All About Mars, and the Tumbling Potato in the Sky

Note: I almost didn’t do this post, figuring pretty much everybody already knows everything about Mars already, right? But I ended up doing it because a) I’ve been following Mars* across the sky for months now and b) the stuff about Mars’ moons turned out to be way freaky cool.

*Speaking of following Mars… Though these Astro-posts may seem a bit random, I’m actually going somewhere with it. My goal is to continue East across the Southern sky, filling in blanks, until I make a complete “wrap-around.” Then someone who’s been following this blog would have a complete map across the sky, with a bunch of neat stories about stars and such along the way. Wouldn’t that be cool? Anyway, that’s the idea- we’ll see where it goes. Got my eye on Hydra and Saturn next…

I usually camp down in the desert a handful of times over the winter, but this past season only did so once, back in January with Arizona Steve. As is my habit I slept out under the stars, and as I often do when camping, woke briefly every few hours, and glanced quickly at the sky each time. My feet were pointed West, and gradually, next to Gemini, a bright orange star tread its way across the sky, setting by the foot of my sleeping bag around 4:30. As we know by now, there are many orange stars in the sky- Betelgeuse, Aldebaran, Pollux- but Mars is brighter than them all.

Mars is fascinating because it’s both so similar to and different from Earth at the same time. It’s (usually*) the 2^nd closest planet to Earth, and, when visible, is either the 2^nd or 3^rd brightest planet in the sky**. In size and mass, it’s pretty much mid-way between the Earth and the Moon. If Earth were a softball, the moon would be a ping-pong ball, and Mars would be (roughly) a racquetball. As Mars has about 1/10^th the mass of Earth, the Moon has about 1/10^th the mass of Mars. The Earth’s surface gravity is about 2 ½ times that of Mars’ (0.38g) which is in turn roughly 2 ½ times that of the Moon’s.

*It can be 1^st, 2^nd or 3^rd depending on where it, Venus and Mercury are in their orbits relative to Earth.

**Usually Jupiter is brighter.

Extra Detail: Mars’ gravity is so much less than Earth’s primarily because it is less massive, but also because it is less dense. Surface gravity is dependent on both mass and density, which is why Mercury, which is less massive but denser, has a higher surface gravity than Mars.

What I love most about Mars is that it’s the only thing you can look up at which has- like Earth- both ground and sky.

Mars And My Family

My father was* an electrical engineer. He worked for 4 companies in his entire career, a number I beat by age 30. In the mid-1970’s he worked for Itek Optical Systems Division, a subsidiary of Litton Industries, the company that developed and produced the cameras for the Viking Lander program. After the successful completion of the mission, my father and the rest of his team received as a gift a bound coffee-table book full of color photos of the Martian landscape and sky. Today this doesn’t sound like a big deal, but in 1977, to a sci-fi-obsessed 13 year old kid, before Internet or (in our house at least) color TV, it was amazing. One day my dad just brought home a picture book from another planet. I’d seen pictures from the Moon of course, but Mars was way different. The surface was that striking orange, compared to the endless gray of the lunar surface, but the big difference was sky. It wasn’t just a rock in space- the place had sky. It may have been the wrong color, but it was really sky.

*The past tense in this instance indicates his career, not his life. My dad is alive, healthy and happily retired.

Every other planet in the solar system besides Earth and Mars has either no sky or no surface (or neither of either.) The small planets and dwarf planets- Mercury, Pluto, Ceres, Sedna, Eris et al- are all too small to retain atmospheres; their “sky” is the permanent inky black of space. The big planets- Jupiter, Saturn, Uranus and Neptune- may well have a sky, if you’re up high enough in the atmosphere, but no surface on which to stand and view it. Venus has a hard surface, but is forever wrapped in a shroud of super-heated, crushingly-dense cloud cover*. Only Mars and Earth have ground and sky.

*I once read (forget the source) that Venus’ atmosphere is so dense that if it were clear, light at the surface would be bents such that you could see clear around the planet in the sky above.

Mars has sky because it has an atmosphere, though it’s only 0.6% as dense as Earth’s, so thin that- as anyone who saw Total Recall knows- a human would require a pressurized spacesuit to survive. The atmosphere is overwhelmingly composed of carbon dioxide (95%), with a small amount of nitrogen (2.7%) and traces of other gases. Mars’ “air” is so thin not just because of its lower gravity, but because it lacks a magnetic field to shield the planet from cosmic radiation, which gradually ionizes and strips gases from the atmosphere.

Extra Detail: Interestingly, it appears that Mars had a magnetic field in the distant past and that, like our magnetic field, it periodically reversed polarity. Scientists theorize that a few billion years back Mars’ outer core cooled and solidified enough to shut down the convection currents producing the field.

When I first saw color photos of the Martian surface, I was reminded of the American Southwest, which I’d only seen in photos at the time, and when I eventually made to places like Moab- but before I knew much about Mars- I wondered if I was seeing something like Mars, but the resemblance is purely coincidental.* The orange of the Martian surface isn’t the orange of (sedimentary) slickrock, but rather the orange of rust- ferrous oxide (FeO).

*Well, mostly coincidental. Really red slickrock- like much of the Entrada formation- has that color because it has a fair amount of iron in it, and the iron has oxidized. But the formation processes of Utah slickrock and Martian surface-rock are way, way, completely different.

The ferrous oxide dusts in the atmosphere give the Martian sky its strange and lovely orange/pink hue, making for spectacular sunsets. Mars has sunsets and sunrises about as often as we do; the Martian day is 24 hours and 40 minutes long. Mars also has seasons; its axis is tilted 25 degrees, compared with 23.5 degrees for Earth. Of course the seasons are each about twice as long as ours, as the Martian year is about 687 (Earth) days long.

Mars has polar ice caps (pic left) up to 2 miles thick, and over the long seasons these caps grow and recede annually. The ice of the caps is primarily water. Though liquid H2O on the Martian surface appears to be extremely rare*, it’s still abundant in the ice caps. In winter, another layer of ice forms atop the ice caps and surrounding polar areas, but this ice is dry ice, frozen CO2 condensed out of the atmosphere, and fallen as snow. In the spring as these “snows” sublimate**, huge winds blow off the ice caps, giving rise to dust storms hundreds of miles across. Every few decades*** dust storms develop on such a scale that they envelope the entire planet, which has a surface area roughly equivalent to all the landmasses of Earth.

*It’s still unresolved as to whether liquid water ever flows on the Martian surface nowadays, though there have been tantalizing hints in recent years.

** Sublimate = convert from solid to gas, with no intermediate liquid phase.

***Observed in 1971 and 2001 (pic above).

Side Note: Although the winds in such storms can reach speeds of a couple hundred miles per hour, they don’t pack the punch of Earth-winds at that speed, due to the low density of the Martian atmosphere.

