An aspect of research in chemical evolution is laboratory synthesis of organic molecules under conditions which, according to astronomical evidence, are similar to conditions on the primitive Earth. Scientists have synthesized amino acids and the purine and pyrimidine compounds that make up nucleic acids using materials that probably comprised the primitive atmosphere of Earth. Electric sparks and ultra-violet radiation have provided energy to tie simple substances together to make the long-chain molecules that characterize life.

The second stage in research on the origin of life involves the analysis of ancient rocks and sediments of the Earth for fossile evidence of the early steps in the development of life. Precambrian rocks, ranging in age up to 3.4 billion years, are being studied for evidence of biological activity. Chart SB 69-489 summarizes the physical and chemical evidence of early biological activity on the Earth. The cross-hatched areas represent affirmative findings.

In other words, at every point where you see the cross-hatched blocks, evidence of life existing in this ancient sediment has been found.

We are not yet certain which of the organic materials found in Precambrian rocks are of biological origin. We hope for satisfactory answers from a technique that utilizes the fact that organic polymers rotate light beams in different directions according to their sources. A third stage in our investigation into the origin of life is the study of strange, microscopically small, cell-like structures that have some of the properties of living cells. Biologists call them microspheres and they were first produced artificially in the laboratory. Very similar

structures now have been found in Precambrian quartz, suspended in totally enclosed water droplets. Chart SB 69-15513 shows microspheres in an ancient quartz crystal.

The naturally occurring microspheres have not yet been chemically analysed precisely, but preliminary analyses indicate that they are composed of organic material.

Microspheres display enough of the traits that we associate with life that they might easily be confused with micro-organisms if we had encountered them for the first time on a strange planet. However, we know from our study of artificial microspheres that their dynamism is a relatively simple interaction of physical and chemical factors. There is no evidence of the much more complex intelligence that serves to maintain the system of organization of living things. Chart SB 6915516 compares Precambrian microfossils of almost certain biological origin with the artificial microspheres produced in the laboratory. The structural similarities are striking. This comparison illustrates the difficulty of identifying primitive life and its immediate prebiological

ancestors.

As a progmatic test of biological theory, scientists are trying to assemble or reassemble living cells from cellular components. Already there has been success in the artificial production of deoxyribonucleic acid and of cytoplasmic components from cellular extracts. Complete cell reassembly appears to be possible in the future.

Until recently the capacity to modify existing organisms has been limited to the relatively crude techniques of hybridization and of inducing random mutation. Studies in molecular biology, cellular biology, and systems theory are making possible the alteration of the character of living things by synthesis of desired genes and the alteration or inactivation of harmful genes and viruses. New methods of chemotherapy and theoretical pharmacology can be based upon these studies. Indeed, precise selective control of heredity will be by far the most important achievement in biomedical history.

Still another area of study in exobiology concerns the ability of Earth organisms to adapt to environmental extremes. The fundamental utility of the information and control system associated with life is to make living things adaptable so they can survive and maintain their identity even though conditions change. Perhaps the most significant fact of life is that the organism with the more complex information system is more adaptive. Man stands at the top of the evolutionary tree because he is the most adaptive organism on Earth.

Our studies of adaptation are aimed at two problems; prediction of life on another planet, on the basis of the capability of Earth organisms to adapt to a similar environment, and prediction of the likelihood of contaminating another planet, with Earth organisms, placing indigenous life in danger.

Survival and growth of micro-organisms are studies in a simulated Martian environment. Why do we focus special attention on the environment of Mars? The reason is that our present knowledge suggests that Mars is the most likely habitat for life away from Earth in the solar system. Chart SB 69-15559 shows the simulation chamber which will be used for tests of life detection and organic analytical devices proposed for use on a Martian lander mission.

Expeditions into the dry valleys of the Antarctic have produced information on life in a climate with many of the characteristics of the Martian surface. Not only are temperatures similar, there is a similar lack of available water for biological activity. Bacteria, fungi, and algae were found in many soil samples from the Antarctic valleys (Chart SB 67-2218). However, significant concentrations of carbon were found in samples from which no living organisms could have been cultured. This paradox yielded to the power of our newly gained techniques in organic geochemistry. The carbon was found to be of living origin. The carbon is the fossil residue of organisms that were alive millions of years ago when the region experienced a different climate. It is coal dust.

In order to conduct a similar analytic process on Mars in Calendar Year 1973, we face the need to complete the development of automatic and miniaturized life detection equipment for the Viking missions. The automatic instruments will detect bio-organic matter, metabolic activity, and growth of organisms.

By heating samples to the gaseous state, biologically significant molecules can be identified on the basis of their peculiar affinities for an array of absorbent material. The heating process is called pyrolysis, and the differential absorption process is called chromatography. It is possible with these processes to identify all of the substances of major biological significance except the nucleic acids. When the gas chromatograph is coupled with a mass spectrometer (Chart SB69521) a chemical analyzer of great power is produced. The combined