Sciency Words: Baily’s Beads

February 16, 2018

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:


This is going to be a quick one. I sort of blew all my writing hours this week finishing the first episode of my new short story series: Omni-Science. I don’t regret that. Writing Omni-Science felt awesome, and I hope you liked reading it.

The writing prompt that inspired Omni-Science was this photograph of the “Mondretti cylinder.”

That’s a very strange and mysterious image, certainly strange and mysterious enough to get the machinery in this writer’s brain started. But being the science nerd that I am, I also recognized that this is actually a time-lapse/composite image of a solar eclipse, showing off the “Baily’s beads” effect. (Also when I downloaded the image, the file name had the words “Baily’s beads” in it, which removed any doubts I had about what I was really looking at.)

As I’m sure you know, the Moon is not a smooth, perfect sphere. It’s covered in craggy terrain, and so during an eclipse, just before the Sun disappears entirely behind the Moon, the last rays of sunlight peak out from the gaps between mountains and craters and so forth. As a result, those of us who are using proper safety gear get to see these “beads” of light around the edges of the Moon.

I’m guessing Francis Baily was not the first person to notice this, but in 1836 he became the first to explain it in a paper for the Royal Astronomical Society titled “On the remarkable phenomenon that occurs in total and annular eclipses of the sun.” Those 19th Century English astronomers certainly did have a way with words, didn’t they?

Sciency Words: Moon Village

February 9, 2018

In this week’s episode of Sciency Words, the Moon would like to ask a question, the same question it’s been asking since 1972:

The answer is we humans may be returning to the Moon fairly soon, perhaps within the next decade, but this time we’ll be bringing a far more diverse set of flags to add to the Moon’s collection.

The European Space Agency, also known as the E.S.A., is taking the lead on the next round of Moon missions. For the last few years, Johann-Dietrich “Jan” Wörner, the current E.S.A. director-general, has been talking up the idea of building a Moon village near the Moon’s south pole, a region where large quantities of water ice have been detected.

Apparently interest in Wörner’s Moon village has been growing steadily to the point that Wörner has been quoted saying the village is already “more or less a fact.” I have a feeling the recent successful test of SpaceX’s Falcon Heavy rocket will accelerate that growth in interest.

But my biggest question about this, and the reason I felt this was worthy of a Sciency Words post, is this: why aren’t we talking about a Moon base? Why is it a village? Apparently the terminology was a very deliberate choice. On the E.S.A. website, Wörner writes:

By ‘Moon Village’ we do not mean a development planned around houses, some shops and a community centre. Rather, the term ‘village’ in this context refers this: a community created when groups join forces without first sorting out every detail, instead simply coming together with a view to sharing interests and capabilities.

I remember in first or second grade painting a mural as a class project. Each student was free to paint whatever he or she liked within the guidelines set by the teacher. The Moon village sounds like a similar concept to me, with every participating country or company or other privately funded group doing their own thing within the broader guidelines set by the E.S.A.

I just hope the end result is not quite the eyesore that that mural was when I was a kid.

Sciency Words: Jeans Escape

February 2, 2018

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:


Once upon a time, there was a molecule on Mars that dreamed of going to space. In fact, once upon a time there must have been a whole lot of molecules in the Martian atmosphere that wanted to go to space, and they apparently succeeded because today Mars’s atmosphere is mostly all gone.

Several factors must have contributed to the success of this molecule-scaled space program. One factor was temperature. The temperature of a gas is really a measure of the average velocity of the molecules in that gas. But remember, that’s the average velocity meaning some individual molecules may be considerably faster or slower than average.

As gas molecules bounce off each other, some of them may also gain or lose momentum, and in some cases a molecule might gain enough momentum to achieve escape velocity (11 kilometers per second on Earth, or 5 kilometers per second on Mars).

At that point, that molecule could achieve its dream and fly off into space (assuming it doesn’t collide with any other molecules on the way out). This can happen with virtually any gas on any planet, but it works best for light-weight molecules (like hydrogen or helium) on low gravity worlds (like Mars).

This process is sometimes called thermal escape, but in the scientific literature I’ve read it seems to be more commonly referred to as Jeans escape.

Sir James Hopwood Jeans was a British mathematician and astronomer. In the early 20th Century, he published prolifically on subjects ranging from star formation to blackbody radiation to the thermal properties of planetary atmospheres. It was this planetary atmospheres work that first led to the idea that a planet could gradually lose its atmosphere to space.