Speaking of ice, Mars has clouds. Not the wet, cumulus-style clouds I blogged about up in Montana, but cirrus clouds, like we get here way up high in the stratosphere on Earth and are composed not of water droplets, but of ice crystals. But on Mars, there are 2 types of cirrus clouds: H2O and CO2, with CO2 clouds typically occurring at higher (and colder) altitudes.

Mars is superlative in other ways. It boasts a canyon, Valles Marineris, that is 2,500 miles long and 4 miles deep- 9 times as long and 4 times as deep as the Grand Canyon- and which was apparently formed by ancient water flows. Mars’ highest peak- Olympus Mons- is an extinct volcano 3 times the height of Everest. If such a peak stood on Earth, it would tower far into the stratosphere, higher than any jetliner could fly.

But when I look at Mars at night, I’m most fascinated by what an observer there would see looking back. With air so thin, the night sky must be fantastic. Under ideal conditions far from cities, a human observer can see some 2,000* stars on a clear night. How many could one see from Mars? 10,000? 50,000? And which “star” would be the brightest?

*At one time. About 6,000 are visible total.

All About Phobos

This one’s a little tricky, because probably the brightest “star” would the smaller of its 2 moons. Mars has 2 moons, Deimos and Phobos. Both are far smaller than our moon, and irregularly shaped. Phobos, the larger, is only 17 miles in diameter at its widest point. Our own, freakishly-large, moon is more than 2,000 miles in diameter! But Phobos appears fairly large in the Martian sky- about 1/3 the size of our own moon- because- and this is the coolest thing about Phobos- it orbits only ~3700 miles above the planet’s surface (compared with ~238,000 miles for our own moon.) This closeness has 3 weird effects. The first is that to a Martian observer, a “Phobean month” is only 11 hours long. And weirder still, Phobos rises in the West, and sets in the East.

No, Phobos isn’t retrograde*; it’s so low/close that its orbit is sub-geosynchronous. A geosynchronous orbit is that distance at which the orbiting object is always “above” the same point on the planet, and appears to be stationary in the sky. Geosynchronous orbit around Earth is at a height/distance of 66,000 miles, and many satellites orbit the Earth at this distance for this reason. Our moon is well above/beyond this distance, and so our day is shorter than our month, and our moon appears to rise in the East, and set in the West, like, well everything else. But Phobos orbits Mars faster than the planet is turning, so it appears to move East across the sky, in a direction opposite to everything else in the sky!

*Pretty much everything in the solar system rotates and orbits in the same direction- counterclockwise, when viewed from above the Earth’s North Pole. There are exceptions, where things rotate or orbit clockwise, and these exceptions are called retrograde. Venus and Uranus, for example, have retrograde (and really weird- though for different reasons) rotations, as does Pluto. Similarly, some number of moons of the outer planets have retrograde orbits. Most of these are really small moons, and are thought to have been asteroids captured by the gravitationals field of the planets which they now orbit. But Neptune’s retrograde moon Triton is pretty respectable-sized- a large marble compared to the ping-pong ball of our moon.

Keep in mind that a retrograde moon might still appear to move East to West across the sky, depending on its orbital radius and speed, and the host-planet’s rotational speed. But that’s all beside the point. Neither of Mars’ moons is retrograde (though both are suspected to be captured asteroids); Phobos is just really low/close.

The third weird thing about Phobos (pic right) is that it orbits so low- and roughly around the Martian equator- that it’s quite low in the sky at middle latitudes, and completely invisible in the polar regions, or at any latitude above around 70 degrees. Phobos orbits its planet more closely than any other moon in the solar system. Its orbit is unstable and it’s expected that in about 50 million years it’ll either crash into the surface, or break up and form a ring around the planet.

Side Note: There’s a fourth weird thing about Phobos, which while not directly related to its close-ness, is evident to a Mars-based observer because of it- its shape. It’s not spherical, but rather sorta-kinda elliptical/potato-shaped. So it looks like this giant tumbling potato going the wrong way across the sky.

Deimos is also sorta-kinda elliptical/potato-shaped, but is far/small enough that it wouldn’t be obvious to a naked-eye Mars-based observer.

A Bit About Deimos

Deimos, the smaller moon (pic left), is only 9 miles across at its widest, and orbits somewhat further out, around 12,000 miles above the surface. At night it appears as a very bright star, slightly brighter than Venus appears to us. Its orbit is just above/beyond geosynchronicity, so it travels across the sky in the “right” direction (East-to-West), but appears to do so more slowly than it’s really moving. Deimos orbits Mars once every 30 hours, but takes almost 3 days from moonrise to moonset, as it slowly falls behind the planet’s rotation.

So the brightest “star” in the Martian sky is a weird Venus-like thing that travels clear across the sky in just 3 days. But the 2^nd brightest star is Earth. Earth is an inferior* planet to Mars, so it only appears in the Eastern or Western skies, near dawn or dusk. It’s a bright bluish star, but often appears white because of the reddish tint of the Martian sky. Our moon is also visible, as a smaller white star close by. Both present phases to Mars as inferior bodies- such as Mercury, Venus, and the (less-than-full) Moon- do to us, and the phases of both are always the same relative to a Martian observer.

*”Inferior” in astronomy means closer to the sun. “Superior” denotes further from the sun.

Almost 2 years ago, I blogged about climbing a remote peak out in the West Desert. When I summitted and read the register, I learned that I was the first person to stand there for 462 days. I’ve had that experience several times on peaks, being the first person there to visit in as long as 3 ½ years. Whenever I do, I’m always awed by the thought of so many days and nights having passed in that spot with nothing happening. No one talking or walking or laughing or thinking or anything else. Though perfectly reasonable rationally, on an intuitive level it just seems somehow not quite believable, not quite possible, that nothing could happen in a place for so long.

Of course anywhere on Earth, stuff is happening; birds pass by, bugs crawl past, flies buss, lichens grow. But when you look up at Mars, you’re looking at a world- a real world- with ground and sky and moons and sun and stars, where, really, nothing ever happens, and hasn’t happened for billions or years, if ever. Not just a mountaintop, but a whole planet. Just rocks, sand, ice and wind, an endless succession of days and nights for longer than you can ever imagine. It just boggles my mind.

Anyway, that’s what you’re seeing when you look up at that bright orange star East of Gemini.

Race Camp Part 2: Singletrack Hooky with Tyler2

Four helmet-cam videos in this post. First two are a bit geeky, second two rock.

