NASA/Goddard/Arizona State University
NASA/Goddard/Arizona State University

How Are Moon Maps Made?

NASA/Goddard/Arizona State University
NASA/Goddard/Arizona State University

At the 46th annual Lunar and Planetary Science Conference in Houston last week, I met some of the planetary scientists who use the Lunar Reconnaissance Orbiter to craft maps of the moon—those spectacular, highly detailed images that appear in textbooks and online, and which are so ubiquitous that it rarely occurs to us to ask, “How was this done?” Planetary geologic mapping, as I learned, is not merely the result of clever computer algorithms painting photographs onto wireframe spheres (though computers have their place). Rather, human hands painstakingly refine such maps. Here is what a few scientists told me about mapping the moon and other celestial bodies.

The maps are huge.

The detail captured by the Lunar Reconnaissance Orbiter is extraordinary, capable even of focusing on the lunar footpaths left by the Apollo astronauts. When China put a rover on the moon in 2013, planetary scientists used the LRO to track the rover’s progress to counter the skepticism some had of information released by the Chinese government. Sure enough, the lander Chang’e 3 landed, and the rover Yutu roved.

Such level of detail comes at a price. The map files can be enormous. One-hundred-meter-per-pixel “global maps” clock in around 20 gigabytes for a single file. One map of the moon’s north pole—a mosaic comprised of thousands of separate images—came in at 3.3 terabytes (for a tiny slice of the moon). How big is this? If you printed the map out, it would cover a football field and then some. The map of the northern lunar pole was generated with the help of a program called the Integrated Software for Imagers and Spectrometers. It was tricky work, and planetary scientists had to deal with converging longitudes and lighting issues endemic to mapping poles. Consistency of lighting, especially, proved a challenge, but is essential for accuracy.

When you want precise work, you need a human brain.

Computers are great at stitching together maps from image sources, but the resulting product is not always usable. The reason is that computers don’t see images; they see only pixel values. Mapping issues that might stump the most powerful computer can sometimes be solved in seconds by the human brain, which has an uncanny ability to recognize when something is not quite right. The work of mapping a planet, asteroid, or moon is tedious work and requires meticulous, pixel-perfect effort on the part of scientists to get things usable for the wider field of planetary science.

Scanning celestial bodies isn’t like Star Trek.

The geological mapping of other worlds sometimes uses astronomical spectroscopy to measure electromagnetic radiation. Instruments on satellites and orbiters gather data from celestial bodies to map such things as minerals in rocks and soil. To actually interpret that data, however, scientists need laboratory measurements against which to compare. One problem: the laboratory measurements taken on Earth have a bias for this planet. To increase accuracy, geologists have to adjust conditions, and can use chambers able to manipulate pressures, temperature, and atmosphere to make things more like the body in question. They then create a database of their measurements to match with the data collected by instruments on such satellites as the Lunar Reconnaissance Orbiter.

Creating laboratory spectra is slow, meticulous work, and there’s a lot to it. It requires the characterization of thousands of different minerals calibrated to the data from orbiters. Furthermore, the viewing geometry of instruments—where the instrument is versus where the sun is versus where the surface of the moon is—can create differences, and planetary scientists must account for all such variables.

Planetary bodies change—a lot.

Planetary scientists use the measure of crater density—the number of craters of a given size range in a given area—to date in relative terms the age of the lunar surface. Older surfaces will have more craters than younger surfaces. In working out the relative age of the moon’s surface, however, not all craters are created equal. There are “primaries” and “secondaries.” Primaries are when bodies crash into the moon, as you’d expect. Secondaries are the result of the debris from the craters created by the primaries. (Think stones skipping on water.) Obvious secondaries have characteristic shapes and often overlap or result in a herringbone pattern, and must be removed from the crater count.

There are landslides on the moon.

Mapping the moon is made even more challenging because the face of the moon is always changing, which is why the Lunar Reconnaissance Orbiter has proven vital. Each LRO dataset essentially reveals a brand new moon. In the time between the start of the LRO mission and today, there have been over 10,000 surface changes recorded by planetary scientists. LRO data on surface changes allow scientists to constrain the impact flux on the moon, which is to say that ages derived from crater counts are becoming increasingly accurate as scientists learn the flux of impacting objects and the creation of craters in our current timescale. Because of LRO data, we now know that the surface of the moon is dynamic.

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Who Started Casual Fridays?
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iStock

For employees at the mercy of an office thermostat, Casual Fridays provide some much-needed relief during frigid winters and the scorching months of summer. Though many offices are beginning to loosen their dress codes permanently, plenty of employees still cling to this one day a week when wearing shorts won't raise any eyebrows and that T-shirt won't result in an email from HR. But Casual Friday didn't begin just as a cure for discomfort in the workplace; there was also money to be made. 

In the 1960s, Bill Foster, president of The Hawaiian Fashion Guild, plotted to find a way to sell more of the colorfully designed Aloha shirts to their residents with the launch of "Operation Liberation," which gave two shirts to every member of the Hawaii House of Representatives and the Hawaii Senate. The purpose of this campaign was to persuade the politicians to allow government workers to wear the lightweight shirts not only to beat the heat in the summer months, but also to support the state’s garment industry. The custom took off in 1966 and was given a familiar name, "Aloha Friday."

Technology giant Hewlett-Packard claims to have sparked the spread of casual wear in the workplace around the same time in the San Francisco Bay area. Called "Blue Sky Days," this Friday custom wasn't just limited to clothing: HP's founders—Bill Hewlett and David Packard—wanted people to take these days to think of more creative ideas and initiatives outside of their normal routine. This idea soon caught on throughout Silicon Valley and, eventually, into other industries.