Or at least it was the first time we humans knew anything about it. The atmospheric gas molecules of Mars figured it out a long, long time before that.

Sciency Words: Triangular Trade

January 26, 2018

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 I’m really stretching my conception of science-related terms so we can talk about:


When I was a kid, I had an extensive collection of cards from Star Wars: The Customizable Card Game. At one point, I was trying to trade with a friend to get his Millennium Falcon card, but I didn’t have anything my friend wanted. So we got a third person involved and set up a three-way trade. My extra Princess Leia card went to this third person, who then gave a rare star destroyer to my friend, who then gave me the Millennium Falcon I needed to complete my rebel fleet.

This was sort of like what happens in triangular trade. Like nerdy kids trading Star Wars cards (or non-nerdy kids trading, I don’t know, baseball cards or something), cities or regions or countries set up three-way trade arrangements for their exports. This kind of arrangement served as the basis for much of the world economy in the 18th and 19th Centuries, during the Age of Colonialism.

The most commonly cited example (unfortunately) is the slave trade, where the trade routes between Europe, Africa, and the Americas actually traced out a big triangle across the Atlantic Ocean. European nations exported manufactured goods to their African colonies, which then exported slaves to the American colonies, which then exported things like sugar, cotton, tobacco, etc to Europe.

Obviously triangular trade is more of a historical term than a sciency thing, but much like the word thalassocracy, I feel like this old, history-related term might become applicable again in a far-out, Sci-Fi future where humanity is spreading across the Solar System. And the reason I think that is because Robert Zubrin, one of the foremost Mars colonization advocates in the U.S., wrote about triangular trade in his book The Case for Mars and also in this paper titled “The Economic Viability of Mars Colonization.”

To quote Zubrin from his “Economic Viability” paper:

There will be a “triangle trade,” with Earth supplying high technology manufactured goods to Mars, Mars supplying low technology manufactured goods and food staples to the asteroid belt and possibly the Moon as well, and the asteroids and the Moon sending metals and possibly helium-3 to Earth.

So everybody wins! The people of Earth win, the colonists on Mars win, and all the prospectors and mine workers in the asteroid belt win! Even our moonbase wins (this part might seem counterintuitive, but the delta-v to reach Earth’s Moon from Mars is actually lower than the delta-v to reach the Moon from Earth). And this time, slavery isn’t involved!

Unless the high technology being exported from Earth includes robot slaves who then… hold on, I have to go write down some story ideas.

Sciency Words: Chemofossils

January 19, 2018

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:


On Wednesday, I made up a bunch of numbers for the odds that we will find life on (or bring life to) Mars. The odds, in my inexpert judgment, are pretty low for finding anything presently alive on Mars, but I’d say there’s a 50/50 chance we’ll find the fossilized remains of life that existed there in the past. Now if only our rovers were equipped with digging gear!

But after writing Wednesday’s post, I learned that there are, in fact, many different kinds of fossils, including body fossils, trace fossils, ichnofossils, and chemofossils. And according to this article by Claire Cousins, a planetary scientist working on the European Space Agency’s upcoming ExoMars rover, it’s these chemofossils that will probably be our first real evidence of ancient Mars life.

The word chemofossil is, as you may have guessed, a combination of the words chemical and fossil. I was unable to find out who coined the term, but it seems to have happened fairly recently. According to Google Ngrams, it starts appearing in literature in the 1970’s.

Chemofossils are the telltale chemicals left behind by dead and decaying biomaterial. Even if an organism becomes totally decomposed, there may still be a sort of residue that suggests some sort of past biological activity. A good example, which Cousins cites in her article, are amino acids that share the same chirality.

Finding amino acids on Mars would be mildly interesting, but amino acids can come from just about anywhere. However, if those amino acids all have “left-handed” chirality (or “right-handed” chirality), well… the only natural phenomenon we know of that picks and chooses the chirality of amino acids is life.

Now since I’m still in the mood for making up numbers, I’m going to say there’s a 99% chance someone will announce they’ve detected chemofossils on Mars, BUT we will spend the following decade or two arguing about whether or not they really did. As Claire Cousins writes, discovering life on Mars “[…] will be a gradual process, with evidence building up layer by layer until no other explanation exits.”

