April 19, 2011
Business is humming if you’re in the business of extra-solar planets, exobiology or exoenvironmental studies.
Recently, it was announced that scientists had determined that liquid water and hydrocarbons were present on Saturn’s moon Enceladus. They made this determination using Cassini’s plasma spectrometer, which had found specific ions characteristic of water in motion. (It never ceases to amaze me how scientists can tease information out of data using the most obscure scientific facts.)
That makes at least 4 worlds (Earth, Mars, Enceladus, and Europa) in our solar system where liquid water and other ingredients necessary for life have been found to be present now or in the past, or probably so.
Finding liquid water in so many places in one star system, and even in places once deemed unlikely if not impossible, must give one pause when discussing the likelihood of life on other worlds.
On Earth, so-called extremophiles have extended the range of environments in which we might seek out and find life on other worlds, from freezing cold water to steaming hot geothermal vents, and even radioactive water from nuclear reactors.
Robotic spacecraft have returned enormous amounts of data from both the inner and outer solar system for the study and comparison of extraterrestrial environments, and what those environments might say about the possible places where live might somehow or someday find a foothold.
And the number of worlds and star systems available for study and comparison has grown to the hundreds. Planetary systems of one kind or another have now been found to be common.
One scientist studying extrasolar worlds recently made the bold calculation (rough and somewhat speculative even by his own admission) that 15% of stars in our galaxy have systems resembling ours; that is to say, having several gas giant outer worlds and several small rocky inner worlds.
So if worlds and environments for possible life are increasingly found to be potentially plentiful, where is everybody? That is the heart of the so-called “Fermi’s Paradox”.
In 1960, Dr. Frank Drake devised what is usually called the Drake Equation in an effort to find a quantitative way to answer that question. While not providing an answer by itself, Drake’s objective for the equation was to devise a template for calculating a possible answer based upon the assumptions plugged into its variables. That 15% suggestion would be one of those variables.
As a lay person, I’ve given a lot of idle thought to the question of how likely it is for life to evolve on a world, and how likely it is for ‘intelligent’ life (or what I prefer to call “technology-prone life” or “technophilic biology”, since I often question this species’ intelligence) to appear in a world’s ecosystem.
I think that Earth gives us an interesting, if statistically invalid, example.
Let’s start with the age of the Earth at about 3.5-4 billion years. The most basic and primitive forms of life on Earth are believed to have formed over 3 billion years ago; that is to say, shortly after the Earth formed. The implication here is that life may be a natural stage of a planet’s evolution, if the environment permits.
Multicellular life may not have developed until just 1.7 billion years ago, so this biological leap took quite a while, implying that it’s a less likely development.
It took another 1.2 billion years for plants and invertebrate animals to take hold. That’s only 400-500 million years ago, and quite recent on geological timescales. So again, the suggestion is that this stage is also one of decreasing probability, since it took so long to occur.
Now, according to our best information, biology puttered along while evolving varying degrees of complexity and sophistication until, relatively speaking, recent times without the appearance of a significant tool-making species. So that’s nearly 4 billion years of biological evolution without a technologically-inclined animal appearing on our world.
It was less than 5 million years ago – yesterday, in relative terms – that hominids appeared, leading to us.
From this, one must conclude that animals like us are unlikely; perhaps a one-off event.
So here’s how my admittedly unqualified lay conclusion would be summed up regarding the presence of life in our galaxy:
* Basic biology (simple one-celled creatures) of one kind or another: Highly probable, given a suitable environment.
* Complex biology (plants, multicellular animals with specialized subsystems): Less likely, but common.
* Technophilic biology: Rare, and possibly the rarest kind of evolutionary accident.
In this scenario, the universe presented in Isaac Asimov’s “Foundation Series” – a star-faring, galaxy-spanning human society which has encountered no other intelligent alien life – becomes more likely. The Star Trek/Star Wars scenario of a universe teeming with technophilic species becomes much less so.
It would be exciting to imagine meeting other high-tech species someday and comparing notes with them regarding science, history, and evolution.
Sadly, I just don’t think it likely.
On the other hand, it makes our world and species that much more precious, and our place in the Universe much more significant.
Let’s not screw it up.
Originally Posted on TGDaily.com, Feb 13th 2010 by Michael R. Honig