Recently, these stories popped over the desk (might as well address them all at once):
From Dirk Schulze-Makuch at AirSpaceMag:
Life May Have Begun in Ocean Sediments, According to New Theory
During the Hadean time period, more than four billion years ago, the Earth was much more active than it is today, and hot water percolated through Earth’s crust in many places. The submarine crust, being covered by water, would have protected any primitive organisms from ultraviolet radiation. The porosity and chemical reactivity of the sediments between the crust and the seawater are critical in Westall’s model, as it is thought to have led to miniature “chemical reactors” that enhanced formation of the organic building blocks needed for life.
While I applaud the thorough analysis done by Westall and her co-authors, personally I’m still skeptical of a submarine origin for life. My thinking is that cycles of drying and wetting are much more powerful for accumulating organic building blocks, and these would more likely occur at water-land boundary zones than in a submarine setting. Also, while protection from ultraviolet radiation is certainly an advantage for life today, it may not have been as important for early life. Many organic reactions are actually enhanced by ultraviolet radiation. More.
Large concentrations of sulfites and bisulfites in shallow lakes may have set the stage for Earth’s first biological molecules
Also on this theme, from ScienceDaily:
The researchers found that a class of molecules called sulfidic anions may have been abundant in Earth’s lakes and rivers. They calculate that, around 3.9 billion years ago, erupting volcanoes emitted huge quantities of sulfur dioxide into the atmosphere, which eventually settled and dissolved in water as sulfidic anions — specifically, sulfites and bisulfites. These molecules likely had a chance to accumulate in shallow waters such as lakes and rivers.
“In shallow lakes, we found these molecules would have been an inevitable part of the environment,” says Sukrit Ranjan, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “Whether they were integral to the origin of life is something we’re trying to work out.”
Preliminary work by Ranjan and his collaborators suggest that sulfidic anions would have sped up the chemical reactions required to convert very simple prebiotic molecules into RNA, a genetic building block of life.Paper. open access – Sukrit Ranjan, Zoe R. Todd, John D. Sutherland, Dimitar D. Sasselov. Sulfidic Anion Concentrations on Early Earth for Surficial Origins-of-Life Chemistry. Astrobiology, 2018; DOI: 10.1089/ast.2017.1770 More.
Note: In the two accounts above, we must be assuming that ocean sediments and shallow lakes are similar.
From Richard A. Lovett at Cosmos:
Solar superstorms may have helped set stage for life
“The early Earth was continuously exposed [to them],” NASA physicist Chigomezyo Ngwira told a NASA-sponsored symposium called ‘Environments of Terrestrial Planets Under the Young Sun: Seeds of Biomolecules,’ this week in Greenbelt, Maryland.
Radiation from these solar superstorms would have pumped energy into the early Earth’s upper atmosphere, with some of the radiation penetrating deeply enough to create a cascade of chemical reactions extending all the way into the lower atmosphere, Ngwira says.
The storms would have deposited 100 times more energy into the upper atmosphere than modern ones, adds Vladimir Airapetian, an astrophysicist at NASA Goddard. This would have heated the upper atmosphere to hundreds of thousands of degrees and caused it to balloon outward, where gases like hydrogen could be easily lost to space. More.
There are a lot of “would have’s” in this discussion.
From Richard A. Lovett at Cosmos:
“Nuclear geyser” may be origin of life
Life may not have originated in the primordial soup of an ancient pond, according to scientists, but rather in a “nuclear geyser” powered by an ancient uranium deposit.
Shigenori Maruyama of Tokyo Institute of Technology says the idea came from what chemists know about crucial compounds in our own bodies.
Many of these compounds – including DNA and proteins – are polymers formed from chains of smaller building blocks.
Each of these molecules serves a different purpose in the body, but something they all have in common, says Nicholas Hud, a chemist from Georgia Institute of Technology, Atlanta, is that a molecule of water is released when each new building block is added. More.
This all sounds so much like one of those intractable squabbles in classics over whether the ancient Greek poet Homer really wrote the Iliad. Isn’t the problem about the same in both cases? Lack of definitive, serious evidence?
If evolution is a history, the origin of life is a history with no definitive data.
See also: Origin of life: Rob Sheldon on “lies, damn lies, and models”
What we know and don’t know about the origin of life