Made in Space: the A-T-G-C bases of our DNA! 🌎 ☄

A bombshell published in Nature today: All of the bases in DNA and RNA have now been found in meteorites, providing further support to the hypothesis that life’s precursors arrived on Earth from abiotic origins in space.

This new work used more detailed analysis methods and doubled the DNA bases discovered in the rare CM2 meteorite falls. Seems like a good time to show what those carbonaceous, water-rich space rocks look like, from the most recent pristine CM2 — Aguas Zarcas — a witnessed fall in Costa Rica, 2019. The prior best sample arrived in 1969, the Murchison fall in Australia, and has been the subject of extensive study.

Like Murchison, Aguas Zarcas is loaded with organic compounds. It is rich in water, carboxylic acids, sugar alcohols, aromatic hydrocarbons, and amino acids that are rare in biology with isotopes that confirm their extraterrestrial origin. Oh, and the meteoritic carbon molecules exhibit the same left-handed chirality bias as biology on Earth.

So how did meteorites jump-start life on Earth? I just finished a freshly published meteorite book, Impact, and chapter 5 covered these carbonaceous chondrites. Well, a big banger early on wiped out all possibility of life on Earth; the meteor impact that dislodged what is now our moon also created a magma ocean across the planet that would have been a destructive 1000°C bake of any complex organic molecules that might have existed prior. But then came the water and carbon-rich CM meteorites, adding an estimated 275 metric tons of carbon compounds to Earth every day!

And where did these complex organic molecules come from? The abiotic assumption is that they were basic molecules trapped in ice water beyond the orbit of Jupiter, where it is cold enough for ice to persist, and maintain the proximity or organic clusters. UV radiation energized the formation of more complex molecules from the basic molecules.

“And if it was not incredible enough that the organic building blocks that our deep ancestors turned into life were delivered by meteorites, consider that the ubiquity of the raw materials, energy required, and simplicity of creation means that complex organic molecule-rich bodies are almost certainly commonplace in the Universe. If life formed on Earth due to organic materials that formed abiotically in outer space, then that suggests that any planetary body in the Universe with reasonable conditions for chemical reactions and a little luck has a reasonable opportunity to develop life. This is the idea of molecular panspermia.” — Impact, p.136.

A total of 144 different scientific papers have already been written about Aguas Zarcas; many more are in the pipeline. One article titled “The Aguas Zarcas (CM2) meteorite: New insights into early solar system organic chemistry” summarizes the excitement: “To date, the CM2 class of carbonaceous chondrites has provided the most detailed view of organic synthesis in the early solar system. Organic‐rich chondrites actually observed falling to Earth (“Falls”), for example, the Murchison meteorite in 1969, are even more rare. The April 23, 2019 fall of the Aguas Zarcas meteorite is therefore the most significant CM2 fall since Murchison. Samples collected immediately following the fall provide the rare opportunity to analyze its bulk mineralogy and organic inventory relatively free of terrestrial contamination.”

The MetBull writeup says it “emits a powerful Murchison-like odor, though with a more prominent compost-like scent.”

On the left in the photo above: the fresh, somewhat glassy, fusion crust from the heat of hitting Earth’s atmosphere. Is is very thin, and the interior faces little thermal flux. Meteorites are cold to the touch when they land, the thermal mass being quite cold in space.

On the right: So many chondrules, from the early formation of our solar system condensing out of nebular gases. There are also CAI grains (the earliest matter condensed in our solar system, with heating from radioactive Al26). CM2 Murchison also contains some of the the oldest minerals (presolar grains) at 7 bilion years old. That is a half time of our Universe. The two-tone here? From meteorite-hunter Michael Farmer: “The lower part (beige) is an air break that instantly ‘frosted’ then stopped burning. The top is a fresh break on impact”

• Nature paper on Murchison. “We’ve completed the set of all the bases found in DNA and RNA and life on Earth, and they’re present in meteorites,” says astrochemist Daniel Glavin of NASA’s Goddard Space Flight Center.

• From nanoscale infrared analysis of Aguas Zarcas and its Fine-Grained Rims (FGR) around the chrondrules: “they may have contributed prebiotic material to early Earth. Fine-grained rims (FGRs) and organic-rich dark clasts are particularly interesting features. The presence of organics embedded within these FGRs may further indicate that they may have formed in the solar nebula as well.” — ACS Earth Space Chem 2021

An artifact from the Future Ventures’ 🚀 Space Collection.