The days at Race Camp were spent on the road of course, but it’s just too wrong to come down to St. George and not bring the mtn bike, so Thursday AM I snuck out early and hit Barrel Roll. I blogged about this trail over a year ago in my Botany of St. George Series. Here’s a ~5 minute-long helmet-cam clip. Almost all the shrubs on this stretch are Blackbrush or one of 2 species of Mormon Tea- Ephedra Viridis and E. Torreyana. The Viridis is bright green, and broom-like, with the stems all pointed up. The Torreyana is a light blue-green, usually lower to the ground, and the stems stick out at all kinds of angles. If you watch closely, you can easily pick the 2 out.

Or don’t, and just watch the clip for a singletrack fix. I don’t care, it’s just filler. But isn’t it pretty?

Video #1 Notes

The day before it rained, so the air was super-clear on this ride. The snow-dusted mountains in the distance right when the clip starts are the Beaver Dam Mountains. The lower slopes on the far side of the range are studded with Joshua trees. Soon (about 0:10) the Entrada sandstone cliffs of Snow Canyon swing into view to the North/Northwest. Entrada is the smooth, (usually) reddish sandstone layer which occurs above the Navajo formation. The fabulous arches of Arches National Park and the hoodoos of Goblin Valley are carved out of it, and if you’ve ever ridden Bartlett Wash, you’ve pedaled on it. In general it’s not quite as high-traction as Navajo sandstone, but is often smoother.

At about 1:52 you can see the snowy Pine Valley Range to the North come into view on the left side of the screen, and to the right of Snow Canyon. At around 2:30 you’ll see a band of cliffs across the gorge in the low foreground. This is Land Ridge, atop which runs the Tempi’po’op trail, which I blogged about in the petroglyph post. A better view of Land Ridge appears at around 3:20.

On Saturday, after 3 days of hard road-riding, I and one other teammate- Tyler2 from last year’s High Uintas Classic- forsook the road and broke out the mtn bikes for a fast JEM/Hurricane/Gould Rim loop before the weather turned foul.

Tangent: I’m just curious- how many readers besides me played hooky in school? I did, just twice, both in 7th grade. One time we went bowling, the other I can’t remember what we did. The first time, my confederate and I- let’s call him “David Galante”- called in to school as each other’s mothers to excuse ourselves. (Why we didn’t just call in as our own mothers, I’m not sure- maybe at the time it seemed less scary to impersonate someone else’s mom.) Since neither of our voices had changed, the calls went fine.

The second time, I decided to blow off calling in, figuring (correctly) that the bureaucracy was to clumsy to track down a kid with no other (known) behavioral issues. But David called in, and the school secretary didn’t believe him. She hung up and called David’s house, immediately reaching his mother.

Nested Tangent: How does it work these days, what with caller-ID and all? Do kids still fake-call-in-sick as their parents? Where from? Do they have to swipe Mom’s phone?

Fortunately, David’s mother had both a quick mind and perhaps of a bit of criminal free-spirited streak as well, and covered for David, saying oh yes, that was me calling in… Cool mom. I wonder how David turned out…

We rode the loop counterclockwise, and in this first clip are riding South along Hurricane Rim, descending into China Wash.

Tangent: I love switching back and forth between road and mtn bikes. I find that after 3 or 4 days on one, the other feels fantastic- almost liberating. The road bike feels incredibly light and fast and precise after a few days on the mtb, while in the reverse case the mtb feels powerful, smooth and thrilling. I don’t get roadies who never mtb- don’t they get burned out? I’ve a bit more sympathy for mtbers who never road-ride (I was one for many years) but still love switching from one to the other.

Video #2 Notes

I blogged about this ride as the classic “Bench Level” ride in the Botany of St. George series. In that post I mentioned how one of the cool things about this ride is that it dips in and out of the botanical Mojave, as defined by the upper limit of creosote. The descent into China Wash is one of those transitions. At around 10 seconds in, you’ll see creosote- tall spindly shrubs with distinct olive-hued leaves- start to appear alongside the trail. As a reminder, this is the Mojave race of creosote, chromosomally hexaploid, with 78 chromosomes. The snow-covered mesa in the background is Gooseberry Mesa; behind and to the right is Little Creek Mountain.

OK, now for the good stuff. We descended to the Hurricane T/H, crossed highway 59 and picked our way up the jeep road to the Gould Rim trail. Up, up, up. We had to modify our route a bit to avoid some bad clay-mud, but eventually found our way up high on JEM trail, ready for the descent.

Video #3 Notes

The video starts in a small wash draining the cliff-band ringing the base-bench of Gooseberry Mesa. Soon we leave the wash, and at 1:35, as we roll off the end of an earthen “spine”, things get fast. Soils up here are clay, and still had enough moisture from storms earlier in the week to be hard-packed, tacky, and dust-free- pretty much perfect. At around 2:00, the cloud-capped range that appears in the background is the Pine Valley Range, possibly the world’s largest laccolith, as described in this post. We’re several hundred feet higher here than we were in the China Wash video, and you’ll notice there’s not a creosote bush in sight.

Wow! That was fun! We spent the next 15 minutes or so rapidly descending, then rolling, more of the same, until we arrived at the “cherry-stem” of the loop leading back to our vehicle. This stretch hugs the rim of a tributary-of-a-tributary, then the tributary, and finally the Virgin River Gorge itself.

Video #4 Notes

At about 30 seconds we start running along the first of the 3 rims (tributary-of-tributary). I’ve ridden this many times, but this was the first time I’d seen water running in the bottom. At around 2:00, as we start riding the second rim (tributary), I look back and down to the left at a small, muddy waterfall emerging from the mouth of the tributary-of-tributary we were just riding alongside.

The tributary soon joins the Virgin River Gorge proper, and at 3:25- the point of maximum exposure- you can see the rain & snowmelt-swollen Virgin River below.

Well, that was a fun vacation. Spring is around the corner. Can’t wait to get back down to the desert.

Race Camp Part 1: Asphalt, Canyons and Faults

What’s this? A whole week without posting?* Yikes! What is the world coming to? Well I didn’t post because… yeah, yeah- you think you know already- I was real busy with work, right? Wrong! I was on vacation. Specifically, I was attending “Race Camp.”

*Don’t worry- I’ll get back to Mars soon enough.

My new team goes down to St. George every March for 4 or 5 days of early-season riding and such in an outing called ‘Race Camp.” It’s about the cushiest “camp” I’ve ever attended: 3 of the guys have- or have friends/family with- places in town, so I slept in a soft bed every night. After a few weeks of not-enough sleep, the riding all day and sleeping 8 hours/night thing was pretty sweet.

