11 Spectacular Facts About the Moon

Matt Cardy/Stringer, Getty Images
Matt Cardy/Stringer, Getty Images

The Moon is Earth’s closest satellite in our solar system, but in many ways, we hardly know our neighbor. Scientists aren’t entirely sure how it formed, and other facts, like its shape (more egg-like than spherical), and the consistency of its surface (dusty but firm), were confirmed only recently. With the 50th anniversary of the Apollo 11 Moon landing this year, and NASA preparing to return to the lunar surface for the first time in decades, it’s time to brush up on these facts about the Moon—from colorful names for full moons to the first landing on the dark side of the Moon.

1. The Moon may have formed when a giant object in the solar system hit Earth.

Scientists aren't in total agreement on how the Moon formed, but the most widely accepted theory is the giant impact hypothesis. According to this theory, an object the size of Mars called Theia collided with Earth 4.5 billion years ago when the solar system was still new and chaotic. The impact dislodged matter from Earth’s crust, and the debris attached to whatever was left of Theia through the force of gravity.

This scenario would explain why the Moon is made up of lighter elements found in Earth’s outer layer, but it still leaves some questions unanswered. If the giant impact hypothesis is correct, about 60 percent of the Moon should consist of the impact object. Instead, its composition is almost identical to that of Earth. There are alternative explanations: one posits that the Moon is a space object that got caught in Earth’s orbit, and another one suggests the Moon and Earth formed at the same time, but none is as popular as the giant impact theory.

2. The Moon is the perfect size for solar eclipses.

Moon covering sun during solar eclipse.
Masashi Hara/Getty Images

A lucky set of circumstances make total solar eclipses, as seen from Earth, possible. The Moon is just the right size and distance from our planet to appear as the same size as the Sun in the sky. When the Moon passes between the Sun and the Earth, it covers the Sun perfectly with an impressive corona illuminating its edges. If it were any smaller or farther from Earth, it would look like a blot on the Sun during a solar eclipse.

3. A full Moon has different nicknames in different seasons.

A full moon can have many colorful names, but they don’t always describe a special celestial phenomenon. Some are used to refer to a full moon that appears during a certain time of year. A harvest moon, which is the full moon closest to the autumn equinox, is the best-known example, but there are many others, including a wolf moon (first full moon of January), strawberry moon (June), and sturgeon moon (August).

4. It’s the largest moon in the solar system relative to its planet.

Our Moon isn’t the largest in the solar system (that distinction goes to Ganymede, one of Jupiter’s 79 moons), but it is the biggest in relation to the planet it orbits. With a diameter of 2159 miles and a surface area of 14.6 million square miles, the Moon is a little more than one-fourth the size of Earth. The dwarf planet Pluto has an even smaller moon-to-planet ratio. Pluto’s largest moon Charon is nearly the size of its host body, leading some astronomers to refer to the pair as a double-dwarf planet.

5. The Moon is shaped like a lemon.

The Moon may look perfectly round in the night sky, but it’s actually more of an oval shape. It came out wonky billions of years ago when super-hot tidal forces shaped its crust, heating up some areas hotter than others to form a lemon shape rather than a perfect sphere. Gravitational forces from Earth have helped to exaggerate the Moon’s oblong appearance over eons.

6. Scientists thought Moon dust would cause lunar landers to sink.

Lunar module over moon's surface.
NASA/Newsmakers

When preparing to send missions to the Moon, some scientists feared that a thick layer of dust on the body’s surface would cause complications. One of the strongest proponents of the dust theory was Thomas Gold, an astrophysicist at Cornell University. He insisted that the Moon was covered in seas of dust soft and thick enough to swallow a lunar lander. Though the Moon’s surface is dusty, the layer is too thin to cause problems, as the successful landings of the Soviet Luna 9 and the American Surveyor spacecrafts proved in 1966.

7. The Moon is international property.

Astronauts Buzz Aldrin and Neil Armstrong may have planted an American flag on the Moon in 1969, but it belongs to the world. Countries like the Soviet Union and the U.S. made sure of that at the height of the space race in 1967 when they signed the Outer Space Treaty, a document declaring that the Moon would be a “global commons” and any resources discovered there would be used for the good of the world overall. In keeping with the spirit of the agreement, NASA shared soil samples taken from the Moon with Soviet scientists upon the Apollo 11 mission's return.

8. Humans have left strange things on the Moon.

Since the first people landed on the Moon in 1969, its surface has been home to more than just dust. Earth artifacts left on the Moon by astronauts include two golf balls, an obscene Andy Warhol doodle, and a message from Queen Elizabeth II. Eugene Cernan, Apollo 17 commander and one of the last people to walk on the Moon, traced his daughter’s initials into the soil when he visited in 1972. Without any wind or weather on the Moon, the letters TDC could remain there forever.

