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Content Benchmark E.8.B.2
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Earth Science
Atmospheric Process and Water Cycle
Solar System and Universe
Earths Composition and Structure
Content Areas
Nature of Science (NOS)
Life Science
Earth Science
Physical Science

Students know the solar system includes a great variety of planetary moons, asteroids, and comets. I/S

Mankind has been intrigued by the cosmos, perhaps since we were first capable of cognitive thought. As we’ve gazed upon the night sky, our imaginations have run wild. We have seen mystical beings in the patterns of stars (Figure 1) and attributed to them powers and control over our daily lives and future destinies (think astrology, horoscopes and the Zodiac) ( and,

Figure 1. Leo the Lion

We observed that some stars seemed to wander across the sky. These wandering stars (planets) found places both in Greek and Roman mythology as gods and goddesses ( The appearance of comets was a source of terror to our ancestors, as comets were thought to foreshadow disaster ( Figure 2 is from the 11th century Bayeux Tapestry which appeared in the sky during the battle of Hastings. England was conquered by the French army, and King Harold II died in the battle.

Figure 2. Depiction of comets as an evil omen

Earth’s closest celestial body has spurred our dreams and mind’s eye, as well. Who didn’t grow up looking for the Man in the Moon (Figure 3)? Which of us didn’t long for a taste of the Moon’s green cheese? And how did the cow manage to jump over the Moon?

Figure 3. The Man in the Moon from Le Voyage Dans La Lune

Students are taught at a young age that the planets orbit our sun, and that the Moon orbits Earth. Our moon is the most obvious non-planetary satellite, easily visible to the naked eye. Comets are likely the second solar object recognized not as a planet, but still as an object which orbits the sun. Edmund Halley, in 1705, calculated the orbit of what he believed to be the same comet which had visited previously in 1531, 1607, and 1682. His calculations were supported when the comet (now his namesake) reappeared in 1758 ( In the 1950s, Jan Oort and Gerald Kuiper postulated two primary sources for comets, the Oort Cloud which is found as a spherical cloud surrounding our solar system, ( and ( and the Kuiper Belt, which exists as a disk within the plane of the ecliptic, just beyond Neptune’s orbit ( (Figure 4).

Figure 4. The Oort Cloud and Kuiper Belt
( From

Many people have seen meteors (shooting stars), but it took longer to correlate Earth’s periodic meteor showers with comets. The Workshop on Dust in Planetary Systems 2005 reported, “The idea that the fragmentation of comets is a source of meteoroids causing meteor showers on Earth was first proposed following the 1872 and 1885 Andromedid storms, which followed the breakup of lost comet 3D/Biela in 1832, and the continued fragmentation of the comet observed in the returns of 1846 and 1852.” (

While periodic meteor showers were found to correspond with current and old cometary orbits, there have occurred meteor strikes on Earth which did not originate in conjunction with comets. Asteroids, the source for these other meteors, were discovered in 1801 by Giuseppe Piazzi, though neither he nor his contemporaries would realize the relationship. Piazzi was searching the region of space between the orbits of Mars and Jupiter (Figure 5), in the general area predicted by the Titus-Bode Law (purported by early astronomers to calculate planetary distances from the Sun) to hold a yet undiscovered planet.

Figure 5. Location of Asteroid Belt

Initially, Piazzi thought he had discovered a comet, but upon analyzing its orbit, realized it did behave more like a planet than a comet in its path of revolution about the Sun. He named this first asteroid, the largest ever cataloged, Ceres ( A few more asteroids were detected in the years after Piazzi’s discovery, and by the end of the 19th century, a few hundred asteroids had been located. It has been calculated that the combined mass of all the asteroids is less than that of Earth’s moon ( Once astronomers understood that the asteroid belt contributes heavily to the meteorites impacting Earth, they began detailed studies of the orbital paths of the asteroids, paying particular attention to asteroids whose orbits bring them very close to Earth (Near Earth Asteroids) ( Of particular concern is Apophis, an asteroid which, on April 13, 2029, will pass by Earth at a distance of 22,000 miles (just beneath the level of Earth’s high-altitude artificial satellites) (
). If Apophis were to impact the Earth, it would likely have results similar to or exceeding the impact event which resulted in the extinction of dinosaurs.

The meteorites which strike Earth are derived primarily from comets or asteroids, but some have origins from our Moon and from Mars. These latter meteorites are believed to have been blasted, respectively, from the crust of the Moon and the crust of Mars when those solar bodies were themselves impacted by meteorites. Characteristics of all the types of meteorites which have been found on Earth are described at the following web site

Earth has a moon. We’ve know this since humans first watched the night (and even daytime) sky. But do other planets have moons? The answer is yes! Interestingly, the first moons orbiting a planet other than Earth were discovered not on the planet nearest Earth with moons (Mars) but on Jupiter, a planet almost eight times as far from Earth as is Mars. In 1610, Galileo was studying Jupiter through his telescope. Over a period of several weeks, he realized what had appeared to be stars nearby Jupiter (which kept changing their positions) were actually bodies in orbit about Jupiter. These are the Galilean moons knows as Io, Europa, Ganymede and Callisto for more information visit

As telescopes have improved, and as we have sent exploratory satellites to visit the planets in our solar system, we have discovered that the only planets without moons are Mercury and Venus. Earth has one moon, Mars has two, the Jovian planets all have several moons, and Pluto (if you still elect to call this recently demoted solar body a planet) has three known moons.

