Sciency Words: The YORP Effect

~ J.S. Pailly ~ 12 Comments

Hello, friends!  Welcome to another episode of Sciency Words, a special series here on Planet Pailly where we talk about the definitions and etymologies of scientific terms.  In today’s episode, we’re talking about:

THE YORP EFFECT

Picture a windmill.  As the wind gets stronger or weaker, the windmill spins faster or slower, right?  Okay.  Now replace the windmill with an asteroid orbiting the Sun, and replace the wind with sunlight.  Over long periods of time, sunlight can make the asteroid spin faster or slower.  Sunlight can also change an asteroid’s axis of rotation.  This is known as the YORP Effect (not to be confused with the Yarkovsky Effect).

Definition of the YORP Effect: In astrophysics, the YORP effect is what happens when reflected and/or absorbed sunlight generates “thermal torque” on an asteroid.  Reflected sunlight exerts a very small (but non-zero) amount of force on the surface of an asteroid.  Absorbed sunlight radiates away from the surface of an asteroid as heat, exerting an additional small (but non-zero) amount of force.  Due to the irregular shapes and material consistencies of asteroids, it’s hard to predict exactly what this thermal torque will do, but over long enough periods of time it can dramatically change an asteroid’s rotation rate and axis of rotation.

Etymology of the YORP Effect: The term was coined in 1999 by American geophysicist David Rubincam.  The YORP Effect, as we currently know it, combines the previous research of Ivan Yarkovsky, John O’Keefe, Vladimir Radzievskii, and Stephen Paddack.  YORP is therefore an acronym of the names Yarkovsky, O’Keefe, Radzievskii, and Paddack.

This all started with Ivan Yarkovsky and his Yarkovsky Effect, which we talked about in last week’s Sciency Words post.  The Yarkovsky Effect has to do with the way sunlight affects the orbital trajectory of an asteroid.  The Yarkovsky Effect was lost to science for a while, then it was reintroduced in 1951.  Shortly after that reintroduction, other scientists started wondering what other effects sunlight might have on an asteroid, which ultimately led to this idea of a thermal torque effect, which we now call the YORP Effect.

To be clear, the Yarkovsky Effect and the YORP Effect are two different effects—one related to an asteroid’s orbital trajectory, the other to an asteroid’s rotation rate and axis of rotation.  They’re caused by the same thing—sunlight—but they are two different effects.

In 2007, observations of an asteroid named 2000 PH5 helped confirm that the YORP Effect is real.  The asteroid had been monitored closely over the course of about four years, and astronomers found that its rotation rate was steadily increasing.  This increase could not be explained by gravitational interactions alone, nor by collisions with other asteroids or any other known effects.  Therefore, by process of elimination, only the YORP effect was left as a possible explanation.  Asteroid 2000 PH5 was subsequently renamed 54509 YORP to honor its help in confirming the YORP Effect.

And in 2013, an asteroid named P/2013 R3 literally YORP-ed itself apart.  The YORP Effect caused the asteroid to spin so fast that it started flinging chunks of itself away.  There may have been some previous collision or other catastrophic event that made P/2013 R3 more fragile; still, in the end, it was the YORP Effect that caused the final destruction of that asteroid.

So if you’re an asteroid flying around in space, be careful.  It may be fun YORP-ing and Yarkovsky-ing around the Solar System, but you don’t want to Yarkovsky yourself into hitting a planet, and you don’t want to YORP yourself into self-disintegration either.

WANT TO LEARN MORE?

P.S.: The DART Mission is scheduled to crash itself into an asteroid tonight at 7:14 p.m. East Coast time in the U.S. (also known as 23:14 GMT).  If you’re interested, NASA TV will be live streaming the collision on their YouTube Channel.  It would not surprise me if the Yarkovsky and YORP Effects are mentioned as part of NASA TV’s science commentary.

NASA’s DART Mission: Brace for Impact!!!

~ J.S. Pailly ~ 12 Comments

Hello, friends!

We are only a few days away from what is, in my opinion, the #1 most important space story of the year.  No, I’m not talking about the launch of Artemis 1.  And no, this has nothing to do with the Webb Telescope either.  I’m talking about NASA’s DART Mission.