9. The "dark side of the Moon" is the result of synchronous rotation.

Even though the Moon is constantly rotating, only one side of it is visible from Earth. This is because the Moon is locked in synchronous rotation. It takes the Moon just as long to complete one full rotation as it does for the body to orbit around the Earth once, so the same side always faces our planet. This isn’t a coincidence—the Earth’s gravitational forces have gradually pulled the tip of the slightly oblong Moon to point toward the planet, creating something called tidal lock.

In January 2019, the Chinese space agency landed the first lunar probe on the unexplored dark side of the Moon. The Chang'e 4 spacecraft sent the first photographs of a massive impact crater on the dark side to Earth, giving scientists their first glimpse of that unknown region.

10. One astronaut was allergic to the Moon.

Apollo 17 astronaut Harrison “Jack” Schmitt discovered the hard way that some people are allergic to Moon matter. Following a survey of a valley in the Sea of Serenity, he climbed back into the crew’s lunar module and tracked in a lot of Moon dust with him. The dust affected him as soon as he removed his spacesuit, triggering red eyes, sneezing fits, and other symptoms that lasted two hours.

11. Humans are going back to the Moon soon.

After completing several manned missions to the Moon, NASA ended the Apollo program in 1972 as budgets tightened and public interest waned. That means most people alive today have never witnessed a manned lunar landing, but now, following a hiatus nearing 50 years, NASA is finally preparing to return to the Moon. The next manned lunar expedition will be ready to launch “no later than the late 2020s,” according to the space agency. One of the goals will be placing a command module, called Gateway, in the Moon’s orbit that astronauts can reuse over multiple missions.

A Rare ‘Full Cold Moon Kiss’ Is Coming This Week—Here’s How to See It

jamesvancouver/iStock via Getty Images
jamesvancouver/iStock via Getty Images

Every year ends with a cold moon—the name given to a full moon that appears in December. The full cold moon that's lighting up skies in 2019 will come with a bonus spectacle for sky-gazers. As Forbes reports, a planetary "kiss" between Saturn and Venus will coincide with the last full moon of the year. Here's what you need to know about the astronomical events.

What is a Full Cold Moon Kiss?

The full moon of each month has a unique nickname associated with the time of year it occurs. A cold moon happens as temperatures drop and winter settles in, hence the name. December's full moon has also been called the long nights moon by some Native American tribes and the moon Before Yule in Europe, according to Travel and Leisure.

This year's moon will be visible the night of December 11 through the morning of December 12. On this same night, the planets Venus and Saturn will appear closer than usual in the night sky. The celestial bodies will be less than 2° apart and share a celestial longitude, a phenomena known as a conjunction or a planetary "kiss."

How to See the Full Cold Moon Kiss

During twilight on Tuesday, December 10, the bright planet Venus and the dimmer planet Saturn will arrive at their closest conjunction, 1.8° apart, above the southwestern horizon. The following evening, they'll be just .01° further away. Stick around the night of Wednesday, December 11 to catch the full cold moon, which reaches peak illumination at 9:12 p.m. on the West Coast and at 12 minutes after midnight on the East Coast.

Not planning on staying up late to see the moon reach its fullest state? Moonrise on December 11 will be just as spectacular. When the moon surfaces around sunset, it will appear larger and more reddish in color in the sky. Meanwhile, Venus's and Saturn's kiss will be visible 180º away.

[h/t Forbes]

First-Ever Map of Titan Reveals That Saturn’s Moon Is a Lot Like Earth

NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho
NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho

If there's any life in this solar system outside Earth, we likely won't find it on Mars or even on another planet. Saturn's moon Titan is the place in our celestial neighborhood that's most similar to our own home, and it's where scientists think we have one of the best chances of discovering life. Now, as Nature reports, newly visualized data shows just how much Titan has in common with Earth.

Between 2004 and 2017, the NASA spacecraft Cassini performed more than 100 fly-bys of Saturn's moon. Titan is unique in that it's the only moon in the solar system with clouds and a dense, weather-forming atmosphere. This has made it hard to study from space, but by flying close to the surface, Cassini was able to capture the landscape in an unprecedented level of detail.

Map of Titan.
The first global geologic map of Titan.
NASA/JPL-Caltech/ASU

NASA's new map of Titan, published in the journal Nature Astronomy, reveals a varied world of mountains, valleys, plains, and sandy dunes that starkly contrast with the desolate wastelands we've seen on neighboring planets. It's also home to seas and lakes, making it the only place in the solar system other than Earth with known bodies of liquid. But instead of water, the pools mottling the moon's surface consist of liquid methane.

Even with its Earth-like geology and atmosphere, chances of finding life on Titan are still slim: Temperatures on the surface average around -300°F. If life does exist there, it's likely limited to microbes in the moon's craters and icy volcanoes.

It will be a while before NASA is able to study Titan up close again: NASA's next drone mission to the body is set for 2034. Until then, scientists have plenty of data recorded by Cassini to teach them more about how the moon formed and continues to change.

[h/t Nature]

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