In other words, I doubt that discovering chemofossils will definitively prove that life once existed on Mars. But I do think chemofossils will be the first “layer of evidence” we find.

Sciency Words: Airy-0

January 12, 2018

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:


Airy-0 is a small crater on Mars. There’s nothing particularly strange or noteworthy about it. Mars has lots of craters. Or at least, Airy-0 wouldn’t be noteworthy if not for some arbitrary decisions made on Earth over the course of the last few centuries.

In the 1830’s, Earth-based astronomers wanted to know the length of a Martian day, so they picked a dark, easily-identifiable surface feature and used that as a reference point to determine the planet’s rate of rotation. 19th Century astronomers also decided to use that dark surface feature to calculate latitude lines on the Red Planet. In other words, that dark feature (now known as Sinus Meridiani) became the reference point for the Martian prime meridian.

Then in the 1970’s, when NASA’s Mariner 9 space probe began sending back the first detailed maps of Mars, a specific crater within the Sinus Meridiani region was chosen to serve as a better, more precise reference point for the prime meridian. That crater was named Airy-0 in honor of George Biddell Airy, the astronomer who built the Airy Transit Circle telescope at the Greenwich Observatory in England.

I find this extremely fitting. The location of Airy’s telescope is used to define Earth’s prime meridian, so it makes sense that Airy’s crater on Mars would be used to define the prime meridian of Mars. But unfortunately, there seems to still be some uncertainty about Airy-0’s exact location.

Apparently the crater is small enough that space craft can have trouble locking onto it from orbit, and according to this paper from 2014, it turns out Airy-0 is approximately 47 meters east of where it was previously estimated to be. That’s a discrepancy of 0.001º latitude, which may not seem like much, but it’s enough to be problematic for science.

Three pictures of Airy-0 in increasingly high resolution over the past few decades. Airy-0 is the large crater in the top of each picture. Image courtesy of Wikipedia.

So Airy-0 will continue to be subject to intense scrutiny by us Earthlings, not so much because of anything intrinsically special about it but because, for the purposes of Martian cartography and Martian timekeeping, we really, really need to know exactly where Mars’s prime meridian is.

Sciency Words: The Darian Calendar

January 5, 2018

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 1986, aerospace engineer and polymath Thomas Gangale published a paper titled “Martian Standard Time” in which he outlined a calendar which could be used by Martian colonists in the future. Gangale named this calendar the Darian calendar after his son, Darius, and he describes the idea in greater detail on his website (click here).

According to the Darian calendar, the Martian year begins on or around the vernal equinox, when the sun is directly above the planet’s equator and spring is just beginning in the northern hemisphere. Because the Martian year is nearly twice as long as Earth’s, we get twenty-four months rather than twelve.

The names of the months alternate between the Latin and Sanskrit names for the Zodiak constellations. Thus the month of Sagittarius (the first month of the year) is followed by Dhanus, then Capricornus, then Makara, then Aquarius, and so on until you get to Scorpius and then Vrishika (the last month of the year). Each month has 28 days… sorry, 28 sols… except Kumbha, Rishabha, Simba, and Vrishika (the 6th, 12th, 18th, and 24th months, respectively) unless it’s a leap year, in which case Vrishika is 28 sols long.

And regarding leap years, there are a lot of them: six every decade, so leap years are actually more common than regular years. But then every hundred years we have to take a leap sol away, and then every five hundred years we have to put it back—I know, this is starting to sound complicated, but it’s not that much worse than what we have to do to keep the Gregorian calendar balanced on Earth.

If you’re wondering about the days of the week (I mean, sols of the week), Gangale thought of that too. Each Mars week is made up of seven sols with names that hark back to the ancient Latin names for the days of the week:

Sol Solis (Sunday)
Sol Lunae (Monday)
Sol Martius (Tuesday)
Sol Mercurii (Wednesday)
Sol Jovis (Thursday)
Sol Veneris (Friday)
Sol Saturni (Saturday)

Also, Gangale designed his calendar so that each date always falls on the same sol of the week. The 1st of Sagittarius is always a Sol Solis, for example. That’s pretty convenient, I think, although it also works out that every month the 13th is always on a Sol Veneris (a Friday), which seems rather unlucky.

The question, of course, is will Martian colonists actually adopt this as their calendar? I don’t know, but it seems certain aspects of the Darian system—such as the way it handles leap years—have already been borrowed for other Mars-related research purposes.