What the Weather Is Like on Other Moons and Planets

On Earth, we get snow, rain, fog, hail, and sleet, and all of them are basically the same thing: water. For a true change of weather, you need to go to other worlds. Here's a tour of what to expect on a trip through our solar system.

Mars: Dry Ice Snow

Scientists have known for years that the polar caps of Mars are made of a combination of water ice and dry ice (or frozen carbon dioxide—the same stuff that makes fog when you dump it into a pot of water). But how does it get there? The ice caps grow and recede with the seasons (in the Hubble images above, the carbon dioxide is receding with the onset of spring), so either the carbon dioxide is freezing directly out of the atmosphere, or it's snowing. Scientists working with data from Mars Reconnaissance Orbiter recently solved the puzzle: MRO detected clouds of carbon dioxide crystals, and clear evidence of snow falling out of them. The snow would not fall as flakes, but as tiny cuboctohedrons (which have eight triangular faces and six square faces). On the surface, Mars snow probably looks like granulated sugar.

Venus: Sulfuric Acid Rain

Once thought to be our sister planet, Venus is, in actuality, a hellhole. The surface is over 462 degrees C (864 degrees F)—easily hot enough to melt lead—and the atmospheric pressure is about 92 times the pressure on Earth at sea level. It's also bone dry (water is baked out of the soil). But high up above the slowly rotating surface, where the winds whip violently, Venus is enshrouded by clouds of sulfuric acid (shown here in ultraviolet light from the Hubble Telescope). When it rains, the acid falls down to about 25 km before evaporating—at these temperatures, even sulfuric acid can't stay liquid. The vapor rises back up to recondense as clouds, giving Venus a liquid cycle confined entirely to the upper atmosphere.

Io: Sulfur Dioxide Snow

Venus isn't the only hellhole in the solar system. Jupiter's moon Io would fit the bill pretty well, too. It's riddled with active volcanoes, covered in brimstone, and hiding a subsurface ocean of lava. And it snows the sort of snow you might get when Hell freezes over, because it too is made of brimstone: sulfur, and, more specifically, sulfur dioxide, which were detected when the Galileo orbiter flew through the volcanic plumes on its kamikaze mission in September 2003. Molten sulfur, heated to the boiling point below the surface of Io by torturous tidal flexing, sprays out of the volcanoes like a geyser would spray water on Earth. In the cold, airless void of space, the sulfur dioxide quickly crystalizes into tiny flakes; most of it falls back to the surface as a fluffy yellow snow. Galileo's sensors indicated that the particles were very small, perhaps 15-20 molecules apiece, so the snow would look extremely fine on the surface.  In the photo above, the broad white semi circle of material is sulfur dioxide snow from a plume called Amirani.

Titan: Methane Rain

Titan is Saturn's largest moon, and the pictures revealed by Cassini and the Huygens lander show a world that looks surprisingly Earthlike, with riverbeds, lakes, and clouds. (The radar image above shows the shores of Kraken Mare, the largest known lake on Titan, with rivers flowing into it.) But this is deceptive. Titan is much colder: What looks like rock is water ice, and what looks like water is natural gas. A methane cycle (much like the water cycle on Earth) exists on Titan, driving seasonal rains that follow patterns (much like the ones tropical monsoons follow on Earth). When the season is right, the rain falls, filling vast but shallow basins bigger than our Great Lakes. As the seasons change, the lakes slowly evaporate. The vapor makes its way up into the atmosphere and condenses into clouds; the clouds drift to the other hemisphere as the weather shifts, and when the rain falls, it starts the next loop of the cycle.

