extra-terrestrial life Archives - The Spacewriter's Ramblings

Life Elsewhere in the Universe?

does cosmic life exist on worlds like this

An artist’s concept of Kepler-62f, a super-Earth-size planet in the habitable zone of a star smaller and cooler than the Sun. Could places like this harbor life? Credit: NASA/Ames/JPL-Caltech.

Cosmic life: it’s a fascinating topic that comes up as soon as I mention I’m interested in astronomy and space. A couple of weeks ago I participated in an interview with Taia Handlin, who used it to create a podcast as part of her Biology of the Blog series. During our conversation, which was quite wide-ranging, she asked me about cosmic life — that is, life elsewhere in the universe and whether I believed it existed. It’s a fair question. I told her that I do think there’s life elsewhere in the universe, although I wouldn’t characterize it in the realm of “belief”. We don’t have evidence — yet — about actual life “out there”, but that evidence can be found as we do more exploration.

The Evidence for Cosmic Life

So, what IS evidence of life and its prevalence in the universe? We only have one example of life in the cosmos, and that’s right here on Earth, with its many and varied life forms. So, we can be forgiven a bit for thinking that we have a lot of evidence already. Or that we just have to look for conditions that created our kind of life, but in other places. Of course, the reality will be quite a bit broader than our current perception.

The standard mantra has been to look for habitats that offer life what it needs: water, warmth, and food. Those are very general requirements, and we know that life has managed to exist in some pretty hostile environments. That’s what the science of astrobiology is designed to figure out — just what the conditions really ARE that would be favorable to life. Through their efforts, astrobiologists may well expand our definitions of cosmic life and where it can exist.

The first steps in understanding the chances for life besides here on Earth are to understand all the conditions under which it thrives here. There are places on our planet that mimic (or are very similar to) places on Mars, for example. If life can exist in those regions, then could it exist on Mars, too? That’s a fair question, and I suspect we’ll be able to answer it more fully when we actually get to those Martian places and see for ourselves if life is there. Or was in the past.

Also, too, we need to recognize that some forms of cosmic life may not need conditions like these on Earth to survive. That’s what drives inquiry into the possibility of life on such places as Europa (which is subject to Jupiter’s gravity and radiation belts) and Titan. Heck. And, beyond our solar system, astronomers are finding worlds that exist in regions around stars, places where the conditions might be ripe for life to form (or have formed at least once). Finding those exoplanets, determining if they have life, and understanding their life forms (if they have them) will be a major step in determining the prevalence of life across our galaxy. I suspect that we’ve been very conservative in our definitions of life and the places it inhabits. That’s understandable — you have to put some constraints on your working definitions, and the beauty of science is that it’s self-curing. That is, once we find something that goes beyond our definitions, we can adjust those definitions and our theories to accommodate actual data points.

So, there may well be life out there. We just haven’t found it yet. That’s what I think is going on.

In Carl Sagan’s book Contact (and in the subsequent movie) when Ellie Arroway asks her dad if there’s life out there, he responds by saying, “The universe is a pretty big place. It’s bigger than anything anyone has ever dreamed of before. So if…it’s just us… seems like an awful waste of space. Right?”

That’s how I answered Taia in our interview, because as soon as I read that in the original book by Carl Sagan, it resonated with what I’ve felt all along — life is out there, waiting to be discovered. And, I don’t think a cosmos that has evolved to let us perceive it would have only one incidence of beings with eyes, ears, and brains to figure it all out.

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.

The Spacewriter's Ramblings

Category Archives: extra-terrestrial life

Cosmic Life: Our Search for ET