A team of researchers from the United States and Canada has found evidence for 4.55-billion-year-old sodium-rich alkaline fluids in the Tagish Lake meteorite, a unique piece of the Solar System’s main asteroid belt.
A fragment of the Tagish Lake meteorite. Image credit: Mike Zolensky, NASA’s Johnson Space Center.
The Tagish Lake meteorite is a carbonaceous chondrite retrieved from an ice sheet in Tagish Lake, northwestern British Columbia, Canada, in 2000.
Due to the pristine nature and recovery of this space rock, its insoluble and soluble organic compounds such as amino acids, amines, and hydrocarbons are highly important for better understanding of the evolution of prebiotic life in our Solar System.
The team, led by Dr. Lee White from the Royal Ontario Museum, used atom-probe tomography, a technique capable of imaging atoms in 3D, to target molecules along boundaries and pores between framboidal magnetite grains that likely formed on the crust of the parent asteroid of the Tagish Lake meteorite.
There, the researchers discovered water precipitates left in the grain boundaries on which they conducted their study.
These electron images show magnetite framboids in the Tagish Lake meteorite: the larger spherical to hexagonal structure within the thin section (A) is constructed of numerous framboidal aggregates, as imaged during FIB (focused ion beam) analysis of the sample (B); the abundance of carbonaceous material within the framboids is correlated with the tightness of packing, with deformed regions incorporating higher quantities of carbon; for reference, the lift-out location for atom probe microtip preparation is highlighted in (A). Image credit: White et al, doi: 10.1073/pnas.2003276117.
“We know water was abundant in the early Solar System, but there is very little direct evidence of the chemistry or acidity of these liquids, even though they would have been critical to the early formation and evolution of amino acids and, eventually, microbial life,” Dr. White said.
“Our research provides the first evidence of the sodium-rich (and alkaline) fluids in which the magnetite framboids formed.”
These fluid conditions are preferential for the synthesis of amino acids, opening the door for microbial life to form as early as 4.55 billion years ago, according to the team.
“Amino acids are essential building blocks of life on Earth, yet we still have a lot to learn about how they first formed in our Solar System,” said co-author Beth Lymer, a Ph.D. student at York University.
“The more variables that we can constrain, such as temperature and pH, allows us to better understand the synthesis and evolution of these very important molecules into what we now know as biotic life on Earth.”
The study was published this week in the Proceedings of the National Academy of Sciences.
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Lee F. White et al. Evidence for sodium-rich alkaline water in the Tagish Lake parent body and implications for amino acid synthesis and racemization. PNAS, published online May 11, 2020; doi: 10.1073/pnas.2003276117