Enceladus: Water and Ammonia Snow

Enceladus is one of the most active moons of Saturn. The south polar region especially is riddled with geysers that shoot water and ammonia hundreds of miles into space. Most of that leaves Enceladus altogether, forming Saturn's E ring. The rest falls back down, forming deep, powdery snow that would put the best "white smoke" of the Rockies to shame. But the snow falls very slowly. By mapping the snowdrifts, scientists have found that although the snow barely accumulates over the course of a year, the snow has been falling on some spots for tens of millions of years. Because of this, the snowpack is over 100 meters deep. And it's all light, fluffy snow; an unwary skier might disappear into the powder if he hit a particularly deep patch. This photo above shows Cairo Sulcus, a grooved feature in Encealdus' active south, its sharp edges softened by millenia of gentle snowfall.

Triton: Nitrogen and Methane Snow

Titan is cold enough to liquify methane, but Neptune's moon Triton is colder still. Voyager 2 discovered that Triton's surface is suspiciously new, and it's not just from volcanic resurfacing; the southern polar region also appears to be covered partially in a light, fluffy material that could only be snow. But while our snow is white and Io's snow is yellow, Triton's snow is pink. It's made of a mixture of nitrogen and methane. Like Io and Enceladus, the snow comes from geysers that blast liquid high up into space, where it freezes into fine particles that fall down as snow onto a terrain pockmarked by nitrogen/methane permafrost. Because of its color and the curious texture of the southern polar region, scientists call it "cantaloupe terrain."

Pluto: Nitrogen, Methane, and Carbon Monoxide Snow

Pluto has an awful lot in common with Triton, and apparently that includes snow. Although Pluto has never been seen close-up, careful observations with the Hubble Space Telescope suggest that it experiences snows of nitrogen, methane, and possibly carbon monoxide. Like Triton, this makes its surface very pinkish. Depending on the process that desposits it (geysers or frost or "diamond dust" snowfall, where the stuff just freezes straight out of the air and falls), this could be a fine powder or big, spiky piles of frost. We'll know more when NASA's New Horizons spacecraft visits; right now, it's about halfway there.

Jupiter: Liquid Helium Rain

The environments on gas giant planets are extreme in many ways; one is that there is a depth within them at which the atmospheric pressure is so great that exotic forms of matter appear, such as metallic helium and hydrogen. If the models are correct, above Jupiter's rocky core lies a deep ocean of liquid metallic hydrogen. Helium is a little harder to compress into a metallic form, so it doesn't mix with this ocean. It is heavier than hydrogen, though; scientists believe it falls through the metallic hydrogen ocean like droplets falling through the atmosphere, until it gets deep enough to become metallic.

Uranus and Neptune: Diamond Rain

Uranus and Neptune aren't really Jovian worlds; they're much colder than Jupiter or Saturn, and contain high fractions of water, leading some to call them ice giants. Another thing they contain is methane—lots of it, pressurized into a liquid state inside the giant planets. Methane is a hydrocarbon; under the right conditions (and models predict such conditions on Uranus and Neptune), the carbon within it can crystallize out as tiny diamonds. On Earth, "diamond dust" means superfine particles of ice suspended in the atmosphere on very cold days, but the phrase might be more literally true on Uranus and Neptune. The diamonds aren't accessible; they continually rain down towards the interior of the planets to be lost forever in a vast diamond ocean.  Fans of Arthur C. Clarke may recognize this idea as part of the inspiration for "2061."

Bonus — The Sun: Plasma Rain

The Sun represents 99 percent of the mass in our solar system, so fittingly, it has what may be the most extreme precipitation in the solar system: plasma rain. Unlike the others on this list, you can actually see it from Earth. Huge loops of plasma are lifted up into space above the photosphere (what is generally considered the "surface" of the Sun) and suspended by magnetism, until finally something snaps and material is hurled violently into space in a coronal mass ejection. Not all of the material escapes, however; a lot of it falls back down as coronal rain. The video above, from June 7, 2011, was a particularly big and dramatic coronal mass ejection; look for the bright flashes as material impacts the photosphere.

