Tag: Titan

All These Worlds Are Yours: A Book Review

~ J.S. Pailly ~ 3 Comments

In his book All These Worlds Are Yours: The Scientific Search for Alien Life, author Jon Willis gives you $4 billion. How many authors do that? Okay, it’s imaginary money, and you’re only allowed to spend it on astrobiological research. But still… $4 billion, just for reading a book!

If you’re new to the subject of astrobiology, All These Worlds is an excellent introduction. It covers all the astrobiological hotspots of the Solar System and beyond, and unlike most books on this subject, it doesn’t gloss over the issue of money.

There are so many exciting possibilities, so many opportunities to try to find alien life. But realistically, you can only afford one or maybe two missions on your $4 billion budget. So you’ll have to pick and choose. You’ll have to make some educated guesses about where to look.

Do you want to gamble everything on Mars, or would you rather spend your money on Titan or Europa? Or do you want to build a space telescope and go hunting for exoplanets? Or donate all your money to SETI? Willis lays out the pros and cons of all your best options.

My only complaint about this book is that Enceladus (a moon of Saturn) didn’t get its own chapter. Instead, there’s a chapter on Europa and Enceladus, which was really a chapter about Europa with a few pages on Enceladus at the end.

oc11-enceladus-is-angry

I agree, Enceladus. On the other hand, Enceladus is sort of like Europa’s mini-me. So while I disagree with the decision to lump the two together, I do understand it.

In summary, I’d highly recommend this book to anyone interested in space exploration, and especially to those who are new or relatively knew to the subject of astrobiology. Minimal prior scientific knowledge is required, although some basic familiarity with the planets of the Solar System would help.

P.S.: How would you spend your $4 billion? I’d spend mine on a mission to Europa, paying special attention to the weird reddish-brown material found in Europa’s lineae and maculae.

Who’s Eating Titan’s Acetylene?

~ J.S. Pailly ~ 5 Comments

The first Monday of the month is Molecular Monday, the day I write about my least favorite subject from school: chemistry.

Molecular Mondays Header

I’d planned to write something about ammonia today. Ammonia might (might!) serve as a good substitute for water in some alien biochemistry.

But then I was reminded of something. Something important. Something I’m kicking myself for not covering before. So once again, let’s turn our attention to Saturn’s largest moon: Titan.

oc03-titan-acetylene

Making Acetylene on Titan

As we’ve discussed previously, methane gas and other chemicals break apart in Titan’s upper atmosphere. This allows carbon, hydrogen, nitrogen, and possibly other elements to recombine in new ways. The result is a mishmash of organic chemicals collectively refered to as tholins.

Tholins tend to be sticky, yucky, and orange. They slowly fall to Titan’s surface, covering the moon with sticky, yucky, orange sludge. One chemical in the tholin mix should be acetylene (C2H2). In fact, acetylene is a fairly simple molecule compared to the rest of the tholin gunk on Titan, so we should find lots of it.

But we don’t. We’ve detected little to no acetylene accumulation on Titan’s surface. Maybe this means there’s something wrong with our detection techniques. Or maybe some as-yet-unidentified chemical process breaks up acetylene molecules as they fall through Titan’s atmosphere.

Or maybe (maybe!) something eats the acetylene as soon as it touches the ground.

Eating Titan’s Acetylene

I first read about this a few years ago in Astrobiology: A Very Short Introduction. It came up again, in greater detail, in the book I’m currently reading: All These Worlds Are Yours. The case of Titan’s missing acetylene is a hot topic for astrobiologists.

There’s a rather simple chemical reaction that might (might!) explain what’s going on.

C2H2 + 3H2 –> 2CH4 + energy

That’s one acetylene molecule reacting with three hydrogen molecules to produce two methane molecules and some energy. The kind of energy that weird Titanian microorganisms could use to survive (maybe).

In my opinion, it still seems unlikely that life could have evolved on the surface of Titan, if only because liquid methane (Titan’s “water”) is not a good solvent for amino acids. But unlikely is not the same as impossible.

It’s worth noting at this point that a few other weird things are happening on Titan. Hydrogen gas seems to mysteriously disappear near Titan’s surface, and no one has adequately explained how Titan replenishes its atmospheric methane (all the methane should have turned into tholins by now).

If Titan does have an acetylene-eating, hydrogen-breathing microbe that expels methane as a waste product, that would conveniently solve three mysteries at once. I can’t help but think, though, that this might be a little too convenient to be true.

