Space

Is ET dead – and are we next?

CSIRO Parkes radio telescope searching for signs of intelligent life in space
CSIRO Parkes radio telescope searching for signs of intelligent life in space
View 3 Images
Associate Professor Charley Lineweaver from the ANU Planetary Science Institute
1/3
Associate Professor Charley Lineweaver from the ANU Planetary Science Institute
Aditya Chopra from the ANU Planetary Science Institute
2/3
Aditya Chopra from the ANU Planetary Science Institute
CSIRO Parkes radio telescope searching for signs of intelligent life in space
3/3
CSIRO Parkes radio telescope searching for signs of intelligent life in space

With thenumber of potentially habitable exoplanets in our galaxy alone estimated to be in thebillions, many wonder why we are yet to see signs or hear from intelligentalien life. A pair of astrobiologists from the Australian National University (ANU) Research School of Earth Sciences hypothesize the reason may be that ET could be long dead. According to Aditya Chopra and Charley Lineweaver, conditions on young planets are so volatile that if life doesn't evolve fast enough to stabilize the environment, it will quickly become extinct.

One of the biggest wet blankets in the search for intelligent life is the Fermi Paradox. According to the most reliable accounts, in 1950 physicist Enrico Fermi was having lunch at the Los Alamos National Laboratory with Emil Konopinski, Edward Teller, and Herbert York. During the meal, Fermi asked why is it that in a Universe supposedly teeming with life, we haven't encountered any other civilizations yet. Making some back of an envelope computations, Fermi concluded that even the laziest intelligent species would spread throughout our galaxy in only 50 million years. So, he asked, where are they?

There have been a number of responses to the Fermi Paradox, such as the Rare Earth Hypothesis, which states that the conditions on Earth where life arose are so complicated that they're very unlikely to be duplicated. Another is the Hansen Filter, which speculates that life may be very common in the Universe, but something prevents it from advancing far enough to achieve interstellar contact. This can include asteroid strikes, geological catastrophes, supernovae, gamma ray bursts, nuclear war, environmental mismanagement, or social upheavals such as the Shoe Event Horizon.

Aditya Chopra from the ANU Planetary Science Institute
Aditya Chopra from the ANU Planetary Science Institute

The question that Chopra and Lineweaver posed was, does this filter exist before or after the point where intelligent life develops? They have posited what they call a "Gaian Filter" or Bottleneck, which is based on the fact that the emergence of life on a young, rocky planet requires more than just adequate warmth and liquid water. It also requires, among other things, a certain degree of stability – stability that the life itself helps to establish.

Basically, what the astrobiologists are arguing is that life isn't just a passenger on the planet it inhabits, but that it interacts with its environment and alters it. On Earth, the early environment was extremely hostile to more advanced forms, but as simple organisms developed, they stabilized the environment by doing things like changing the carbon dioxide in the environment into oxygen while removing the methane. Eventually, Earth's biosphere created a dynamic system that regulates the environment and keeps it capable of sustaining life despite asteroids, super volcanoes, and major shifts in climate. This is particularly true in terms of greenhouse gases.

"Most early planetary environments are unstable," says Chopra. "To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable."

Associate Professor Charley Lineweaver from the ANU Planetary Science Institute
Associate Professor Charley Lineweaver from the ANU Planetary Science Institute

Chopra and Lineweaver point out that four billion years ago Venus, Earth, and Mars were very similar, yet today Venus is a hellhole of intense pressure, temperatures high enough to melt lead, and sulfuric acid rains, while Mars is a desiccated ball of sand with scarcely any atmosphere that is constantly bombarded with hard radiation. Something in their early history caused them to diverge, with the pair saying that one possibility is that life evolved on Earth fast enough to overcome sudden shifts in the environment and kept the planet habitable. On Venus and Mars, life didn't get a chance to take hold and was wiped out.

"One intriguing prediction of the Gaian Bottleneck model is that the vast majority of fossils in the universe will be from extinct microbial life, not from multicellular species such as dinosaurs or humanoids that take billions of years to evolve," says Lineweaver.

A particularly interesting point about the hypothesis is that it gives Earthlings a real stake in seeking traces of extinct life on Mars. The scientists argue that if fossil microbes are found on the Red Planet, it means that the Great Filter that sieves out life is probably behind us and we have passed the greatest hurdles of our existence. However, if there are no microbes there, it means that the filter may be ahead of us and we have an uncertain future to navigate.

