Follow the twisted limbs of your family tree to its primordial origins for billions of years in the past and you will find that we all originate from dust rich in organic chemistry.
The origin of this organic dust has been the subject of debate for more than half a century. Now, researchers have found the first evidence of organic materials essential for life on Earth on the surface of an S-type asteroid.
An international team of researchers has recently conducted an in-depth analysis of one of the particles recovered from the asteroid Itokawa by the Japanese Space Agency’s original Jabai (JAXA) Hayabusa mission in 2010.
Most meteorites on Earth come from S-type asteroids like Itokawa, so knowing that they could contain essential ingredients for life on our planet is a significant step forward in our understanding of how formation conditions could arise. of life. To date, most research on organic material has focused on carbon-rich asteroids (class c).
Analyzing the sample, the team found that the organic material that came from the asteroid itself has evolved over time through extreme conditions, incorporating water and organic matter from other sources.
This is similar to the process that took place on Earth and helps us better understand how the first forms of terrestrial biochemistry could be simply an extension of the chemistry that takes place within many asteroids.
“These findings are really exciting as they reveal complex details of an asteroid’s history and how its evolution is so similar to that of prebiotic Earth,” says Earth scientist Queenie Chan of Royal Holloway University in London. .
Evolutionary models can take us about 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 can come together to form incredibly complex molecules capable of self-organizing into things that behave like RNA, proteins. and fatty acids.
In the 1950s, while researchers were first studying the complicated question of how the simplest ingredients could spontaneously cook an organic soup, experiments showed that conditions on the earth’s surface could do enough work.
Nearly seven decades later, our focus has been on the slow, steady chemical processes of the same rocks that have aggregated in worlds like ours.
The tests are not hard to come by. It is now clear that a constant rain of rock and ice billions of years ago could have produced cyanide molecules, the ribose of sugar, and even amino acids, along with a generous donation of water, to the Earth’s surface. .
But the degree to which the chemistry of meteorites could have been contaminated by things on Earth leaves some doubt.
Since Hayabusa’s return a decade ago, more than 900 dirt particles of virgin asteroids extracted from their payload have been separated and stored in a clean JAXA room.
Less than 10 have been studied to detect signs of organic chemistry, but all were found to contain molecules formed primarily of carbon.
Itokawa is what is known as a stony (or siliceous) asteroid class or class s. After the first studies on its material, it is also believed to be a normal chondrite: a relatively unmodified type of space rock that represents a more primitive state of the inner solar system.
Given that these types of asteroids make up a good portion of the minerals that break into our planet and are generally not believed to contain much of organic chemistry, these early findings were intriguing, to say the least.
Chan and his colleagues took only one of these dust grains, a particle 30 microns wide with a shape similar to the continent of South America, and conducted a detailed analysis of its composition, including a study of its water content.
They found a rich variety of carbonate compounds, including signs of disordered polyaromatic molecules of clearly extraterrestrial origin and graphite structures.
After being studied in great detail by an international team of researchers, our single-grain analysis, nicknamed ‘Amazon’, has preserved primitive (unheated) and processed (heated) organic matter within a period of ten microns (a thousandth of a centimeter) away, ”says Chan.
“The heated organic matter indicates that the asteroid had warmed to more than 600 ° C in the past. The presence of unheated organic matter very close to it means that the fall of primitive organic products went reach the surface of Itokawa after the asteroid has cooled down “.
Itokawa has had an exciting history for a rock that has nothing better to do than float idling around the Sun for several million years, having been modified with good cooking, dehydrated and rehydrated with a new material coating. cool.
While its history is not as exciting as the history of our own planet, asteroid activity describes the firing of organic material in space as a complex process and is not limited to carbon-rich asteroids.
Late last year, Hayabusa2 returned with a sample of a class C asteroid near Earth called Ryugu. Comparing the content of its payload with that of its predecessor will undoubtedly contribute to a further understanding of the evolution of organic chemistry in space.
The question of the origins of life and its apparent singularity on Earth is a question to which we will seek answers for a long time. But each new discovery points to a story that extends far beyond the ponds and warm ponds of our newborn planet.
This research was published in Scientific reports.