September 26, 2013
Some 46 Martian days after landing on Mars in August 2012, after traveling nearly 1,000 feet from its landing site, Curiosity came upon a pyramid-shaped rock, roughly 20 inches tall. Researchers had been looking for a rock to use for calibrating a number of the rover’s high-tech instruments, and as principal investigator Roger Wiens said at a press conference at the time, “It was the first good-size rock that we found along the way.”
For the first time, scientists used the rover’s Hand Lens Imager (which takes ultra-high resolution photos of a rock’s surface) and the Alpha Particle X-ray Spectrometer (which bombards a rock with alpha particles and X-rays, kicking off electrons in patterns that allow scientists to identify the elements locked within it). They also used the ChemCam, a device that fires a laser at a rock and measures the abundances of elements vaporized.
Curiosity, for its part, commemorated the event with a pithy tweet:
I did a science! 1st contact science on rock target Jake. Here’s an action shot pic.twitter.com/pzcgH6Bk
— Curiosity Rover (@MarsCuriosity) September 22, 2012
A year later, the Curiosity team’s analysis of the data collected by these instruments, published today in Science, shows that they made a pretty lucky choice in finding a rock to start with. The rock, dubbed “Jake_M” (after engineer Jake Matijevic, who died a few days after Curiosity touched down), is unlike any rock previously found on Mars—and its composition intriguingly suggests that it formed after molten rock cooled quickly in the presence of underground water.
The new discovery was published as part of a special series of papers in Science that describe the initial geologic data collected by Curiosity’s full suite of scientific instrumentation. One of the other significant findings is a chemical analysis of a scoop of Martian soil—heated to 835 degrees Celsius inside the Sample Analysis at Mars instrument mechanism—showing that it contains between 1.5 and 3 percent water by weight, a level higher than scientists expected.
But what’s most exciting about the series of findings is the surprising chemical analysis of Jake_M. The researchers determined that it is likely igneous (formed by the solidification of magma) and, unlike any other igneous rocks previously found on Mars, has a mineral composition most similar to a class of basaltic rocks on Earth called mugearites.
“On Earth, we have a pretty good idea how mugearites and rocks like them are formed,” Martin Fisk, an Oregon State University geologist and co-author of the paper, said in a press statement. “It starts with magma deep within the Earth that crystallizes in the presence of one to two percent water. The crystals settle out of the magma, and what doesn’t crystallize is the mugearite magma, which can eventually make its way to the surface as a volcanic eruption.” This happens most frequently in underground areas where molten rock comes into contact with water—places like mid-ocean rifts and volcanic islands.
The fact that Jake_M closely resembles mugearites indicates that it likely took the same path, forming after other minerals crystallized in the presence of underground water and the remaining minerals were sent to the surface. This would suggest that, at least at some time in the past, Mars contained reserves of underground water.
The analysis is part of a growing body of evidence that Mars was once home to liquid water. Last September, images taken by Curiosity showed geologic features that suggested the one-time presence of flowing water at the surface. Here on Earth, analyses of several meteorites that originated on Mars have also indicated that, at some point long ago, the planet held reserves of liquid water deep underground.
This has scientists and members of the public excited, of course, because (at least as far as we know) water is a necessity for the evolution of life. If Mars was once a water-rich planet, as Curiosity’s findings increasingly suggest, it’s possible that life may have once evolved there long ago—and there may even be organic compounds or other remnants of life waiting to be found by the rover in the future.
September 23, 2013
Most people think of history as a series of stories—tales of one army unexpectedly defeating another, or a politician making a memorable speech, or an upstart overthrowing a sitting monarch.
Peter Turchin of the University of Connecticut sees things rather differently. Formally trained as a ecologist, he sees history as a series of equations. Specifically, he wants to bring the types of mathematical models used in fields such as wildlife ecology to explain population trends in a different species: humans.