Tangent: Which reminds me, someday I want to do a post on sleep, and how phenomenally weird it is. Think about it- you do stuff all day and then you get tired. Real tired. So tired that you lie down and lapse into unconsciousness. Now under other conditions when you lapse into unconsciousness- fainting, passing out, exhaustion-collapse- it’s considered a serious medical situation, and people will call an ambulance, or if they’re on an airplane, the pilot or maybe head flight attendant will come on, and ask if there’s a doctor on board the aircraft.

Nested Tangent: That’s like the only time I ever wish I were a doctor. Seriously, 99.99% of the time I have absolutely no desire whatsoever to be a doctor. Oh I know they make good money and get respect and all, but I just couldn’t do it. You probably think it’s because I get grossed out by blood or organs or what-not, but that’s not it. No, what turns me off is having to listen to people complaining, and when you’re a doctor, all you hear is people complaining all day- my toe hurts, I’m fatigued, my hair hurts, I’m dying of such-and-such, I’m hosting an alien predator organism, blah, blah,- all day long. I’m way too self-involved and non-empathetic to deal with all that. But when the pilot asks for the doctor on board, and some guy or lady stands up and starts walking back, you- and everyone else on the plane- thinks, “Wow! He/she is probably going to save someone’s life! He/she is so awesome!”

You know what I wish? That just once- just one time- the pilot would come on and say, “Ladies and Gentleman, we have a Sales Emergency. If there is a Salesman onboard this flight, would you please identify yourself to the flight attendant?” And then I’d stand up and start walking back, and everyone would be looking at me and thinking, “Wow! A salesman! He’s probably going back there to close a deal! He is so awesome!”

But every day, pretty much all of us lapse into unconsciousness, and it’s totally no big deal; 99.9999% of the time, you wake up just fine. And not only do you wake up just fine, you feel better. You didn’t eat or drink anything, no one injected you with anything, you just lay there, doing nothing. How does that make you feel so good? Anyway, that’s why I want to do a post on sleep. But I couldn’t do any research on it last week. Because I was too busy biking. And sleeping.

So no research, no good science, but some great helmet-cam footage. This first one is really just FYI. In several race-season posts last year I referenced a “double paceline.” Here’s what it looks like when you’re in one. This was Friday as we rolled through Sand Hollow, on our way out to Zion NP.

Note: One thing about all of these videos- from time to time you’ll see the camera suddenly swivel to the side about 90 degrees. When this happens, I’m actually looking back. But when you look back on a bicycle, your head only actually swivels maybe 90-110 degrees; the rest of the look-back is done but moving your eyes. BTW, all the YouTube videos here are in HD, so toggle up to 720p to view.

We continued on and up through Hurricane, La Verkin, Virgin, Rockville, Springdale and finally to Zion National Park. Once in the park we soft-pedaled our way up to the end of the road, by the mouth of Zion Narrows.

All About Zion

Utah has 5 national parks. They’re all great, but Zion is probably tops for sheer majesty. The centerpiece of Zion NP is Zion Canyon, which has been carved out of the Southern edge of the uplifted Markagunt Plateau by the North Fork of the Virgin River. The Markagunt is of course a) one of the 3 high plateaus of Southern Utah and b) the only one of the 3 I haven’t properly blogged about yet (though I keep promising to do so.) As the plateau has lifted and tilted, the river has gradually worn away at the layers of underlying sedimentary rock beneath. It’s estimated that the canyon is deepening by about an inch a century or so, and probably more in wetter times, such as the most recent ice age.

As you stand in the bottom of Zion Canyon, the towering cliffs around you are Navajo sandstone, a formation formed from petrified sand dunes somewhere around 200 million years ago. Navajo is the “classic” slickrock. Moab’s slickrock trail rolls across it, and most of the best slot canyons on the Colorado Plateaus are carved out of it. In little-known places down on the Navajo Reservation in Northeastern Arizona, it forms long, endless waves, where you can surf a bike for hours without seeing another soul.

Immediately below the Navajo, forming the low, broken slopes rolling down to the canyon bottom, is the Kayenta formation. In many areas across the Colorado Plateau, Kayenta is prime rock for finding dinosaur tracks (Triassic species).

Extra Detail: Wonder what’s under you? Probably the Wingate formation, which is what the high walls of lower Twin Corral Box Canyon are made of…

Tangent: Here’s a way to tell native Utahns from non-natives: Natives always refer to the park as “Zion’s”, with a (presumably possessive) “s” at the end. Non-natives always just call it “Zion.” I don’t know why this is; “Zion” isn’t a guy; it’s a term that refers to the biblical land of Israel. How did it come to be used in the possessive form? Utahns of all sorts, BTW, both native and non-native, pronounce it “ZIGH-un.” Only out-of staters say “ZIGH-on.” While we’re on the topic, only out-of-staters say “ALL-tuh”, when speaking of the ski resort Alta. Utahns say “Al-tuh”, where the fist syllable is pronounced like the first syllable in “Alex.”

Here’s a clip of Teammate-Brian and I, who dallied up top, zipping down-canyon to catch the pack, picking up Legendary Courtney en route. This clip has some nice shots of the high canyon walls.

Together we pacelined quickly back the way we’d come up, until we finally approached the big drop down to La Verkin. In this clip, about 35 seconds in, Teammate-Perry takes off, I jump on his wheel, and together we hammer down the descent at about 45MPH, rotating leads to maintain the break.

Extra Detail: This hill we’re descending by the way, isn’t just any hill- it’s the Hurricane Fault, the westernmost edge of the Markagunt (and I believe entire Colorado) Plateau. When we drop this hill, we’re actually crossing geologic provinces, from Colorado Plateau, to Basin and Range, the province which continues clear to the Sierra Nevada. (Damn- I tell you what: For a glorified video-filler, this post’s got some kick-ass geology…)

It was a long, great day. Here’s one more clip, that’s mainly for out-of-staters. If you’ve never visited Zion NP before, but always wanted to, here’s your chance- 11+ minutes of footage rolling up-canyon from just above Zion Lodge. The riding isn’t very exciting, but the scenery’s great.

So, weren’t those pretty videos? That’s nice, because tomorrow’s videos will knock your socks off.

Next Up: Tyler2 And I Play Hooky.

Gemini and Secret Languages

I can’t believe it’s March already. It’s easy for the cold months to run into one another, but little hints, like later sunsets, and Robins chirping at dawn have been reminding me of the coming spring.

The night sky has changed as well. The Northern Astro-Clock has progressed considerably. Check out the relative positions of the Big Dipper and Cassiopeia at 8PM below.

These are roughly the same positions as they held at 6AM back in October during AstroWeek, which makes perfect sense: we’ve progressed 5 out of 12 months since then, and the sky has similarly progressed 10 out of 24 hours over the same period of time.

