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What the Weather Is Like on Other Moons and Planets

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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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8 of the Weirdest Gallup Polls
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Born in Jefferson, Iowa on November 18, 1901, George Gallup studied journalism and psychology, focusing on how to measure readers’ interest in newspaper and magazine content. In 1935, he founded the American Institute of Public Opinion to scientifically measure public opinions on topics such as government spending, criminal justice, and presidential candidates. Although he died in 1984, The Gallup Poll continues his legacy of trying to determine and report the will of the people in an unbiased, independent way. To celebrate his day of birth, we compiled a list of some of the weirdest, funniest Gallup polls over the years.


According to this Gallup poll, 75 percent of Americans have at least one paranormal belief. Specifically, 41 percent believe in extrasensory perception (ESP), 37 percent believe in haunted houses, and 21 percent believe in witches. What about channeling spirits, you might ask? Only 9 percent of Americans believe that it’s possible to channel a spirit so that it takes temporary control of one's body. Interestingly, believing in paranormal phenomena was relatively similar across people of different genders, races, ages, and education levels.


In this poll, Gallup tried to determine the popularity of heliocentric versus geocentric views. While 79 percent of Americans correctly stated that the Earth revolves around the sun, 18 percent think the sun revolves around the Earth. Three percent chose to remain indifferent, saying they had no opinion either way.


Gallup first measured anti-Mormon sentiment back in 1967, and it was still an issue in 2011, a year before Mormon Mitt Romney ran for president. Approximately 22 percent of Americans said they would not vote for a Mormon presidential candidate, even if that candidate belonged to their preferred political party. Strangely, Americans’ bias against Mormons has remained stable since the 1960s, despite decreasing bias against African Americans, Catholics, Jews, and women.


This 2010 poll amusingly confirms the stereotype that southerners are more religious than the rest of the country. Although 42 percent of all Americans attend church regularly (which Gallup defines as weekly or almost weekly), there are large variations based on geography. For example, 63 percent of people in Mississippi attend church regularly, followed by 58 percent in Alabama and 56 percent in South Carolina, Louisiana, and Utah. Rounding out the lowest levels of church attendance, on the other hand, were Vermont, where 23 percent of residents attend church regularly, New Hampshire, at 26 percent, and Maine at 27 percent.


Although 76 percent of Americans knew that the United States gained independence from Great Britain as a result of the Revolutionary War, 24 percent weren’t so sure. Two percent thought the correct answer was France, 3 percent said a different country (such as Mexico, China, or Russia), and 19 percent had no opinion. Certain groups of people who consider themselves patriotic, including men, older people, and white people (according to Gallup polls), were more likely to know that America gained its independence from Great Britain.


This Halloween-themed Gallup poll asked Americans about their habits and behavior on the last day of October. Predictably, two-thirds of Americans reported that someone in their house planned to give candy to trick-or-treaters and more than three-quarters of parents with kids reported that their kids would wear a costume. More surprisingly, 31 percent of American adults claimed to believe in ghosts, an increase from 1978, when only 11 percent of American adults admitted to a belief in ghosts.


This recent Gallup poll is funny in a sad way, as it sheds light on the tragicomic life of a millennial. In this poll, well-being is defined as having purpose, social support, manageable finances, a strong community, and good physical health. Sadly, only 5 percent of working millennials—defined as people born between 1980 and 1996—were thriving in these five indicators of well-being. To counter this lack of well-being, Gallup’s report recommends that managers promote work-life balance and improve their communication with millennial employees.


If you seem to feel more stress, sadness, anxiety, and pain than ever before, Gallup has the proof that it’s not all in your head. According to the company’s worldwide negative experience index, negative feelings such as stress, sadness, and anger have increased since 2007. Unsurprisingly, people living in war-torn, dangerous parts of the word—Iraq, Iran, Egypt, Syria, and Sierra Leone—reported the highest levels of negative emotions.

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Earth's First-Recorded Interstellar Visitor Gets Its Closeup—And a Name
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In October, scientists using the University of Hawaii's Pan-STARRS 1 telescope sighted something extraordinary: Earth's first confirmed interstellar visitor. Originally called A/2017 U1, the once-mysterious object has a new name—'Oumuamua, according to Scientific American—and researchers continue to learn more about its physical properties.

Fittingly, "'Oumuamua" is Hawaiian for "a messenger from afar arriving first." 'Oumuamua's astronomical designation is 1I/2017 U1. The "I" in 1I/2017 stands for "interstellar." Until now, objects similar to 'Oumuamua were always given "C" and "A" names, which stand for either comet or asteroid.

'Oumuamua moved too quickly through space to orbit the Sun, which led researchers to believe that it might be the remains of a former exoplanet. Long ago, it might have hurtled from an unknown star system into our solar system. Far-flung origins aside, new observations have led some researchers to conclude that 'Oumuamua is, well, pretty ordinary—at least in appearance.

'Oumuamua's size (591 feet by 98 feet) and oblong shape have drawn comparisons to a chunky cigar that's half a city block long. It's also reddish in color, and looks and acts like asteroids in our own solar system, the BBC reports. Its average looks aside, 'Oumuamua remains important because it may provide astronomers with new insights into how stars and planets form.

University of Wisconsin–Madison astronomer Ralf Kotulla and scientists from UCLA and the National Optical Astronomy Observatory (NOAO) used the WIYN Telescope on Kitt Peak, Arizona, to take some of the first pictures of 'Oumuamua. You can check them out below.

Images of an interloper from beyond the solar system — an asteroid or a comet — were captured on Oct. 27 by the 3.5-meter WIYN Telescope on Kitt Peak, Ariz.
Images of 'Oumuamua—an asteroid or a comet—were captured on October 27.

U1 spotted whizzing through the Solar System in images taken with the WIYN telescope. The faint streaks are background stars. The green circles highlight the position of U1 in each image. In these images U1 is about 10 million times fainter than the faint
The green circles highlight the position of U1 in each image against faint streaks of background stars. In these images, U1 is about 10 million times fainter than the faintest visible stars.
R. Kotulla (University of Wisconsin) & WIYN/NOAO/AURA/NSF

Color image of U1, compiled from observations taken through filters centered at 4750A, 6250A, and 7500A.
Color image of U1.
R. Kotulla (University of Wisconsin) & WIYN/NOAO/AURA/NSF


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