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Wikimedia Commons // Public Domain
15 Riveting Facts About Alan Turing
Wikimedia Commons // Public Domain
Wikimedia Commons // Public Domain

More than six decades after his death, Alan Turing’s life remains a point of fascination—even for people who have no interest in his groundbreaking work in computer science. He has been the subject of a play and an opera, and referenced in multiple novels and numerous musical albums. The Benedict Cumberbatch film about his life, The Imitation Game, received eight Oscar nominations. But just who was he in real life? Here are 15 facts you should know about Alan Turing, who was born on this day in 1912.

1. HE’S THE FATHER OF MODERN COMPUTER SCIENCE.

Turing essentially pioneered the idea of computer memory. In 1936, Turing published a seminal paper called “On Computable Numbers” [PDF], which The Washington Post has called “the founding document of the computer age.” In the philosophical article, he hypothesized that one day, we could build machines that could compute any problem that a human could, using 0s and 1s. Turing proposed single-task machines called Turing machines that would be capable of solving just one type of math problem, but a “universal computer” would be able to tackle any kind of problem thrown at it by storing instructional code in the computer’s memory. Turing’s ideas about memory storage and using a single machine to carry out all tasks laid the foundation for what would become the digital computer.

In 1945, while working for the UK’s National Physical Laboratory, he came up with the Automatic Computing Machine, the first digital computer with stored programs. Previous computers didn’t have electric memory storage, and had to be manually rewired to switch between different programs.

2. HE PLAYED A HUGE ROLE IN WINNING WORLD WAR II.

Turing began working at Bletchley Park, Britain’s secret headquarters for its codebreakers during World War II, in 1939. By one estimate, his work there may have cut the war short by up to two years. He’s credited with saving millions of lives.

Turing immediately got to work designing a codebreaking machine called the Bombe (an update of a previous Polish machine) with the help of his colleague Gordon Welchman. The Bombe shortened the steps required in decoding, and 200 of them were built for British use over the course of the war. They allowed codebreakers to decipher up to 4000 messages a day.

His greatest achievement was cracking the Enigma, a mechanical device used by the German army to encode secure messages. It proved nearly impossible to decrypt without the correct cipher, which the German forces changed every day. Turing worked to decipher German naval communications at a point when German U-boats were sinking ships carrying vital supplies across the Atlantic between Allied nations. In 1941, Turing and his team managed to decode the German Enigma messages, helping to steer Allied ships away from the German submarine attacks. In 1942, he traveled to the U.S. to help the Americans with their own codebreaking work.

3. HE BROKE THE RULES TO WRITE TO CHURCHILL.

Early on, Bletchley Park’s operations were hampered by a lack of resources, but pleas for better staffing were ignored by government officials. So, Alan Turing and several other codebreakers at Bletchley Park went over their heads to write directly to Prime Minister Winston Churchill. One of the codebreakers from Bletchley Park delivered the letter by hand in October 1941.

“Our reason for writing to you direct is that for months we have done everything that we possibly can through the normal channels, and that we despair of any early improvement without your intervention,” they wrote to Churchill [PDF]. “No doubt in the long run these particular requirements will be met, but meanwhile still more precious months will have been wasted, and as our needs are continually expanding we see little hope of ever being adequately staffed.”

In response, Churchill immediately fired off a missive to his chief of staff: “Make sure they have all they want on extreme priority and report to me that this had been done.”

4. HE HAD SOME ODD HABITS.

Like many geniuses, Turing was not without his eccentricities. He wore a gas mask while riding his bike to combat his allergies. Instead of fixing his bike’s faulty chain, he learned exactly when to dismount to secure it in place before it slipped off. He was known around Bletchley Park for chaining his tea mug to a radiator to prevent it from being taken by other staffers.

5. HE RODE HIS BIKE 60 MILES TO GET TO THE FIRST DAY OF SCHOOL.

Though he was considered an average student, Turing was dedicated enough to his schooling that when a general strike prevented him from taking the train to his first day at his new elite boarding school, the 14-year-old rode his bike the 62 miles instead.

