National Aeronautics and Space Administration Logo
Follow this link to skip to the main content
Image of the Moon and Earth
Image of the Moon and Earth
Image of the Moon and Earth
NASA Banner
Moon: NASA's Lunar Portal
Return to Solar System Exploration
Moon Facts
Moon Fact
Once in a Blue Moon

About every 2.5 years an extra full moon, called a "Blue Moon" occurs.

The term Blue Moon is believed to have originated in 1883 after the eruption of Krakatoa. The volcano put so much dust in the atmosphere that the moon actually looked blue in color. This was so unusual that the term "once in a Blue Moon" was coined.

EYES on LADEE: Explore the Moon in 3D
Moon Facts
First Step

The first human being walked on the moon on 20 July 1969.

The Moon Festival

Did you know the Chinese and Vietnamese have a festival each year to celebrate the moon?

Weightless? Not Quite

Gravity on the moon is only 1/6 of that found on Earth.

Earth Lashing

Every month when the moon gets a lashing from Earth's magnetic tail. This has consequences ranging from lunar "dust storms" to electrostatic discharges.

Ancient Rocks

Moon-rock ages range from about 3.2 billion years in the maria (dark, low basins) to nearly 4.6 billion years in the terrae (light, rugged highlands). Active geologic forces, including plate tectonics and erosion, continuously repave the oldest surfaces on Earth whereas old surfaces persist with little disturbance on the moon.

One Small Step ...

In 2009, a NASA team restored the first grainy video of Neil Armstrong's first step on the moon.


Total weight: of the moon is 74 sextillion km (that's 81 quintillion tons).

Inverted Moon

As the astronomical telescope with its inverted image came into use, astronomers adopted the habit of representing the way they saw the moon -- upside down. This practice was followed until very recently. Lunar images are now constructed and stored digitally and can be displayed at any orientation. The moon is now typically shown right side up.

Moon Rocks

Between 1969 and 1972 six Apollo missions brought back 382 kg (842 pounds) of lunar rocks, core samples, pebbles, sand and dust from the lunar surface. In addition, three automated Soviet spacecraft returned important samples totaling 300 g (approximately 3/4 pound).

Moon Rocks

Rocks from the moon are similar to three kinds of igneous rocks that are found here on Earth: basalt, anorthosites and breccias.


Seeing the Earth rise from the moon never gets old.

Orange Rocks on the Moon

How did orange soil appear on the moon? This mystery began when astronaut Harrison Schmidt noticed the off-color patch near Apollo 17's Taurus-Littrow landing site in 1972. Astronauts scooped up some of the unusual orange soil for inspection back on Earth. Lunar geologists now think that the orange soil was created during an ancient fire-fountain.

Constant Companion

It takes about a month for the moon to orbit Earth (27.3 days to complete a revolution, but 29.5 days to change phases from new moon to new moon).

Stuffed Crust

The crust on the far side of the moon is thicker than the crust on the near side.

The far side highlands appear to have formed early in the moon's history, when a magma ocean (shaped by tides caused by Earth's gravity) heated the moon's floating crust non-uniformly. Since then, the magma ocean has solidified.

Is There an Atmosphere on the Moon?

Relative to Earth, the moon is highly depleted in iron and in volatile elements that are needed to form atmospheric gases and water. However, there is an atmosphere.

Surface Boundary Exosphere

The atmosphere of the moon, called a surface boundary exosphere, is likely the same type of atmosphere found on many other planets.

Mighty Minotaur

LADEE will be launched on an five-stage Minotaur V rocket. The first three stages of the Minotaur V are former Peacekeeper ballistic solid rocket motors. The fourth and fifth stages are commercial motors.

Out of Shape

The moon is not round, but is in fact egg-shaped with the large end pointed towards Earth.

Moon Day

A lunar day (or the time it takes from sunrise to sunrise) on the moon is approximately 708 hours.

How the Moon Was Formed

The moon was formed ~4.5 billion years ago (about 30-50 million years after the origin of our solar system) out of debris thrown into orbit by a massive collision between a smaller proto-Earth and another planetoid, about the size of Mars.

    1     2     3    
    Show All
Print This Page
> NASA Science Mission Directorate
> Budgets, Strategic Plans and Accountability Reports
> Equal Employment Opportunity Data
   Posted Pursuant to the No Fear Act
> Information-Dissemination Policies and Inventories
> Freedom of Information Act
> Privacy Policy & Important Notices
> Inspector General Hotline
> Office of the Inspector General
> NASA Communications Policy
> NASA Advisory Council
> Open Government at NASA
Last Updated: 11 Jul 2013