For eons now, asteroids have been zipping and zooming past our planet.  Every once in a while, one of those asteroids will hit our planet, causing anywhere from minor to major to global mass extinction event levels of damage.  But on Monday, September 27, 2022, humanity will perform our first ever experiment to see if it’s possible to smack an incoming asteroid away.

The asteroid in question is named Dimorphos.  Dimorphos is not actually a threat to us, but if we’re going to perform an experiment like this, Dimorphos is a rather convenient target for target practice.  That’s because Dimorphos is not just an asteroid; it’s also a moon (or should I call it a moonlet?) orbiting a larger asteroid named Didymos.

When the DART spacecraft crashes into Dimorphos, the force of the impact will change Dimorphos’s orbit around Didymos.  It should be fairly easy for astronomers to measure this change, and thus it should be fairly easy to judge how effective DART was—and just how effective DART would have been against an asteroid that was actually threatening us.

Oh, and just in case anyone’s concerned that DART might accidentally knock Dimorphos out of its original orbit entirely and send it hurtling our way, thus ironically causing the very disaster this mission was meant to help prevent—don’t worry.  Didymos’s gravitational hold on Dimorphos is strong.  No matter what happens on this mission, Didymos is not going to let her little moonlet go (another reason why Dimorphos was selected as the target for this experiment).

So on Monday, September 27, 2022, there will be a head-on collision between an asteroid/moonlet and a NASA spacecraft.

An Italian-built spacecraft named LICIACube will be positioned nearby to observe the experiment.  A multitude of Earth-based telescopes will also be watching.  The European Space Agency also plans to send a follow-up mission (named Hera) in 2026, to check up on Dimorphos after its post-impact orbit has had some time to settle down.

Life on Earth has never been able to defend itself from incoming asteroids before.  Life on Earth has never had the ability to even try, until now [citation needed].  Obviously asteroids are not the only threat to life on our planet.  Obviously this is not the only challenge we need to overcome.  But the DART Mission is a huge first step.  A true giant leap.  No, DART probably won’t get the same kind of love and attention as Webb or Artemis 1, but still I’d say this is the #1 most important space story of the year.  This may be one of the most important science experiments in all of Earth history.

WANT TO LEARN MORE?

P.S.: I said life on Earth has never before had the ability to defend itself from incoming asteroids.  Technically speaking, we cannot be 100% sure that’s true.  Click here to read my post on the Silurian Hypothesis.

Sciency Words: The Yarkovsky Effect

~ J.S. Pailly ~ 12 Comments

Hello, friends!  Welcome to another episode of Sciency Words, a special series here on Planet Pailly where we discuss the definitions and etymologies of scientific terms, in order to expand our scientific vocabularies together!  Today’s Sciency Word is:

THE YARKOVSKY EFFECT

Imagine an asteroid orbiting the Sun.  Every once in a while, this asteroid passes alarmingly close to Earth.  If you’re familiar with Kepler’s laws of planetary motion, you may expect that scientists could predict, with pinpoint accuracy, where that asteroid will be years, decades, or even centuries into the future.  However, there are certain physical forces acting on asteroids that are not accounted for in Kepler’s laws.  One of those physical forces is known as the Yarkovsky Effect.

Definition of the Yarkovsky Effect: In astrophysics, the Yarkovsky Effect is a thermal force that affects the orbit of asteroids.  Like most planets, asteroids rotate; therefore, you could say that asteroids have day-night cycles.  During daytime, the surface of an asteroid absorbs heat from the Sun.  At night, the asteroid’s surface cools off by radiating heat out into space.  This radiating heat generates a very, very, very small amount of thrust.  Over time, that small amount of thrust can dramatically change the orbital trajectory of an asteroid.

Etymology of the Yarkovsky Effect: The Yarkovsky Effect is named in honor of Polish/Russian civil engineer Ivan Yarkovsky, who first described a similar “heat engine” effect in 1888, and who later published a pamphlet on the topic in 1901.  Yarkovsky’s work would have been lost to history, except that Estonian physicist Ernst Öpik recalled reading Yarkovsky’s 1901 pamphlet and reintroduced the idea to the physics community in 1951.

Yarkovsky was more of a science hobbyist than a professional scientist.  He had a day job working on railroads.  In his free time, he read a lot about science, and he did a lot of thinking.  He performed his own experiments, occasionally, and he came up with some interesting ideas that sound like utter nonsense today, but which must have made sense in the context of late 19th Century science.  Even the Yarkovsky Effect, as Yarkovsky originally described it, was tied up with a now defunct scientific theory called ether theory.

