothesis, called the giant impact hypothesis, is that the Moon was formed when Earth was about 70 million years old. Under this hypothesis, an object from space, called Theia, collided with Earth and sent trillions of tons of magma and rock into Earth's orbit. Eventually, gravity pulled all of this material together to form the Moon. It is supported by the fact that the material studied from the Moon's surface is close in composition to the materials on Earth's surface. In the animation, you see the Sun in yellow, Earth in blue, and Theia in black. It shows how Theia may have collided with Earth and sent fragmented material into orbit around Earth. The explosive impact that likely led to the formation of the Moon would have produced a huge amount of energy, leaving the surface of the Moon in an initially molten state. This means that its surface would have been hot and fluid, like magma inside Earth today. The magma eventually cooled and hardened so that the Moon now has a solid surface.

Sunlight

Sunlight is emitted from the Sun's photosphere. Only a fraction of the light that travels from the Sun reaches Earth. It travels in a range of energies, including visible light, ultraviolet light, and infrared radiation. Visible light exists at energies that we can perceive with our eyes. Ultraviolet and infrared radiation are not perceived by our eyes, but their effects can still be detected. For example, ultraviolet radiation causes sunburn when you spend too much time in the Sun. Sunlight allows photosynthesis to take place. During this process, green plants use sunlight and oxygen to produce the materials they need to grow.

Sunspots

Sunspots are the most noticeable surface feature of the Sun . They are dark areas characterized by lower temperatures than their surroundings. Sunspots are only visible with special light-filtering lenses. They exhibit intense magnetic activity

The Chromosphere

The chromosphere is the zone that lies directly above the photosphere, and is part of the solar atmosphere. The chromosphere is heated by energy from the photosphere.

The Convection Zone

The convection zone surrounds the radiative zone. In the convection zone, hot material from near the Sun's center rises, cools at the surface, and then plunges back downward to receive more heat from the radiative zone. This movement helps to create solar flares and sunspots, which you will read more about later on.

The Core

The core is the innermost, or central, layer of the Sun. Its temperature is around 27 million degrees Celsius. In the core, nuclear reactions combine hydrogen atoms to form helium, releasing vast amounts of energy in the process. The energy released then begins to moves outward, towards the outer layers of the Sun.

Interior

Like Earth, the Moon has a distinct crust, mantle, and core. The crust is composed mainly of the minerals oxygen, silicon, magnesium, and aluminum. The mantle is composed of the minerals, olivine and orthopyroxene. Analysis of moon rocks indicates that there may also be high levels of iron and titanium in the lunar mantle. The composition of the Moon's core is not known for sure, but it is probably made mostly of iron with some sulfur and nickel. This information is gathered both from rock samples gathered by astronauts and from unpiloted spacecraft sent to the Moon.

Category 1: Mercury 100 Mercury is the ____ planet. hottest most weathered smallest 200 Mercury's atmosphere is ______. very thick virtually non-existent similar to Earth's 300 Mercury has no weather core temperature 400 How many moons does Mercury have? 0 2 5

Answers 1. 3 Feedback: Mercury is the smallest planet in the solar system. 2. 2 Feedback: Mercury's atmosphere is virtually non-existent. 3. 1 Feedback: Mercury has no weather becaus e its atmosphere is too insufficient. 4. 1 Feedback: Mercury has no moons.

Asteroid Belt

Content: Asteroids are objects that are smaller than the planets and that orbit the Sun. A major belt of asteroids is just after Mars in the inner solar system. Audio: Asteroids are objects that ar e smaller than the planets and that orbit the sun. Just after Mars in the inner solar system, there is a major belt of asteroids. In a way, they mark the boundary between the inner and outer solar system. They are between Mars, part of the inner solar system, and Jupiter, part of the outer solar system. Asteroids are made mainly of rocky and metallic minerals. They range in size from microscopic to hundreds of kilometers across. While there are millions of asteroids within the asteroid belt, spacecraft are still able to routinely pass through it without incident. The asteroids were probably never able to merge together and form a larger planet because of gravitational influences from Jupiter. [Image]: http://en.wikipedia.org/wiki/File:InnerSolarSystem-en.png

