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Follow the twisted members of your family tree to its primordial origins billions of years in the past and you will find that we are all grown from dust rich in organic chemistry.
The origin of this organic dust has been debated for more than half a century. Now, researchers have found the first evidence of organic material essential for life on Earth on the surface of an S-type asteroid.
An international team of researchers recently conducted an in-depth analysis of one of the particles reported from the asteroid Itokawa by the original Hayabusa mission of the Japanese Space Agency (JAXA) in 2010.
Most of Earth’s meteorites originate from S-type asteroids like Itokawa, so knowing that it could have contained ingredients essential to life on our planet is an important step forward in our understanding of how the conditions for the formation of life could arise. So far, most research on organics has focused on carbon-rich asteroids (class c).
Examining the sample, the team found that organic matter from the asteroid itself had evolved over time under extreme conditions – incorporating water and organic matter from other sources.
This is similar to the process that happened on Earth and helps us better understand how the earliest forms of Earth biochemistry might simply be an extension of the chemistry that takes place inside many asteroids.
“These findings are truly exciting because they reveal intricate details about the history of an asteroid and how its evolutionary path is so similar to that of prebiotic Earth,” says Earth scientist Queenie Chan of the Royal Holloway University, London.
Evolutionary models can take us some 3.5 billion years back to a time when life was little more than competing nucleic acid sequences.
Take a step back and we are forced to consider how elements such as hydrogen, oxygen, nitrogen and carbon could come together to form incredibly complex molecules capable of self-organizing into substances that behave. like RNA, proteins and fatty acids.
In the 1950s, when researchers first contemplated the thorny question of how simpler ingredients could spontaneously cook organic soup, experiments showed that conditions on the Earth’s surface could do enough work.
Nearly seven decades later, our attention has turned to the slow, steady chemical processes inside the very rocks that have aggregated into worlds like ours.
The evidence is not hard to find. It’s now clear that a steady rain of rocks and ice billions of years ago could have delivered cyanide molecules, ribose sugar, and even amino acids – with a generous donation of water – to the surface. of the earth.
But the extent to which the chemistry of meteorites could have been contaminated by things on Earth leaves some room for doubt.
Since Hayabusa’s return ten years ago, more than 900 pristine asteroid dirt particles taken from its payload have been separated and stored in a JAXA cleanroom.
Fewer than 10 have been studied for signs of organic chemistry, but all contain molecules mostly made up of carbon.
Itokawa is what is called a class of stony (or siliceous) asteroids, or class S. After early studies of its material, it is also believed to be an ordinary chondrite – a type of space rock. relatively unmodified representing a more primitive state of the inner solar system.
Considering that these types of asteroids make up a good chunk of the minerals that break down on our planet, and are generally not thought to contain a lot of organic chemistry, these early findings were intriguing to say the least.
Chan and his colleagues took just one of these dust grains, a 30-micron-wide particle shaped much like the South American continent, and conducted a detailed analysis of its composition, including a study of its content of water.
They found a rich variety of carbon compounds, including evidence of disordered polyaromatic molecules of clearly extraterrestrial origin and graphite structures.
“After being studied in detail by an international team of researchers, our analysis of a single grain, dubbed ‘Amazon’, preserved both primitive (unheated) and processed (heated) organic matter to less than ten microns (a thousandth of a centimeter). away, ”Chan says.
“The organic material that was heated indicates that the asteroid had been heated to over 600 ° C in the past. The presence of unheated organic material very close to it, means that the fall of primitive organic material has arrived at the surface of Itokawa after the asteroid cools. “
Itokawa has had an exciting story for a rock that has nothing better to do than float lazily around the Sun for a few billion years, after being altered with good cooking, dehydrated, and then rehydrated with a fresh layer of fresh material.
Although its history is not as exciting as the history of our own planet, the asteroid’s activity describes the cooking of organic matter in space as a complex process and is not limited to carbon-rich asteroids. .
Late last year, Hayabusa2 returned with a sample of a C-class near-Earth asteroid named Ryugu. The comparison of the contents of its payload with those of its predecessor will undoubtedly bring even more knowledge on the evolution of organic chemistry in space.
The question of the origins of life and its apparent uniqueness on Earth is a question we will seek answers to for a long time. But each new discovery points to a story that extends far beyond the safe, warm puddles of our newborn planet.
This research was published in Scientific reports.
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