Saturn's Titan: "A Unique World in the Solar System" -- Could Life There be Methane Based?
Dynamics of Earth's Core Linked to Movement of Tectonic Plates

Stephen Hawking on Non-Carbon-Based Alien Life


At the 50th anniversary celebration of NASA on October 1, 2008, Stephen Hawking, then Newton's heir as the Lucasian Professor of Mathematics at the University of Cambridge, was asked the question, “Are we alone?” His answer was short and simple: "probably not."

Hawking outlined three possibilities: One, that there is no life out there; and two, somewhat pessimistically, that when intelligent life gets smart enough to send signals into space, it is also busying itself with stockpiling nuclear bombs.

Hawking, known not only for his sharp mind, but his also for his biting sense of humor, prefers option number three: "Primitive life is very common and intelligent life is fairly rare," he quickly added: "Some would say it has yet to occur on earth. "We should be careful if we ever happen upon extraterrestrial life, Hawking warns. Alien life may not have DNA like ours: "Watch out if you would meet an alien. You could be infected with a disease with which you have no resistance."

What we normally think of as 'life' is based on chains of carbon atoms, with a few other atoms, such as nitrogen or phosphorous, Hawking observed in his lecture, Life in the Universe. We can imagine  that one might have life with some other chemical basis, such as silicon, "but carbon seems the most favorable case, because it has the richest chemistry."

The Earth was formed largely out of the heavier elements, including carbon and oxygen. Somehow, Hawking observes, "some of these atoms came to be arranged in the form of molecules of DNA. One possibility is that the formation of something like DNA, which could reproduce itself, is extremely unlikely. However, in a universe with a very large, or infinite, number of stars, one would expect it to occur in a few stellar systems, but they would be very widely separated."

Other prominent scientists have warned that we humans may be blinded by our familiarity with carbon and Earth-like conditions. In other words, what we’re looking for may not even lie in our version of a “sweet spot”.  After all, even here on Earth, one species' “sweet spot” is another species' worst nightmare. In any case, it is not beyond the realm of feasibility that our first encounter with extraterrestrial life will not be a solely carbon-based fete.

Alternative biochemists speculate that there are several atoms and solvents that could potentially spawn life. Because carbon has worked for the conditions on Earth, we speculate that the same must be true throughout the Universe. In reality, there are many elements that could potentially do the trick. Even counter-intuitive elements such as arsenic may be capable of supporting life under the right conditions. Even on Earth some marine algae incorporate arsenic into complex organic molecules such as arsenosugars and arsenobetaines.

Several other small life forms use arsenic to generate energy and facilitate growth. Chlorine and sulfur are also possible elemental replacements for carbon. Sulfur is capable of forming long-chain molecules like carbon. Some terrestrial bacteria have already been discovered to survive on sulfur rather than oxygen, by reducing sulfur to hydrogen sulfide.

Nitrogen and phosphorus could also potentially form biochemical molecules. Phosphorus is similar to carbon in that it can form long chain molecules on its own, which would conceivably allow for formation of complex macromolecules. When combined with nitrogen, it can create quite a wide range of molecules, including rings.

So what about water? Isn’t at least water essential to life?

Not necessarily. Ammonia, for example, has many of the same properties as water. An ammonia or ammonia-water mixture stays liquid at much colder temperatures than plain water. Such biochemistries may exist outside the conventional water-based "habitability zone". One example of such a location would be right here in our own solar system on Saturn's largest moon Titan.

Hydrogen fluoride methanol, hydrogen sulfide, hydrogen chloride, and formamide have all been suggested as suitable solvents that could theoretically support alternative biochemistry. All of these “water replacements” have pros and cons when considered in our terrestrial environment. What needs to be considered is that with a radically different environment, comes radically different reactions. Water and carbon might be the very last things capable of supporting life in some extreme planetary conditions.

NASA's recent controversial  announcement of the discovery of the possibility of arsenic-based life in Mono Lake fits hand-in-glove with NASA's strategy to expand the search for life beyond Earth to extreme non-carbon-based life. No discovery that we can make in our exploration of the solar system would have greater impact on our view of our position in the cosmos, or be more inspiring, than the discovery of an alien life form, even a primitive microbial one.

The discovery over the past decade of extreme life forms thriving on Earth at the super-heated walls of Ocean volcanic vents and in the interior regions of the planet's crust, led to a seminal 2009 report, The Limits of Organic Life in Planetary Systems, by the National Research Council (NRC). The NASA sponsored report recommended that the search for beyond Earth’s solar system should be widened throughout the Universe to include the possibility of  “weird” life.

"Nothing," the report concludes, "would be more tragic in the American exploration of space than to encounter alien life and fail to recognize it.”