6. HE TRIED OUT FOR THE OLYMPICS.

Turing started running as a schoolboy and continued throughout his life, regularly running the 31 miles between Cambridge and Ely while he was a fellow at King’s College. During World War II, he occasionally ran the 40 miles between London and Bletchley Park for meetings.

He almost became an Olympic athlete, too. He came in fifth place at a qualifying marathon for the 1948 Olympics with a 2-hour, 46-minute finish (11 minutes slower than the 1948 Olympic marathon winner). However, a leg injury held back his athletic ambitions that year.

Afterward, he continued running for the Walton Athletic Club, though, and served as its vice president. ”I have such a stressful job that the only way I can get it out of my mind is by running hard,” he once told the club’s secretary. “It's the only way I can get some release."

7. HE WAS PROSECUTED FOR BEING GAY.

In 1952, Turing was arrested after reporting a burglary in his home. In the course of the investigation, the police discovered Turing’s relationship with another man, Arnold Murray. Homosexual relationships were illegal in the UK at the time, and he was charged with “gross indecency.” He pled guilty on the advice of his lawyer, and opted to undergo chemical castration instead of serving time in jail.

8. THE GOVERNMENT ONLY RECENTLY APOLOGIZED FOR HIS CONVICTION …

In 2009, UK Prime Minister Gordon Brown issued a public apology to Turing on behalf of the British government. “Alan and the many thousands of other gay men who were convicted as he was convicted under homophobic laws were treated terribly,” Brown said. "This recognition of Alan's status as one of Britain's most famous victims of homophobia is another step towards equality and long overdue." Acknowledging Britain’s debt to Turing for his vital contributions to the war effort, he announced, “on behalf of the British government, and all those who live freely thanks to Alan's work I am very proud to say: we're sorry, you deserved so much better."

His conviction was not actually pardoned, though, until 2013, when he received a rare royal pardon from the Queen of England.

9. … AND NAMED A LAW AFTER HIM.

Turing was only one of the many men who suffered after being prosecuted for their homosexuality under 19th-century British indecency laws. Homosexuality was decriminalized in the UK in 1967, but the previous convictions were never overturned. Turing’s Law, which went into effect in 2017, posthumously pardoned men who had been convicted for having consensual gay sex before the repeal. According to one of the activists who campaigned for the mass pardons, around 15,000 of the 65,000 gay men convicted under the outdated law are still alive.

10. HE POISONED HIMSELF … MAYBE.

There is still a bit of mystery surrounding Turing’s death at the age of 41. Turing died of cyanide poisoning, in what is widely believed to have been a suicide. Turing’s life had been turned upside down by his arrest. He lost his job and his security clearance. By order of the court, he had to take hormones intended to “cure” his homosexuality, which caused him to grow breasts and made him impotent. But not everyone is convinced that he died by suicide.

In 2012, Jack Copeland, a Turing scholar, argued that the evidence used to declare Turing’s death a suicide in 1954 would not be sufficient to close the case today. The half-eaten apple by his bedside, thought to be the source of his poisoning, was never tested for cyanide. There was still a to-do list on his desk, and his friends told the coroner at the time that he had seemed in good spirits. Turing’s mother, in fact, maintained that he probably accidentally poisoned himself while experimenting with the chemical in his home laboratory. (He was known to taste chemicals while identifying them, and could be careless with safety precautions.)

That line of inquiry is far more tame than some others, including one author’s theory that he was murdered by the FBI to cover up information that would have been damaging to the U.S.

11. HIS FULL GENIUS WASN’T KNOWN IN HIS LIFETIME.

Alan Turing was a well-respected mathematician in his time, but his contemporaries didn’t know the full extent of his contributions to the world. Turing’s work breaking the Enigma machine remained classified long after his death, meaning that his contributions to the war effort and to mathematics were only partially known to the public during his lifetime. It wasn’t until the 1970s that his instrumental role in the Allies' World War II victory became public with the declassification of the Enigma story. The actual techniques Turing used to decrypt the messages weren’t declassified until 2013, when two of his papers from Bletchley Park were released to the British National Archives.

