Making Life?

In the 1920's scientists Oparin and Haldane  theorized that given a planet like the early Earth, with a reducing atmosphere (ie one with no oxygen), high UV radiation, and the basic chemical elements, then it might be possible to create organic molecules from inorganic precursors.  In 1953 Miller and Urey tested their predecessors' ideas with a famous experiment that they said simulated those conditions.  Sure enough it worked.  They mixed water vapor, hydrogen, methane and ammonia and passed high-energy electrical discharges through the "soup".  Within a few days they had made several organic compounds and amino acids - the building blocks of life.  The experiments were modified and repeated and many chemicals, including all the twenty amino acids, lipids, sugars and the purine and pyramid-like bases of nucleic acids.   If oxygen gas was added, however, the processes failed.

However the experiment, which is now sometimes repeated in school laboratories, did show that the basic organic compounds that are necessary building blocks for life could be easily synthesized from elementary materials and "natural" conditions.  Having the building blocks, though, is a long way from having the building! Imagine the building blocks of life as a tub of Lego parts, with life itself represented by a model that you may be able to build from the parts - a dune-buggy, perhaps.

To make the dune-buggy you need to undertake a series of very precise steps selecting parts in the right order, orientating them, and then slotting them into place.  Creating a living entity is a similar process, as far as we understand.  But we only have a vague idea of how to fit the parts together, at least from first principles.  All we are able to do is the equivalent of shaking the tub of Lego and tipping it out on the floor, hoping a dune-buggy may spontaneously appear.  And how likely is that?  There is virtually no chance at all.


In nature, there is a solution to the dune-buggy problem.  It is DNA.  The DNA is both the plan and the means of issuing orders to make the "dune-buggy" of life.   But take away the instructions and nature is back to "tipping the tub",  just as it was before the first life appeared.  The big mystery of life is not how it is assembled, but how did the first set of assembly instructions come into being, apparently in a dumb Universe without intelligent intervention?

Despite the initial euphoria, the Miller-Urey experiment took us no further than repeating that very question in our quest to understand how life came about.  It was, and remains, a long way from giving us the answer to the origin of life and the means to create it from first principles.

By the 1980's ideas about the early Earth had changed and the Miller-Urey experiment was considered irrelevant.  It no longer represented the conditions of the early Earth, according to the new theories.  However now Miller and Urey's experiment is being revived, not in its original form, but in a form that mimics conditions that are thought to exist in deep space.

Life from Deep Space

(Right) Members of the Laboratory Astrophysics Group, at NASA Ames, are researching the origins of life in deep space:  the team and some of their apparatus. © NASA, 1998

Recent work by a team of scientists led by Lou Allamandola at NASA Ames Research Center at San Jose, has shown how such compounds may form from basic elements and molecules in interstellar space.    He and his colleagues created a vacuum chamber, cooled it to a very low temperature of 10 K above absolute zero - typical of interstellar space - and released into it some minute gaseous quantities of water, hydrogen, nitrogen, oxygen, and carbon-monoxide, along with some grains of sand - SiO2.


PAH coronene (C24H12) Molecule - One of the molecules produced. © NASA, 1999
They bombarded this with ultraviolet light and to their amazement, within a short time new and complex chemicals had formed around the silicate grains.  These included ketones, formaldehyde, polycyclic aromatic hydrocarbons (PAH), ammonia, methane, methanol, alchohols of various kinds, poly-oxymethylenes and dozens of other highly complex organic chemicals - some of which were unknown and had no name!

What was most surprising, though, was the fact that the chemical residues formed into vesicles similar to those found in the Murchison meteorite by David Deamer.   The vesicles created in the vacuum chamber have some interesting and significant characteristics.  One end is hydrophilic and the other end is hydrophobic - they  both love and hate water!   This enables molecules to be self-organizing in the presence of water and this ability, or characteristic, is a simple sorting process that may go some way towards understanding how life could self-organize, without some intelligent presence overseeing its assembly.   In fact the vesicle behaves like a lipid, which is a fatty or oily bio- (rather than just an organic) molecule that is a major component in living cells and serves a variety of important functions.

The most important of these functions is the creation of a boundary, enclosure or membrane,  that isolates whatever is inside from the harsh and potentially destructive Universe outside.  Surrounding and isolating a cocktail of potentially life-making chemicals in this way, where they can carry out their processes without external perturbations, must be vitally important if life is to "get started".   If it is possible for lipids to form from "raw", inorganic chemicals, by simple processes that would be common in space, then a major factor in understanding the origins of life has been discovered.

It is a step closer, towards self-assembling our "dune-buggy" of life.   We now tip the parts out on to a tray, they now remain together, half of them no longer roll away across the floor to get lost or trodden on!   But it is still a long way from a complete buggy. If  we take a logical approach, though, we might finally assemble the buggy by putting sub-assemblies together - wheels, engines, chassis.  The final buggy is then made from a few sub-assemblies.  Did life happen by the same process?  If so how did the subassemblies self-assemble?
Could it have been by natural physical processes that create structure? We can see this happening throughout the non-living world. Spheres form from liquid in free-fall.  Tornadoes (Twisters) are helical in structure, like DNA.  Crystals form amazing geometric shapes.  All these are a form of structure and assembly.  They are just three examples and there are many more.  Can you think of any?

Meanwhile back in the space simulation chamber, further development of the chemicals continued as the experiment progressed.  Compounds known as quinones and alkaloids developed from the PAH's.    Alkaloids are common in plants, where they play a crucial role in many aspects of a plant's life.   Quinones assist in the electrons' mobility inside living cells.   They are used in photosynthesis in plants and bacteria, and in animal cells where they become muscle and brain "food".

It is becoming clear that life precursors could be created in space, from the simplest of chemicals and in the most unpromising of conditions.   The question that now occurs is this:  did life start in space, or was it that the chemical precursors of life could form in space and rain down on the planet as comets and other space debris?

The second option is quite likely, but the true origin of the first living cell is still as elusive as ever.  But major breakthroughs happened in the last decade of the last millennium and perhaps the answers to our fundamental questions about life will be answered soon.


Dr Allamandola © NASA, 1999
The team at NASA Ames are hopeful that perhaps they are only a short step from seeing life spontaneously come into existence.  As Dr Allamandola says: " When I see this kind of complexity forming under exceedingly simple conditions, I begin to really believe that life is a cosmic imperative."  The full story is at  Life from a dirty snowball.

Meanwhile, in Calcutta, India, a team at the  S N Bose National Centre for Basic Science has produced a mathematical model of how chemicals would evolve in a large cloud of interstellar dust and gas 7 light-years across which is collapsing under its own gravity.   The cloud contained 12 elements, including Hydrogen, Carbon and Nitrogen.  and it contracted for a million years.  The simulation resulted in the production of Anadine, which is one of the bases for DNA.  The full story is at Seeds of life.

This is another step closer to building the buggy!

Now take the Life in Space Knowledge Challenge

Complex organic molecules form quickly in old stars

Possible Astronomical Implications for the Origin of Life-chemical synthesis in the circumstellar environment,

NASA's Thursday Classroom - Life on the Edge

David Deamer - article

David Deamer - personal

Create space! - making vesicles

The process - a vesicle

Exobiology links

Jason Dworkin

Dr. Louis Allamandola

Welcome to the Astrochemistry Lab - PAH Dust Ice

Teachers Wormhole


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