In a paper published with colleagues today in the Proceedings of the National Academy of Sciences, he presents a mathematical model (shown on the left of the video above) that correlates well with historical data (shown on the right) on the development and spread of large-scale, complex societies (represented as red territories on the green area studied). The simulation runs from 1500 B.C.E. to 1500 C.E.—so it encompasses the growth of societies like Mesopotamia, ancient Egypt and the like—and replicates historical trends with 65 percent accuracy.
This might not sound like a perfect accounting of human history, but that’s not really the goal. Turchin simply wants to apply mathematical analysis to the field of history so that researchers can determine which factors are most influential in affecting the spread of human states and populations, just as ecologists have done when analyzing wildlife population dynamics. Essentially, he wants to answer a simple question: Why did complex societies develop and spread in some areas but not others?
In this study, Turchin’s team found that conflict between societies and the development of military technology as a result of war were the most important elements that predicted which states would develop and expand over the map—with those factors taken away, the model deteriorated, describing actual history with only 16 percent accuracy.
Turchin began thinking about applying math to history in general about 15 years ago. “I always enjoyed history, but I realized then that it was the last major discipline which was not mathematized,” he explains. “But mathematical approaches—modeling, statistics, etc.—are an inherent part of any real science.”
In bringing these sorts of tools into the arena of world history and developing a mathematical model, his team was inspired by a theory called cultural multilevel selection, which predicts that competition between different groups is the main driver of the evolution of large-scale, complex societies. To build that into the model, they divided all of Africa and Eurasia into gridded squares which were each categorized by a few environmental variables (the type of habitat, elevation, and whether it had agriculture in 1500 B.C.E.). They then “seeded” military technology in squares adjacent to the grasslands of central Asia, because the domestication of horses—the dominant military technology of the age—likely arose there initially.
Over time, the model allowed for domesticated horses to spread between adjacent squares. It also simulated conflict between various entities, allowing squares to take over nearby squares, determining victory based on the area each entity controlled, and thus growing the sizes of empires. After plugging in these variables, they let the model simulate 3,000 years of human history, then compared its results to actual data, gleaned from a variety of historical atlases.
Although it’s not perfect, the accuracy of their model—predicting the development and spread of empires in nearly all the right places—surprised even the researchers. “To tell the truth, the success of this enterprise exceeded my wildest expectations,” Turchin says. “Who would have thought that a simple model could explain 65% of variance in a large historical database?”
So why would conflict between societies prove to be such a crucial variable in predicting where empires would form? “To evolve to a large size, societies need special institutions that are necessary for holding them together,” Turchin proposes. “But such institutions have large internal costs, and without constant competition from other societies, they collapse. Only constant competition ensures that ultrasocial norms and institutions will persist and spread.”
The model shows that agriculture is a necessary but not sufficient precondition for a complex society, he says—these states can’t form without farming, but the persistent presence of competition and warfare is necessary to forge farming societies into durable, large-scale empires. Conventional analyses of history could come to this same conclusion, but they wouldn’t be able to demonstrate it in the same mathematically-based way. Using this approach, on the other hand, Turchin’s group could remove the influence of warfare and see the model’s accuracy in describing real historical data plummet.
Of course, there are limitations to viewing history through math—humans are more complicated than numbers. “Differences in culture, environmental factors and thousands of other variables not included in the model all have effect,” Turchin says. “A simple general model should not be able to capture actual history in all its glorious complexity.”
Still, the model is a unique and valuable tool. Going forward, Turchin’s team wants to develop it further—adding more nuance (such as including the quality of agricultural productivity, rather than merely toggling if farming exists in a given area or not) to improve on that 65 percent accuracy. Additionally, they’d like to expand the model, applying it to more recent world history and also pre-Columbian North America, if they can find relevant historical data.
Based on his experiences so far, Turchin thinks they’ll be successful in developing a model that better reflects the the rise and fall of civilizations. “It turns out that there is a lot of quantitative data in history,” he says, “you just have to be creative in looking for it.”
September 10, 2013
Rising gas prices and a dangerously low world panda population–what if someone told you that we soon could have one solution to both these problems? If it seems too good to be true, think again; scientists at Mississippi State University are conducting research on the feasibility of using pandas to help solve our biofuel woes, a step that could lead to a bump in conservation efforts and a drop in fuel expense. The secret to the solution? It’s all in the panda’s poop.
