How exotic alien life could thrive in the giant molecular clouds of deep space

a gray-black dark nebula spreads through space, obscuring dozens of background stars
(Image credit: KPNO/NOIRLab/NSF/AURA/T. A. Rector. Image processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab))

An astronomer has outlined a way for methane-producing life to thrive in the molecular clouds of deep space, opening up a new pathway to understanding the potential origins and diversity of life.

Space is hostile to life. There's no abundant air. All of the water is frozen. Everything's all spread out. And there's deadly radiation bombarding everything. There's no way that life as we know it could find a habitable home in the depths of  interstellar space

Sure, a bacterium or even something more sophisticated, like a tardigrade, might be able to enter into a hibernation state and weather the ravages of deep space. But at best, that would only allow that organism to transit through space on its way to some more clement location.

Related: Extreme microbes in salty Arctic water could aid search for life on Mars 

But life is surprisingly robust and inventive. We have detected microorganisms in some of the most hostile environments on Earth: buried under Antarctic ice sheets; deep underground, far from the light of the sun; lofting through the upper atmosphere; thriving in superheated vents; and more. 

Life has managed to find every possible niche on Earth, and the most inventive life-forms are probably archaea. These single-celled organisms, which sit somewhere between bacteria and eukaryotes, are the jacks-of-all-trades among Earth's life.

In fact, archaea come in so many diverse forms that we've only begun identifying and categorizing them, as many species push the boundaries of life so much that we have a hard time spotting them. Archaea have been found using almost every possible energy source available on Earth, including sugars, ammonia, carbon metals and sunlight.

This means that, if we want to look for exotic forms of alien life, we should turn to archaea for inspiration. And according to Lei Feng, an astronomer at the Purple Mountain Observatory and the University of Science and Technology of China, we should especially look at the ability of some archaea to use methane as a source of energy.

Writing in an article yet to be peer-reviewed, Feng outlines how archaea-like organisms might thrive in one of the most unlikely places in the galaxy: giant molecular clouds.

Molecular clouds are huge complexes of gas stretching over 100 light-years across. They are typically cool, with temperatures only 10 to 100 degrees above absolute zero. Most importantly, they are the birthplaces of stars; when pieces of a cloud destabilize and gravitationally collapse, they can rapidly form a new batch of stars. Some of those stars then die, enriching the cloud with heavy elements — like methane.

Sitting light-years from the warmth of a star, hypothetical life in a molecular cloud could not use photosynthesis as a source of energy. And free oxygen is not abundant, so the energy pathways available to humans wouldn't work, either. But there's another source of energy that uses methane. On Earth, some archaea combine carbon dioxide with hydrogen to generate methane and water, which is a chemical reaction that releases energy.

Molecular clouds feature abundant reserves of carbon dioxide. And if that weren't enough, any living creatures could also use carbon monoxide in a similar reaction, or turn to acetylene. This means there are several plausible chemical pathways a hypothetical methane-based life-form could use to generate energy.

But would there be enough raw materials to sustain life? This is the million-dollar question and the subject of Feng's paper. Feng took the proportions of all the ingredients in a typical molecular cloud to examine how much energy would be available and found that it was over five times the amount needed to sustain basic methane-based life.

We currently do not know if life could maintain these chemical reactions at the extremely low temperatures found within molecular clouds. But Feng proposed a way to test this radical idea. The presence of abundant life within a cloud would dramatically alter the cloud's chemical balance, just as the presence of life on Earth changes the chemistry of the atmosphere. If we spot a molecular cloud with an exceptional amount of methane, we might just be observing a home for life.

This work has important implications for our understanding of the origins of life. If life can arise on its own outside a planetary environment, this would bolster the case for panspermia, the idea that life pervades the universe and seeds itself in newly born planets. 

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Paul Sutter Contributor

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.

  • Questioner
    Without liquid water it is hard for me to imagine life being viable on an ongoing basis.

    Liquid water is a dense cradle of fragmentary chemistry. Ionic tags can be held at abeyance until something is ready to combine it with a polar opposite constituent.
    Organisms on Earth utilize methane for energy, but i am quite sure that is in some context of water.

    In youth i always wondered why air (O2 & N2) were 'lighter' than a molecule of water (H2O).
    Mathematically it didn't add up.
    Only when I understood the incredible polarity of water getting electrio-polarly entangled with itself did the greater density of water than air make sense.

    Unless one can come up with an alternative fluid (chemical context) which is a dense storm of electric polarity as is water i have a hard time thinking biochemical life would be possible.
  • billslugg
    In your youth, you were comparing air with liquid water?
    Air is heavier than water vapor.

    Water has a molecular weight of 18.01 g/m.
    Air has a molecular weight of 28.96 g/m.
    Water vapor rises.
  • Questioner
    Water at the Earth's surface (pressure) doesn't become vapor until 212F.
    Air doesn't become liquid except at extremely cold temperatures.
    It takes a lot more energy to vaporize water because it has to overcome all that electrostatic bonding.
    Electrostatics make liquid water quite dense.
  • billslugg
    Water has vapor above it no matter what the temperature. On a warm day, the Sun will evaporate water from your lawn and it will rise to form clouds.

    Yes, water has a very high heat of evaporation due to its strongly polar nature.
  • Questioner
    Water vapor by definition would be a water molecule(s) whose vector characteristics surpass its (their) electro-polar interactiveness (connectedness).
    Location as well as speed would be relevant.
    Water in an enclosed container would complicate the precise definition.

    Water is highly cohesive.
    It beads in freefall.
  • billslugg
    "Location as well as speed would be relevant.
    Water in an enclosed container would complicate the precise definition." - Questioner

    Heisenberg uncertainty principle prevents knowing the exact velocity and location of a particle at the same time.
  • Questioner
    My main point is that water is highly polar & can sustain an ion in solution because the opposite pole on the water molecules rotate/shift to balance the electric charge.
    And yet the water molecules don't covalently bond with it because their internal covalent bonds are stronger.
    This allows elaborated juggling of chemistry in the manner biochemical life operates.
    Unless some other chemical context is available to have electro-polar opposites in molecular proximity, life is hard to imagine.
    Perhaps in freefall if enough electrostatic noise is available something might work, but the manipulatable, controllable, reliable aspects of water seem nearly impossible to top.
  • billslugg
    There is good reason liquid water might exist inside a molecular cloud. A cloud progresses from a near vacuum to a star. There are many pressure/temperature regimes the cloud went through, some of which might have allowed water.
  • Questioner
    Yeah randomly, intermittently,
    but in a relatively consistent basis that some replicating organic molecule that forms being able to reliably create the same response it needs to operate?
    Pardon my doubts.
  • Questioner
    Let me add a quote from the article:

    "All of the water is frozen."

    Hard to work with ice.
    But whatever.