Molecular Monday: Liquid Water vs. Liquid Methane

~ J.S. Pailly ~ 13 Comments

Molecular Mondays Header

Welcome to Molecular Monday! On the first Monday of the month, we take a closer look at the atoms and molecules that make up our physical universe. Today, we’re comparing some of the properties of:

LIQUID WATER AND LIQUID METHANE

So you’re a moon or other planetary body, and you want to get some biochemical action going on. First, you need some organic substances. Titan has set a great example with the tholin haze that forms spontaneously in its atmosphere.

Next, you need a liquid to dissolve that organic material in, in the hopes that the organic material will recombine as amino acids, peptide chains, and ultimately DNA. But which liquid should you choose? Liquid water (as seen on Earth) or liquid methane (as seen on Titan)?

Pick Water!

Water (H2O) makes an excellent solvent for our purposes because it’s a polar molecule. There are two big reasons for water’s polarity.

  • First, oxygen has an extremely high electronegativity, meaning oxygen atoms like to yank electrons away from other atoms. Within a water molecule, oxygen’s electron-hogging tendencies cause it to become negatively charged, while the two hydrogen atoms become positive.
  • Second, you know how water molecules have that Mickey Mouse shape? Because of that shape, with the two hydrogen atoms bent toward each other, the positive charges accumulate on one side of the molecule and the negative charge accumulates on the other.

Thus, water is a polar molecule, and it’ll go around interacting with other polar molecules, like tholins or amino acids.

Don’t Pick Methane

Unlike water, methane (CH4) is a nonpolar molecule. Why?

  • Carbon is slightly more electronegative than hydrogen, but not by much, so the atoms in a methane molecule share electrons almost equally. This minimizes the electric charges that might build up inside the molecule.
  • Methane molecules are symmetrical, with the carbon atom in the center and the four hydrogens evenly spaced around in, like the four corners of an equilateral pyramid.

Sp05 Methane vs Water

Any electrical charges in a methane molecule balance out, due to the molecule’s symmetry. And those charges are fairly weak anyway, due to the similar electronegativities of carbon and hydrogen.

I won’t be so bold as to say life can’t develop in a liquid methane environment, but the idea does seem a bit farfetched in light of the chemistry. Polar molecules like tholins just aren’t likely to dissolve in a methane lake, like the lakes found on Titan.

On the other hand, the universe keeps surprising us, and the giant lake monster I recently met on Titan might dispute my assessment of Titan’s biochemical potential.

P.S.: Titan’s lakes also contain liquid ethane, but that doesn’t really change anything. Ethane is also nonpolar.

How to Fly on Titan

~ J.S. Pailly ~ 3 Comments

My trip to Titan is almost over. Soon, I’ll have to find some other planet or moon to blog from. But before I leave, there’s one last thing I want to do: fly.

Titan’s atmosphere is about 50% denser than the atmosphere on Earth. Combine that with the low surface gravity (a mere 14% of Earth normal) and it should be possible, theoretically, for me to put on some wings and flap around in the sky like a bird.

Taking my cue from the myth of Icarus, my artificial wings will not be made of wax, although it’s cold enough here on Titan that there’d be no danger of wax wings melting.

So with my non-wax wings strapped to my arms, I leap into the air, and….

Ag31 Flight on Titan 1

Okay, that didn’t go according to plan, so I turn to the Internet for help (the wifi on Titan is surprisingly good, by the way). I soon find this helpful article from the Journal of Physics Special Topics.

One option is that I try to get a running start. I’m really going to have to sprint here; average human running speed (6 m/s) won’t cut it. I need to reach a minimum of 11 m/s. And…

Ag31 Flight on Titan 2

… nope. I’m a nerd, not an athlete. Sprinting isn’t my thing.

So my next option is to build bigger wings. According to the paper from Physics Special Topics, the total area of my wings needs to be at least 4.7 m2. I’ll go for 5 m2, just to be safe.

The good news is that once I’m off the ground, I won’t need to use much energy to stay aloft. Flying on Titan should be “effortless and relatively easy […] without any sort of propulsion device.” Sounds like just a little light flapping should do the trick.

Okay, so here we go.

Ag31 Flight on Titan 3

P.S.: The Journal of Physics Special Topics may be my new favorite scientific periodical, with articles covering topics like cows jumping over the Moon, the effects of general relativity on Santa Claus, and the atmospheric loss caused by opening a portal between Earth and the Moon (as depicted in the video game Portal 2).

