Life on Titan is a cosmic puppy; small, rare, and virtually impossible to find. You know, when we think of extraterrestrial life, we imagine complex ecosystems, bizarre life forms, maybe even nascent civilizations. But no. New simulations of theUniversity of Arizona reveal that, if life exists on Titan, its total mass is about that of a small dog.
That’s it. Less than one cell per liter of water, scattered across a subterranean ocean the size of a planet. Not exactly the teeming alien hive we were hoping for. But in this desolate space lies a miracle: Even in such extreme conditions, life may have found a way to exist.
Titan's Cold Promise
Titan has always been one of the most promising hopes in the search for extraterrestrial life in our solar system. Despite its industrial-freezer temperatures (-179 °C), this moon of Saturn has surprisingly favorable characteristics: a thick nitrogen-rich atmosphere, lakes filled with methane and ethane, and an impressive variety of hydrocarbons and organic aerosols.
It's as if nature had set up an open-air organic chemistry laboratory, except that that sky is 1,4 billion kilometers away from us. Even more fascinating is the subsurface ocean that lies beneath a 40 to 100 kilometer thick ice crust. This ocean, about 483 kilometers deep, is heated by hydrothermal activity caused by tides generated by Saturn's mass.
Our new study shows that this supply may only be sufficient to support a very small population of microbes with a total weight of a few kilograms at most: the equivalent of the mass of a small dog.
Life on Titan: When Simulations Dampen the Enthusiasm
The job of science is to study: I always repeat it to you, when research makes us dream and also when it brings us back down to earth.
The international team led by Antonin Affholder ofUniversity of Arizona e Peter Higgins ofHarvard University used computational simulations to “model” the most likely ecology on Titan.
The results? Disappointing for space romantics like me. Life on Titan will be microbial and likely very different from life on Earth. The real issue is not whether there are ingredients for life (those are abundant on the surface), but how those ingredients get to the subsurface ocean where life could develop.
Life on Titan? A Hamburger Without Fries
The study focused on the fermentation, a metabolic process that does not require oxygen and that probably evolved very early on Earth. In particular, the researchers examined the fermentation of glycine, the simplest known amino acid.
The simulation revealed a fundamental problem: Although glycine or its precursors are abundant on Titan's surface, very little of this amino acid manages to penetrate in the buried ocean. Titan's microbes would therefore be like diners in front of a very rich menu, but with arms too short to reach it.
A bucket of life in a planetary ocean
The end result is sobering: if there is life on Titan, the amount is so small it could fit in a bucket. Affair He put it in terms we can understand:
Such a small biosphere would average less than one cell per liter of water in Titan's entire vast ocean.
This discovery has practical implications for future space missions. Finding traces of life on Titan will be like looking for a needle in a cosmic haystack. Or, more precisely, like looking for a microbe in a planetary ocean.
Research, published on The Planetary Science Journal, it doesn't completely destroy our hopes, but it certainly scales them down. It's as if the universe is saying to us: "Life is possible, but don't rely too much on me to find it."
Yet even if the mass of all the potential microbes on Titan is equivalent to that of a Chihuahua, there is something deeply exciting in the thought that life could have thrived up there, even in such extreme conditions. A microscopic cosmic dog is better than no dog at all, right?