However, the spread of this casual trend on the mainland resulted in haphazard, sometimes sloppy attire in the workplace. To help clarify the issue, and to promote his own brand, Rick Miller of Dockers stepped in with an ingenious marketing plan. In 1992, he sent an eight-page “Guide To Casual Business Wear” to approximately 25,000 human resource managers to distribute to their employees. This kickstarted the Dockers brand by popularizing the khaki pant and redefining what is acceptable attire in the workplace.

Now, many nations adopt a Casual Friday approach for similar reasons. In 2005, Japan implemented a Cool Biz policy that granted a summer dress code during hot weather months, in exchange for a more moderate temperature in office buildings. This meant offices were saving energy by keeping their temperature at no less than 82.4°F, but workers could breathe a bit easier in business casual tops and sneakers.

Blame the fashion industry, the unbearable heat, or simply an evolving cultural attitude. The likes of Bill Foster’s Aloha Friday and Rick Miller’s “Guide To Casual Business Wear” gave employees permission to dress for comfort on the job—for at least one coveted day of the week.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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How Does Catnip Work?
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If you have a cat, you probably keep a supply of catnip at home. Many cats are irresistibly drawn to the herb, and respond excitedly to its scent, rubbing against it, rolling around on the floor, and otherwise going nuts. There are few things that can get felines quite as riled up as a whiff of catnip—not even the most delicious treats. But why does catnip, as opposed to any other plant, have such a profound effect on our feline friends?

Catnip, or Nepeta cataria, is a member of the mint family. It contains a compound called nepetalactone, which is what causes the characteristic catnip reaction. Contrary to what you might expect, the reaction isn’t pheromone related—even though pheromones are the smelly chemicals we usually associate with a change in behavior. While pheromones bind to a set of specialized receptors in what’s known as a vomeronasal organ, located in the roof of a cat's mouth (which is why they sometimes open their mouths to detect pheromones), nepetalactone binds to olfactory receptors at the olfactory epithelium, or the tissue that lines the mucus membranes inside a cat’s nose and is linked to smell.

Scientists know the basics of the chemical structure of nepetalactone, but how it causes excitement in cats is less clear. “We don’t know the full mechanisms of how the binding of these compounds to the receptors in the nose ultimately changes their behavior,” as Bruce Kornreich, associate director of the Cornell Feline Health Center, tells Mental Floss. Sadly, sticking a bunch of cats in an MRI machine with catnip and analyzing their brain activity isn’t really feasible, either from a practical or a financial standpoint, so it’s hard to determine which parts of a cat’s brain are reacting to the chemical as they frolic and play.

Though it may look like they’re getting high, catnip doesn’t appear to be harmful or addictive to cats. The euphoric period only lasts for a short time before cats become temporarily immune to its charms, meaning that it’s hard for them to overdo it.

“Cats do seem to limit themselves," Michael Topper, president of the American Veterinary Medical Association, tells Mental Floss. "Their stimulation lasts for about 10 minutes, then it sort of goes away.” While you may not want to turn your house into a greenhouse for catnip and let your feline friend run loose, it’s a useful way to keep indoor cats—whose environment isn’t always the most thrilling—stimulated and happy. (If you need proof of just how much cats love this herb, we suggest checking out Cats on Catnip, a new book of photography from professional cat photographer Andrew Martilla featuring dozens of images of cats playing around with catnip.)

That said, not all cats respond to catnip. According to Topper, an estimated 70 percent of cats react to catnip, and it appears to have a genetic basis. Topper compares it to the genetic variation that causes some individuals to smell asparagus pee while others don’t. Even if a cat will eventually love the smell of catnip, it doesn’t come out of the womb yearning for a sniff. Young kittens don’t show any behavioral response to it, and may not develop one until several months after birth [PDF].

But some researchers contend that more cats may respond to catnip than we actually realize. In one 2017 study, a group of researchers in Mexico examined how cats might subtly respond to catnip in ways that aren’t always as obvious as rolling around on the floor with their tongue hanging out. It found that 80 percent of cats responded to catnip in a passive way, showing decreased motor activity and sitting in the “sphinx” position, an indicator of a relaxed state.

There are also other plants that have similar effects on cats, some of which may appeal to a wider variety of felines than regular old catnip. In a 2017 study in the journal BMC Veterinary Research, researchers tested feline responses to not just catnip, but several other plants containing compounds similar in structure to nepetalactone, like valerian root, Tatarian honeysuckle, and silver vine. They found that 94 percent of cats responded to at least one of the plants, if not more than one. The majority of the cats that didn’t respond to catnip itself did respond to silver vine, suggesting that plant might be a potential alternative for cats that seem immune to catnip’s charms.

Despite the name, domestic cats aren’t the only species that love catnip. Many other feline species enjoy it, too, including lions and jaguars, though tigers are largely indifferent to it. The scent of the plant also attracts butterflies. (However, no matter what you’ve heard, humans can’t get high off it. When made into a tea, though, it reportedly has mild sedative effects.)

The reason Nepeta cataria releases nepetalactone doesn’t necessarily have to do with giving your cat a buzz. The fact that it gives cats that little charge of euphoria may be purely coincidental. The chemical is an insect repellant that the plant emits as a defense mechanism against pests like aphids. According to the American Chemical Society, nepetalactone attracts wasps and other insect predators that eat aphids, calling in protective reinforcements when the plant is in aphid-related distress. That it brings all the cats to the yard is just a side effect.

Because of this, catnip may have even more uses in the future beyond sending cats into a delighted frenzy. Rutgers University has spent more than a decade breeding a more potent version of catnip, called CR9, which produces more nepetalactone. It’s not just a matter of selling better cat toys; since catnip releases the compound to ward off insects, it’s also a great mosquito repellant, one that scientists hope can one day be adapted for human use. In that case, you might be as excited about catnip as your cat is.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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