While the rotation/advance of the Northern sky has been fun to watch, the progression of the Southern sky has been much more exciting. Rather than a slowly-turning wheel, the Southern sky has been a procession of new constellations climbing out of the East, one after the other. When we first started watching back in October, Orion would be center-stage in the Southern sky at ~6AM. Now it’s there at ~8PM, and by dawn it’s long since set.

Tangent: This has been one of the coolest things about this winter for me. I did AstroWeek back in October kind of on a lark, but it got me interested in the night-sky, and this has been the first year ever that I’ve really paid attention to the changing stars. Oh, I always knew a constellation or two and some odd astro-factoids, but I never really put it all together before, the way it’s coming together for me this year.

Lots of people I think get curious about the stars and get a book or chart or whatever and try to check stuff out all at once, then get distracted or what-not and never get a feel for the “map” up above us. My advice to any novice star-watcher is this: Start slowly. Pick one-just one- constellation and really get to know it. It doesn’t matter if you know anything about the stars (though obviously, that’s what I get off on) but just get a feel for the positions, brightness and color hues of the members of that constellation. When you know it well enough that it starts to seem familiar, like an old friend, pick another one next to it, and start to do the same, paying attention to how the 2 fit together. A natural way to progress is to take the next constellation East, as it rises in the sky above you over a few weeks.

After a while, “chunks” of sky will start to fit together, and large stretches of night-sky will become as familiar as your neighborhood, yard or office park. But unlike those places, even when you’re far from home, you can look up at night and quickly get a reassuring twinge of familiarity, of something you know and can count on, when you’re thousands of miles from friends and family.

2 weeks ago I landed in San Jose at night. It was one of those small Canadair jets where you all mill around on the tarmac for a bit, waiting for your roller-bags to be brought around. I’d been traveling a lot and working long hours, and I was feeling a bit down and beat up. I looked up and recognized the Southern sky- Orion, Auriga, Pleiades, Aldebaran, Gemini- the same familiar view from my own back yard- and suddenly I felt grounded, reassured, and well, not alone somehow all at the same time.

I’ve mentioned Gemini in passing a couple of times; it lies North and East of Orion, or as you’re looking South at the “upright” Orion, it’s above it and to the left. It’s not quite as obvious as Orion or the Big Dipper, but easy enough to spot that once you find it, you’ll almost always pick it out right away (sort of like Auriga.) “Gemini” refers to the mythological twins, Castor and Pollux, for whom the brightest, and Northern/topmost stars of the constellation are named.

Tangent: As most longtime readers know, 2 of my children- Twin A and Twin B*- are- yes, that’s right- twins. When people learn you have twins, they often ask questions about them. Some of these questions (“Are they identical?”, right after I’ve told the questioner they’re boy-girl) are just plain dopey, but most are just curious. One of the most common is: “What’s it like to have twins?”, to which my honest answer is: “It’s like having 2 kids the same age.” Really, that’s what it’s like. They don’t look particularly much alike, they don’t have a secret language, and one doesn’t say “ouch” when you poke the other with a pin (though in fairness, I haven’t actually tried that**.)

*They were named Twin A and Twin B by the OB during the first ultrasound, in the order in which he located them. As it turned out, they were born in the same order.

**Yet.

Nested Tangent: When I answer the “secret language” question (always in the negative, of course) the questioner always seems a bit deflated. People so want twins to have a secret language or special connection or telepathic powers. But it just isn’t the case. Sometimes I try to console the disappointed questioner by offering some other mental-prowess factoid in our family, such as Bird Whisperer’s ability to recall endless animal-related facts, or my own ability to recite the entire prologue from Bitchin’ Camaro, but these feats never seem to deliver what the questioner was looking for.

It’s an interesting question though, because you know who does often have a secret language? Married couples, that’s who. Think about it- if you have a long-term spouse or partner, I’m betting the 2 of you have code-words for things you want to communicate but don’t want others to understand*. Awesome Wife and I have number of code-words we use. One example is “boob job”, for which we use the word trabajo (Spanish word for “job”.)

*My own birth family used the Greek words for things like “money”, “tip”, “shut up”, or “woman of questionable moral character.”

Of course lots of people around here speak Spanish, and for a time we wondered whether trabajo was really a great code-word choice. Then one day about 4 years ago, coincidentally I found myself in a Mexican resort hot tub with 4 other guests, none of whom I knew. 2 were an American couple, who through their interactions with the waiter, had made clear that they spoke zero Spanish, and the woman sported a rather impressive (but frankly improbable) trabajo. The other 2 guests were Mexican men, both doctors, on vacation from Mexico City. So I chatted a bit with the doctors, in Spanish, and then asked them- carefully- what a boob job was called in Spanish. I had to ask it in a roundabout way, so as to avoid any obvious English cognates which the Americans might pick up on. So I said something like, “When a woman has had medical construction to the front part of the chest to make larger those specific parts, what is it called in Mexico? A trabajo?” It took a few tries, but finally one understood. “No,” he explained helpfully, “it’s not called a trabajo, we call it SILICONE…” thereby clearly and loudly articulating the one cognate I’d been hoping to avoid…

And generally they interact with one another much like other similar-aged siblings- sometimes best of friends, sometimes arch-enemies. What is different about having twins is 2 things. First, you tend to notice differences in development- walking, talking, reading, times-tables, bike-riding, skiing- much more so than you do between ordinary siblings. And second, you have absolutely zero patience for anyone else’s singleton-oh-having-a-baby-and-getting-up-in-the-night-is-so-hard story. Until you have newborn twins (or other multiples), you have absolutely no idea what “hard” is.

Castor and Pollux are the brightest stars in Gemini, and the easiest to pick out. Right off the bat, if you stare at them for just a bit, you’ll notice something pretty cool- they’re different colors. Pollux, on the left/Southeast and just a titch brighter, is orange, while Castor is appears white.

Pollux is orange, because, like Betelgeuse and Aldebaran, it’s another late-in-life, helium-fusing red giant. At 34 light years it’s closer than either of those stars, practically right in the neighborhood. But that’s not the cool thing about it. No, the cool thing about Pollux is that it is the easiest star in the sky to find that we know has a planet. That’s right- if you want to know you’re looking at a star with planets, just look up at Pollux.

To be sure, the planet we know of orbiting Pollux isn’t anything like Earth, but rather a giant almost 3 times the size of Jupiter. Bigger planets are easier to find* than little planets, so it doesn’t mean that Pollux doesn’t have smaller, Earth-sized planets, just that we haven’t found them.

*Specifically, Astrometry- or the detection of position changes of a star due to gravitational influences- and Transit Method- slight dimming of a star due to a partial “eclipse” by an orbiting body- both work better the larger the exoplanet in question.

