1. Moon
   Sun
2. Mars
   Jupiter

The Moon is a satellite because it orbits around the Earth. A natural satellite orbits a planetary body or asteroid. Earth's moon is its only natural satellite.

1. Waning Crescent phase
   Full phase
2. New phase
   Waning Gibbous phase

On the day of a new moon phase, the Moon's orbit moves it between the Sun and the Earth. The Moon and the Sun rise and set roughly around the same time.

1. Big Bang
   Giant-impact
2. Quantum
   Relativity

According to the giant-impact hypothesis, the Moon formed from debris that resulted from the collision of Earth with an object the size of planet Mars approximately four billion years ago. Earth's moon is the largest moon relative to planet size, compared to moons of other planetary bodies in our solar system.

1. One-sixth Earth's diameter
   One-fourth Earth's diameter
2. One-eighth Earth's diameter
   One-third Earth's diameter

The Moon maintains a relatively short distance from Earth. Because of its size and distance from Earth, the Moon is the most prodigious structure in Earth's sky. The Moon's diameter is 3476 kilometers.

1. 7 billion years
   4 billion years
2. 2 billion years
   1 million years

Theoretically, the Moon is between 4 billion and 4.5 billion years old. Earth formed approximately 4.5 billion years ago. It is believed that a smaller planetary body hit Earth sometime later in its development, and a portion of the debris from that collision went into orbit and helped form the Moon.

1. 27 days
   360 days
2. 24 hours
   57 weeks

It actually takes the Moon 27 days, 7 hours and 43 minutes to complete a full revolution around planet Earth. This orbital period of the Moon is called its siderial period, a period with respect to distant stars.

1. Always east to west
   Same as Earth's rotation
2. North to south
   South to north

The Moon appears to move across Earth's sky in an east to west direction because of Earth rotational direction. The Earth rotates on its axis counterclockwise in an eastward direction when viewed from above the North Pole.

1. Air
   Water
2. Nothing
   Carbon

The Moon has no atmosphere, so it has no weather patterns. Without an atmosphere, the Moon's temperatures during the day are very hot (100 degrees Celsius), and during the night temperatures are very cold (-173 degrees Celsius).

1. Moon's core
   Earth
2. Sun
   Meteorites

The Moon does not have its own source of light. Instead, the Moon behaves like a mirror, reflecting the light of the Sun, which is why the Moon shines so prominently in Earth's night sky.

1. Edwin "Buzz" Aldrin
   Neil Armstrong
2. John F. Kennedy
   No one

Neil Armstrong was the first person to step on the Moon during the Apollo 11 lunar landing mission, which occurred on July 20, 1969. Edwin "Buzz" Aldrin was the second person to set foot on the Moon during the Apollo 11 mission.

1. Liquid-to-gas water transformation
   Ice-to-liquid water transformation
2. Ocean tides
   Coal-to-diamond transformation

In 1687, English scientist Isaac Newton mathematically explained the rhythmic rising and falling of the oceans. Gravitational forces between the Earth and the Moon cause ocean tides. The Moon pulls more forcefully on the side of Earth closest to it, and less on the side furthest from it.

1. 100,400 kilometers
   384,400 kilometers
2. 94,550 kilometers
   400 kilometers

At its closest approach, the Moon is 363,104 kilometers from Earth, and at its farthest distance, the Moon is 405,696 kilometers from Earth. According to NASA, thirty Earths could fit between the Moon and Earth.

1. Mars
   Earth
2. Jupiter
   Venus

Jupiter is also the largest planet in our solar system, and fifth in distance from the Sun. Of Jupiter's moons, "Ganymede" is the largest, with a diameter of 5,268 kilometers.

1. Earth's orbit
   Earth's gravity
2. Sun's orbit
   Moon's orbit

As the Moon orbits the Earth, we observe different lunar phases depending on which side of the Moon is facing the Sun. The side facing the Sun is always illuminated. Specific configurations of dark and light areas of the Moon's surface are what we call Moon phases.

1. Russia
   United States
2. France
   Germany

Although United States citizens Neil Armstrong and Edwin "Buzz" Aldrin took the first steps on the Moon, Russia made the first successful landing on the Moon. Russia's unmanned spacecraft from its Luna 9 mission made the first soft landing on the Moon in February 1966.

1. Lunar eclipse
   Solar eclipse
2. Night
   Day

In general, an eclipse occurs when one celestial body completely or partially obscures another. During a solar eclipse, the Moon obscures the Sun. An optical illusion makes the Moon appear larger during total, or complete, eclipses.

1. Full phase
   Waxing Crescent
2. First Quarter phase
   New phase

The Moon's First Quarter phase occurs after the Waxing Crescent phase. During the First Quarter phase, the Moon appears to be shaped like the letter "D" because the Moon's western half is illuminated.

