Asteroid material in chondritic Vigarano class alteration type 3 (CV3) meteorites provide a good record of complex chemistry present when or before our Solar System was formed 4.57 billion years ago, according to a team of researchers from Harvard University and PLEX Corporation.
PAH molecules overlaid on the Taurus Molecular Cloud, a large blue-white cloud made of gas and dust with large and small stars of varying luminosities interspersed throughout. Image credit: M. Weiss / Harvard & Smithsonian Center for Astrophysics.
“Molecular clouds are regions within the high vacuum of space where there is a low level content of hydrogen, helium, and small molecules containing hydrogen, lithium, carbon, nitrogen, and oxygen, extending to ethylene glycol and poly-aromatic hydrocarbons,” said Harvard University’s Dr. Julie McGeoch and Dr. Malcolm McGeoch of PLEX Corporation.
“It is predicted that glycine, the simplest amino acid, should be able to form, but it has not been observed, possibly due to its polymerization that is exothermic in the conditions of warm, dense, molecular clouds.”
“In meteoritic material derived from asteroids, we observed a number of glycine polymers.”
In the new study, the researchers examined individual amino acid polymers in several CV3-type meteorites (such as Acfer 086 and Allende).
The polymers form organized structures, including crystalline nanotubes and a space-filling lattice of regular diamond symmetry with density estimated to be 30 times less than water.
“Because the elements required to form our polymers were present as early as 12.5 billion years ago, and there appears to be a gas phase route to their formation, it is possible that this chemistry was and is present throughout the Universe,” Dr. Julie McGeoch said.
Three layers of hydrogen-bonded edge-to-edge polymer; each layer has four polymer rods bonded at a central vertex; atoms are colored as follows: hydrogen white, carbon black, nitrogen blue, oxygen red, silicon pink, and iron green. Image credit: Julie Elizabeth Mary McGeoch & Malcolm William McGeoch.
Preventing terrestrial contamination was a top priority for the scientists.
They devised a clean room method using a clean stepper motor with vacuum-brazed diamond bits to drive several millimeters into the meteorite sample before retrieving newly etched material from only the bottom of the hole.
Several drill bits were used in a single etch, all being cleaned with ultrasonification.
The resulting micron scale meteorite particles were then placed in tubes and stored at minus 16 degrees Celsius.
Polymers were induced to diffuse out of the micron particles via Folch extraction, which involves two chemical phases related to different solvents with different densities.
Mass spectrometry revealed the existence of the polymers, which were composed of chains of glycine with additional oxygen and iron.
They had a very high deuterium-to-hydrogen-isotope ratio that confirmed their extraterrestrial origin.
“Going forward, we hope to get more detail of the glycine rods via continued X-ray analysis,” the authors said.
“Other polymers in the same class remain to be characterized and could reveal the energetics of polymer formation.”
The team’s results were published in the journal Physics of Fluids.
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Julie E.M. McGeoch& Malcolm W. McGeoch. 2021. Structural organization of space polymers featured. Physics of Fluids 33, 067118; doi: 10.1063/5.0054860