When it comes to biofuels, the market is dominated by one word: ethanol, a biofuel made from corn. Though ethanol is the most widely used biofuel, it isn’t necessarily touted as a perfect replacement for fossil fuels–in fact, the benefit of ethanol is been hotly debated since its creation.
The debate goes a little something like this: in order to fill the tank of an SUV with ethanol fuel, you need to use enough corn to feed a single person for an entire year. A 2012 paper published by the New England Complex Systems Institute cites ethanol as a reason for the increasing price of crops since 2005. And even environmental groups steer clear of ethanol, citing the massive amounts of fossil fuel needed to render corn a useable biofuel product and the propensity of companies to buy land in developing countries to grow the lucrative biofuel rather than food for local consumption.
Ashli Brown, a researcher at Mississippi State University, thinks she’s found the answer to this alternative fuel conundrum. By taking corn byproducts–the husks, the stems and cobs–ethanol could be created without dipping into the edible parts of corn, reducing the chance of a food shortage and price spike. The issue is that to break down these materials, which are extremely high in lignocellulose, or dry plant matter, a special pretreatment process is required. The process is extremely costly and not very time-efficient, using high temperatures, high pressures and acid to break down the dry plant matter before it can become ethanol. To circumvent this problem, Brown and other researchers have been looking for a natural solution–bacteria, which could help with the breakdown of the lignocellulose material.
Biofuel companies have been seeking a natural method to break down plant material for a while; so far, termites have been a favorite for chewing through the woody material. But it turns out there might be a better–and cuter–animal that can help produce biofuel
. The intestines of pandas are remarkably short, a physical attribute which means their intestines have come to contain bacteria with unusually potent enzymes for breaking down their woody diet of bamboo in a short amount of time.
“The time from eating to defecation is comparatively short in the panda, so their microbes have to be very efficient to get nutritional value out of the bamboo,” Brown, the researcher heading the work, said. “And efficiency is key when it comes to biofuel production—that’s why we focused on the microbes in the giant panda.”
The study began more than two years ago, when Brown and a team of researchers began looking at panda feces. In 2011, they identified these super-digesting microbes are present in panda feces, but they had yet to specify the type and amount of microbes present until now. Using the poop from two giant pandas–Ya Ya and Le Le in the Memphis Zoo–Brown and her team performed DNA sequencing on microbes in their samples, identifying more than 40 microbes in the panda feces that could be useful to the breakdown and creation of biofuels.
To grow these microbes on an industrial scale
, Brown believes that scientists could put the genes that produce those enzymes into yeasts--these yeasts could then be mass-produced and harvested for biofuel production. The process would go something like this: Large pits of corn husks, corn cobs, wood chips, and other forms of discarded fibrous material are covered with the genetically altered yeasts. As the microbes digest woody substances, they quickly turn it into sugar, which would then be allowed to ferment. Over time and after filtering out solids and any excess water, you would have ethanol, distilled from woody waste products.
Pandas aren’t the only animal that subsists on a grassy diet, but their physiology makes them a unique candidate for breaking down plant byproducts in a hyper-efficient way. Pandas have the same digestive track as any other bear; unlike cows or other herbivores, pandas don’t have an extra stomach where hard lignocellulostic material is pretreated before being digested. Instead, they have the intestinal system of a carnivore, and yet manage to extract enough nutrients from their herbaceous diet to survive.
“Because their retention time is very short—they’re constantly eating and they’re constantly pooping—in order to get the material for nutrition, they have to be really quick at breaking it down and extracting the sugars,” Brown explained. “Many microbes produce celluloses that breakdown lignocellulostic biomass, but it’s about how efficiently or how effectively they do it.” When it comes to a panda, Brown notes, their microbes are some of the most efficient scientists have seen at breaking down the woody material of a plant.