Pollux’s planet lies roughly the same distance from Pollux as Mars does from our own Sun, but due to Pollux’s size it appears far larger- nearly 6 times as large- in the sky as our sun does in ours. Planets around red giants have so far appeared to be pretty rare, possibly because such planets don’t fare so well when a star becomes a giant.

*Though as it turns out, we’ve already looked at one other “be-planeted” red giant- Ain- just to the West and slight North of Aldebaran.

Side Note: As it turns out, there are 2 other planet-bearing stars within Gemini. The first, HR 2877 Geminorum, lies slightly outside the main constellation. It’s known planet is 6.5 times the size of Jupiter and orbits at a distance similar to that between Venus and our sun.

The second, HD 54554 Geminorum, is a yellow-white dwarf star lying inside the constellation. Its planet, nearly 5 times the mass of Jupiter, has highly elliptical orbit, ranging about 130 million miles to more than 300 million miles from the star, with a “year” of ~3.5 Earth-years. Imagine if our sun increased in size and shrank every year by more than 2 times!

But cool as Pollux is, Castor is even cooler, the most complex multiple star system we’ve looked at yet. Through a half-decent telescope, it appears as a double star. The 2 stars, Castor A and Castor B, are both hydrogen-fusing white stars*, orbiting each other once every 445 years, in a highly elliptical path, which brings them as close together as about 70 times the distance from Earth to the Sun, and as far apart as almost 138 times the Earth-Sun distance. But it turns out that each of these 2 stars has another, closer companion. Castor A’s close-companion (Castor Aa), is small orange star about half the mass of the sun, and orbits the main star every 9 days at a distance of 11 million miles. Castor B’s close companion (CastorBb) is a small red star, also of about ½ a solar mass, orbiting the main star every 3 days at a distance of less than 3 million miles.

*This makes them Class A stars. Our sun, which shines yellow-white, is Class F.

Extra Detail: Both of these small companions BTW, are spectroscopic doubles, meaning that they’re too close to be distinguished by telescope, but instead are detected by analyzing variations in the spectrum of the (apparent single) star which are cause by the close companions orbiting one another.

So Castor’s not a double star, it’s a quadruple. But wait- we’re not done yet! Orbiting this elliptical foursome at roughly 10 times the (average) distance between Castor A & B, and completing its circuit around them every 14,000 years, is another star, Castor C, which turns out to be yet another spectroscopic double! This double is 2 small red stars, each with about 60% the mass of the sun, which lie just over 3 million miles apart and orbit each other every 19 hours. So Castor is actually a sextuple system, consisting of 2 double stars orbiting one another, which together are orbited by another double star! Wow, that’s one complicated star.

Another interesting thing about Castor is that, like Mizar, Merak, Alioth, Phecda and Megrez in the Big Dipper, Castor appears to be part of a moving group, that is a bunch of stars of similar age, composition and presumably origin, which are headed in the same direction. But the Castor Moving Group doesn’t include any other stars in Gemini, which is one of those constellations in which practically none of the stars have much of anything to do with one another*. From our perspective it’s a broadly scattered group of a couple dozen stars, including Fomalhaut in Pisces and Vega** in the Summer Triangle.

*For example, Pollux is 34 light years away, Castor 51, and Mekbuda 1200 light years distant! Mekbuda is the true monster of Gemini; if it were in the position of our sun it would occupy a full 30 degrees of sky.

**A bright, fascinating star whose eventual fate might impact life here on Earth. I plan to blog about it come Summer.

In between Pollux and Castor, on a clear night, you may spot a dim star between the two, closer to Pollux. This is Sigma Geminorum, which may not look like much, but if your vision extended into the X-Ray end of the spectrum this would be far and away the brightest star in Gemini, and one of the brightest in the entire sky. Sigma Gemini is a double star, consisting of a giant and a dwarf that have become tidally locked*, with the same sides always facing each other (like the Moon and Earth.) This locking has effectively sped up the rotation of the giant, amping up its magnetic field, which in turn is heating the corona of the star and making it shine brightly in the X-Ray spectrum.

*I explained tidal locking in this post.

Mebsuta, a supergiant 900 light years away, is interesting in that it’s a late-in-life star of about 9 solar masses, right on the cusp of ending it’s life in a supernova, like Betelgeuse. But stars less than about 10 solar masses, end up as white dwarfs (as our sun will.) Mebsuta’s close enough to the limit that it could go either way- maybe blow up, but probably just burn out…

Practically every star in Gemini has a cool story, but we’ll wrap it up with just one more- Wasat. This star is classified as a “subgiant”, which means that its hydrogen core is just giving out, and it’s morphing into a giant. But that’s not the cool thing. Wasat lies within 0.2 degrees of the ecliptic, the path that the sun travels across the sky. Since the planets orbit the sun on a rough plane, this means that pretty much every visible planet* passes by Wasat at some point.

*Visible, as in naked-eye visible, is the important qualifier here. All the naked-eye visible planets (Mercury, Venus, Mars, Jupiter, Saturn, and maybe, sorta, possibly if you have phenomenal eyesight and the sky is super-clear Uranus) orbit pass within 7 degrees of the ecliptic. Pluto is off by as much as 17 degrees, and distant Eris is off by 44 degrees.

If fact, if you’ve been watching Gemini of late, you’ve no doubt noticed the huge orange star- brighter than any star in Gemini proper- just to the East of Wasat. That’s no star of course, but rather the “star” of this winter’s sky- the Red Planet.

Next Up: All About Mars

Wednesday Helmet-Cam Filler + I Need Your Business Advice

I’m probably not going to get another serious post in before the weekend. Though I’m not traveling this week, my new boss and about a dozen of my new colleagues are out at our office this week for our 4-day “Q1 Ops Review.” I’m still coming up to speed on my new employer’s terminology, but about a day and half into the meeting I figured out that “Ops Review” means “Really, Really Long Meeting.” We’re on all day, and then have dinners in the evening, so I’ve got pretty much no time for research.

Business Advice Tangent: No, I’m not giving any. I’m asking for some. This one’s really for Wasatch Front readers who are Red Iguana fans*. I need your advice. First 2 nights I took them to “nice” restaurants. Tonight they want Mexican. The best Mexican on the Wasatch Front is of course the Red Iguana, but they don’t take reservations, and there are 12 of us, and I know we’ll end up waiting at least 25-30 minutes. But it’s one of the few really great meals they could get in Salt Lake that they couldn’t get back in Connecticut. Should I do it?

*And if you’re not, why do you live here?