Still, even if his starting assumptions were off track, Yarkovsky stumbled upon the truth at least one time.  Asteroids do have “heat engines,” as Yarkovsky described it.  Asteroids do have these naturally occurring thermal propulsion systems, powered by sunlight, which can mess with their orbits.  The challenge for astrophysicists today is that the Yarkovsky Effect is kind of random (or if it isn’t random, in the truest sense of the word, then it may as well be).

Asteroids are irregularly shaped.  Sometimes, they rotate on more than one axis (I once read a paper that called this multiple axis rotation “chaotic tumbling”).  And in terms of mineral composition, asteroids are made of all sorts of crazy stuff.  Different minerals can absorb and radiate heat in different ways.  So the Yarkovsky Effect pushes asteroids around, but because of all the variables I just mentioned, it’s hard to say which direction the Yarkovsky Effect will push at any given time.  It’s also hard to say how hard of a push the Yarkovsky Effect might give.

Which is why missions to study asteroids—missions like the recent ORISIR-REx Mission or the upcoming DART Mission—are so important.  We may never understand asteroids perfectly, but we do need to understand them better.  There are so many asteroids that fly alarmingly close to Earth.  It would be nice if astrophysicists could predict, with pinpoint accuracy or something near to it, where those asteroids will be years, decades or centuries into the future.

WANT TO LEARN MORE?

I used the following sources to write this blog post.  The one at the bottom is kind of a long read, but it tells the fascinating story of Ivan Yarkovsky, a man who was nearly forgotten by history.  For those of you who are interested in the history of science, it is well worth a read.

Sciency Words: Stochastic

~ J.S. Pailly ~ 11 Comments

Hello, friends!  Welcome to another episode of Sciency Words, an ongoing series here on Planet Pailly where we take a closer look at the definitions and etymologies of science or science-related terms.  Today on Sciency Words, we’re talking about:

STOCHASTIC

There are no true synonyms, according to American writer Roy Peter Clark.  Sure, two words may mean basically the same thing.  Two words may be so similar in meaning that you could use them interchangeably.  But there will still be some subtle difference between them, some slight shade of connotation that separates them.  The word “stochastic” is almost a synonym for “random.”  Almost.

Definition of stochastic: In statistics, a stochastic process is a process that is best modeled using a random probability distribution.  The process being modeled may, in fact, be random, or it may not.  The important thing is that a stochastic process is a process that scientists have modeled as if it were random.

Etymology of stochastic: The word comes from an ancient Greek word meaning “to aim in the right direction” or “to guess.”

Lots of things in the world are not truly random, but they may as well be.  The weather.  The economy.  Chemical reactions.  Changes in animal populations.  The orbital drifting of asteroids and comets.  Modeling these things in a strictly deterministic way would be mindbogglingly complicated and utterly impractical.  So scientists create stochastic models instead—models that include some random element to represent the super complicated parts that are impractical to model any other way.

These stochastic models are not perfect, but (as the etymology suggests) they aim us in the right direction, and they allow scientists to make pretty good guesses about what might happen with the weather, or the economy, et cetera, et cetera.

WANT TO LEARN MORE?

I try to avoid telling you to just go read Wikipedia, but the article about this on Wikipedia is actually pretty good.  Most of the other sources I looked at (or tried to look at) were super math heavy.  And you know how I feel about math.

#IWSG: We’ll Fly When We’re Ready

~ J.S. Pailly ~ 19 Comments

Hello, friends!  Welcome to this month’s meeting of the Insecure Writer’s Support Group, a blog hop created by Alex J. Cavanaugh and co-hosted this month by Kim Lajevardi, Cathrina Constantine, Natalie Aguirre, Olga Godim, Michelle Wallace, and Louise – Fundy Blue.  To sign up for IWSG and to learn more about this amazingly supportive group, click here!

In my last two blog posts, I wrote about the Indian space program and the American space program.  Both have suffered recent delays and setbacks.  Both are still moving forward with their space exploration plans, despite those setbacks.  Whenever I read about real life space programs, I’m always struck by the parallels between space exploration and writing.

