No Calls From ETs? They Might Be Extinct
I know it’s a tough call for the alien fans out there (and I have to confess, I DO think that there’s life out there somewhere), but a group of astrobiologists led by Dr. Aditya Chopra and Professor Charley Lineweaver (at Australian National University) has predicted that life on distant worlds isn’t being found because it’s likely to be extinct already. If what they’re saying is true, then the galaxy could be a pretty sparsely populated place indeed.
Extinction seems like a tough fate, but think about where life typically is expected to arise: newborn planets. Such places are not tranquil neighborhoods where happy little baby microbes flourish and evolve to become multi-celled life, and eventually grow up to build Starbucks franchises everywhere.
No, these infant worlds are harsh places. Really harsh. They get blasted by their stars (which themselves are young and feisty). Their atmospheres are toxic to most (if not all) forms of life. They might lose their magnetic fields, and then their atmospheres. Or, they might suffer incredible impacts that melt the surface over and over again. Whatever happens, when conditions do settle down and allow the formation of simple microbes, things can change through rapid global cooling and heating. These episodes can easily wipe out any simple one-celled life forms before they have a chance to take the first step up the evolutionary ladder. These early life forms can be quite fragile, and may not evolve quickly enough to ride out the swift changes on their home worlds.
Worlds and Alien Life
The science of astrobiology looks at the conditions needed to make a world welcome (or at least less-hostile) to life. A habitable world needs warmth, water, and some sort of food for the life to eat (and that can take many forms). It also has to have some way to regulate the greenhouse gases in its atmosphere to keep the surface relatively temperate so life can take hold and spread. That’s tough to do when the early atmospheres are so unstable. Yet, Earth managed to do it — albeit with a few mass extinctions along the way. Life still took hold and thrives today.
Smacking Down Life in our Solar System
The “perfect” places for life to arise do exist in the galaxy. Wet, rocky planets are out there. Many have the “stuff” needed to created and sustain life. It certainly worked on Earth, but our planet may have gotten lucky. And, the fact that we just haven’t gotten any signals from life forms whose microbial and multi-celled ancestors survived the turbulent early years of their planets, has raised questions for years.
Look at the other planets that formed in our neighborhood: Venus and Mars. They had the same ‘starting assets’ as Earth, but Venus took a wrong turn and now it’s a hellish volcanic planet smothered in heavy CO2 clouds and sulfuric acid rains. Mars went the other way, lost its magnetic field, then its atmosphere, and froze. No life has been found on either world, although it’s possible we might find remains of ancient microbial life on Mars. If it did exist there, it didn’t adapt fast enough or work to stabilize its environment. Life did help stabilize Earth’s early climate, and that helped make it much more habitable for the life forms that did evolve.
Cutting the Signal from Alien Life Before it Starts
If it’s true that infant planets don’t provide a good place for life, or that the life that does manage to rise up can’t survive the unstable climate changes on those baby worlds, then this might explain why we haven’t gotten any hint of intelligent life “out there”. It may not have actually have had time to arise, or its predecessors were snuffed out. Researchers have called this problem the “Gaian Bottleneck”, which is a colorful term for early extinction on nearly all young planets.
If this bottleneck really is occurring, then when and if we DO get to other worlds (Mars and beyond), we may well find a lot of fossils of extinct microbes. That’s because life forms such as humans, dogs, cats, cows, horses, whales, flowering plants, trees, insects, and so on, take millions of years to evolve. If their predecessors rise up on a planet with an inhospitable, rapidly changing environment, there just isn’t going to be enough time for intelligent life to evolve.
It’s an interesting idea, this Gaian Bottleneck. The longer we go without a signal or trace of life elsewhere in the universe, the more scientists may have to admit that time is not on the side of intelligent life that can send signals out to announce its presence. And, as someone who things that there probably IS out there, this theory may explain that — even if there ARE aliens out there — they may be much rarer than we hoped.