Life without water

Imagine, for a moment, something that means "life" to you. What do you see?

A tree?

A vibrant reef?

One of those tiny humans your friends are always talking about?

You may notice that all of those things have something in common--they have a whole boatload of water in them.

Refreshing.

You see, dear reader, here on planet Earth water is considered to be the "solvent of life". Water dissolves more compounds than any other solvent known to humanity. It plays a crucial role in a huge number of biochemical processes--there are so many enzymes that require water to function that I can't even. Water can be found in all three phases of matter in our planetary climate (here's hoping we still have the solid form in a few centuries). Speaking of which, water also helps regulate our climate because of its high heat capacity.

Wow. H2O sounds pretty sweet, in a flavorless sort of way. No wonder everyone gets so excited when NASA releases another report with evidence of water on Mars.

As sarcastic as those reports might be.

Ok, so, real talk for a minute. You already know I'm not going to just talk about how great water is, because you read the title of this post. What, then, will I suggest as an alternative?

It turns out there are several that people much smarter than I have bandied about. One that could exist in our own solar system is methane. On Titan, one of Saturn's moons, it is so cold that small hydrocarbons like methane and ethane are liquid. There are vast oceans and rivers of the stuff, and when it rains, you bet your bottom it's raining men. I mean, methane.

Artist renderings are the best renderings.

Of course, it is quite chilly on Titan (-179°C, or -290°F, whichever is your poison), so things would probably happen much slower than they do here on Earth. Another option is formamide, which has a large range of temperatures in which it is liquid and can do things like help synthesize DNA bases (a comforting fact for us Earthlings). More promising still is ammonia, which is liquid in about the same temperature range as water (-107°F to 204°F), as long as you crank up the atmospheric pressure to 60 times what we're used to. It's also great at dissolving lots of different things, which is handy if you'd like to synthesize lots of different things.

Needless to say, we'll really have to think outside the box and keep our minds open to even find life of this sort--by necessity, it would be completely different from what we're used to. So how would we find these lifeforms, if indeed they do exist?

Let us harken back to middle school science class, or some similarly far away time, wherein we learned of:

Our first step is to conceive a hypothesis! Now, we know that any life form, big or small, watery or methaney, must 1) consume things, 2) convert these things to other things to obtain energy, and 3) excrete the byproducts of conversion. For example, plants consume sunlight, water, and carbon dioxide to produce glucose, and they excrete oxygen.

Therefore, if we observe a region that is becoming depleted in carbon dioxide and enriched in oxygen, we might assume that there are plants there. Perhaps you now see where I am going. We do not know how strange, non-water-based beings might work, but we do know how chemistry works. If we take a system, say Titan, and we lay out all of the chemicals and environmental conditions (temperature, pressure, weather patterns) that are likely to occur there, we can start to think about what reactions could take place there, and then reduce that down to the reactions that would give off energy for an organism to use.

At that point, we have hypotheses to test. We could put forth that an organism can consume hydrogen, acetylene, and ethane for energy, and exhale methane as a waste product. Now we mosey on over to Titan and we start looking for the disappearance of hydrogen, acetylene, and ethane, combined with a mysterious increase in methane. Is it life? Maybe not. But from here we can make further assumptions and test them, and so on and so forth.

And you know what's funny? It does seem like there is some "unkown process" consuming--you guessed it--hydrogen, acetylene, and ethane on the surface of Titan....

Reference for that last zinger: Stevenson J, Lunine J, & Clancy P (2015). Membrane alternatives in worlds without oxygen: Creation of an azotosome. Science Advances 1(1):e1400067. doi: 10.1126/sciadv.1400067

Microbiota, invasive species, and Star Trek

So I've had a notion knockin' around in my noggin, and for once it doesn't involve me just regurgitating interesting facts at you. You may have noticed that the title of this post seems somewhat...erratic. Don't worry, we'll clear up that confusion posthaste.

As my fellow Trekkies well know, the crew of the starship Enterprise (my personal favorite was NC 1701-D, but this applies to all) were frequent visitors to new and unknown worlds, many of which happened to have their own suspiciously humanoid* life forms.

Now, those of us who are up to date on our yogurt commercials will also know that the human body, and indeed every multicellular organism we've dared to study, is just brimming with bacteria, viruses, and even a few fungi for funsies. Thusly, it is fairly safe to assume that if we did find other multicellular life, those life forms would probably be teeming with unicellular organisms themselves.

And if in addition to a working knowledge of Star Trek and fermented dairy products you also know that a baby giant tortoise has not been seen in the Galapagos isles for over a century because of rats introduced by humans, then either you see where this is going or you need another cup of coffee!

That's right! I'm wondering why none of the aliens ever get irritable bowel syndrome from being visited by humanity!

Sorry, that might have been too much of a leap. Basically, would we even be allowed on another civilization's planet? Smallpox wiped out the Native Americans, could our microbiota not just as easily massacre innocent Martians? Conversely, perhaps the Martians would inadvertently massacre us!

At the same time, one has to recognize that microbes have evolved to inhabit absolutely every single ecological niche in which earthly life can exist. This raises the point that perhaps there would be no niche for a human microbe to invade on planet Vulcan. They're all full!

I regret to say that I don't have enough frequent flyer miles to get to Romulus right now, so I have no empirical evidence to sway you one way or the other. But maybe this is something to think about when we finally do find our way to the stars.

*If you remember the two part episode in The Next Generation where they explain this, let's be friends.