The research was published in Astrobiology

Source: ANU

15 comments
Bob
Interesting thoughts but Mars has no magnetic field to shield it from radiation and not enough gravity to hold an atmosphere. Venus is close enough to the sun to suffer much more intense solar flares and an sustain exceedingly high temperatures. Neither planet would have ever been a candidate for life. The earth is a very unique place and while many optimists go on about possible billions of habitable planets and intelligent life evolving,the odds are slim that all the correct conditions will exist. If ET is or ever was out there we very likely missed him by billions of years in time and billions of light years in space.
MattII
And all of this is assuming that they aren't responding because they're not there, rather than they're not in a position just yet to respond. Any civilisation with pre-digital technology is unlikely to spot it, and there may come a point at which radio is considered as archaic as smoke signals so they won't bother listening. Also, the Wow! signal cane in in 1977, a little over 38 years ago, while the star it supposedly came from is over 200 light-years away, so of course we haven't received a reply yet, they won't receive ours for another 160+ years.
Daishi
It's worth mention that not only would a planet need to be sustainable enough to sustain life but at a stability that allows it for a very long time as only just recently in our history did we aquire the ability to transmit and understand radio communication and we don't don't know how much time we have left here. This window could end up being a mere blip in the earths long timescale. Intelligent life on other planets could very much be more like the zerg than from starcraft than the mostly polite hairless monkeys we are. It might take a million suitable planets before we find one that took a similar path and is at a similar stage in evolution to ours. I like what Neil deGrasse Tyson said about it. We share 99% of our DNA with apes and are very similar but we view them as animals. If only a 1% difference appears that great to us imagine how a civilization much more advanced than our own could view us. We might be less intelligent and less capable than the food they eat. Cattle for instance are no doubt more intelligent than life on most planets. If there is life that's intelligent enough to communicate and travel through space far enough to reach this planet I don't think I would want to test our weaponry against theirs. Think about it this way, if we discover a planet less sophisticated than ours and travel there do we inhabit it at cost to them or just risk living on the only planet we have in order to leave them alone? Clearly we would chose to invade and if life there tried to defend against it we would certainly attack the same way we do here when we displace wildlife or even groups of people. The odds of another civilizations being capable of radio communication and space travel being behind us on the evolutionary curve are pretty slim making us the hunted beasts of that relationship. Another interesting thought is if some far away form of life successfully created AI that AI would in theory be able to evolve/adapt fast enough to survive the extinction event responsible for wiping out the species that creates it. This means if we do encounter another form of intelligence that is not our own it may not even be biological. Even we have already created rovers that survived martian climate for several years, it's humans that struggle to survive the depths of space. AI could very well be our own solution to mining asteroids and establishing facilities on mars or elsewhere. Even on earth we are on the verge of a major transition in robotic vs human labor.
gizmowiz
There is a lot of intelligent life out there even more advanced than we are. The problem is it exists on different timelines. We have only been able to survey the universe at large for about 100 years. The chances of us finding that other life nearby within that same 100 years is tiny at best--they seldom overlap. There well may be a super intelligent life form out there but hasn't started up yet. Or another has but faltered before we had the IQ to detect them.
Toffe Carling
I like how are these people are soooo busy saying there is no other life. It is like they sooo desperatly want us to stop looking. Or if THEY could not find then surley no one else can. Simply put it is too early to say any thing, we dont have enought data to suport ider veiw. And frankly is there even intelligent life on earth?
George W. Groovy
I saw a show on TV where aliens landed on earth and had a book called "To Serve Man" and everyone thought they were here to help us out. Turned out it was a cook book!
Lbrewer42
My comment will raise emotions - but true science does not pay attention to personal opinions. emotions and desires. This whole article is speculating about a major, unscientific theory called evolution. It has not been conclusively proven - in facvt its very far from it when only scientific evidence is studied. Basic genetics is in stark contrast to evolution, the carbon dating methods we use are based on many assumptions, etc., and yet we keep going. Don't emote - do the actual research for yourself. No one can truly be educated if they will not study both sides of an issue. The fact is most people who won't look at both sides of an issue are afraid for their pride.
Douglas Bennett Rogers
We don't yet have any basis for ascessing life in the universe. If we find microbes on mars, it will be a great leap forward. It may be that humanoids are common and that we were splined into this biosphere. That would explain the rapid rise of civilization around 3000 BC and why people are a little too tall and fat for Earth gravity.
Daniel Gregory
Single cell organisms give way to micro-organisms. Micro-organisms give way to larger complex organisms. Soon we have insects and invertebrates. Then came the lizards. Then the dinosaurs. ---reset---- Mammals give way to primates. Primates give way to Neanderthals. Neanderthals give way to homosapiens. Homosapiens give way to Artificial Intelligence. ---reset--- Imagine if the rest of the universe follows the last pattern. It's not that Aliens aren't out there. We're just not considered intelligent or worthy of contact. When AI evolves, then Earth might become part of the community.
Wolf0579
According to a US Army Intelligence briefing from the late 90's I was privy to, we have been "hosts" to an entity that did not originate on this planet. We have film and video "up the wazoo" showing spectacularly superior means of transportation. Yet, science has been warned off by the continued ridicule that has been programmed into people's minds. It is highly possible (read probable) that there are civilizations in existence in our galaxy, that could be as old as 3 billion years. It's likely that there won't be any big showing until there is a single world government.
Thanks for reading our articles. Please consider subscribing to New Atlas Plus.
By doing so you will be supporting independent journalism, plus you will get the benefits of a faster, ad-free experience.