Feature

Extraterrestrial Organics -- the Origin and Future of Life

Extraterrestrial materials could have started life on Earth, and may help it spread throughout the galaxy.

Dr Michael Mautner

Complex carbon compounds found in meteorites may have provided an extraterrestrial source of organic material for early life on our planet, and could prove a useful source for the future expansion of life in our solar system and beyond, suggests a NASA-funded programme under way in Lincoln's Soil Science Department.

Could the infall of extraterrestrial organics have played a role in the origin of life? For these purposes, can the organics be released effectively in early planetary environments? If so, can the released organics form biological structures? And after early life does arise, can they continue to provide necessary nutrients?

Working on these questions have been myself, a physical chemist; Dr Robert Leonard, an environmental biologist; and Professor David Deamer, a biophysicist at the University of California, Santa Cruz.

In the meteorite, the organic material -- material which contains carbon -- is trapped in a mineral matrix, much of it in the form of an insoluble, coal-like polymer. On the early Earth, meteorite and interplanetary dust particles containing trapped organics would have landed in the ocean and eventually encountered undersea volcanoes or hydrothermal vents [Life in Hot Water, August 95].

To simulate these conditions, we subjected powdered meteorite samples to pressurised water at temperatures from 120^oC to 350^oC, at pressures encountered at depths of 20 metres to over 1,200 metres. We found that up to 50% of the organics were released under these conditions, possibly including some known components that can be microbial nutrients, such as amino acids and organic acids, and even some of the coal-like polymer.

Could the released organics contribute to the origins of life? One essential requirement would be the formation of biological membranes that must enclose every cell. Therefore, we examined the membrane-forming ability of the released material and some of its components. The experiments showed that the released organics concentrated at the air-water surface and showed surface activity which is required for membrane-forming capability. Furthermore, at high concentrations and controlled acidity, some of the released materials actually formed stable microscopic vesicles bounded by membranes. Such membranes would have been essential for the formation of early cells, to separate the living matter from the surrounding solution and to allow concentrated solutions that are required for biological processes.

After contributing to the formation of early microorganisms, could the extraterrestrial materials serve an additional role by providing nutrients to the early life-forms? As a first test of this question, we extracted organic materials from samples of the meteorite that fell near Murchison, Australia, using again water-based extraction at relatively mild undersea-like conditions, at 120C, to extract about 10% of the organic material. The extracts were inoculated with cultures of a common environmental microorganism that was identified tentatively as Flavobacterium oryzihabitans, and with the soil microorganism Pseudomonas maltophilia. We observed that in the meteorite extracts, the microbial populations grew larger by factors of 10-1,000 than in controls in pure water.

The observations showed that microorganisms can indeed derive nutrients from actual extraterrestrial materials, using up to 3% of the released organics. These results extend the findings of planetary scientist Carol Stoker and co-workers, who found that a synthetic mixture called tholin, formed under simulated planetary conditions, can be utilised by soil microorganisms. The Lincoln University study now shows that microorganisms can grow on actual extraterrestrial materials.

Feeding and Seeding Future Life

The microbial observations of this study have implications not only about the past, but also about the future. Work started in the 1970s by Professor Gerard K O'Neill of Princeton University, followed by NASA study panels and on-going work at the Space Studies Institute in Princeton, New Jersey, US, shows that lunar and asteroid materials can be used to construct large, comfortable space colonies that can ultimately house trillions of humans in our solar system, and ultimately, beyond. The carbon compounds essential to organic life could be obtained from asteroid materials similar to meteorite organics. Microbial processing would be able to convert the asteroid organics directly to biomass for soil additives, animal feed and food. Ultimately, the meteorite organics would be converted into human populations.

To extend the microbial experiments in relation to early evolution, we need to know if the meteorite organics can support primitive microorganisms called archaebacteria, which are the most representative living examples of early life. As to future uses, we would like to identify, and possibly develop, microorganisms that can convert meteorite organics, especially the abundant coal-like polymer, most efficiently to useful biomass.

Ultimately, the microbial observations also have implications about the possible planting of life throughout the galaxy. New studies, including results from the Hubble Space Telescope, show that as many as half of all the new stars that are forming continually in nearby space contain planetary systems. Seeding these planetary systems would make life virtually indestructible, through large numbers and diversity. By dispersing and evolving throughout space, the unique, intricate patterns of living matter can ultimately become a dominant feature of in physical universe. Pursuing this "panbiotic" or "biocosmic" expansion of life is possibly the most important human purpose.

The panbiotic programme can be started by sending microbial payloads to newly formed stars, using solar sailing or other advanced propulsion methods, to seed young planets where no other life could yet have arisen. This gives our terrestrial life-form further opportunities to develop and diversify, while avoiding ethical concerns about interference with possible local biota. Our observations suggest that well-chosen microbial payloads will grow on the organics found in those new planetary environments. In the new solar systems, life will find planets that remain habitable for billions of years. Hopefully, the ensuing evolution will ultimately lead to intelligent beings who will in turn propagate space -- human existence can then reach a truly cosmic purpose.

Dr Michael Mautner is with Lincoln University's Soil Science Department.