And Brown thinks that using pandas for their poop could lead to more than a greener economy: it could also lead to increased conservation for the animals, who have seen their numbers in the wild drop to a dangerous 1,600 (though there has been recent luck with breeding pandas in captivity, like the new baby panda at the National Zoo). “These studies also help us learn more about this endangered animal’s digestive system and the microbes that live in it, which is important because most of the diseases pandas get affect their guts,” said Brown.
Brown notes that if the panda becomes valuable to the market for more reasons than its incredibly adorable demeanor, it might spark greater steps toward conservation–a move that could be mutually beneficial to pandas and humans alike.”It’s amazing that here we have an endangered species that’s almost gone from the planet, yet there’s still so much we have yet to learn from it. That underscores the importance of saving endangered and threatened animals,” she said. “It makes us think—perhaps these endangered animals have beneficial outputs that we haven’t even thought about.”
August 20, 2013
The saying goes that one person’s waste is another’s treasure. For those scientists who study urine the saying is quite literal–pee is a treasure-trove of scientific potential. It can now be used as a source of electric power. Urine-eating bacteria can create a strong enough current to power a cell phone. Medicines derived from urine can help treat infertility and fight symptoms of menopause. Stem cells harvested from urine have been reprogrammed into neurons and even used to grow human teeth.
For modern scientists, the golden liquid can be, well, liquid gold. But a quick look back in history shows that urine has always been important to scientific and industrial advancement, so much so that the ancient Romans not only sold pee collected from public urinals, but those who traded in urine had to pay a tax. So what about pee did preindustrial humans find so valuable? Here are a few examples:
Urine-soaked leather makes it soft: Prior to the ability to synthesize chemicals in the lab, urine was a quick and rich source of urea, a nitrogen-based organic compound. When stored for long periods of time, urea decays into ammonia. Ammonia in water acts as a caustic but weak base. Its high pH breaks down organic material, making urine the perfect substance for ancients to use in softening and tanning animal hides. Soaking animal skins in urine also made it easier for leather workers to remove hair and bits of flesh from the skin.
The cleansing power of pee: If you’ve investigated the ingredients in your household cleaners, you may have noticed a prevalent ingredient: ammonia. As a base, ammonia is a useful cleanser because dirt and grease–which are slightly acidic–get neutralized by the ammonia. Even though early Europeans knew about soap, many launderers preferred to use urine for its ammonia to get tough stains out of cloth. In fact, in ancient Rome, vessels for collecting urine were commonplace on streets–passers-by would relieve themselves into them and when the vats were full their contents were taken to a fullonica (a laundry), diluted with water and poured over dirty clothes. A worker would stand in the tub of urine and stomp on the clothes, similar to modern washing machine’s agitator.
Even after making soap became more prevalent, urine–known as chamber lye for the chamber pots it was collected in–was often used as a soaking treatment for tough stains.
Urine not only made your whites cleaner, but your colors brighter: Natural dyes from seeds, leaves, flowers, lichens, roots, bark and berries can leach out of a cloth if it or the dyebath aren’t treated with mordant, which helps to bind the dye to the cloth. It works like this: molecules of dye called chromophores get wrapped inside a more complex molecule or a group of molecules; this shell housing the dye then binds to the cloth. The central nugget of dye is then visible but is protected from bleeding away by the molecules surrounding it. Stale urine–or more precisely the ammonia in it–is a good mordant. Molecules of ammonia can form a web around chromophores, helping to develop the color of dyes as well as to bind it to cloth.
Specific chamberpots dedicated to urine helped families collect their pee for use as mordants. Urine was so important to the textile industry of 16th century England that casks of it–an estimated amount equivalent to the urine stream of 1000 people for an entire year–were shipped from across the country to Yorkshire, where it was mixed with alum to form an even stronger mordant than urine alone.
Pee makes things go boom: Had enough with cleansing, tanning, and dyeing? Then why not use your pee to make gunpowder! Gunpowder recipes call for charcoal and sulfur in small quantities, both of which for aren’t too hard to find. But the main ingredient–potassium nitrate, also called saltpeter–was only synthesized on a large-scale in the early 20th century. Prior to that, makers of gunpowder took advantage of the nitrogen naturally found in pee to make the key ingredient for ballistic firepower.
