Why is sugar sticky?

It's easy to confuse white sugar and table salt. But add a bit of water to these seemingly identical twins, and they're suddenly completely different animals. Both salt and sugar crystals start to dissolve in water, but sugar gets sticky and salt doesn't. Why is that?

Hydrogen bonds are the key to sugar's stickiness. Hanging out on its own, sugar is a solid, its molecules made of carbon, hydrogen and oxygen atoms. The crystals are intact and don't stick to one another — you can easily sift and pour sugar. But in the presence of a liquid, the formerly strong oxygen-hydrogen bonds in the sugar will start to break, and the loose hydrogen atoms will look for something else to stick to.

Some of the hydrogen atoms will stick to the closest surface, some will grab onto the hydrogen molecules in the liquid, and some will bond with another hydrogen or oxygen atom in the sugar. The result: a sticky mess. If you hold sugar in your hand, even a tiny amount of sweat can make things start to get sticky. Salt, on the other hand, is made of sodium and chlorine, so when it dissolves in water there's no hydrogen floating around to stick to anything.

But what about water?

Its molecules are made partly of hydrogen, too — why doesn't it become sticky like sugar when combined with some other substance? It has to do with the fact that sugar is much more complex than water. A molecule of sugar contains 12 carbon atoms, 22 hydrogen atoms and 11 oxygen atoms — and many more hydrogen bonds than a molecule of water. When those bonds in the sugar get busted up, there's more opportunity for the molecules to grab onto whatever they're in contact with, including other sugar molecules. And the new bonds are more secure because there are so many of them — it's harder to pull them apart.

Each water molecule, on the other hand, is composed of only two hydrogen atoms and one oxygen atom, so it doesn't have as many "sticky spots." Water adheres better to surfaces than it does to itself — it beads up, forms puddles or soaks into the carpet.

Source - www.howstuffworks.com

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Juno shatters scientists' Jupiter theories in just 365 days

LAST JULY 4TH, NASA's Juno spacecraft slowed its record breaking pace just enough to get caught in the pull of Jupiter's gravity. (The timing, according to NASA, was just a very patriotic coincidence.) Either way, Independence Day 2016 was the last time the Juno mission pumped its brakes. In the year since, the 66-foot solar-powered craft has given scientists more and weirder Jupiter data than they ever thought possible.

So, in honor of Juno's first year orbiting the hitherto mysterious gas giant, here's a rundown of the mission's greatest scientific hits so far.

The Design

Without a good spacecraft and mission plan, Juno never would have left orbit. The Lockheed Martin-built spacecraft itself is an engineering marvel: It has traveled further from Earth (1.7 billion miles!) than any solar-powered craft preceding it, and at speeds never before achieved by a man-made object. Juno's engineers also had to protect the craft's delicate instrumentation—which does everything from snap photos to analyze the gas giant's core—from deep space's pipe-burstingly cold temperatures, not to mention Jupiter's powerful radiation and electric field.

None of which would have been helpful if the mission design didn't allow all that fancy machinery to collect good data. Fortunately for Juno, that hasn't been an issue, even though its flight plan is unconventional in the extreme. Not only are Juno's orbits way, way lower than usual—at their lowest points, just 2,500 miles above Jupiter's famous storm clouds—unlike previous Jupiter missions, they're closely spaced to allow the craft to map the entirety of the planet. "Now that we've had such success, we can say the design is one of our greatest achievements," Scott Bolton, Juno's principal investigator told WIRED in May.

The Poles

The other eccentricity of Juno's orbit is that it isn't equatorial. Instead, it skims over Jupiter's north and south poles, which no one had ever seen before because of Jupiter's very slight axial tilt. (Most planets are tipped over enough for scientists to get a look at their poles from Earth, but Jupiter is practically straight up and down.) Turns out they're stunning—shockingly blue compared to the rest of the planet's stripy orange and white, and covered in cyclones that could swallow Earth whole.

The Atmosphere

So far, Juno has only completed one close pass of Jupiter—what Juno's team calls a science orbit. And while there are still a number of them to go (12 or more, thanks to an engine glitch that actually ended up shielding the spacecraft from additional radiation damage), the results of the first have already challenged long-held scientific theories about gas giants.

Seriously: Jupiter's auroras get energized by pulling electrons out of polar regions (the opposite of how the process works on Earth); and the gas giant's atmosphere, magnetic field, and gravity field are way more mobile and variable than scientific wisdom would have suggested. It's gotten to the point where planetary scientists (including Bolton) wonder if any of their assumptions about gas giants were right.

Which doesn't mean Juno is discouraging scientists. It's the opposite, really. Juno was always meant to rewrite (or at least fill in missing bits of) planetary history. According to theories Juno hasn't yet busted, Jupiter is the planet that started it all in this solar system—its composition is essentially the same as the Sun's, except it's enriched with heavier elements like carbon and nitrogen. So, it's the Sun plus the ingredients for life soup. And while scientists and space fans will have to wait for the next few science orbits to learn what that means, with Juno's track record, whatever answers the spacecraft sends Earthward will likely be field-shaping, and unexpected. So happy first anniversary, Jupiter and Juno. We can't wait to see what science your next year together will bring.

Follow NASA's Juno Mission on Twitter @NASAJuno

Source - www.wired.com