Tag: Titan

Molecular Monday: Are There Amino Acids on Titan?

~ J.S. Pailly ~ Leave a comment

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 looking at:

AMINO ACIDS ON TITAN

Captain’s Log

Stardate 8116.3

My spaceship has completed orbital insertion at Saturn. During last year’s Mission to the Solar System, I missed the opportunity to explore Saturn’s largest moon, Titan, in any detail. I intend to correct that error.

Titan may or may not support life, but one thing is certain: it is a chemically active world. And that chemical activity is vaguely reminiscent to the biochemistry found on Earth.

While my spaceship is still on approach to Titan, this seems like a good time to review what I’ve learned so far about amino acids.

Anatomy of an Amino Acid

  • Amino Group: a structure on one side of an amino acid that can serve as a base in acid/base chemistry.
  • Carboxyl Group: a structure on the opposite side of the amino acid that can serve as an acid for acid/base chemistry.
  • Alpha Carbon: A single carbon atom separating the amino and carboxyl groups, preventing them from accidentally reacting with each other. Some amino acids also include a beta carbon, a gamma carbon, or even a delta carbon, further separating the amino and carboxyl groups.
  • The Side Chain: A chain of atoms dangling from the alpha carbon. These side chains vary in composition and complexity, giving each amino acid its own unique flavor (sometimes literally).

Functionality of Amino Acids

  • Peptide Bonds: The amino group of one amino acid can link up with the carboxyl group of another, forming a peptide bond (a water molecule is produced as a byproduct). This process can be repeated over and over, forming incredibly long peptide chains.
  • Proteinogenic Amino Acids: While there are hundreds (perhaps thousands) of different amino acids, life on Earth uses only twenty-three of them in the formation of proteins. We humans use only twenty-one.
  • Chirality: Side chains can be attached to one side of an alpha carbon or the other. Life on Earth only uses amino acids with side chains on the “left” side. Right-sided side chains are incompatible with our DNA, and we can’t use them for the construction of proteins (though our bodies can use some of them for other purposes).

When I arrive on the surface of Titan, I do not know what I will find. Amino acids? Probably. Peptide bonding? Maybe. Long peptide chains, like some sort of proto-DNA? It’s possible.

We’ll just have to wait and see what happens when I get there.

Saturn’s Story: Rings, Moons, and Alien Life

~ J.S. Pailly ~ 7 Comments

Where did Saturn’s rings come from? It is possible that the rings were always there, that they formed 4.5 billion years ago along with the rest of the Solar System. However, it seems more likely—a heck of a lot more likely—that the rings formed recently.

About 100 million years ago, Saturn would have had a different collection of moons than it does today. Then catastrophe struck. Moons started ramming into each other, or perhaps they strayed too close to Saturn (crossing the Roche limit) and were ripped apart by Saturn’s gravity.

Sp03 Poor Unfortunate Moon

The rings we see today are basically the icy debris left by that previous generation of moons. It’s also starting to look like many of Saturn’s current moons also formed around that time, accreting from the rubble.

Enceladus may be one of those newly formed moons. Enceladus is of particular interest to astrobiologists. Its subsurface ocean would be an ideal environment for life, but as I said last week, that’s only if life has had sufficient time to evolve. 100 million years doesn’t give evolution a much time to do its magic.

However, astrobiologists have taken a keep interest in another of Saturn’s moons: Titan. So I want to mention something important. Titan is not a young moon. It did not coalesce from lunar debris 100 million years ago. Titan is probably 4.5 billion years old, making it as old as Saturn, as old as the Solar System itself.

In fact, Titan would have been there when that previous generation of moons was destroyed. Titan would have watched it happen.

Ap09 Titan and Saturn's Rings

So while I’m less confident about the prospects of Enceladian life than I used to be, the odds of finding life on Titan are as good as they ever were.