Sciency Words: Regolith

November 18, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


For a long time, I assumed this was another example of having one word for something here on Earth (soil) and a completely different term for the same thing on another planet (regolith). But no, we have regolith here on Earth too; however, other planets and moons do not appear to have soil, strictly speaking.

American geologist George Perkins Merrill is credited with coining the word regolith back in 1897. The term is based on two Greek words meaning “rock blanket.” I don’t know about you, but that conjures up a strange mental image for me. I mean, who’d want to snuggle up under a blanket of rocks?

But after doing further research, I think Merrill was being pretty clever with this one. Regolith is defined as a layer of loose gravel, sand, or dust covering a layer of bedrock.

As for the distinction between regolith and soil, I think it’s best to define soil as a special kind of regolith: regolith that contains enough organic ingredients to support plant life.

By that definition, Earth has both regolith and soil while places like the Moon and Mars only have regolith. That being said, a lot of people (including professional astro-scientists) go ahead and talk about Martian soil when they really mean Martian regolith.

Unless, of course, Martian regolith turns out to have more organic matter in it than we thought!

One Last Thing About the Eclipse

August 30, 2017

This hasn’t been much of a research week for me. I’m more focused on the fiction side of my writing at the moment, rather than the science stuff.

So today I’m just sharing some artwork, something I didn’t quite get done in time for the eclipse.

You know, we are kind of lucky that we have these total solar eclipses. By some amazing coincidence, our large Sun and small Moon appear to be the same size in Earth’s sky, allowing the Moon to perfectly cover up the Sun.

That doesn’t happen anywhere else in the Solar System. That perfect planet-moon-star alignment is likely rare, perhaps even unique in our galaxy. So whenever we make first contact with aliens, and they start bragging about their luminous forests or crystal waterfalls or whatever, we Earthlings will have a unique and beautiful thing to brag about to: we have total solar eclipses.

Recommended Reading: Earth in Human Hands

August 14, 2017

Welcome to another edition of Recommended Reading here on Planet Pailly, a special series devoted to books that I think you should read. Today I’m recommending Earth in Human Hands: Shaping Our Planet’s Future by David Grinspoon.

If you’re a fan of Star Trek, especially if you’re one of those fans who takes Gene Roddenberry’s vision of a utopian future for our planet seriously, then you really need to read this book. 24th Century Earth, according to Star Trek, will be a paradise; Earth in Human Hands tells the story of how we could make that fictional paradise a reality.

Now I should make it clear that this is not explicitly a book about Star Trek (though as I read it, I couldn’t help but notice the parallel). This is actually a book about the Anthropocene, which is something of a controversial term. I’ve written about it previously here and here. The basic idea is that human activies have already had such a dramatic impact on our planet that we’ve initiated a new epoch of Earth’s geological history. The Holocene is over; the Anthropocene has begun.

Up until now, the changes we’ve caused have been, for the most part, inadvertent. We might even be forgiven for our mistakes, since we didn’t realize for a long time what we were doing. But Grinspoon’s premise is that the time is coming when we will stop making inadvertent changes and start making changes that are deliberate and intentional. First, we’ll want to undo some of the damage we’ve caused, and then we’ll start to reengineer our environment to make our lives more comfortable and secure the planet’s biosphere against natural disasters.

To be clear, Grinspoon is not saying we’re there yet. We do not have the knowledge or technology to reengineer our planet—but we may be heading in that direction. If so, the Anthropocene might not be an age of ecological disaster but rather a golden age for planet Earth, under the wise and benevolent stewardship of the human species.

Admittedly this is a hyper-optimistic vision for our future, but then again so was Star Trek. So if Star Trek’s utopian Earth is something you believe in, something you’d like to see become a reality, then David Grinspoon’s Earth in Human Hands is the book for you.

Sciency Words: Noösphere

August 11, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


Earth has a lot of “spheres.” There’s the atmosphere, which is the sphere of air surrounding our planet, and the lithosphere, which is the sphere of rock making up our planet’s crust and upper mantel. Earth has a hydrosphere (all of Earth’s surface water) and a biosphere (all of Earth’s organisms, collectively).

Over time, scientists have come to appreciate how all these “spheres” are interconnected with each other, maintaining conditions on this planet that are just right for life. At the risk of sounding New Agey, it’s almost like Earth is alive, like Earth is a single organism, and we’re just small parts of a greater whole. If so, perhaps we can add one more sphere to the list: the noösphere.

The term noösphere (pronounced either new-o-sphere or know-o-sphere) was coined in the 1920’s by a Jesuit priest named Tielhard de Chardin. The word comes from two Greek words: nous, meaning mind, and sphere, meaning sphere. In other words, the noösphere is the sum total of all the knowledge and intelligence on our planet.

Or going back to the New Agey stuff, the noösphere is Earth’s mind. We humans are like cells in Earth’s body, but we’re not just any old cells: we’re Earth’s brain cells. You might even say Earth has started to develop a new level of intelligence, a noösphere 2.0, as all us brain cells form a new series of neural connections with each other (in other words, the Internet is making Earth smarter).

Of course we could push this analogy too far. Are human beings really worthy of being compared to brain cells? Is the Internet really making our planet smarter?

While I’m not ready to declare humanity to be Earth’s brain, I do think the concept of the noösphere is interesting and warrants some discussion. The various spheres of our planet are interconnected, sometimes in weird and surprising ways; so how does the noösphere—the accumulated knowledge and intelligence of all humanity—contribute to (or detract from) the greater whole?