1. New Moon
   Waxing Crescent Moon
2. Full Moon
   Third Quarter Moon

During the Full Moon phase, the Moon's entire disk is illuminated by the Sun's light. A Gibbous Moon has an illuminated area which is greater than a semicircle and smaller than a circle.

1. Moon
   Sun
2. Jupiter
   Mars

As Moon orbits Earth, it hovers near the equatorial plane of Earth, which is an invisible extension of Earth's equator into space. The position on the Earth directly beneath the Moon is never more than 29 degrees south or north of the equator.

1. Rain
   Meteoroids
2. Erosion
   Winds

During the birth of our solar system, debris from asteroids colliding with planetary bodies created meteoroids, some of which crashed into the Moon's surface and created impact craters. Scientists believe this phenomenon occurred during the first half billion years of the solar system's formation.

1. Two
   Six
2. One
   Three

Mars's moons, Deimos and Phobos, orbit close to the planet's surface. Phobos is the larger moon and is positioned closer to the surface of Mars. As with Earth's moon, Phobos's orbital period is equal to its rotational period, so its face remains the same from the view of the planet.

1. Cheese Moon
   Rare Moon
2. Orange Moon
   Blue Moon

The time between one Full Moon and the next is normally 29.5 days. However, every few years it is possible for a second Full Moon to appear in a calendar month. When this happens, one Full Moon occurs at the beginning of the month and the other Full Moon, the Blue Moon, happens at the end.

1. Helene
   Maria
2. Selena
   Luna

"Maria" is the plural form of "mare," which is the Latin word for "sea." Early astronomers thought the dark areas were oceans. Subsequent Moon explorations revealed that these regions appear darker than the other light-colored areas because of their basaltic rock composition and were formed by volcanic eruptions that occurred many years ago.

1. Luna
   Selene
2. Maria
   Verona

The Greeks worshiped the Moon goddess at the New and Full Moon phases. "Helios," the sun god, was her brother (or sometimes her father), and "Eos," goddess of the dawn, was her sister.

1. Earth
   Mars
2. Jupiter
   Venus

The Moon provides information about how the Earth was formed. Since the Earth's moon has no atmosphere, its surface is much more stable than that of Earth, which has changed considerably from geological shifting, volcanic eruptions and erosion.

1. Pies
   Rocks
2. Gold
   Diamonds

Astronauts have collected 842 pounds of rock samples from the Moon. The oldest rocks that were collected are 4.5 billion years old.

1. 63 days
   11 days
2. 29.5 days
   24 hours

A synodic period is the time it takes for a celestial body to return to the same or roughly the same position in relation to the Sun, as observed from Earth. The Moon's synodic period, or synodic month, coincides with its period of lunar phases.

1. 0.1667 g
   12 g
2. 16 g
   9.22 g

The Moon's gravity is one-sixth the gravity of Earth. The Moon's gravitational pull is not factored into Earth's net acceleration yielded to its affected objects.

1. 1,500 kilometers per hour
   5,000 kilometers per hour
2. 500 kilometers per hour
   3,683 kilometers per hour

While traveling at this rate of speed, the Moon travels a distance of 2,290,000 kilometers. And it takes the Moon 27 days to rotate on its axis, so it appears to be completely still to observers on Earth.

1. Luna
   Veronica
2. Sicily
   Helena

"Luna" is the Latin word for moon. Romans established temples for the Moon goddess on Palatine and Aventine hills, two of seven hills on which ancient Rome was built.

1. Rivers
   Sun
2. Meteoroids and comets
   Earth's atmosphere

The Moon does not have its own source of water. Meteoroids and comets from space that contain water pound the Moon. The Moon retains some of this water at its poles, but most of the water drifts into space.

1. Thirteen
   Six
2. Twelve
   Zero

Earth's mountains are abrupt elevations that formed as a result of colliding tectonic plates. The Moon does not have tectonic plates. Its surface structures are formed as a result of scarring from a continuous pelting of comets, meteoroids and asteroids from space.

1. 10% or less
   59%
2. 100%
   Only 5%

Lunar librations are oscillations that are real or ostensible to the eye. Parts near the edge of the Moon that are usually not visible from Earth sometimes become visible. Although one hemisphere of the Moon is always facing away, observers from Earth can see more than 50 percent of the Moon because its axis is slightly higher than the Earth's axis.

1. 2,600 kilometers
   600 kilometers
2. 23,500 kilometers
   13 kilometers

A meteorite crater, or impact crater, is a large hollow cavity on the Moon's surface that is caused by an explosion or impact from another celestial body. The Moon's largest crater is called "South Pole -- Aitken Basin." It measures 2,600 kilometers in diameter and is located on the Moon's far side.

1. Shuttle vehicle
   Moped
2. Lunar roving vehicle
   Dune buggy

Astronauts used the lunar roving vehicle (LRV) during the Apollo 15, 16 and 17 missions. LRVs, also referred to as "moon buggies," are electric transport vehicles designed to navigate the Moon's low-gravity surface.