Amazing stuff!
Notice the abstract speaks of a six step process, but it lists only five steps! The significance and abstract also contained some misspellings or ambiguous spellings (which I corrected).
"One surprising discovery made by the researchers was that the mineral borate, which was expected to interfere with essential prebiotic processes by latching onto key ingredients and preventing further reactions, actually had the opposite effect. Instead, borate helped with the chemical reactions by sweeping away unwanted byproducts and maintaining the pH levels required for RNA synthesis. ..."
From the significance and abstract:
"Significance
RNA may have been the first informational molecule to support Darwinian evolution, and life, on Hadean Earth and/or Noachian Mars. Thus, any model that produces RNA from simple organic molecules is relevant to understanding how life emerged under an “RNA First” hypothesis.
Here, we analyze one model to form prebiotic RNA, finding that all steps are compatible with each other and with noncontroversial geochemical and geodynamical models.
Perhaps coincidentally, these steps most likely occurred 4.3 billion years ago, ca. 100 Mya before some molecular clocks approximate the divergence of the kingdoms of Earth life (ca. 4.2 Ga), and 200 Mya before isotopically “light” carbon is seen in 4.1 Ga zircons, perhaps the oldest trace of life on Earth.
Abstract
Models for prebiotic synthesis often have many steps, each separately validated by laboratory experiments. The challenge then asks whether these steps work together in natural geological environments, absent human intervention.
Here, we analyze a six-step Discontinuous Synthesis Model (DSM) for the prebiotic formation of RNA, proposed to be the first informational molecule to support Darwinian evolution, and life, on Earth and/or Mars.
DSM requires that borate in multiple steps guide the formation of pentoses from simple carbohydrates and control phosphorylation, in all cases by binding adjacent HO-groups on key intermediates. However, adjacent HO-groups must react in two other steps, which borate might inhibit.
Experiments here show that borate does not inhibit these two other steps, but rather facilitates them. This makes the six-step DSM a “no human intervention” route from simple precursors (1 to 3 carbons, 0 to 2 nitrogens) to oligomeric RNA with predominantly 3’,5’-linkages at least 6 nucleotides long, but possibly much longer.
The process
i) exploits privileged chemistry in
ii) intermittently irrigated aquifers constrained by basalt that
iii) have borate
iv) above a redox-neutral mantle
v) having access to an atmosphere transiently reduced by a Vesta-sized impactor.
i) exploits privileged chemistry in
ii) intermittently irrigated aquifers constrained by basalt that
iii) have borate
iv) above a redox-neutral mantle
v) having access to an atmosphere transiently reduced by a Vesta-sized impactor.
In a possible coincidence, such an impact occurred most likely ca. 4.3 billion years ago (Ga), ~100 Mya before some molecular clocks date the divergence of the three kingdoms of life on Earth (4.2 Ga), and ca. 200 Mya before isotopically “light” carbon is reported in zircons dated at 4.1 Ga. This carbon may be the oldest trace of life ever proposed."