More information on the moons of these planets can be found using the followings URLs:

It should be noted that another category of object found in orbit around planets are “rings.” Rings have been discovered around Jupiter, Saturn, Uranus and Neptune. They appear to have formed from different causes, but all are found within that planet’s Roche Limit (see #4 under Intervention Strategies and Resources for an explanation of the Roche Limit). The rings themselves are small bodies made of dust, rock and ices found in sequences of orbital disks around those planets ( Specific information on the rings of the Jovian planets follow:





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Content Benchmark E.8.B.2

Students know the solar system includes a great variety of planetary moons, asteroids, and comets. I/S

Common misconceptions associated with this benchmark

The following misconceptions were listed on the website for Amazing Space – Myths vs Realities for the Solar System which can be accessed at
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1. Students incorrectly believe the rings of Saturn are solid disks.

Many photographs of Saturn make it appear that there are a series of solid ring-shaped disks of differing widths sequenced about Saturn. Unless more closely inspected, students do not realize that the solid “appearance” is the result of many closely-spaced small fragments. A simple analogy would be that the picture on a television screen appears to be a smooth, solid image when seen from a normal viewing distance. But, get right next to the screen and you can ascertain that the image is made of thousands of discreet pixels.

Further information about planetary rings can be found at and,

2. Students have misconceptions that the solar system is made up of only the Sun and eight planets.

The primary focus of space education in the early grades is on the Sun, planets, and Earth’s moon. Some students get the idea that anything else which might be seen in the solar system entered from outside the solar system. Such a notion is reinforced as people talk of “falling stars” when referring to meteors.

An excellent resource which covers all the objects in our solar system is the Nine Planets website, found at

3. Students incorrectly believe comets are composed of the same material as asteroids

Students might learn that both asteroids and comets contribute to the stream of meteors and meteorites which strike Earth. It may seem logical to them that since meteors are derived from both asteroids and comets, the composition of asteroids and comets would be the same.

For more information on the composition of asteroids and the composition of comets, visit and,

4. Students have difficulty understanding that other stars and galaxies are NOT part of the solar system

As students star gaze and learn about astronomy, they learn names of constellations while also being taught how to recognize and name the planets. It is difficult for students to conceive of the great distances involved, and it is not readily apparent that not only are the stars at different distances from Earth, so are the planets. So…it seems as though the stars and planets are all within the same frame of reference, and therefore all part of the solar system.

The Planetary Society provides a good website with additional information regarding the objects which reside within our solar system (

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Content Benchmark E.8.B.2

Students know the solar system includes a great variety of planetary moons, asteroids, and comets. I/S

Sample Test Questions

1st Item Specification:  Recognize the difference between moons, asteroids, and comets.

Depth of Knowledge Level 1

  1. Each of the following are objects found in our solar system EXCEPT
    1. quasars.
    2. comets.
    3. asteroids.
    4. planets.
  1. Planets known to have rings include each of the following EXCEPT
    1. Uranus.
    2. Mercury.
    3. Jupiter.
    4. Saturn.
  1. Asteroids are located in a
    1. spherical cloud-like region surrounding our solar system.
    2. disk-like layer found a little beyond Neptune’s orbit.
    3. wide belt found within the gaps of the rings of Saturn.
    4. region of space between the orbits of Mars and Jupiter.
  1. Which of the following is an accurate comparison of the orbits of moons, comets and asteroids?
    1. Moons, comets and asteroids all are found in orbit around planets.
    2. Moons orbit planets, but comets and asteroids are in orbit about the sun.
    3. Moons are in orbit about the sun, while comets and asteroids orbit planets.
    4. Moons and comets orbit planets, but asteroids orbit both planets and the sun.
  1. Earth’s moon was first to be seen.  The next moons to be discovered in the solar system were found in orbit around the planet
    1. Jupiter.
    2. Mars.
    3. Saturn.
    4. Venus.
  1. Comets are one of the sources of meteorites which strike Earth.  The other source is
    1. stars.
    2. solar flares.
    3. asteroids.
    4. small moons.

Depth of Knowledge Level 2

  1. Which one of the following answers is the best explanation as to why the gas giant planets have so many moons as compared to the inner planets?
    1. Solar flares burned up the very small moons associated with the inner planets.
    2. The gas giant planets have a stronger gravitational pull capable of holding more moons.
    3. The inner planets rotate so rapidly that they throw off the moons.
    4. New moons periodically grow from the thick atmospheres of the gas giant planets.
  1. Use the diagram below illustrating the main asteroid belt in the solar system to answer the following question.


