Stars, Planets, Life

    Part of the enjoyment of doing research is that ideas pop into your head all the time. Everyone has ideas, but the hard part is to choose which should be subjected to critical tests that have the primary aim of proving them wrong. That’s the most efficient way to discard bad ideas, because most of them in fact don’t work. Only after an idea survives the crucible of initial testing can it be taken more seriously and tested further. Then, if it still survives, you can publish. 

There must have been an abundant source of free energy on the early Earth that could produce the polymers required for natural experiments leading to the origin of life. What was it?

 “May you live in interesting times!” So goes the ancient Chinese curse, and times certainly must have been interesting for Alexander Ivanovich Oparin, who was 23 years old when he graduated from Moscow State University in 1917. Lenin and the Bolsheviks had just seized power, the Czar and his family were imprisoned, then assassinated a year later, and the war between Red and White Russia began.

In the last few columns, I described how laboratory simulations of a volcanic prebiotic environment showed that interesting organic reactions can be driven by the heat and pressure associated with vulcanism. I also described my own studies of volcanic sites on the present Earth, which we call prebiotic analogue environments, and pointed out some of the problems that arise when we try to duplicate laboratory experiments in the real world geothermal conditions. In the comments following the column, Gerhard Adam suggested that ice might be a plausible alternative to a hot site for the origin of life.

When we think of volcanic conditions, our minds leap to images of vast eruptions like Mount St. Helens in Washington State, or lava oozing down the slopes of Kilauea on the Big Island of Hawaii. With my family, I once visited that lava flow.We are used to stones being “rock solid” but here molten orange-hot rock oozes across a two-lane road and pours over a cliff, causing clouds of steam to erupt from the Pacific Ocean.My daughter Ásta, five years old at the time, was understandably very suspicious of the stuff and would not go near the lava flow. It radiated an oven-like heat, even from fifty feet away. 

In 1988, Günter Wächtershäuser published a remarkable idea that excited tremendous interest, even being featured in a Scientific American article. It ran counter to prevailing ideas about the origin of life, and suggested new experimental approaches involving mineral interfaces. Wächtershäuser is a patent lawyer in Munich, Germany who enjoys fabricating intricate and novel approaches to the origin of life, then challenging others to test them. He is greatly influenced by the philosopher Karl Popper, who made the point that explanations are useless unless they are falsifiable.

    Last week I described how John Oro discovered that five hydrogen cyanide molecules (HCN) could react to produce adenine (H5C5N5) one of the primary components of nucleic acids. 

    For life to begin, there had to be a source of organic compounds in the prebiotic environment. We now think that some of the compounds were delivered to the Earth on comets, meteorites and dust particles, but others were synthesized in the atmosphere, hydrosphere and in volcanic conditions. How do we know? This question brings up the important topic of prebiotic simulations. In a simulation, we make a set of assumptions about local conditions on the early Earth, then reproduce those conditions in the laboratory and run experiments to see what happens.

Many people, perhaps most, hate the idea that life might depend on chance processes. It is a human tendency to search for meaning, and what could be more meaningful than the belief that our lives have a greater purpose, that all life in fact is guided by a supreme intelligence which manifests itself even at the level of individual molecules? 

In last week’s column I described how Bill Irvine uses radio astronomy techniques to detect and identify organic compounds in interstellar space. Why is it so important for the origin of life on Earth that organic compounds are scattered throughout our galaxy?

    Last week I described how Fred Hoyle, in 1946,  came up with the idea that carbon is synthesized in hot stars toward the end of their lifetime, and we now know that carbon and the other elements of life are strewn into interstellar space when the star explodes. In his later career, Hoyle was never able to match his earlier triumph of carbon nucleosynthesis, but he certainly tried.

    Last week I described how a boulder-sized meteorite exploded in the skies over Murchison, Australia, forty years ago. The remarkable mix of organic compounds discovered in samples of the meteorite, which included amino acids, confirmed that some of the compounds required for the origin of life could have an extraterrestrial origin, as John Oro had proposed  ten years earlier. But where did the organic compounds come from, and how were they synthesized?