How did Life begin?

his topic is a bit on the periphery of ‘Gene-Environment Interactions,’ but –– without Life on Earth –– we wouldn’t have genes to interact with the environment. 🙂

How and Why did Life come to exist on this planet? Is it simple for life to emerge on many newly formed planets? Or is it the virtually impossible product of a long series of unlikely events? Advances in fields –– as unrelated as astronomy, planetary science and chemistry –– now hold promise that answers to such profound questions may be coming soon. If life turns out to have emerged multiple times in our galaxy (as scientists expect to discover), then that means the path to “development of life” cannot be so difficult. Moreover, if the route from chemistry-to-biology proves simple to traverse, the universe could be teeming with life.

The discovery of thousands of exoplanets [see attached editorial] has sparked a renaissance in origin-of-life studies. In a stunning surprise, almost all the newly discovered solar systems look very different from our own. Does that mean something about our own, very unusual, sys­tem favors the emergence of life? Detecting signs of life on a planet orbiting a distant star is not going to be easy, but the technology for teasing out subtle “biosignatures” is developing –– so rapidly that, with any luck, we may see solid evidence of distant “Life” within one or two decades.

To understand how Life might begin, we must first understand how — and with what ingredients — plan­ets normally form. A new generation of radio telescopes has provided beautiful im­ages of proto-planetary disks and maps of their chem­ical composition. This information is motivating scientists to develop better models of how planets assemble from the dust and gases of a disk. Within our own solar system, the Ro­setta mission (which had visited a comet) has helped us to appreciate early materials that formed Earth. OSIRIS-REx will soon visit an asteroid, and even try to return samples from it, which might give us the essential inventory of the materials that came together in our planet.

Once a planet, such as our Earth — not too hot and not too cold, not too dry and not too wet — has formed, what carbon-hydrogen-oxygen (CHO) chemistry must then develop to yield the Building Blocks of life? In the 1950s the Miller-Urey ex­periment (which zapped with electric pulses, a mixture of water and sim­ple chemicals, to simulate the impact of lightning) demonstrated that amino acids, the building blocks of proteins, are easy to create in a chemical flask (i.e. in vitro). Other molecules of life turned out to be harder to synthesize, however. It is now apparent that we need to completely reimagine the path from chemistry to life. The central reason hinges on the versatility of RNA, a very long molecule that plays a multitude of essential roles in all existing forms of life. RNA can not only act like an enzyme, but it can also store and transmit information. The [attached] excellent editorial provides the Reader with a concise summary.

Nature 10 May 2o18; 557: pp S13–S15

COMMENT: Hi Dan, I like the Panspermia Model. It has had a number of really smart and famous proponents –– including Fred Hoyle, Stephen Hawking, and even S. Steven Potter (ha ha)!!

So, the basic notion is that Life came from Outer Space. Microorganismal life should be able to travel in interplanetary space on dust particles, knocked into space (from the planet of origin) by meteorites or interplanetary collisions. (Actually, there are many meteorites from Mars found on the surface of Earth; at last count, 132 have been found.) Microorganismal life on dust particles can be driven away from a sun by solar wind, and then decelerated by solar wind in another solar system. Upon hitting an atmosphere, the dust particles would float to the surface like a feather, rather than burn like a rock (i.e. a meteor).

But, then, WHERE did the Life in outer space originate?? Well, it has been estimated that there are ~100 billion planets in our Milky Way galaxy. For Life to begin, you only need a one-time accident, an “original incubator planet”, to get things started. And then these microorganisms would be spread throughout the galaxy. The Panspermia Model increases your odds by 100 billion –– because Life would only be required to have started once and then spread. I like those odds.

“Getting Life started” looks to be very, very tricky. Some have compared it to “assembling a wristwatch that happened by chance”, as an argument for Divine Creation. Cells do have a lot of vital parts, and we don’t really have any good models for how you go from organic soups to dividing cells. I do like “the RNA-first” idea of how things might have started, and maybe “somewhere out there” –– ideal conditions one way or another existed for creating the first living cell. Given a hundred billion planets, there would be a lot of possible “sets of starting conditions”.

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