As detailed in the manual Instructions for the Manufacture of Saltpetre, written by physician and geologist Joseph LeConte in 1862, a person hoping to make gunpowder quickly would need “a good supply of thoroughly rotted manure of the richest kind” which is then mixed with ash, leaves and straw in a pit. “The heap is watered every week with the richest kinds of liquid manure, such as urine, dung-water, water of privies, cess-pools, drains, &c. The quantity of liquid should be such as to keep the heap always moist, but not wet,” he wrote. The mixture is stirred every week, and after a several months no more pee is added. Then “As the heap ripens, the nitre is brought to the surface by evaporation, and appears as a whitish efflorescence, detectible by the taste.”
Different regions of the world had their own recipes for gunpowder, but the scientific principle at work is the same: Ammonia from stagnant pee reacts with oxygen to form nitrates. These nitrates–negatively charged nitrogen-bearing ions–then search for positively charged metal ions in the pee-poo-ash slurry to bind with. Thanks to the ash, potassium ions are in abundance, and voila! After a little filtering, you’ve made potassium nitrate.
Urine gives you a whiter smile: Urine was a key ingredient in many early medicines and folk remedies of dubious effectiveness. But one use–and those who’ve tried it say it works–is as a type of mouthwash. While “urine-soaked grin” isn’t the insult of choice these days, a verse by Roman poet Catullus reads:
Egnatius, because he has snow-white teeth, smiles all the time. If you’re a defendant in court, when the counsel draws tears, he smiles: if you’re in grief at the pyre of pious sons, the lone lorn mother weeping, he smiles. Whatever it is, wherever it is, whatever he’s doing, he smiles: he’s got a disease, neither polite, I would say, nor charming. So a reminder to you, from me, good Egnatius. If you were a Sabine or Tiburtine or a fat Umbrian, or plump Etruscan, or dark toothy Lanuvian, or from north of the Po, and I’ll mention my own Veronese too, or whoever else clean their teeth religiously, I’d still not want you to smile all the time: there’s nothing more foolish than foolishly smiling. Now you’re Spanish: in the country of Spain what each man pisses, he’s used to brushing his teeth and red gums with, every morning, so the fact that your teeth are so polished just shows you’re the more full of piss.
The poem not only reveals that Catullus wasn’t a fan of Egnatius, but that Romans used urine to clean and whiten their teeth, transforming morning breath into a different smell entirely. The active ingredient? You guessed it: ammonia, which lifted stains away.
But perhaps one of the most critical uses of urine in history was its role in making the above home remedies obsolete. Urea, the nitrogen bearing compound in urine, was the first organic substance created from inorganic starting materials. In 1828, German chemist Friedrich Wöhler mixed silver cyanate with ammonium chloride and obtained a white crystalline material that his tests proved was identical to urea. His finding disproved a hypothesis of many leading scientists and thinkers of the time, which held that living organisms were made up of substances entirely different than inanimate objects like rocks or glass. In a note to a colleague, Wöhler wrote, “I can no longer, so to speak, hold my chemical water and must tell you that I can make urea without needing a kidney, whether of man or dog; the ammonium salt of cyanic acid is urea.”
Wöhler’s discovery showed that not only could organic chemicals be transformed and produced in the lab, but that humans were part of nature, rather than separate from it. In doing so, he began the field of organic chemistry. Organic chemistry has given us modern medicines, materials such as plastic and nylon, compounds including synthetic ammonia and potassium nitrate…and, of course, a way to clean our clothes or fire a gun without using our own (or someone else’s) pee.
August 8, 2013
If you’re an active Redditor, you might spend time lamenting the fact that some of your most clever, insightful comments get so few upvotes, and the lamest comments of other users sometimes seem to arbitrarily rise to the top.