I mentioned to a couple of them that I was thinking about taking them there, but that there’d be a wait. They said, “Oh we don’t mind, we can have a few drinks at the bar while we wait…” but of course they don’t understand that the wait is outside on the benches, under the heat-lamps. So here’s my wacky idea (these guys like to knock back a few.) I could send our admin over to Wal-Mart* across the way this afternoon and have her pick up like a dozen (non-clear) water bottles, and a couple of six packs. Then I could decant the beers into the water bottles, and when we get there, hand them each a water bottle/beer which they can drink under the heat-lamps while we wait, without getting busted for Utah’s strict open container laws.

*This is another variable: I’ve never asked our admin to by me beer before. But she seems pretty cool. I bet she’d do it if I asked nicely.

Is this a bad idea? Or should I go for it? I know it sounds kind of Fast Times at Ridgemont High, but the thing is, I know these guys will be patient if they’re drinking…

In fact the only non-work time I’m spending this week is pre-dawn frozen singletrack rides, so I thought I’d just do a filler with some quick helmet-cam clips. First up is a piece of Sunday’s Emigration road descent, which I’m including specifically for Enel, who told me he loves road-biking. Actually this was the first time I ran the cam on the road bike. Gives a good feel for the speed, and mid-way through you can see my shadow, with the cam silhouetted atop my helmet.

Next up is a follow-up to a post from last Spring, when I did this graphic, explaining S-Curves on a mtn bike.

At the time I remember thinking, “Man, I wish I had a helmet-cam to show what S-Curves look like…” Finally, 10 months later and 300 miles North, here’s my clip:

Finally, remember the very first helmet-cam video I posted, 2 months ago, right here?

Here’s the same stretch yesterday morning. It’s still cold, but that higher sun angle is starting to do its thing. Spring is coming. The world is about to wake up again. Yeah.

The Dangers of Riding On Clay

I had so much fun riding the antenna hills trails that I returned last Sunday morning to sneak in a ride before flying out for work. I started later than usual, a little before 9:00AM, but it was cold and overcast, and the trail seemed solid, mostly frozen, if not rock-hard. Climbing the Shoreline trail from City Creek I zipped up the switchbacks, and onto the long rolling stretches linking up to the antenna towers road. Flurries blew in repeatedly, and the trail was covered with a think dusting of snow. Visibility was poor, and though the trail is just above downtown, the lack of visibility and other people made it feel as though I was in the middle of nowhere.

Keeping an eye on the time, I returned the same way, and soon began the descent back down the switchbacks into City Creek, and almost instantly knew I’d screwed up. The tires started to slide and throw huge chunks of clay-y mud up onto the bike’s frame, drive-train and me. The mud glommed onto the tires, making the wheels suddenly 2 or 3 times as heavy, and clogged in my brake-calipers, threatening to stop rotation altogether. I cursed and struggled to keep the bike on track, knowing that if I had to walk it, I might miss my flight.

Tangent: You know when I get crankiest? When I realize I’ve done exactly the kind of stupid thing that I’m disdainful of when others do it. I’ve actually blogged about people who ride muddy trails when unfrozen previously, and it pained me to think of another vampire-biker seeing my tracks/ruts and shaking his/hear head.

The most frustrating thing about clay trails is how dramatically a little (unfrozen) water can transform them. Dry or frozen they’re smooth, firm and high-traction- a joy to ride.

But add a little water and they’re sticky, soupy and slippery all at the same time. Wet clay sticks to tires, brakes and other components like nothing else, quickly increasing the bike’s weight by as much as 100% or more. Though it hasn’t (yet) happened to me, I’ve heard stories of bikes abandoned in mud to be retrieved days later, after things have dried out.

I held it together and rode through, clear down to the trailhead and my car. Wasting no time, I heaved the mud-caked bike (weighing probably 40 pounds) atop my vehicle, and drove straight to the do-it-yourself carwash. Foothill-clay-mud is almost impossible to wash off with an ordinary garden hose; I needed the power and warm water of the carwash blaster-nozzle.

Tangent: Yes, yes I know: taking your mtn bike to the carwash is a huge no-no. Water gets in seals, messes up bearings, yada, yada. But like many mtn bikers, I am an occasional closeted carwash visitor. It’s just so much easier and time-efficient than any other conceivable method to remove clay from your bike. I always feel sort of embarrassed, guilty and yet resigned all at the same time when I do it, sort of like a high-school kid who’s just completed an abstinence-only sex ed class: I know the safest thing is not to do it, but simultaneously am aware that given the combination of need and opportunity, I almost certainly will.

So I blasted away, spending the most time on the tires, and eventually the clay relented, loosened its grip and fell away. And as it did so I wondered the same questions I’ve wondered on so many previous carwash visits over the 15 years I’ve lived in Utah: What is clay, and when it gets wet, why is it so sticky, why is it so hard to wash off, and yet why is it so slippery at the same time?

Tangent: Utah mud is a surprise to transplants like me. In other parts of the country, mud is no big deal. People ride through it all the time. In fact mountain bike magazine reviews of tires routinely include descriptions of “mud-shedding” capability. In Utah there’s no such thing. No bike tire sheds mud. A “mud-shedding tire” is an oxymoron.

Utah clay-mud is an even bigger concern for backcountry drivers. Countless unpaved roads in Southern and Western Utah are completely impassable when wet. When I drive deep solo into the backcountry, I generally pack along a mountain bike as an escape pod, meaning that if I break down or get stuck, I can reasonably bike 50, 60, 80 miles or more to pavement and assistance. But in mud, my escape pod is as immobile as my vehicle; there’s nothing to do but wait, either for sun (to dry) or cold (to freeze.)

Ranchers and other folks who routinely drive around the Utah backcountry in fall/spring/winter typically bring along tire-chains, and if you look closely at deep, dried-out tire-ruts on many desert-clay roads, you’ll noticed that they’re cross-hatched with chain-marks.

All About Clay

When off-road and not on solid rock or pure sand, we tend to think of what we are traveling over as “dirt”. Dirt, as it turns out is way, way complicated. A cubic meter of soil contains literally trillions of living things, and constitutes an incredibly complex and sophisticated ecosystem. Soil is fascinating in that it is the fundamental connecting layer between the organic and inorganic worlds, and it’s worth a whole blog in its own right. But in this post we’re going to focus on the fundamental inorganic components of soils- their mineral particles.

Mineral particles are characterized as sand, silt or clay, and all are basically teensy-weensy chips of rock. Rocks are constantly being eroded and broken down, and these smaller particles are products of this process.

