In 1981 and in 1984, I offered at the University of Houston, CLC, a course on Space Telescope, the first of its kind. The 22 graduate students were assigned research projects of their own choosing designed for ST. Several chose the detection of planets of other stars, showing the popularity of the search for extraterrestrial life. Space Telescope's six instruments can be used for this purpose in several ways, and the students, most of them scientists and engineers at the NASA Johnson Space Center, proposed to use most of these after ST is launched in 1986 or 1987. The student proposals require a significant fraction of ST observing time over a period of five to ten years, indicating the over-subscription that faces the ST Science Institute. In this paper, I summarize the capability of ST instruments, and recount the techniques likely to be most effective in using them to detect planets of other stars.

Absolute astronomical accelerometry is a new proposed technique specifically optimized to detect small radial velocity changes (i.e. accelerations) of either the Sun or a star; it is intended for the two problems of stellar seismology and the search for extrasolar planetary systems. In both cases the computed performance is such that positive results should be obtainable in a large number of cases with a moderate size telescope. Essentially the method involves two separate and simultaneous servo loops. In the first a variable path-difference Fabry-Perot interferometer is adjusted so that its bandpasses track the fluctuations of the lines in the stellar spectrum. Then a tunable laser tracks the fluctuations of the FP and one has only to measure the beat frequency from a stabilized laser. The result is absolute i.e. obtained solely in terms of frequencies and the speed of light. All instrumental or spectral characteristics drop out; no calibration is required. Furthermore the method can be demonstrated to approach closely a so far never computed photon noise limit for radial velocities.

Various methods outlined for indirect planetary detection would greatly benefit (in some cases require) the determination of the planetary orbital plane, which is theoretically equivalent to the stellar equatorial plane. Determining the stellar space orientation, therefore, would greatly benefit extrasolar planetary detection.

We utilize stellar rotation periods determined from short-term variations in Call H&K sunspot emission combined with both stellar radii measurements and Doppler broadened spectral line profiles to get the stellar inclination to the line of sight.

The clocklike, on the plane-of-the-sky component determination utilizes the concentration of sunspot associated plage areas at central stellar latitudes when viewed in Call H or K emission. One can perform Call H&K emission speckle interferometry to measure the clocklike angle of this stellar Call H&K emission band, modeling it as an elliptical intensity distribution. Both components should be determinable to within ten degrees for at least resolvable fifth magnitude stars.

Voyager discovered nine simple organic molecules in the atmosphere of Titan. Complex organic solids, called tholins, produced by irradiation of simulated Titanian atmosphere are consistent with measured properties of Titan from ultraviolet to microwave frequencies, and are the likely main constituents of the observed red aerosols. The tholins contain many of the organic building blocks central to life on Earth. At least 100 m and possibly kms thickness of complex organics have been produced on Titan during the age of the solar system, and may exist today as submarine deposits beneath an extensive ocean of simple hydrocarbons.

With the discovery of the first polyatomic molecules, NH3, H2O and H2CO in 1968/9 there was immediate speculation as to how far biological chemical evolution - from atoms to small carbon compounds of biological significance - could have occurred in the Galaxy. There was also potential conflict with the canonical scientific view of the origin of life, traceable to the production of simple bio-molecules from the influence of energetic atmospheric events on the simple gaseous mixture (CH4, H2, H2O and NH3) presumed to compose the atmosphere of the very young Earth.

We report recent investigations of the organic chemistry of relatively nearby cold, dark interstellar clouds. Specifically, we confirm the presence of interstellar tricarbon monoxide (C3O) in Taurus Molecular Cloud1 (TMC-1); report the first detection in such regions of acetaldehyde (CH3CHO), the most complex oxygen-containing organic molecule yet found in dark clouds; report the first astronomical detection of several molecular rotational transitions, including the J=18−17 and 14−13 transitions of cyanodiacetylene (HC5N), the 101−000 transition of acetaldehyde, and the J=5−4 transition of C3O; and set a significant upper limit on the abundance of cyanocarbene (HCCN) as a result of the first reported interstellar search for this molecule.