Earth did not accumulate oxygen during the first roughly 3 billion years, or form an ozone layer until about 1.5 billion years ago. There is considerable emphasis on looking for contemporary Earth atmospheres that have oxygen and an ozone layer, but, the report hits home, we should also be using models with different anaerobic microbial non-carbon ecosystems, atmospheres that might parallel the different stages in the evolution of Earth's atmospheres over 4 billion years, and conditions that could indicate the presence of a tectonically active planet.

The report pointed out that the exploration of the planet is concentrated on looking for places where liquid water exists -- which goes along with the idea of where life is found on the Earth. However, they emphasize that liquids such as ammonia, methane, and formamide could also be the building blocks for life.

Saturn's moon, Titan is a perfect candidate: the discovery of evidence of liquid water-ammonia on Titan provides the potential for life-bearing polar fluids outside what is normally regarded as the habitable zone.

The Daily Galaxy via and

Get 'The Daily Galaxy' in Your Facebook News Feed!


Excellent news. Otherwise nothing else could be expected from Stephen Hawkins. Reality, science, knowledge,philosophy, ideology and a superb sense of humanity.

Re: "Watch out if you would meet an alien. You could be infected with a disease with which you have no resistance." - That's a naive statement - yes you would certainly have no resistance to a 'disease' that evolved extra-terrestrially, but you would also be almost certain to not even be susceptible to it in any way. Our own diseases are tailor-made for US and evolve with us through the aeons. Stephen Hawking should really not speak so publicly and authoritatively on this topic - stick to black holes Steve!

Were we ever to have direct contact with an alien race here on Earth, they would control the interaction. I stands to reason that worrying about what say, do, or broadcast would be entirely moot. If they wanted to interact they would, and if they wished to be our friends, they would be our friends.

But if they had other motives, we could not prevent those motives. Let's say for discussion their society had advanced by just 1000 years in technology (a very conservative estimate unless the light speed barrier is surmountable), they would be like gods to us. Remember, we have gone from the hand held calculator to an iPhone in just 40 years. Technology is exponential. And if this species caould travel through wormholes, I would guess we would also be at some disadvantage.

To your health,

Dr Z

Like the one on your bum, eh Jake :)

Its just one amazing mans opinion homie!!!

All right! More food for the BBQ! I wonder what formamide based life with a little chipotle glaze would be like?

All right! More food for the BBQ! I wonder what formamide based life with a little chipotle glaze would be like?

We should all put our hearing aids on (yes collectively) so we can listen properly! Bunch of old f*rts! Oh, it's raining now...

I find it pretty silly to speculate on something that we haven't a shread of information about. Any speculation could be 100% correct or 100% incorrect.... or fall on any point in between.


Mr. Hawking has again succeeded in shedding no more light on this subject than the rambling of the guy who stands on the end of my street spouting his own theories. He has become a bitter scientist who hedges his bets on everything, touts the wonders of this universe, but also claims to be very sure of what may, or will not according to him, happen to our consciousness once our bodies fail completely. Thanks Steve for telling us all the answers!! Oh wait... your ideas are just theories as well. Well, thanks anyway.

Man, you guys get bitchy in here. Anyway. If any alien life form is anything like us I would hate to meet them.

People on here are bitchy because they all think they're scientists.

Y'know, the man is famous for a reason?

A deadly intelligent mind, and some whit to accompany it.

Hawking has lost his fucking mind...and he doesn't recognize the intelligence of animals or plants...if a bird can fly using wings, why would it build a plane?

Hawking is trolling...I ain't mad at him...

Q above said: "I find it pretty silly to speculate on something that we haven't a shread of information about..."

Silly? Perhaps.

But I have to say that it sure is fun, and mind-stimulating, and awe-inspiring to imagine such possible scenarios as encountering a possible alien intelligence that operates on an entirely different chemistry and biology than we do!

(And history has shown, what the human mind can fantasize and imagine about, often comes to pass, and drives us to explore, and reach new goals.)

So I guess perhaps there is nothing too silly or wrong with a little bit of fun and healthy speculation bounded by the known laws of physics and chemistry.

So i say: speculate and live a little! At the very least, it will make you more fun at parties!

"Watch out if you would meet an alien. You could be infected with a disease with which you have no resistance." Hawking is not alone in this idea. Al Popoff even coined the term alienosis a few years ago. Alienoses are diseases communicable from extraterrestrial organisms — sentient beings, animals, plants, quasi-living creatures, or still unknown life forms. Humans are still alive because they aren't here: the extraterrestrials and their alien microbes. Popoff states that in the near future, humans should build up a reliable space defense system — a complex network of interacting humans, AI, sophisticated software, and machines, protecting our present habitat, the Solar System, from pathogens, quasi-alive forms, intelligent machines, machine swarms controlled by AI, and any alien life forms which could pose a threat to the terrestrial life or would dangerously change our environment. There is no other way the human race to survive.

