The Moon A look at our nearest neighbor

The Moon A look at our nearest neighbor in Space!

What is the Moon? • A natural satellite • One of more than 96 moons in our Solar System • The only moon of the planet Earth

Location, location! • About 384, 000 km (240, 000 miles) from Earth • 3, 468 km (2, 155 miles) in diameter (about ¼ the size of Earth)

Birth of the Moon First Stage • Moon was once part of the Earth. • A large body collided with Earth creating debris • Earth’s gravity eventually caused the Moon to form

Second Stage • Initially a sphere of molten rock • Eventually, this mix of rock separated. Third Stage • The outer surface cooled, forming a crust. • Craters started to form from impact with meteoroids. • Meteoroids decreased • Moon cooled completely • Moon changed little in 3 billion years

Cut to the Core • Crust - about 70 km thick • Mantle • Core - radius is 300 -425 km

The Moon’s Surface • No atmosphere • No liquid water • Extreme temperatures – Daytime = 130 C (265°F) – Nighttime = 190 C (-310 F) • 1/6 Earth’s gravity

The Moon’s Surface • Lunar rocks and dust covering the surface is called the regolith • 1 – 6 meters deep • The lack of an atmosphere let many more meteorites strike the moon’s surface, creating this layer of crushed rock. • Anorthosites = light-colored, coarse-grained rocks in the lunar highlands. • Breccia = contains fragments of other rocks that have melted together

Lunar Features - Highlands • Mountains up to 7500 m (25, 000 ft) tall • Rilles (trenchlike valleys)

Lunar Features - Craters • • Bowl shaped depressions Up to 2500 km (1, 553 miles) across Most formed by meteorite impact on the Moon Some formed by volcanic action inside the Moon

Lunar Features - Craters • Marks left from displaced debris after impacts are called rays

Lunar Features - Maria • Originally thought to be “seas” by early astronomers • Darkest parts of lunar landscape • Filled by lava after crash of huge meteorites on lunar surface 3 -4 billion years ago • Mostly basalt rock

Craters Maria

Movements of the Moon • • Orbit is an ellipse, not circular Apogee (farthest from Earth) Perigee (closest to Earth) Revolution – Moon orbits the Earth every 27 1/3 days The moon rises in the east and sets in the west The moon rises and sets 50 minutes later each day Rotation – Moon turns on its axis every 27 days Same side of Moon always faces Earth

Often Referred to the…. Dark Side of the Moon

Far Side of the Moon • First seen by Luna 3 Russian space probe in 1959 • Surface features different from near side – More craters – Very few maria – Thicker crust

It’s Just a Phase • Moonlight is reflected sunlight • Half the moon’s surface is always reflecting light • From Earth we see different amounts of the Moon’s lit surface • The amount seen is called a “phase”

Waxing and Waning • • • New moon Waxing Crescent moon First Quarter moon Waxing Gibbous moon Full moon Waning Gibbous moon Third Quarter moon Waning Crescent moon New moon

FOUR MAIN SHAPES FULL QUARTER CRESCENT GIBBOUS

Moon Phases New Moon – the moon is between the sun and the earth, and we see the unlighted side. No lighter area of the moon is visible from Earth. As the sun continues to move, part of the moon becomes visible. When the size of the visible portion is increasing, and we first see a sliver of the moon, it is called the waxing-crescent phase

When the moon has moved through one quarter of its revolution, the moon looks like a semicircle, called a firstquarter phase. The lighted portion of the moon continues to increase, making it larger than a semicircle which is called the waxing-gibbous phase.

Halfway through its orbit, the Earth is in between the Sun and the Moon, creating a full moon phase. The entire half of the moon is reflecting light off the sun at this phase The moon continues, now decreasing in the amount of lighten surface. When the moon is not full anymore, but decreasing back to a semicircle, it is called a waning-gibbous pha Eventually, the moon reaches a semi-circle again, called the last-quarter phase. The moon continues, now decreasing in the amount of lighten surface. When the moon is not full anymore, but decreasing back to a semicircle, it is called a waning-gibbous phase.

Eventually, the moon reaches a semi-circle again, called the last -quarter phase. The light continues to decrease, when finally only a sliver of the moon is visible, which is called the waning-crescent phase.

The moon is now back where it started, and the process repeats. The whole process takes 29. 5 days (an extra 2 days is needed from the 27. 3 days for the moon to get back to its original position) This means that you usually have one of each phase per month. Sometimes, two full moons happen in one month. The second full moon of a month is usually called a blue moon.

Plane of earth’s orbit Moon Earth Moon Plane of lunar orbit

Lunar Eclipses • Moon moves into Earth’s shadow, darkens the Moon – Umbra: center, all sunlight is blocked – Penumbra: outer part of shadow sunlight partially blocked. • About 2 -3 per year • Last up to 4 hours

Solar Eclipses • Moon moves between Earth and Sun • Moon casts a shadow on part of the Earth • Total eclipses rare – only once every 360 years from one location!

The Tides • Tides caused by pull of Moon’s gravity on Earth • High tide – – Side facing Moon and side away from Moon – Every 12 hours, 25 ½ minutes • Low tide – – On sides of Earth