Do Not Go Swimming on Titan

~ J.S. Pailly ~ 7 Comments

I’ve made a friend on Titan: a giant, multi-tentacled monster that swims around in Titan’s lakes of liquid methane. Today, my new friend invited me to go swimming with him. While that does sound like fun, there are a few problems with that idea:

  • I can’t exactly change into my swimming trunks. There’s no oxygen in Titan’s atmosphere, so I need my bulky spacesuit. But even if that weren’t a problem….
  • Liquid methane is a cryogenic fluid. It’s not quite as cold as liquid nitrogen, but still… If I stick my toe in the methane, my toe will probably flash freeze and shatter. But even if that weren’t a problem….
  • I would sink straight to the bottom of the lake. Liquid methane is significantly less dense than water and significantly less dense than the human body. I wouldn’t be able to float, and I certainly wouldn’t be able to swim.

However, I didn’t want to disappoint my new friend, and I did come prepared for a possible excursion over a methane lake. So I hurried back to my spaceship and grabbed my boat.

Ag24 Lake Monster of Titan

Life on Titan: Infrared Eyes

~ J.S. Pailly ~ 2 Comments

I’ve been exploring the surface of Titan for several weeks now. During my time here, I have not discovered alien life, but alien life sure has discovered me. Fortunately, the Titanian lake monster I met on Friday is friendly, and he was super excited about meeting someone “from the stars.”

“Wait,” I said, “you know about the stars?”

“Oh yes,” the lake monster said. “I look up at them, twinkling in the night, and also the great orb with the rings around it.”

This really left me flummoxed. I can’t see Saturn at all from the surface of Titan (and I was pretty upset about it too). I certainly can’t see the stars. I can’t even see the Sun through all the tholin haze layered up in Titan’s atmosphere.

However, the tholin haze does allow certain wavelengths of light to pass through, mostly in the infrared part of the spectrum. The haze is almost completely transparent at a wavelength of 2000 nanometers (nm), which is how the infrared camera on the Cassini spacecraft has been able to photograph Titan’s surface.

The human eye can only detect light between roughly 400 and 700 nm. That’s because humans evolved on a planet where the 400 to 700 nm range is dominant, while life on Titan evolved in an environment where infrared light shines the most clearly.

So my new lake monster friend sees in infrared, possibly right around the 2000 nm range, and when he looks up into the sky he can see the Sun and stars and even Saturn, while all I see is gloomy orange haze.

Sciency Words: In Situ

~ J.S. Pailly ~ 6 Comments

Sciency Words PHYS copy

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 all expand our scientific vocabularies together. Today’s term is:

IN SITU

Today I’m continuing to blog from the surface of Titan, Saturn’s largest and most mysterious moon. No more reading about Titan in books and journals or on the Internet. Right now, I can do my Titan research “in situ,” as the real scientists would say.

Ag19 Life on Titan

“In situ” basically means “on location.” It comes from the Latin words for “on” and “location.” Alternative translations include “in the place” or “situated in,” but I think “on location” works best for our purposes.

Just about any time you find the phrase “in situ” in a scientific text, you can mentally substitute the words “on location” without changing the meaning of the sentence one bit.

  • The Mars rovers conduct in situ experiments to identify Martian geological features.
  • In the future, colonists cannot depend on supply missions from Earth for all their needs. They’ll have to make use of in situ resources.
  • Triton (Neptune’s largest moon) probably didn’t form in situ, but was captured by Neptune’s gravity after forming elsewhere.

Regarding in situ planetary science, contrast it with the observational science done using telescopes or laboratory experiments that attempt to recreate conditions on other worlds. Or you could contrast in situ research against something like a sample return mission, where material is brought back to Earth rather than analyzed on location (I mean, in situ).

Meanwhile on Titan

While in situ research has its advantages, it’s still only as good as the human doing the research. If life exists on Titan, it’s bound to be very different from life on Earth, with biochemistry totally unlike our own.

I can’t just look into a methane lake and see if any alien microbes are swimming around. I have to know what to look for before I look. I have to know which experiments to do before I do them. Which is why I still have to read books and journals and Internet articles about Titan. Otherwise, I might miss something important.

P.S.: Ah! It’s got my leg! Send help!

Can You See Saturn from Titan?

~ J.S. Pailly ~ 5 Comments

As I continue my exploration of Titan, there’s something I was really hoping to see.

Ag10 Saturn in the Sky

Like Earth’s moon, Titan is tidally locked. That means as Titan orbits Saturn, the same side of the moon is always oriented toward the planet.

So in theory, all I have to do is make my way to the Saturn-facing hemisphere, look up in the sky, and behold the majesty of the Ringed Planet.