Whether we’re talking about space or writing, we’re talking about big ambitions.  Big aspirations.  We’re talking about a lot of hard work (but the fun kind of hard work, the exciting kind of hard work).  We’re also talking about constant setbacks and delays, with certain financial realities looming over us at all times.

A couple years ago, I published my first novella-length Sci-Fi story on Amazon Kindle.  My plan was to follow up, quickly, with a sequel.  Around the same time, I also launched a store on RedBubble so I could sell prints of some of my art.  And then… setbacks.  Delays.  Real life problems.  It was like trying to plug fuel leaks on the Artemis 1 rocket.  As soon as I fixed the problem here, I’d discover liquid hydrogen was spraying all over the place over there.

I can report that 2022 has been a better year for me.  Slowly—very slowly—my writing and my art have gotten back on track.  I’ve been blogging more.  I’m making progress on my next Sci-Fi novella.  Also, I’ve started uploading new art to my RedBubble store for the first time in two years.  But writing takes time.  Art takes time.  As much as I want to rush forward with all my creative dreams, I need to be patient with myself.

After NASA scrubbed the launch of Artemis 1 not once but twice last week, NASA Administrator Bill Nelson had this to say: “We’ll fly when we’re ready.”  Right now, as I get back into the rhythm of writing and illustrating, that’s my mantra.  My muse and I… we’ll fly when we’re ready.

Artemis 1: Haters Gonna Hate

~ J.S. Pailly ~ 18 Comments

Hello, friends!

My gosh, certain people sure do love doling out criticism.  Even the slightest mistake or delay, and the critics come out in droves, robed in all their smugness.  I see this all the time as a writer and an artist, and on Monday I saw a smattering of critics online smugly criticizing NASA’s Artemis Program.

On Monday morning, NASA had to scrub the launch of Artemis 1, an uncrewed test flight of the spacecraft that will soon return American astronauts to the Moon.  Apparently there was trouble with one of the engines.  Most people, I think, understand that technical problems happen and that safety must come first.  But a few folks out there saw this as an opportunity to take cheap shots at NASA, the U.S. government, and America as a whole.

Now look… (heavy sigh)… okay, there are some valid criticisms to be made about all those things.  The United States has problems.  NASA has problems.  The Artemis Program, in particular, has been politicized from the start, and whenever things get political in the U.S., bad decisions ensue.  But even if none of that were the case, even if NASA could somehow operate independently of Congress and politics, problems would still crop up.

Taking time to stop and fix the problem with Artemis 1’s engine—that’s not a sign of weakness.  That’s not a failure.  If anything, it shows that the people at NASA are doing their jobs, taking the proper precautions, and learning from past mistakes.  Ignoring the engine issue—plowing ahead with the original plan, regardless of the danger—potentially allowing a multi-billion dollar spacecraft to blow up on the launchpad?  That would have been a real failure.

But no, a few people out there think delaying the launch for a few days is a “huge embarrassment” for America.  There will always be people like this who act super smug while lobbing lazy criticism at others.  Whether you’re a national space agency or just some writer/illustrator on the Internet, try to ignore this sort of criticism if you can (or rant about it on your blog, if you must—just don’t dwell on it for too long).

WANT TO LEARN MORE?

Fran, from My Hubble Abode, posted a wonderful video on YouTube reacting to some of the nonsense people have been saying about the Artemis 1 launch delay. Click here to check it out!

Sciency Words: Gaganaut

~ J.S. Pailly ~ 9 Comments

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we take a closer look at the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:

GAGANAUT

Back in the day, there were only two words for “person who goes to space.”  There were astronauts and there were cosmonauts, with the only meaningful distinction being that astronauts came from the United States and cosmonauts came from the Soviet Union.  Today, multiple space agencies use the word astronaut.  It’s almost (but not quite) a generic term now.  But Russia still uses the word cosmonaut, Chinese astronauts are actually called taikonauts, and just last week I learned that astronauts from India are to be referred to as gaganauts.

Definition of gaganaut: A person from India or otherwise associated with the Indian Space Research Organization (ISRO) who travels to space.

Etymology of gaganaut: Formed by analogy with astronaut and cosmonaut.  The “gaga-” part traces back to a Sanskrit word meaning “the sky,” while “-naut” comes from Greek and means “sailor.”