As it turns out, a trio of researchers—Lev Muchnik of the Hebrew University of Jerusalem, Sinan Aral of MIT and Sean J. Taylor of NYU—recently decided to apply one of the basic tools of science to investigate this phenomenon: the randomized controlled experiment. And by teaming with a social news site to randomly vote on thousands of comments and closely track how they did afterward, the researchers proved that the very first vote a particular item receives—and not just its intrinsic merit—has an outsized influence on its overall fate.
Their new study, published today in Science, relied upon research they did between December 2010 and May 2011. In the paper, they say that it was conducted on “a social news aggregation web site similar to Digg.com and Reddit.com,” but they don’t disclose which particular site it was, because they say the site’s administrators are nervous about the risk to user privacy.
Nevertheless, they describe a bunch of features (the ability to submit links, make comments, vote up or down each post and comment, and a front page populated by the most popular posts) that are a core part of Reddit, and they even use screenshots of Reddit to illustrate them. Suffice to say that if they didn’t do the experiment using Reddit, they did so with an extremely similar site.
During that five-month window, they analyzed 101,281 comments on the site—all posted by normal, unwitting users—as part of the experiment. The comments were randomly assigned into one of three different groups: those that would receive the “positive treatment” (automatically getting one upvote right after being posted), the “negative treatment” (automatically getting a downvote instead) or the control (simply being passed along with no artificial vote).
The vast majority of the comments (95,290) were simply part of the control group—users of the site interacted with these comments with no outside influence from the researchers. The researchers then split the remaining comments between positive and negative at roughly the same ratio that upvotes and downvotes occur naturally on the site: 4049 comments got the positive treatment, receiving an automatic upvote that had nothing to do with their content, while 1942 comments got an arbitrary downvote instead.
The researchers had a hunch that when the site’s users voted on the comments, they were significantly influenced—whether consciously or not—by the votes that had come beforehand. The very first vote, in that case, would be particularly pivotal, because it’d be the only vote the second voter would see. By influencing that voter one way or another, it could potentially influence the third voter, and then the fourth, with cascading effects that influence thousands of votes and produce what the researchers call “herding effects.”
When they analyzed the overall performance of the comments included in the experiment, as represented by the 308,515 subsequent ratings they got in total, their hunch was confirmed: Getting an upvote at the start made the second vote 32 percent more likely to be positive, as compared to the control. The effect was also passed down the line to subsequent voters in much the way the researchers expected, as at the end of the five months, those in the “positive treatment” group had an overall rating (calculated by subtracting the number of downvotes from number of upvotes) 25 percent higher than those in the control group.
Interestingly, though, when applied to the “negative treatment,” the phenomenon seemed to be reversed: Comments that got an arbitrary downvote were actually more likely to receive an upvote from the second voter
. The researchers speculate that this represents users’ desire to “correct” unfair downvotes for a comment that didn’t deserve them for any obvious reason.
The experimenters also analyzed the data based on which of the site’s topic areas (i.e. subreddits) the comment fell within—business, culture and society, politics, IT, fun, economics, general news. Comments in the politics, culture and society, and business areas exhibited the greatest herding effects, suggesting that the phenomenon of upvoting in these topic areas was the subject to being significantly yet arbitrarily
influenced by the votes that came beforehand, rather than the content of the comment.
It’s easy to imagine how the findings—basically, that our judgement of something is heavily skewed by our knowledge of how others have already judged it—apply to all sorts of situations that go beyond Reddit, both in real life and online. Previous work has already shown that the comments on a Facebook profile picture can influence how attractive we deem it, and if a news article posted on Facebook garners a lot of “likes,” aren’t we more likely to read it? Politicians, meanwhile, have long known that creating the impression of popularity can often be just as important, in an election, as articulating specific positions that merit support.
But does the desire to correct downvotes reveal something inherently optimistic about our society—that we don’t want to watch something undeservedly crash and burn? Does the herding effect of upvotes mean that if we’re not ourselves successful, we’d like to be on the peripheries of successes, regardless of how deserving that success may be?
For the Redditors, the study proves something they probably already suspected, but alas, have no control over anyway: Getting that first upvote can make all the difference.