Legitimate human scientists are often content to observe other cultures and species while taking pains to avoid interfering with them. Intelligent off-planet visitors may be observing similar ethical (and hygienic) considerations.

As far as we have come a whole planet, Most of us lack the ability to see subtly, meaning we have probably at least once come into contact with a non earth life form and not even known it. It has been proven that inorganic particles (such as dust) can form into coumpounds that mimic many of the signs of life, this only occurs when suspended in a plasma. From this alone, i think the human race is still far to ignorant of life beyond itself to identify such things.

Heartbreaking to see so many people spout hatred towards Dr. Hawking for speaking on this matter. The fact remains that life forms, that are not from our carbon based tree of life, exist and they exist here on earth. Which is in-excusable evidence that life can, and most likely does elsewhere.

I understand the temptation to view our bias toward carbon-based life as arbitrary. If there were an infinite number of elements to choose from, it would be reasonable to suggest that it's just our lack of imagination that limits us to think of our own type of life as the only kind.

However, we know the set of elements that are available. (and for those without a chemistry background, yes, indeed we know that there aren't a bunch of elements that we have not yet discovered - finding a new element useful for life would be exactly analogous to finding a new integer between 1 and 50 that nobody had previously noticed).

We also have some reasonable expectations of the kind of things life would need: Namely the means of storing and replicating data encoding the instructions for creating a life form (at least somewhat functionally analogous to DNA or RNA). You'd probably want to start with something with tinker-toy properties; something that can form a versatile chain that can bond with a wide variety of elements. Turns out Carbon works pretty well, but you go through the complete list (periodic table of elements) and consider all of the options, and the only alternative worth a closer look happens to be Silicon. But when you take a closer look at what is possible with Silicon, you find that Silicon is simply way less cool than Carbon. So much less cool, that a Silicon analog of RNA just isn't in the cards.

So I would say that if there is non-carbon based life in the universe, it would not be based on chemistry. In which case we can speculate like crazy: perhaps life made out of subatomic super-string clumps, or maybe civilizations pop in and out of existence consisting of magnetic flux patterns on the surface of a neutron star. See? My imagination is just fine, but I don't think that Silicon based life can emerge.

Hey, wow, this was totally unexpected: I was just thinking about integers between 1 and 50, wondering if I was missing something. I think I found a new one: 4ಇ. Does anyone know if any mathematicians have found 4ಇ before?

Until we find life that originated somewhere else besides our own planet, we can only speculate. There are two major theories on the creation of life. First, the spontaneous creation of life due to chemical interactions is the most accepted. That is what allows scientists to speculate on life being formed under completely different conditions; ie; if that is possible using carbon based compounds, than certain other compounds like silicon could give the same results as carbon, the "life" then created would be completely different. Then there is "panspermia" that life originated somewhere else and it was transferred here by Asteroids with frozen pockets of water (ice) within. I believe in the second theory, Panspermia, because that would lead to the possibility of a Universe full of life, compared to the first, which would lead to a very sparsely inhabited Universe considering the odds.

life beyond carbon compounds is indeed possible from known chemistry,however where it has evolved ,merits,demerits of that life over life as we are familiar with may be question we can only ask.Even in own environment as humans cannot communicate with say ants or othrwise,hence intellegent life elsewhere may find humans not interesting enough to interact

we are not alone to search aliens....what do you think our folks never try it or our folks do not have brain...all our brain are some copy of our folks and they are much more powerfull brain than ours. so first search what the path folks searching to find aliens.there isn't only theory of relativity that show existing of alien.there are many more advance theory that are present in our histories book.I think we think first about output of our folks about aliens...

"Some ancient alien theorist believe... "

The problem is our present lack of graphene- or quantum based massiv parallel and beyond computing power.

If an environment as an extract of the universe can be fully simulated, the DNA-type chemistry may be a solution to all the equations resulting from the physics governing the chemistry.

I wonder, if other solutions are either found for our or in other envionments like Titan.
Silicone-based lifeforms e.g. would change our focus and our carbon-biased brain.

Alien life could no have a material body... like an organized energy system or such. It could "use" the minerals to performa body somehow, and discard it when it´s no longer needed.
Lifeforms could just manipulate the quantum subparticles, not in a technological way but in a mind volitive way (as the way we call "magic")
Lifeforms could be monosubstantial in a fieldmesh organizer (like terminator 2) using any simple monosubstance like hidrogen or such...
Lifeform could be in front of us RIGHT NOW and it mught be so unbelievable and unconceivable for us that we wouldn´t be capable to eve see it.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.


Post a comment

Your Information

(Name is required. Email address will not be displayed with the comment.)