Aside from national origin, there’s still no real difference between astronauts, cosmonauts, taikonauts, and gaganauts.  They all travel to outer space.  They all do basically the same job.  They all have the same United Nations granted status as “envoys of Mankind” (not that that’s been super relevant yet, but someday… you never know!).

I guess the main takeaway from this is that “astronaut” is not a truly generic term.  It is a term used by most space agencies, but not all of them.  And each of the terms currently in use—astronaut, cosmonaut, taikonaut, and now gaganaut—come with certain cultural and perhaps also political connotations.  Just something to keep in mind whenever we talk about people who go to space, specifically or generically.

The Indian Space Research Organization (ISRO) had originally planned to launch its first crewed mission in December of 2021, according to Wikipedia, but COVID threw a wrench into those plans.  So it will be a few more years before the gaganauts get to fly.

Carcinization in Science Fiction

~ J.S. Pailly ~ 9 Comments

Warning: This post contains spoilers for The Time Machine by H.G. Wells and Project Hail Mary by Andy Weir.  This post may also contain spoilers for Tomorrow News Network books that I have not yet written.

Hello, friends!

In my research process, there comes a point where my brain switches over from learning science facts to making up science fiction.  Over the last month of so, I’ve been doing a ton of research on carcinization.  In that time, I have not become an expert on this topic—not by a long shot.  But at this point, I have learned enough science facts for my brain to switch over to Sci-Fi mode.

Carcinization is commonly defined as the process of evolving into a crab.  This has happened a surprising number of times, leading to Internet memes about crabs being some sort of “ultimate life form” or some sort of evolutionary end goal.  Given how common carcinization is (or at least how popular the memes about it are), I’ve often thought that we should see way more crab monsters in science fiction.  And nothing in my recent research has dissuaded me from that opinion.

Of course, giant crab monsters have appeared in Sci-Fi before.  The nameless time traveler in H.G. Wells’ The Time Machine has a close call with some giant crabs:

Can you imagine a crab as large as yonder table, with its many legs moving slowly and uncertainly, its big claws swaying, its long antennae, like carters’ whips, waving and feeling, and its stalked eyes gleaming at you on either side of its metallic front?  Its back was corrugated and ornamented with ungainly bosses, and a greenish incrustation blotched it here and there.  I could see the many palps of its complicated mouth flicking and feeling as it moved.

The word carcinization didn’t exist yet when Wells wrote The Time Machine, but the idea of carcinization did.  As far back as the mid-to-late 1800’s, scientists were already puzzling over “the many attempts of Nature to evolve a crab.”  With that in mind, I think H.G. Wells knew exactly what he was doing when he populated the Earth of the distant future with giant, hungry crab monsters.

More recently, a crab-like extraterrestrial appeared in Project Hail Mary, by Andy Weir.  I’m pretty sure Weir even used the word carcinization in his book, to help explain how this crab-like species could exist (though after spending about twenty minutes flipping through my copy of Project Hail Mary, I couldn’t find the reference—it’s possible I’m misremembering things).  Fortunately for the protagonist of Project Hail Mary, the crab-like extraterrestrial he meets turns out to be friendly.  An important ally, in fact!

After all the research I’ve done, I feel pretty comfortable exploiting the concept of carcinization for a Sci-Fi story.  And given that H.G. Wells and Andy Weir already did this, I feel like I’m putting myself in good company, too.  Now I do not currently have a release date set for the next Tomorrow News Network novella, but I can tell you that I’m working on it, and there will be giant crabs from outer space.  Will they be friendly crabs, like the crab-like alien from Project Hail Mary?  Or will they be hostile, like the future crabs from The Time Machine?

Okay, yeah, they’re definitely hostile. Sorry for the spoiler.

WANT TO LEARN MORE?

Please check out some of my previous posts on carcinization, as well as my post on orthogenesis (a closely related concept).

Sciency Words: Flora and Fauna

~ J.S. Pailly ~ 11 Comments

Hello, friends!  Welcome to another episode of Sciency Words, a special series here on Planet Pailly where we talk about the definitions and etymologies of science or science related terms.  In today’s post, we’re talking about two words:

FLORA AND FAUNA

So this weekend, I was thinking about alien life, as I often do, and it occurred to me that the words “plant” and “animal” are woefully inappropriate words to apply to extraterrestrial organisms.  That got me wondering if maybe the words “flora” and “fauna” would be better.