I’m sorry to report that today science has crushed my dreams. Titan is shrouded in a haze of aerosol particles called tholins. The tholin haze is not as dense as you might assume (which is why I thought I might be able to see Saturn).

But this diffuse haze extends from the surface all the way up to an altitude of approximately 300 km. For the sake of comparison, typical Earth clouds form at altitudes between 3 and 12 km, and the unofficial boundary between Earth’s atmosphere and space is about 100 km up. So you could say that Titan’s haze is 200 km taller than Earth’s entire atmosphere (and Titan still has a few more atmospheric layers above the haze too).

Dense or not, there’s more than enough tholin haze overhead to block my view of Saturn. In fact, it’s enough that I can’t tell which way the sun is.

Ag10 Saturn Not in the Sky

Of course, Titan does experience seasonal changes which can affect the tholin haze. Maybe if I came back at a different time of year (Titan’s year equals almost 30 Earth years), I might be able to see something. But I doubt it.

First Steps on Titan

~ J.S. Pailly ~ 12 Comments

Your first steps on a new world should be an auspicious occasion. With that in mind, I have just landed on Titan. I’ve opened the hatch of my spaceship. I’m descending the ladder. I’m taking my first step….

Ag08 First Steps on Titan

I should have expected this. Titan may be too cold for liquid water, but it’s the right temperature and pressure for liquid methane.

There’s enough liquid methane (and also liquid ethane) to form lakes and rivers. It rains liquid hydrocarbons, and the ground is saturated with this stuff. Add tholins to the mix, and you’ve really got yourself in a sticky situation.

When the Huygens probe landed on Titan in 2005, it found surface conditions that the Huygens team compared to crème brûlèe: a layer of soft, gooey material with a thin, hardened crust on top.

No one can say for sure if the Huygens landing site is truly representative of the entire surface of Titan, but still… I should have expected to get my space boots dirty.

And here’s another thing I should have expected. You see, Titan has an atmosphere (approximately 95% nitrogen, less than 5% methane). In fact, Titan’s atmosphere is slightly denser than the atmosphere on Earth, so sound waves travel pretty well. Which means that as I trudge across the Titanian landscape, I can actually hear my space boots squishing in the mud.

P.S.: One more thing I should’ve thought about sooner. I’m going to have to figure out a way to clean my spacesuit before getting back into my spaceship. All this hydrocarbon gunk is going to become a real fire hazard once I’m back in an oxygen-rich environment.

Sciency Words: Tholin

~ J.S. Pailly ~ 6 Comments

Sciency Words BIO copy

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 all expand our scientific vocabularies together. Today’s term is:

THOLIN

My travels through the Solar System have once again brought me to Titan, Saturn’s largest moon. My spacecraft has commenced landing procedures, and I am currently descending through a haze of aerosol particles called tholins.

The term tholin was coined in a 1979 paper co-authored by Carl Sagan. The word comes from two similar sounding Greek words, one meaning vault (as in the great vault of the heavens) and the other meaning mud. Apparently Sagan toyed with the idea of naming this stuff “star-tar.”

Back on Earth, tholins can be created in the lab. Just take some simple organic compounds like methane and ethane and zap them with UV light or an electric current. You’ll end up with this yucky, orange gunk all over the bottom of your test chamber.

Here on Titan, the same thing is happening due to photolysis. When chemicals like methane (CH4), ethane (C2H6), ammonia (NH3), and formaldehyde (CH2O) get irradiated by sunlight, they break apart and recombine as new, more complex structures.

Ag05 Tholins on Titan

Tholins fill the air as a dense, orange haze. They cover the ground below as orange sludge. They’re also starting to coat the viewport of my spaceship with an orangey film that, I suspect, will be a real pain to scrub off.

While tholins have been notoriously difficult to analyze in the lab, they seem to be a mishmash of organic molecules. It’s hard to say which organic molecules are present, but some of them appear to be extremely large, extremely complicated organic compounds.

It’s easy to imagine amino acids, peptide chains, or even some sort of proto-DNA emerging from tholins, provided the tholins are allowed to dissolve in some sort of aqueous solution (note to self: double check Titan’s liquid methane lakes for dissolved tholins).

I can’t say for certain if there’s life on Titan, but I have to admit with all these tholins lying around, conditions are ripe for some sort of biochemistry to get started.

Links

What in the World(s) are Tholins? from the Planetary Society.

How Titan’s Haze Help Us Understand Life’s Origins from Astrobiology Magazine.