|Feature Article - October 2020|
|by Do-While Jones|
Did life on Earth begin in hostile hot springs?
Despite what you were probably taught in school, there is no plausible scientific explanation for how life began.
Science News might have led you to believe that life began in hot springs.
David Deamer, a biophysicist at UC Santa Cruz, has spent four and a half decades exploring how life on our planet may have begun. He started out studying lipids, oily molecules that make up the membranes surrounding cells. Deamer, a big proponent of hot springs as the source of life’s start, has shown that conditions at terrestrial hot springs can produce bubblelike vesicles, with an outer layer made up of lipids. Such structures may have been the ancestral precursors of modern-day cells (SN: 7/3/10, p. 22). 1
After more than 40 years studying the origin of life, he must certainly know what he is talking about. Life must have begun in a hot, wet place. But wait!
Nicholas Hud, a chemist at Georgia Tech in Atlanta, studies the origins of life from a slightly different perspective: He explores how DNA and RNA nucleotides originated. He agrees that molecules are more likely to link together by condensation reactions on land, where wet-dry cycles can occur, than in the ocean. These reactions produce water; the formation of such a chemical bond isn’t energetically favorable when there’s already a lot of water around. “The best place to form that is in a hot, dry place,” Hud says. “The worst place to form it is in a wet, hot place.” 2
So, life had to begin in a hot wet place that was dry.
To Deamer, there are big barriers to putting life’s pieces together near underwater vents: The vastness of the ocean would dilute molecules so they wouldn’t be concentrated enough to drive chemical reactions. Also, there are “no wet-dry cycles underwater.” In his view, repeated evaporation is needed to pull together enough molecules to bump into each other and react to form longer chains. Plus, unlike a hot spring’s freshwater, salty ocean water inhibits the formation of membranes and reactions that link together molecules, he says.
However, Deamer’s hot springs theory has its critics as well. DNA and RNA strands are composed of alternating phosphate and sugar molecules, but sugars “are profoundly unstable in hot spring environments,” says David Des Marais, an astrobiologist at NASA’s Ames Research Center. 3
The Science News article is full of reasons why life could not have originated on land, and reasons why it could not have originated in the water. You can read the article for yourself. The point is, there is no place on Earth where life could have originated, so it had to have originated someplace else.
As researchers study and debate where and how life on Earth first ignited, their findings offer an important bonus. Understanding the origins of life on this planet could offer hints about where to search for life elsewhere, says Natalie Batalha, an astrophysicist at the University of California, Santa Cruz. “It has very significant implications for the future of space exploration.” 4
If they had discovered how life began on Earth, then their findings would have been useful in a search for life elsewhere—but all they have found are places where life could not have begun. Therefore, their findings really tell where not to look!
(Since scientists can’t find an explanation for how life began on Earth, and need to search for the origin of life elsewhere, creationists might offer hints about where to search for the origin of life elsewhere; perhaps in a book—but we won’t.)
The Science News article suggested looking for life elsewhere. Could this notion have been inspired by the discovery of phosphine gas on Venus which they reported just a few days earlier? Of course it was; and so was the New Scientist cover story which appeared almost simultaneously.
This month’s Evolution in the News column, Life on Venus, addresses in detail the news report that started it all. The article you are reading now addresses the reaction to that report.
So far, we’ve looked at what Science News said. Here’s what New Scientist had to say about the origin of life on other planets. They began their article by dismissing life on Mars.
The Red Planet was thrust into the limelight in 1996 when scientists said they had discovered evidence for fossilised life in a Martian meteorite called ALH84001 found in Antarctica. … Today, scientists are less sure about ALH84001 as evidence for life. And while we now think that Mars was once habitable, current prospects for life there are slim. So Mars has started to lose its shine. The phosphine discovery has many wondering if we might see history repeat. 5
We were sure there wasn’t any evidence for fossilized life on ALH84001 in 1996. 6 We expect history to repeat when it comes to Venus, too.
“We invested billions of dollars in looking for life on Mars because of that discovery [ALH84001],” says Sanjay Limaye at the University of Wisconsin-Madison. “So I wouldn’t be surprised at all if we see a similar trajectory here from this initial finding [of phosphine on Venus].” 7
Pardon us for being cynical, but is the university looking for life, or funding? Would they really go on a wild goose chase to Venus if they didn’t expect to find a goose there? Maybe so, if the price was right.
Water and carbon dioxide are molecules that are associated with life. Scientists sometimes get excited when they discover indications of water or carbon dioxide on moons or planets—but those molecules don’t prove there is life there. In fact,
Until this announcement, phosphine hadn’t been on many people’s radar as a biomarker. “There are 16,367 molecules associated with life, by our latest count,” says Clara Sousa-Silva at the Massachusetts Institute of Technology, a co-author on the phosphine discovery paper who has led much of the work on phosphine as a biomarker. “No one was looking for phosphine.” 8
This brings up the question, “How many of those 16,367 molecules should one have to find for it to be sufficient evidence for life?”
When Sousa-Silva was alerted to the presence of phosphine on Venus, however, she and her colleagues worked to find a possible source. After exhausting all options, they concluded it must either be produced on Venus by an unknown chemical process, or life.
So, the phosphine was produced either by life or non-life. If I had a PhD, I might have thought of that.
The New Scientist article goes on to describe several future space exploration projects, and then concludes with these words:
In the nearer term, there are plausible routes to follow up the phosphine finding, and even if a biological source turns out to be unlikely – like with a certain Martian meteorite – the prospect of an era of Venus exploration spurred on by the discovery has many supporters, life or no life.
“If we still haven’t sent anything to Venus in four or five years, or even considered sending anything, it will have been a waste,” says Paul Byrne, a planetary scientist at North Carolina State University. 9
We are among the supporters of Venus exploration. We support science. Unfortunately, it is often necessary to pander to people who aren’t willing to fund research unless they think it will prove that life originated by chance. The dishonesty of that approach makes us uncomfortable; but that’s the world we live in.
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Jack J. Lee, Science News, September 26, 2020, “Did Life Begin in a Place Like This?”, pp. 22-26, https://www.sciencenews.org/article/life-earth-origins-hostile-hot-springs-microbes
5 Jonathan O’Callaghan, New Scientist, September 2020, “Missions to confirm signs of life on Venus are already in the works”, https://www.newscientist.com/article/mg24833024-200-missions-to-confirm-signs-of-life-on-venus-are-already-in-the-works/
6 Disclosure, November, 1996, “That's One Small Step for a Rock-One Giant Leap of Faith”, and Disclosure, January, 1997, “Martian Meteorite Update”
7 Jonathan O’Callaghan, New Scientist, September 2020, “Missions to confirm signs of life on Venus are already in the works”, https://www.newscientist.com/article/mg24833024-200-missions-to-confirm-signs-of-life-on-venus-are-already-in-the-works/