This is hardly a revolutionary insight.  Arik Kershenbaum talks about this in his book The Zoologist’s Guide to the Galaxy.  You see, in the cosmic sense, when we’re considering life across the entire universe, the words “plant” and “animal” are highly Earth-specific terms.  Strictly speaking, plants are organisms belonging to the kingdom Plantae, and animals are organisms belonging to the kingdom Animalia.  These kingdoms are two branches of the tree of life—Earth’s tree of life.  Not Mars’s tree of life.  Not Proxima b’s tree of life.  Earth’s.

Extraterrestrial life forms would belong to the kingdom… who the heck knows?  I guess astro-taxonomists will have to figure that out if/when extraterrestrial life is discovered.  In the meantime, would it make sense to use the words “flora” and “fauna” as generic terms for plant-like and animal-like aliens?  Initially I thought it would, but after doing some research, I’m not so sure.

Definitions of flora and fauna: In ecology, the words flora and fauna refer to all the plants and animals, respectively, found within a particular ecological region.

Etymologies of flora and fauna: The word “flora” traces back to the Latin word for flower.  Fauna comes from the name of an ancient Roman goddess of fertility.

So the words flora and fauna are not exactly synonyms for plants and animals; however, they do include the words “plants” and “animals” in their definitions.  And extraterrestrials, no matter how plant-like or animal-like they may be, would still have to be categorized as something else.

I still feel like referring to alien life forms as flora and fauna is better than calling them plants and animals.  Or at least it’s less wrong.  But it’s still not perfect.  In a distant, Sci-Fi future, new terminology may need to be invented.

WANT TO LEARN MORE?

I highly recommend reading The Zoologist’s Guide to the Galaxy by Arik Kershenbaum.  Obviously we do not know at this point what alien life might be like, but, as Kershenbaum argues, we can make some educated guesses based on the way life on Earth does (or does not) work.

Sciency Words: Critical Zone

~ J.S. Pailly ~ 2 Comments

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we take a closer look at the definitions and etymologies of science or science related terms, in order to expand our scientific vocabularies together.  In today’s post, our Sciency Word is:

CRITICAL ZONE

So I could make this post about climate change, but I won’t.  Certain people would just get angry with me in the comments, and I’m not in the mood for that today.  So instead, I’m going to talk about Earth’s “critical zone” as something that could be relevant to astrobiological research.

Definition of Critical Zone: In Earth sciences, the critical zone is the surface and near surface environment of our planet—in other words, it’s the part of our planet where life lives.  The proper scientific study of Earth’s critical zone will require an interdisciplinary approach, combining geology, biology, hydrology, and other related fields.

Etymology of Critical Zone: The term was first introduced in 1998 by American sedimentary geologist Gail Ashley.  She called it the critical zone because, in her words, “it’s critical for life” and also because it is “critical to know more about it.”  (Source: see the Eos article in the links below.)

Here’s a fun fact that I like to share at parties: there are somewhere between four and five thousand different minerals found here on Earth.  Four to five thousand!  Other planets in our Solar System are known to have only a few hundred, at best.

Why is Earth so mineralogically diverse?  Plate tectonics, for one thing.  Liquid water plays an important role as well.  Some minerals can only form in the presence of liquid water.  But the biggest factor, by far, is life.  Living things do lots of weird chemistry, and all that weird chemistry messed with the planet’s soil and bedrock. Earth’s biosphere affects Earth’s geology.  And Earth’s geology, in turn, affects Earth’s biosphere.  There’s a synergistic relationship between living things and non-living rocks on this planet—and that is what the concept of Earth’s critical zone is all about.

I feel this is a terribly important concept to understand as it relates to Earth.  It’s also something worth bearing in mind as we think about other worlds out there, worlds which may or may not support life of their own.

WANT TO LEARN MORE?

I’m going to recommend this article from Eos, entitled “Critical Zone Science Comes of Age.”  I think that article is a pretty good summary of how critical zone research started and how it’s going, and it includes some quotes from Gail Ashley explaining what she was thinking about when she originally coined this term.

I’m also going to recommend this brief article entitled “‘Critical Zones’ on Mars and Across the Solar System,” which attempts to adapt the concept of the critical zone for other worlds.

And if you want to read more about why Earth is so mineralogically diverse, here’s a piece from EarthDate.org entitled “Minerals Evolve, Too.”