Lemon, Vanilla, Cinnamon

Al claims that lemon’s a Summertime flavor, which is why his coffee shop’s Scone Flavor of the Month in July is lemon even though it doesn’t go well with his coffee. “Give me one of those lemon scones, Al, and an iced tea. It’s a little warm out there this morning.”

“Sure thing, Sy. Say, what’s the latest science-y thing up in the sky?”

“Oh, there’s a bunch, Al. The Japanese Hayabusa-2 spacecraft collected another sample from asteroid Ryugu. NASA’s gravity-sniffer GRAIL lunar orbiter found evidence for a huge hunk of metallic material five times larger than the Big Island of Hawai’i buried deep under the Moon’s South Pole-Aitken Basin. The Insight Mars lander’s seismometer heard its first Marsquake —“

“Quit yanking my chain, Sy. Anything about Jupiter?”

“Gotcha, Al. I know Jupiter’s your favorite planet. As it happens I do have some Jupiter news for you.”

“The Juno orbiter’s still working, I hope.”

“Sure, sure, far as I know. It’s about to make its 13th close flyby of Jupiter, and NASA administrators have green-lighted the mission to continue until July 2021. Lots of data for the researchers to work on for years. Here’s a clue — what’re the top three things that everyone knows about Jupiter?”

“It’s the biggest planet, of course, and it’s got those stripes and the Great Red Spot. Has the planet gotten smaller somehow?”

“No, but the stripes and the Red Spot are acting weird. Had you heard about that?”

“No, just that the Spot’s huge and red and been there for 400 years.”

“Mmm, we’re not sure about the 400 years. But yes, it’s huge.”

“Four times wider than Earth, right?”

“Hasn’t been that big for a long time. Back in the 1870s telescope technology gave the astronomers that ‘four Earths wide‘ estimate. But the Spot’s shrunk in the last 150 years.”

“A whole lot?”

“Last measurement I saw, it’s just barely over one Earth wide. Seems to have gotten a bit taller, though, and maybe deeper.”

“Taller and deeper? Huh, that’s a new one. I always thought of the Spot as just this big oval ring on Jupiter’s surface.”

“Everyone has that bogus idea of Jupiter as a big smooth sphere with stripes and ovals and swirls painted on it. Don’t forget, we’re looking down at cloud tops, like those satellite pictures we get looking down at a storm system on Earth. From space, one of our hurricanes looks like a spirally disk centered on a dark spot. That dark spot isn’t in the clouds, it’s actually the top of the ocean, miles below the clouds. If you were a Martian working with photos from a telescope on Phobos, you’d be hard-put to figure that out. You need 3-D perspective to get planets right.”

Jupiter image courtesy ESA/Hubble

“Those stripes and stuff aren’t Jupiter’s surface?”

“As far as we can tell, Jupiter doesn’t have a surface. The hydrogen-helium atmosphere just gets denser and denser until it acts like a liquid. There’s a lot of pressure down there. Juno recently gave us evidence for a core that’s a fuzzy mix of stony material and maybe-metallic maybe-solid hydrogen but if that mush is real it’s only 3% of the planet’s mass. Whatever, it’s thousands of miles below what we see. Jupiter’s anything but smooth.”

“Lumps and bumps like this bubbly scone, huh?”

“More organized than that, more like corduroy or a coiled garden hose. The white stripes are hundreds of miles higher-up than the brown stripes so north-to-south it’s like a series of extreme mountain ranges and valleys. The Great Red Spot reaches up maybe 500 miles further.”

“Does that have to do with what they’re made of?”

“It has everything to do with that, we think. You know Earth’s atmosphere has layers, right?”

“Yeah, the stratosphere’s on top, then you got the weather layer where the clouds are.”

“Close enough. Jupiter has all that and more. Thanks to the Galileo probe we know that Jupiter’s ‘weather layer’ has a topmost blue-white cloud layer of ammonia ice particles, a middle red-to-brown layer containing compounds of ammonia and sulfur, and a bottommost white-ish layer of water clouds. The colors we see depend on which layer is exposed where.”

“But why’re they stripey?”