  1. Which statement MOST accurately describes the asteroid belt?  The asteroid belt
    1. is located between 2.7 and 22 astronomical units from the sun.
    2. has an orbit which is breaking apart, and it will soon vanish from the solar system.
    3. consists of many individual asteroids scattered in a wide band throughout its orbit.
    4. is located more closely to the orbit of Jupiter than it is to the orbit of Mars.
  1. Moons have more similarities to planets than do asteroids.  Each of the following is a correct example of a similarity between moons and planets EXCEPT
    1. many moons and most planets have measurable atmospheres.
    2. volcanic eruptions have been observed both on moons and planets.
    3. liquid matter has been found to exist on some moons and some planets.
    4. moons and planets both have been discovered with living organisms.
  1. Which of the following statements describing comets and asteroids is accurate?
    1. Comets and asteroids are similar to each other in that both develop tails in the portion of their orbit nearest to the sun.
    2. After comets have burned off all their ices and gases, the leftover rocky debris migrates to a new orbit within the asteroid belt.
    3. Each revolves around the sun, but the orbital period of comets is far greater than is the orbital period of asteroids.
    4. Asteroids are the seed from which comets form as vapors from the solar wind are deposited in icy layers around the rock.

Constructed Response E.8.B.2.

1. Use the diagram and information on the orbits of comets and asteroids to answer the question below. 

Both asteroids and comets are found in orbit about the Sun.  The majority of asteroids are located in a belt between the orbits of Mars and Jupiter.  The white arrow outside Jupiter’s orbit indicates the direction of revolution of asteroids within the asteroid belt.  Comets originate in the Oort Cloud.  The Oort Cloud is a spherical cloud surrounding our solar system, and contains billions of comets.  The many arrows above and below the orbital plane of planets in the solar system show the chaotic orbits of comets, and one comet is pictured in an orbit which takes it into the inner solar system.


  1. Describe similarities and differences of the orbital path of asteroids and the orbital paths of comets.
  2. Two asteroids have been labeled A and B.  Two comets have been labeled C and D.  Identify which of those, the two asteroids or the two comets; most likely have a similar orbital path and period of revolution.  Explain your reasoning.

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Content Benchmark E.8.B.2

Students know the solar system includes a great variety of planetary moons, asteroids, and comets. I/S

Answers to Sample Test Questions

  1. A, DOK Level 1
  2. B, DOK Level 1
  3. D, DOK Level 1
  4. B, DOK Level 1
  5. A, DOK Level 1
  6. C, DOK Level 1
  7. B, DOK Level 2
  8. C, DOK Level 2
  9. D, DOK Level 2
  10. C, DOK Level 2

Constructed Response E.8.B.2 Score Rubric:

3 points

Response addresses all parts of the question clearly and correctly.

  1. Asteroids and comets are similar in that both revolve around the Sun in measurable orbits.  Differences are that asteroids orbit within the plane of the ecliptic and generally in the same direction of revolution, while the orbits of comets are randomly oriented to the plane of the ecliptic and the direction of revolution of comets is widely variable. 
  2. The two asteroids, A and B, will have the most similar orbital path and period of revolution.  This is because they are located within the same plane and are closer to the Sun than are comets C and D.

2 points

 Response addresses all parts of the question and includes only minor errors.

1 point

 Response does not address all parts of the question. 

0 points

 The response is totally incorrect or no response provided. 

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Content Benchmark E.8.B.2

Students know the solar system includes a great variety of planetary moons, asteroids, and comets. I/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. Views of the Solar System

The website, View of the Solar System, provides detailed descriptions on the origin and composition of comets. Animations help students understand how comets orbit our Sun and why they develop tails. Many resources are provided that discuss historic and recent comets.

To access this site, go to

2. Nine Planets

The Nine Planets website is a wealth of information on the solar system. This particular link discusses many aspects of asteroids. The composition of asteroids is addressed, as is their location, their sizes, and historic aspects of asteroids. Photos of various asteroids are included, and links to other sites on asteroids is provided.

To access this site, go to

3. Moons of the Solar System

Space Today Online has a link (Moons of the Solar System) which is quite detailed in its description of the moons of each of the planets which have moons (including Earth’s moon). Information on moons in general is given, and then the moons of the planets are discussed, with extra, outside links provided with which to obtain more information.

To access this site, go to

4. Planetary Rings

This website briefly addresses the characteristics of the rings of each of the ringed planets. It discusses the Roche limit and describes the role of shepherd moons in ring dynamics.

To access this site, go to

5. Planetary Rings Node

This website provides very detailed information on the rings of Jupiter, Saturn, Uranus and Neptune, each at their specific URL, respectively. Images, animations and links to other sites are included.

To access the sites related to the Jovian planets, go to
Jupiter (
Saturn (
Uranus (
Neptune (

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Support Pages

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Sample Questions:
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Intervention Strategies & Resources:
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Benchmark Related Vocabulary

Planetary moon
Solar system