Extra Detail: Factors in rock erosion include of course wind, sun and water. You may think you already “get” the erosive effect of water on rocks: waves, streams and raindrops repeatedly pound on exposed rock, and when frozen, water-ice expands in volume, expanding and propagating cracks and crevices. But water- specifically rain- also has a corrosive chemical effect on rock. Raindrops (H2O) combine with Carbon dioxide(CO2) in the atmosphere to create Carbonic acid (H2C03). Over time, the positively charged hydrogen atoms in the acid molecules replace other positively-charged elements in rocks like limestone and granite, causing them to break into smaller pieces.

Lichens also play an important role in the creation of mineral particles and ultimately soil. Lichens, which cover 8% of the Earth’s surface and are extremely long-lived, produce an array of acids which eat into and break down rock surfaces. Mosses also contribute to soil formation, not by breaking down rock directly (they don’t produce corrosive acids) but by sheltering tiny fungi and other organisms that do produce corrosive acids.

The primary difference between sand, silt and clay particles is size. A grain of sand ranges from 0.05mm to 2mm in diameter, while a grain of silt is anything between 0.05mm and 0.002mm. Clay particles are those under 0.002 mm in diameter.

Note: No, I don’t have an electron microscope. The electron microscopy shots in this post were pulled from this extremely informative slide deck on the Washington State University Dept. of Crop and Soil Sciences website.

To put this in perspective, individual “grains” of clay are smaller than typical bacteria. They’re so small that you can’t even see them under an optical microscope; you need an electron microscope to see them. If a “typical” grain of sand were the size of the Earth, a grain of clay would only be about 16 miles across*.

*My calculation, could be wrong.

Up close, clay particles are generally flattish flakes, which means that have more surface area for their size. They’re typically negatively charged and the combination of negative charge and large surface area means that they bond easily to water molecules. Saturated sand is about 20% water. Saturated clay is about 48% water.

When you walk out of the water onto a sandy beach, wet sand sticks to your bare feet. But if you lie on the dry sand for a few minutes, the sun and wind will dry the water molecules holing the sand grains together and to your skin, and the sand will easily brush off. If you’re impatient, you can walk up to one of those beachside showers or hoses and quickly rinse off. The sprayed water drops will easily penetrate the large gaps between the roundish sand-grains, pushing them apart and away.

But if you walk barefoot in wet clay, and then lay back in the sun, your feet will take much longer to dry. The much smaller spaces between flakes are more difficult for sun and wind to penetrate. And when, eventually, the clay does dry, it’ll still take more effort to dislodge than dry sand; the tiny flattish flakes make almost a little concrete later on your skin. More frustratingly, if you walk over to a shower or hose, it’s way, way harder to wash the clay off. The sprayed water drops have great difficulty penetrating the much smaller gaps between clay-flakes, which are already filled/clogged with adhering water molecules.

This is one of the interesting things about saturated clay; it’s virtually impenetrable to water, creating special concerns for hydrologists, builders and… gardeners. Clay soils hold water well, but they drain poorly. Saturated clay soil in a garden can deprive plant roots of access to oxygen, compromising the health of plants. Clay soils are also subject to expansion, contraction, cracking and crusting as they gain and lose water, which can fracture plant roots or prevent seed germination. Gardeners in heavy clay areas typically need to mix local soils with larger particle things like compost and peat moss.

The prevalence of clay in foothill soils is not only a factor for mountain-bikers, gardeners and builders, but also for wild plants. Clay soils (particularly saturated clays soils) take longer to warm up in the spring, and it’s likely that the heavy clay content in the soil of the Wasatch foothills delays spring blooms by a week or two.

Well, that all makes sense. The small flat particles of clay make it sticky, hard to wash off and generally problematic for mtn bikers. But if it’s so sticky, why is it so slippery? To understand this one, we have to know something about the composition and structure of clay.

The Structure of Clay

Clay is a sheet silicate, meaning a silicon-based substance that forms into 2-dimensional crystalline sheets. Silicon is a common element in rocks, and hence clay. Silicon, atomic #14, has 4 open spots in its 3^rd electron shell, and so “wants” to make 4 electron bonds. Another abundant element is of course Oxygen, atomic #8, which has 2 open spots in its 2^nd electron shell. Together, Silicon and Oxygen comprise Silicon Tetraoxide, SiO4, in which the single Silicon atom binds to each of 4 Oxygen atoms, which each have 1 bond with the Silicon atom, and another bond with a fellow Oxygen atom. Together the 5 atoms form a tetrahedron*, with an Oxygen atom at each corner and the Silicon atom in the center.

*A tetrahedron is 4-sided, with a triangle on each face. It looks, at first glance, sort of like a pyramid, but it’s not. A pyramid is 5-sided, with triangles on 4 sides, and a square on the 5^th/base.

The base of each tetrahedron is an equilateral triangle, and the triangles of adjacent SiO4 tetrahedrons fit together to form a 2-dimensional hexagonal matrix, or sheet. With me so far?

OK, now the pointy-“up” corner of the tetrahedron is connected to an Aluminum molecule, together with other tetra-vertices and bonded hydroxyls (OH) to form AlO6, an octahedron (8-sided). So the tetrahedral Silica layer lies adjacent to an octahedral Alumina layer. At a molecular level then, clay is basically a bunch of stacked, alternating sheets, which is why the flakes are flattish under the electron microscope.

That’s the basics. From here things start to get complicated, and diverge into different clay types. The biggest difference is between so-called 1:1 clays, which alternate tetrahedral and octahedral layers, and 2:1 clays, which consist of octahedral layers sandwiched between 2 tetrahedral layers. The other big differentiator is something called isomorphic substitution, which is a fancy term for the replacement of a Silicon or Aluminum atom by something else, such Aluminum (in the tetrahedral sheet) or Magnesium (in the octahedral layer).

Depending on the exact structure of the clay in question, the clays can be neutrally or negatively charged. If negatively charged the various layers of 1:1 or 2:1 clays are linked with an interlayer of positively charged metallic ions (cations), such as Magnesium or Potassium.

Now here’s the thing: in water-saturated clay, positively-charged water molecules can easily take the place of metallic cations, and when they do, the interlayer becomes fluid and slippery. So when you slip on wet clay, the 2:1 or 1:1 individual layers are sliding across each other.

This effect is most pronounced in many of the 2:1 clays, one of the most common of which is a group called the smectite clays. Smectites are expansive clays, hazardous to build on, as they expand when wet and contract when dry. Later in the summer you’ll see cracks and fissures develop along smectite-rich foothill trails as they dry out.

March is month that rewards flexibility. It might be a good day to bike, or it might be a clay-disaster. It might be a great day to ski, or the snow may turn to sun-baked mashed potatoes. It’s challenging and frustrating to plan more than a day in advance. It’s a weird month, sort of a winding, uncertain bridge to Spring. You know where it’s going to end up, but not how it’s going to get there.