Earth

Content: Earth is the third planet from the Sun and the only planet known to support life. It has an oxygen- rich atmosphere and abundant liquid water. Audio: Earth is the third planet from the Sun and the only planet known to support life. It has an oxygen- rich atmosphere and abundant liquid water. Earth ha s more oxygen in its atmosphere than any other planet, and that oxygen-rich atmosphere is derived from the influence of life on the planet. Early in its geologic history, ancient photosynthesizing organisms altered Earth's early atmosphere and turned it into the oxygen-rich atmosphere of today . Earth's atmosphere makes all animal life on Earth possible. Earth is the only planet among the inner solar system known to have current geological activity. [Image]: http://en.wikipedia.org/wiki/File:The_Earth_seen_from_Apollo_17.jpg

Mars

Content: Mars is the fourth planet from the Sun and is known as the Red Planet. Audio: Mars is the fourth planet from the Sun and is known as the Red Planet. The red color of Mars' surface comes from iron oxide materials in its soil. It has a carbon dioxide atmosphere and a surface covered with extinct and ancient volcanoes. Though t he volcanoes are no longer active, they may have erupted up until about two million years ago. Mars has two moons. [Image]: http://en.wikipedia.org/wiki/File:Mars_Hubble.jpg

Mercury

Content: Mercury is the closest planet to the Sun and the smallest planet in the solar system. It has virtually no atmosphere, no weather, and no moons. Audio: Mercury is the closest planet to the Sun and the smallest planet in the solar system. The name Mercury comes from the Roman god of commerce, travel, and thievery. Mercury most likely received this name due to its fast motion in the night sky; it c an make one complete orbit around the Sun in just 89 days because its orbit is so small. Mercury is a dense planet with high iron content in its core. Its surface is covered with craters, much like our own moon. Mercury has virtually no atmosphere, so during the day it can reach temperatures of 800 degrees Fahrenheit; but at night, when it faces away from the Sun, it dips down to -280 degrees. This is the most extreme temperature difference among all the planets in the solar system. But because Mercury has such a puny atmosphere, it does not have weather. Mercury also has no moons. [Image]: http://en.wikipedia.org/wiki/File:Mercury_in_color_-_Prockter07_centered.jpg

Venus

Content: Venus is the second planet from the Sun. It is the hottest planet in the solar system and has a thick atmosphere of greenhouse gases. Audio: Venus is the second planet from the Sun. It is the hottest planet in the solar system and has a thick atmosphere of greenhouse gases, mostly carbon dioxide. Its atmosphere is so thick that we cannot see its surface, even with powerful telescopes. The surface of Venus is made mostly of basaltic rock. This tells us that it underwent major volcanic activity at so me point in the past. While Venus is similar to Earth in size and distance from the Sun, its climate makes it completely uninhabitable. It is a sweltering 400 degrees Celsius and the thick carbon dioxide atmosphere would choke out any living thing. Also, it probably rains sulfuric acid on Venus. [Image]: http://en.wikipedia.org/wiki/File:Venus_globe.jpg

3. What evidence do we have to support the giant impact hypothesis?

It is supported by the fact that the material studied from the Moon's surface is close in composition to the materials on Earth's surface.

Maria and Terrae

When you look at the Moon from Earth, you notice dark areas and light areas. The dark areas are called maria. They are solid pools of basaltic lava that erupted billions of years ago and hardened. From about 3.0 to 3.5 billion years ago, magma below the Moon's surface frequently erupted in a process known as mare volcanism. Volcanic activity on the Moon stopped about 1.2 billion years ago. The lighter parts of the Moon are called terrae or highlands. They are higher than the maria and include several high mountain ranges. They are believed to be the rims of ancient impact craters. In this image you see points of high elevation in red and points of lower elevation in blue. Notice how the far side of the moon has very few maria but lots of terrae or highlands.

Surface Activity of the Sun

When you think about the surface of Sun, sunlight is probably the feature that comes to mind. But there is much more going on at the Sun's surface than just the emission of sunlight. Click through each of the tabs to learn about some of the Sun's surface features.