In search of extra-terrestrial life and the source of life on earth, mankind moved one step ahead; recently, a group of scientists discovered organic matter in space for the very first time. After a long wait, organic matter with water particles is obtained in the soil of a near-earth asteroid.
Before explaining the details of the recent discovery, I just prefer to explain the background briefly. This will give you a clear understanding of some facts, such as “why should search for extraterrestrial life?” or “Why the recent discovery is so exciting?”
The Evaluation of Life: A Plausible Theory
Approximately, 3.7 billion years back, simple molecules started combining together to produce a bigger molecule, then a few more joined the party, and then a few more… thus the process continued. Eventually, a macromolecule produced that represented something odd, appeared as the very first basic living organism. As the decades passed, the very first organism spread the branch in different manners and gave birth to the plant and animal kingdom on the blue planet.
To date, nobody knows the exact mechanism of the evaluation. Then, what’s the way to know the mechanism of our origin? There two paths to uncover the truth,
- Time travel to billions of years back.
- Find out the extra-terrestrial organic matter and follow up its conversion to microorganisms.
The former one was the dream of the great scientist Stephen Hawking, but we are still far away from the discovery of “time travel”. However, the massive development in space research throughout the world offers new hope, and probably this is the best way to uncover the secret of a green planet.
Recent research in Poland and South Korea uncovered the possible synthetic routes that can afford complex biomolecules from the simple ones (prebiotics). These experiments proved that the simple building blocks of organic compounds could be converted to increasingly complex macromolecules by the involvement of water molecules.
The Origin of Biomolecules
Carbon is the origin of life. Probably, carbon didn’t form during the evolution of the earth because the Big Bang does not provide any evidence about the formation of carbon. Rather carbon particles are known to be formed during the death of the stars; then they spread over the universe as dust particles. Further, during the formation of a new solar system, the carbon particles slowly land on the surface of new planets. Our solar system is an example of such a solar system.
For related explanation: visit HERE – point 4
So, the presence of carbon particles across the universe is very usual. But, every carbon particle is not organic matter, neither all of those can be transformed into life.
Research Efforts for finding Organic matter in Space
“Is there any living creature or even organic matter present in the rest of the universe?”
This has been a topic of debate for decades. So far, water particles were observed in a few parts of the universe, but organic matter was never discovered.
Scientists across the world realized that conducting massive research works on space particles is the only option to uncover life-forming conditions starting from simple organic building blocks.
Carbon is the origin of biomolecules; so, thus far the scientists targeted carbonaceous C-type asteroids (carbon-rich) for successful recovery of organic matters. However, almost all the C-type asteroids were found to be rich with insoluble carbon content, which can’t act as the source of life.
On the other hand, S-type asteroids are indicative of siliceous mineralogical compositions, reside in the inner asteroid belt. These are the second major source of Earth’s meteorites and chondrites (after C-type asteroids). Continuous failures with C-type asteroids forced the scientists to think about the S-type, and a new mission was initiated in 2003, the Hayabusa Mission.
Hayabusa Mission: In search of Organic Matter in S-type Asteroids
Hayabusa Mission of the Japan Aerospace Exploration Agency (JAXA) was one of the major initiations to conduct in-depth research on outer earth space particles collecting from S-type asteroids.
In 2010, the Hayabusa mission returned to earth after the successful recovery of thousands of regolith particles (10‒200 μm) from the near-Earth S-type asteroid, Itokawa.
The collected particles were assigned for laboratory test; after massive analysis of the particles (mineralogy, chemistry, and oxygen isotope compositions) less than 10 particles (among 1000s) were selected for organic matter analysis.
Excitingly all the selected particles were found to contain organic matter that includes:
- A group of category-3 particles composed of carbon [Ref 1-4].
- Organic carbon, which is generally absent in ordinary chondrites [Ref 5].
- Water content.
- Olivine and albite grains.
