8 Astounding Facts About the Asteroid Belt

An artist's conception of the dwarf planet Ceres in the main asteroid belt.
An artist's conception of the dwarf planet Ceres in the main asteroid belt.
ESA/ATG medialab

The asteroid belt tells the story of the creation of the solar system. When it formed, not everything coalesced into a planet. Like LEGO bricks that never made it out of the bucket, these objects were organized by physics into a ring located between the orbits of Mars and Jupiter. This is the asteroid belt. Here are some things you might not know about it.

1. THERE ARE MORE THAN A HALF-MILLION ASTEROIDS.

The asteroid belt in black and white.
iStock

Over a half-million asteroids have been discovered by scientists, with hundreds of thousands yet to be found. They are generally divided into three classes: S-type (for stony); C-type (chondrites, largely composed of carbon, the most common—and perhaps the oldest—of the bunch); and M-type (metallic). The asteroids range in length from 30 feet to 330 miles. For the most part, they are oddly shaped, and, like the planets, spin (though not always so eloquently). Some asteroids have moons; some have two. Not every asteroid is located in the asteroid belt. Some, called Trojans, share the orbit of Jupiter. Some lurk perilously close to Earth. These are called near-Earth asteroids.

2. ASTEROID MEANS "STAR-LIKE."

A night sky with a shooting star.
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The first asteroid was discovered in 1801 by Giuseppe Piazzi, though he didn't know it at the time. He thought he had discovered the long-sought planet between Mars and Jupiter. He named his discovery Ceres, after the Roman goddess of harvest (and namesake to the word cereal, though that word wouldn't be coined until 1818).

Just over a year later, another "planet" was discovered. And another. And another. Eventually, there were so many planets that astronomers threw up their hands and gave the whole group a new classification: asteroid, or "star-like" in Greek. The name was chosen because they appeared, well, star-like in telescopes; they would not resolve as discs as planets do. Ceres's run as a planet lasted about 60 years before it was demoted to asteroid. In 2006, the International Astronomical Union reclassified it again, this time as a dwarf planet. This is the same decision that designated Pluto as a dwarf planet, though there is some debate on this point.

3. ALL THE ASTEROIDS IN IT DON'T ADD UP TO MUCH.

An artists' rendering of the asteroid belt.
iStock

It's likely that illustrations you've seen of the asteroid belt are not drawn to scale. If all of the objects in the asteroid belt were brought together and made into a single ball, its combined mass would only be 4 percent of the size of the Moon. In fact, Ceres alone accounts for one-third of the total mass of the asteroid belt. 

4. FLY YOUR SPACESHIP INTO IT. YOU WON'T HIT ANYTHING.

A little girl plays with a toy rocketship in a space system.
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What’s the biggest misconception that people have about the asteroid belt? Mental Floss asked Dante Lauretta, the principal investigator of the OSIRIS-REx mission to the asteroid Bennu (which once lived in the main asteroid belt before being jarred loose by Saturn and sent on a course for the inner solar system). His response: The Empire Strikes Back. People imagine "that it's this tumbling, highly energetic boulder field with things crashing into each other constantly, and Han Solo has to dodge and weave to avoid collisions," Lauretta says.

But the asteroid belt is downright spacious. If the arcade game Asteroids were real, it would pretty much consist of a ship and a black screen and … nothing to shoot. "When you fly a spacecraft through the asteroid belt, it’s a real challenge to actually get close enough to an asteroid to see it," Lauretta explains. "You have to specifically target it." There are, on average, 620,000–1.8 million miles between asteroids.

5. THE HISTORY OF THE SOLAR SYSTEM IS HIDDEN WITHIN.

An artist's concept of the solar system.
iStock

Back in the 1980s, scientists really set about spectrally classifying each object in the asteroid belt, and they discovered a compositional gradient. There were a lot of dark, carbonaceous objects in the outer asteroid belt, and brighter, "ordinary chondritic," S-type material in the inner asteroid belt. Spectral surveys today are starting to get really detailed, and scientists are getting a good look at objects as small as 6 miles across. As they get into asteroid compositions, they are discovering a fine structure in the compositional pattern, and placing it in the context of the dynamic state of the early solar system.

"Organics and ices are going to be stable farther out [in the belt], and metals and rocks are going to be stable farther in. You expect to see that," says Lauretta. "But now you're starting to see that there really are organic-rich and water-rich materials in the main belt. It's a small fraction of it, but it's a significant fraction. And there's rocky and bright material in the outer belt." That distribution of material is a record of migration of giant planets and the dynamical evolution of the solar system.

"I think we're going to be able to piece together a much more complex, chemical-dynamical coupled model of the evolution of the solar system, and see it almost like the stratigraphic layers of the geologic record. It will tell us the story of the evolution of the belt—not just the initial protoplanetary disk which established that chemistry, but how major events in the evolution of our solar system modified that distribution."

6. SCIENTISTS ARE SEARCHING FOR ITS MOST ANCIENT OBJECTS.

An asteroid in space.
iStock

Presently, planetary scientists are trying to identify and understand the primordial structures in the asteroid belt much in the same way that paleontologists or geologists search for the earliest signs of the origin of life in the geologic record. "That's where the biggest challenge lies," says Lauretta. "There is, in the most ancient examples, a discrete signal that you've got to pull out. It's going to be very tiny."