P.S.: I first learned about the noösphere in David Grinspoon’s recent book Earth in Human Hands, which I’ll be reviewing next week.

Sciency Words: Airglow

July 14, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


Have you ever been floating in space, looked down at the Earth, and noticed a faint halo of green light around the planet? Me neither, but that light is there and it’s called airglow. Why’s it called that?

This is Anders Angstrom, a 19th Century Sweedish research and one of the founders of the science of spectroscopy. He’s the guy who, in 1868, first observed the airglow phenomenon.

As often happens in science, this was a serendipitous discovery. Angstrom was trying to study one thing when he accidentally discovered something else. He was using a spectroscope to measure the emission lines of the aurora borealis—or to put that in plain English, he was trying to find out precisely which colors make up the Northern Lights.

To Angstrom’s surprise, one of the aurora colors—a narrow band of green—was always present in the sky even when the aurora wasn’t happening. Angstrom couldn’t explain this, but over the coming decades other researchers would continue investigating this faint green glow, ruling out one possibility after another: it couldn’t be starlight, or moonlight, or light pollution….

Eventually scientists settled on an explanation involving chemistry. We now know that chemical reactions in the atmosphere release energy in the form of photons. The most noticeable reactions involve oxygen reacting with itself, producing photons of a specific wavelength, a wavelength corresponding to a narrow band of green light.

We’ve also observed airglow on other planets. The different colors we see on Venus, Jupiter, or Saturn can tell us a lot about the chemicals in those planet’s atmospheres. And some day a faint green emission line from an exoplanet may lead us to the discovery of alien life.

Image courtesy of NASA.

I opened this post from a vantage point in space, because as I understand it Earth’s airglow is a lot easier to see from up there. But it can be seen from down here on the ground too if you have sharp eyes, a good camera (or a good spectroscope), and know what to look for. Click here to learn more.

Sciency Words: Technological Geometrization

June 16, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


In 1990, the Galileo spacecraft was on its way to Jupiter and needed to perform a gravity assist maneuver at Earth. This turned out to be a golden opportunity for science. Could a typical NASA space probe equipped with a standard suite of instruments detect signs of life on a planet where we already knew life existed?

In a 1993 paper, Carl Sagan and colleagues presented their findings in this “control experiment for the search for extraterrestrial life.” The paper explores all the things Galileo observed and, more intriguingly, some of the big things Galileo missed. Things like the “technological geometrization” of the planet’s surface, as the paper called it.

As far as I can tell, technological geometrization is not a term that’s stuck in the scientific lexicon, which is a shame. I think it’s a really good term. It refers to the way technologically advanced civilizations would tend to create geometric patterns on their surfaces of their planets.

The planet Coruscant from the Star Wars universe is a great example. The entire planet is urbanized, to the point that natural geological features are completely covered over. From space, all you can see are straight lines and perfect circles—efficient city planning on a global scale.

As another example, back in the 1800’s Percival Lowell and an embarrassingly large number of other astronomers thought they saw canals crisscrossing the surface of Mars. Those canals, if they really existed, would have been clear evidence of a technologically advanced society geometrizing their planet.

Earth’s surface displays only the faint beginnings of technological geometrization: rectangular patches of farmland and the grid patterns of streets and highways. These features are visible from space (Google Earth proves that), but you have to get fairly close to Earth to notice those kinds of details.

Apparently Galileo didn’t get close enough. At an image resolution of 1-2 kilometers per pixel, the technological geometrization of Earth was effectively invisible.

P.S.: That paper by Sagan and Company was a really good paper. It served as the basis for my recent “Alien Eyes on Earth” series.

Sciency Words: Biogenic (Alien Eyes on Earth, Part 5)

June 2, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


A passing alien spacecraft has been observing our little, blue planet for two weeks now, and it’s time they reported their findings back to their homeworld. One word—one scientific term—will feature prominently in their report: biogenic.

Actually, it’ll be the word xygjaflubozux, but that roughly translates into English as biogenic. It’s an adjective meaning “generated by biological processes.”

It’s difficult to impossible to directly detect life forms on a distant planet, so instead good astro-scientists go looking for chemicals that may have biogenic origins.

In the case of Earth, the aliens report they’ve detected an alarming amount of oxygen in the atmosphere. Oxygen is such a highly reactive chemical that it’s hard to imagine how it could persist in a planet’s atmosphere over long periods of time, unless….

Then there’s methane (which we never talked about in this series… oops). The presence of methane is even harder to explain, because methane reacts so readily with oxygen. All that methane should oxidize away within fifty years, unless….

Could it be biogenic oxygen? Biogenic methane? What about some of the other strange chemicals in Earth’s atmosphere, like nitrous oxide? Could there be biological processes at work constantly replenishing these chemicals in Earth’s atmosphere? These questions will be debated among the alien scientific community for many standard cycles to come.

The only unambiguous evidence of life on Earth, from the aliens’ perspective, were those radio signals coming from the planet’s surface. In a sense, you might say these signals have a biological origin, though I doubt human astro-scientists would describe them as biogenic radio emissions. But maybe the word xugjaflubozux has a slightly broader flavor of meaning and could still apply (how should I know? I don’t speak alien!).

This is the final post for my “Alien Eyes on Earth” series. The aliens have to move on and explore other star systems, but something tells me they’ll be back.

Today’s post was inspired by a 1993 paper by Carl Sagan and others. Sagan and his colleagues wanted to know which of Earth’s features can be observed by a passing spacecraft and, perhaps more interestingly, which features cannot.