The isotopic composition of the organic matter overlapped the zone of both terrestrial and extraterrestrial organic matter. That means the terrestrial biochemistry might be an extension of the process of organic matter formation that happens in asteroids or the external universe where the asteroids come from.
A Brief Discussion on the Analysis of Organic Matter
The team of scientists specially described the property of one of the specific Itokawa particles, RA-QD02-0162 (nickname – Amazon) because structurally distinct organic materials were widely distributed across this particle. With the help of energy dispersive X-ray (EDX) spectroscopy and Raman analysis they uncovered the following list of content in Amazon particle:
- Olivine (Fo75–85)
- Low-Ca pyroxene (orthopyroxene En87)
- Clinopyroxene En50Wo50
- High-temperature carbonate
As per the observation of Raman analysis, two peaks appeared at 1350 cm−1 and 1590 cm−1 representing the first-order defect (D) band and the graphite (G) band, respectively, which signified the presence of various carbon materials in Amazon particle. According to their findings, the following points may be highlighted:
- Mature organic components were spread over the whole particle as clusters of finely dispersed grains.
- Mature organic matters were always associated with the pyroxenes.
- Primitive organic material occurred as discrete grains ( < 3 µm).
- These discrete grains were hosted by a crystalline mixture of olivine, albite, pyroxene, and carbonate.
Further, the Raman spectra were studied by heating the material, which suggested the organic structure could be best represented by nanocrystalline graphite and the peak metamorphic temperatures were at least 600 °C. These observations come up with another set of conclusions, which represented the probable steps behind the formation of organic matters on Itokawa-surface:
- At an elevated temperature (600-800 °C), thermal decomposition followed by complete dehydration of the mineral components occurred.
- A complete delocalization of the H2 might happen.
- Triggered the surface-catalyzed reactions at 150 to 700 °C to form organic matter.
- Organic material graphitized further due to prolonged metamorphism.
In past, it has been evidenced that, the surface temperature of near-Earth asteroids can reach up to 900 °C. So, the above-mentioned steps for organic matter formation are very usual in Itokawa.
Primitive organic material represents the sign of “exogenous” origin!
Although mature organic matter seems to be formed via the above steps, extra-terrestrial isotopic signatures were obtained in the spatial distribution of the primitive organic material (POM), which clearly indicated the probability of its “exogenous” origin.
It has been assumed that the graphitization of the POM happened due to the infall of primitive carbonaceous chondrites and interplanetary dust particles (IDPs). For example, A 600 cm long black boulder was observed on the surface of Itokawa, which generated probably due to the collision of carbonaceous chondrite a billion years back; this impactor is definitely among the reasons behind the formation of exogenous POMs.
According to their observation, although organic materials within olivine contained a good amount of H (or hydroxyl), typically OM within the pyroxenes was almost hydrogen-free but enriched with D instead. The δD value of olivine (δD = − 354 ± 104%) was found to be much lower with respect to that for pyroxene (δD = + 328 ± 328‰).
Organic Matter in Space: The Conclusive Remarks
As a conclusion, both primitive and processed organic matter was found within ten microns of distance in a single particle of Itokawa, which evidenced both terrestrial and extra-terrestrial organic matters. The finest explanation about the steps for the OM formation clarified the evolution of life starting from the simplest organic molecules.
Overall, the discovery of organic materials in an asteroid and the explanation of their plausible synthetic routes are definitely huge achievements that will guide the mission of “findings the source of life in the blue planet”. In addition, the exogenous origin of organic matter is a great hint about extra-terrestrial life.
Source: Sci Rep, 11, 5125 (2021)
Other references: (1) Earth Planet Sp 66, 102 (2014); (2) Earth Planet Sp 66, 156 (2014); (3) Earth Planet Sp 67, 20 (2015); (4) Earth Planet Sp 67, 67 (2015); (5) Geochim. Cosmochim. Acta 71, 4380–4403 (2007).