Scientists endeavor to understand what has been preserved from the dawn of the solar system—what they can trust as a true primordial signature of how our planetary system formed—versus what has been eroded or modified or changed over 4.5 billion years of evolution. "Trying to pick out that starting condition and targeting our scientific investigations into those areas is where the greatest challenge lies."

NASA's recently announced Lucy mission to multiple asteroids will help do this. "Everybody thinks those Trojans are the ones that hold that key to the earliest, most primitive material of the solar system," says Lauretta. "The Lucy team can get out there and do some cool science."

7. ASTEROIDS ARE LIKE SNOWFLAKES.

A snowflake in snow on a dark background.
iStock

No two are exactly alike, and each one has its own story to tell. "Every asteroid is a unique world to explore, and that is awesome," says Lauretta. "There is so much diversity and so many challenges out there. When we truly get out there and start poking around, we're going to see some stuff happening that we never even dreamed of."

8. NASA IS GOING BIG ON ASTEROIDS.

An artist's drawing of Dawn firing its engines above Ceres.
NASA/JPL-Caltech

NASA's Dawn spacecraft is currently in orbit around Ceres, where it continues to characterize that object and how it changes as it circles the Sun. (It previously orbited Vesta, making it the only spacecraft to orbit two extraterrestrial bodies.) NASA's OSIRIS-REx will arrive at the asteroid Bennu in August 2018. Earlier this year, the agency approved two missions to small bodies: the spacecraft Psyche will travel to the asteroid 16 Psyche, a mysterious, all-metal world. (It might once have been the core of a protoplanet.) The Lucy mission will travel to five Trojan asteroids that share Jupiter's orbit. The Japanese Space Agency's Hayabusa 2 spacecraft will arrive next year at Ryugu (a.k.a. 1999 JU3), a near-Earth asteroid. Like OSIRIS-REx, it will take a sample and return it to Earth for analysis.

And that analysis is serious business. In the case of samples and meteorites, Lauretta says, "most people don't realize that we pick apart these things grain by grain, atom by atom, isotope ratio by isotope ratio, and put together detailed stories about what happened billions of years ago in our solar system."

A Lunar Crash May Have Left Behind a Library of Human Civilization on the Moon

Matt Cardy, Getty Images
Matt Cardy, Getty Images

SpaceIL, the Israeli-based private space travel nonprofit backed by billionaire Morris Kahn, came up short in their attempt to land the first commercial payload ever delivered on the Moon. Their Beresheet lander crashed last Thursday, April 11, after a technical glitch prompted its engine to power off and then back on, causing it to come in too fast and strike the lunar surface.

While not ultimately successful, the voyage may have still managed to mark a milestone in the history of lunar exploration. The Arch Mission Foundation, which worked with SpaceIL to put a massive amount of information—including the entirety of Wikipedia—on board, announced this week that the digital library may have survived the impact. That would make it the first substantial repository of knowledge to occupy the Moon.

The data, which was dubbed the Lunar Library, holds an impressive wealth of material—the equivalent of roughly 30 million pages in all. In addition to Wikipedia, there are books selected by Project Gutenberg, 60,000 images, language keys, and a curated selection of music. All of this humanity was packed into 25 nickel discs that are each 40 microns thick. The entire library is roughly the size and shape of a DVD.

Arch Mission Foundation believes that the discs could have survived the impact based on what's known about its trajectory and the crash and is working to confirm its existence. Even if it didn't, there's still something to be said for the idea that "archaeological ruins" of human knowledge now exist there.

The Lunar Library wouldn't be the only human relic left behind. Alan Shepard, the fifth man ever to walk on the Moon in 1971, left golf balls after playing a lunar round. In 1969, the crew of Apollo 11 left a 1.5-inch silicon disk containing goodwill messages from prominent figures in 75 countries written microscopically.

SpaceIL intends to pursue a second lunar lander, with a launch date to be announced. While other countries have landed a vehicle on the Moon—the United States, China, and Russia—this would have marked the first time for a private entity.

[h/t Fast Company]

A Blue Moon—May's Flower Moon—Is Coming Next Month

Matt Cardy/Getty Images
Matt Cardy/Getty Images

Exactly how often is "once in a blue moon"? According to NASA, the celestial occurrence isn't especially rare: A blue moon happens about once every 2.5 years. The next blue moon will appear the night of May 18, 2019, and because the event marks the first full moon of May, it will also be a flower moon.

What Is a Blue Moon?

Instead of describing color, like a blood moon, the term blue moon is reserved for an additional full moon that appears within a certain window of time. There are two types of blue moons: monthly blue moons and seasonal blue moons. A monthly blue moon, the more popular of the two definitions, is the second full moon that occurs in a single calendar month. This usage is fairly recent, and likely originated from an error printed in a 1946 issue of Sky and Telescope magazine.

A seasonal blue moon is the older meaning, and it describes the third moon in a season that has four full moons. Each season—winter, spring, summer, and fall—typically sees three full moons, and in the rare event there are four, the third is singled out as the anomaly. This is sometimes the preferred definition of astronomy-minded people because it's based on natural equinoxes and solstices rather than the Gregorian calendar.

When to See the Blue Flower Moon

The full moon set to light up the night sky in May will be a seasonal blue moon. The time of year it occurs—May—makes it a flower moon. The first full moon of each month has a special name: A worm moon is a full moon in April, and a wolf moon is a full moon in January.

To catch 2019's blue flower moon, look up the night of May 18. The Moon will be at its fullest when it's precisely at 180° ecliptic longitude opposite the Sun—which occurs at 5:11 p.m. ET on May 18.

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