For the first time ever, organic matter and water found on an asteroid's surface
[June 7, 2023: Staff Writer, The Brighter Side of News]
Artists rendering of Hayabusa2 approaching asteroid Itokawa. (CREDIT: Creative Commons)
In a breakthrough that adds a new chapter to our understanding of the universe's evolution, scientists have unearthed evidence of organic materials integral to the creation of life on the surface of an S-type asteroid.
This comes after more than half a century of debate about the origins of organic dust rich in complex chemistry, which forms the basic building block of all life as we know it. Akin to tracing the twisted limbs of a sprawling family tree back to its primal roots billions of years in the past, this discovery could fundamentally alter our perception of life's genesis.
The groundbreaking study was conducted by an international team of scientists who performed detailed analysis on a particle sample from the asteroid Itokawa. This sample was originally retrieved by the Hayabusa mission launched by the Japan Aerospace Exploration Agency (JAXA) in 2010.
S-type asteroids like Itokawa are noteworthy as they are the primary sources of Earth's meteorites. Therefore, the revelation that they may harbor the critical ingredients necessary for life formation deepens our grasp of the conditions under which life could potentially originate. Heretofore, the study of organic material has mainly centered on carbon-rich C-class asteroids.
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What's particularly intriguing is that the scientists discovered that the organic material present in the sample has continuously evolved over time, despite extreme conditions. This material has incorporated water and organic matter from external sources, mirroring the evolution of life on Earth. In essence, this suggests that the first stages of Earth's biochemistry could be a continuation of the chemical reactions occurring within asteroids.
Royal Holloway University of London earth scientist, Queenie Chan, enthusiastically stated, "These findings are really exciting as they reveal complex details of an asteroid's history and how its evolution pathway is so similar to that of the prebiotic Earth."
This discovery harks back to the evolutionary models that can trace life's origins back approximately 3.5 billion years when life was essentially competing sequences of nucleic acid. Going further back in time, it's important to decipher how basic elements like hydrogen, oxygen, nitrogen, and carbon interacted to form incredibly intricate molecules, such as RNA, proteins, and fatty acids.
This very detailed view shows the strange peanut-shaped asteroid Itokawa. (CREDIT: JAXA)
The question of how simpler components could self-assemble into an organic soup had been a contentious issue since the 1950s. Experiments showed that Earth's surface conditions might be conducive to such a process. In recent times, however, attention has shifted to the gradual chemical processes within the rocks that coalesced into planets like ours.
It's increasingly evident that a consistent barrage of rock and ice billions of years ago could have transported molecules like cyanide, the sugar ribose, and amino acids, along with substantial amounts of water, to Earth's surface. However, the extent to which the chemistry of meteorites could have been adulterated by Earth-based elements has cast a shadow of uncertainty.
Isotopic composition of the primitive organic material in Amazon. (A) NanoSIMS ion image of H. (B) 12C12C. (C) 12C14N. (D) Isotopic images of the CN-rich region of δD, (E) δ13C and (F) δ15N. (CREDIT: Scientific Reports)
Since Hayabusa's triumphant return to Earth, JAXA has carefully stored over 900 particles of untainted asteroid soil in a specially designed clean room. A study of a handful of these samples revealed they all contained molecules primarily composed of carbon, adding credence to the belief that S-type asteroids could contain organic chemistry.
The Itokawa asteroid belongs to the stony (or siliceous) S-class. It's also thought to be an ordinary chondrite, a type of space rock that offers a snapshot of the early inner Solar System in its relatively unmodified state. The presence of organic chemistry in these asteroids, which constitute a considerable portion of the minerals colliding with our planet, is remarkable, to say the least.
The chemical distribution and mineralogy of Amazon. Image showing Amazon being picked up using a glass needle with platinum wires at JAXA. (CREDIT: JAXA)
The research team undertook a detailed analysis of a single 30 micrometre wide dust grain, codenamed 'Amazon.' They discovered an array of carbonaceous compounds, including signs of disordered polyaromatic molecules of an unmistakably extraterrestrial origin and graphite structures. These findings confirmed that the asteroid had been subjected to temperatures exceeding 600°C in the past, but the existence of unheated organic matter nearby suggested that primitive organics reached Itokawa's surface after it had cooled.
The asteroid's intriguing history is somewhat of a cosmic ballet. Itokawa has been through intense heating, dehydration, and then rehydration with a fresh layer of material. While not as exhilarating as Earth's journey, it does shed light on the intricate process of organic material maturation in space, which isn't confined to carbon-rich asteroids.
An artist's depiction of the Hayabusa2 spacecraft passing near Earth. (CREDIT: JAXA)
Recently, Hayabusa2 brought back a sample from Ryugu, a C-class, near-Earth asteroid. Comparing these samples will undoubtedly enhance our understanding of how organic chemistry unfolds in space.
The question of life's origins remains enigmatic, and it's probable that we'll continue seeking answers for an extended period. Nevertheless, each new discovery is progressively extending the narrative of life's origins from the familiar confines of our home planet to the farthest reaches of the cosmos.
This research was published in Scientific Reports.
For more science and technology stories check out our New Discoveries section at The Brighter Side of News.
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