12. THE TURING TEST IS STILL USED TO MEASURE ARTIFICIAL INTELLIGENCE …

Can a machine fool a human into thinking they are chatting with another person? That’s the crux of the Turing test, an idea developed by Turing in 1950 regarding how to measure artificial intelligence. Turing argued in his paper “Computing Machinery and Intelligence” [PDF] that the idea of machines “thinking” is not a useful way to evaluate artificial intelligence. Instead, Turing suggests “the imitation game,” a way to assess how successfully a machine can imitate human behavior. The best measure of artificial intelligence, then, is whether or not a computer can convince a person that it is human.

13. … BUT SOME CONSIDER IT TO BE AN OUTDATED IDEA.

As technology has progressed, some feel the Turing test is no longer a useful way to measure artificial intelligence. It’s cool to think about computers being able to talk just like a person, but new technology is opening up avenues for computers to express intelligence in other, more useful ways. A robot’s intelligence isn’t necessarily defined by whether it can fake being human—self-driving cars or programs that can mimic sounds based on images might not pass the Turing test, but they certainly have intelligence.

14. HE CREATED THE FIRST COMPUTER CHESS PROGRAM.

Inspired by the chess champions he worked with at Bletchley Park, Alan Turing created an algorithm for an early version of computer chess—although at that time, there was no computer to try it out on. Created with paper and pencil, the Turochamp program was designed to think two moves ahead, picking out the best moves possible. In 2012, Russian chess grandmaster Garry Kasparov played against Turing’s algorithm, beating it in 16 moves. “I would compare it to an early caryou might laugh at them but it is still an incredible achievement," Kasparov said in a statement after the match-up.

15. THERE IS ALAN TURING MONOPOLY.

In 2012, Monopoly came out with an Alan Turing edition to celebrate the centennial of his birth. Turing had enjoyed playing Monopoly during his life, and the Turing-themed Monopoly edition was designed based on a hand-drawn board created in 1950 by his friend William Newman. Instead of hotels and houses, it featured huts and blocks inspired by Bletchley Park, and included never-before-published photos of Turing. (It’s hard to find, but there are still a few copies of the game on Amazon.)

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iStock
NASA Has a Plan to Stop the Next Asteroid That Threatens Life on Earth
iStock
iStock

An asteroid colliding catastrophically with Earth within your lifetime is unlikely, but not out of the question. According to NASA, objects large enough to threaten civilization hit the planet once every few million years or so. Fortunately, NASA has a plan for dealing with the next big one when it does arrive, Forbes reports.

According to the National Near-Earth Object Preparedness Strategy and Action Plan [PDF] released by the White House on June 21, there are a few ways to handle an asteroid. The first is using a gravity tractor to pull it from its collision course. It may sound like something out of science fiction, but a gravity tractor would simply be a large spacecraft flying beside the asteroid and using its gravitational pull to nudge it one way or the other.

Another option would be to fly the spacecraft straight into the asteroid: The impact would hopefully be enough to alter the object's speed and trajectory. And if the asteroid is too massive to be stopped by a spacecraft, the final option is to go nuclear. A vehicle carrying a nuclear device would be launched at the space rock with the goal of either sending it in a different direction or breaking it up into smaller pieces.

Around 2021, NASA will test its plan to deflect an asteroid using a spacecraft, but even the most foolproof defense strategy will be worthless if we don’t see the asteroid coming. For that reason, the U.S. government will also be working on improving Near-Earth Object (NEO) detection, the technology NASA uses to track asteroids. About 1500 NEOs are already detected each year, and thankfully, most of them go completely unnoticed by the public.

[h/t Forbes]

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