~~ Rich Olcott

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Planetary Pastry, First Course

“Morning, Al.  What’s the scone of the day?”

“No scones today, Sy.  Cathleen and one of her Astronomy students used my oven to do a whole batch of these orange-and-apricot Danishes.  Something to do with Jupiter.  Try one.”Great Apricot Spot 1
Cathleen was standing behind me.  “They’re in honor of NASA’s Juno spacecraft.  She just completed a close-up survey of Jupiter’s famous cloud formation, the Great Red Spot.  Whaddaya think?”

“Not bad.  Nice bright color and a good balance of sweetness from the apricot against tartness from the orange.”

“You noticed that, hey?  We had to do a lot of balancing — flavors, colors, the right amount of liquid.  Too juicy and the pastry part comes out gummy, too dry and you break a tooth.  Notice something else?”

“The structure, right?  Like the Spot’s collar around a mushed-up center.”

“Close, but Juno showed us that center’s anything but mushed-up.  <pulls out her smartphone>  Here’s what she sent back.”

GRS 1 @400
Credits: NASA/JPL-Caltech/SwRI/MSSS/Jason Major

“See, it’s swirls within swirls. We tried stirring the filling to look like that but it mostly smoothed out in the baking.”

“Hey, is it true what I heard that the Great Red Spot has been there for 400 years?”

“We think so, Al, but nobody knows for sure.  When Galileo published his telescopic observations of Jupiter in 1610 he didn’t mention a spot.  But that could be because he’d already caught flak from the Church by describing mountains and craters on the supposedly perfect face of the Moon.   Besides, the Jovian moons he saw were much more exciting for the science of the time.  A planet with satellites was a direct contradiction to Aristotle’s Earth-centered Solar System.”

“OK, but what about after Galileo?”

“There are records of a spot between 1665 and 1713 but then no reports of a spot for more than a century.  Maybe it was there and nobody was looking for it, maybe it had disappeared.  But Jupiter’s got one now and it’s been growing and shrinking for the past 185 years.”

“So what is it, what’s it made of and why’s it been there so long?”

“Three questions, one of them easy.”

“Which is easy, Sy?”

“The middle one.  The answer is, no-one knows what it’s made of.  That’s part of Juno‘s mission, to do close-up spectroscopy and help us wheedle what kinds of molecules are in there.  We know that Jupiter’s mostly hydrogen and helium, just like the Sun, but both of those are colorless.  Why some of the planet’s clouds are blue and some are pink — that’s a puzzle, right, Cathleen?”

“Well, we know a little more than that, especially since the Galileo probe dove 100 miles into the clouds in 1995.  The white clouds are colder and made of ammonia ice particles.  The pink clouds are warmer and … ok, we’re still working on that.”

“What about my other two questions, Cathleen?”

“People often call it a hurricane, but that’s a misnomer.  On Earth, a typical hurricane is a broad, complex ring of rainstorms with wind speeds from 75 to 200 mph.  Inside the ring wall people say it’s eerily calm.  The whole thing goes counterclockwise in the northern hemisphere, clockwise in the southern one.”

“So how’s the Great Red Spot different?”

“Size, speed, complexity, even direction.  East-to-west, the Spot is eight times wider than the biggest hurricanes.  Its collar winds run about 350 mph and it rotates counterclockwise even though it’s in Jupiter’s southern hemisphere.  It’s like a hurricane inside-out.”

“It’s not calm inside?”

“Nope, take another look at that Juno image.  There’s at least three very busy bands wrapped around a central structure that looks like it holds three distinct swirls.  That’s the part that’s easiest to understand.” GRS core

“Why so?”

“Geometry.  Adjacent segments of separate swirls have to be moving in the same direction or they’ll cancel each other out.  <scribbles diagram on a paper napkin>  Suppose I’ve got just one inside another one.  If they go in the same direction the faster one speeds up the slower one and they merge.  If they go in opposite directions, one of them disappears.  If there’s more than one inner swirl, there has to be an odd number, see?”

“So if it’s not a hurricane, what is it?”

“Got any donuts, Al?”

~~ Rich Olcott