The chemical evolution of interstellar grains leads ultimately to a composition consisting largely of complex organic molecules. Comparison of infrared absorption spectra of laboratory produced analogue materials with astronomical observations confirm the presence of similar molecules in interstellar space. The abundance of this complex organic matter derived from the strength of the absorption bands is of the order of ten million solar masses and is almost certainly as large or larger than all conceivable planets.

Current research in cosmochemistry shows that crude organic solids of high molecular weight are readily formed in planetary, interplanetary and interstellar environments. What are the components of these intractable materials and how are they connected, if at all, with the beginnings of life? It is proposed here that underlying much of this ubiquitous chemistry is a low energy route leading directly to the synthesis of heteropolypeptides from hydrogen cyanide and water. Evidence from laboratory and extraterrestrial investigations suggests that this hydrogen cyanide polymerization is a truly universal process that accounts not only for the past synthesis of protein ancestors on Earth but also for reactions proceeding elsewhere today within our solar system, on planetary bodies around other stars and in the dusty molecular clouds of spiral galaxies. The existence of this preferred pathway adds greatly to the probability of life being widespread in the universe.

For the first time a laboratory simulation of the effect of the interstellar environment has been used to provide quantitative estimates of bacterial spore survival in the space between the stars. In the diffuse regions between clouds ten percent survival is limited to at most hundreds of years although one in ten thousand may survive for several thousand years. Within common dense clouds the ten percent life expectancy is extended to tens of millions of years because of the severely reduced ultraviolet within these clouds as well as because of the accretion of ultraviolet absorbing mantles on the spores. The random motion of molecular clouds is shown to provide a possible vehicle for transport of spores from one solar system to another. The most hazardous times in such a journey are at the start and finish and, although the requirements for survival during these periods are quantified here, the possibility or probability of their being satisfied remains pure conjecture.

The claims for large biological molecules and for prokaryotic and eukaryotic organisms in the interstellar medium are summarized. These claims are compared with new UV laboratory spectra of numerous specimens. The results are incompatible with these claims.

The major source of circularly polarized flux potentially capable of inducing asymmetric photolysis of a racemic mixture of chiral molecules on the primitive Earth is the daytime sky. The degree of circular polarization (q) depends on the slope and orientation of the local terrain which obscures part of the sky. After allowance for dilution by direct sunlight values of |q| range between about 10−4 and 10−5. The rates of (1) asymmetric photolysis, (2) chiral selection by the electro-weak process and (3) racemization are not yet well enough known for the relative importance of these processes to be definitely established.

The replication of DNA is the process by means of which genetic information is passed from one generation to the next in all living organisms. It is widely believed that a similar process must have become important early in the development of life on the Earth, either before or at the same time as the evolution of protein synthesis. The evolution of any life-form based on familiar chemistry would seem to require the early appearance of some type of residue-by-residue replication, although it might be very different in detail from the one we know.

Paleontological evidence indicates that terrestrial life existed at least 3500 Ma ago, and it is quite possible that the earliest cells arose well before that time. The early appearance of life on Earth suggests that under appropriate environmental conditions the probability of chemical evolution proceeding to the point of biogenesis may be reasonably high. Most of biological history has been the history of microorganisms, with tissue-grade plants and animals characterizing only the most recent 15% or so of the fossil record. Intelligent life has occupied only the latest instant in geological time. The time table of terrestrial evolution is governed more by the particulars of our planet's physical and biological history than by some universal tempo of evolutionary change. One aspect of terrestrial life that is likely to be universal is the organization of populations into efficient biogeochemical systems.

The evolution of bipedalism is considered a critical step in human evolution. To discover how it occurred, and whether it could have occurred elsewhere in the universe, scientists must study the structure of their theories as well as fossils. In particular, they must determine whether such critical steps are a function of the “data” or of the (often unwitting) use of narrative for, it will be shown, scientists tend to make sense of the past by telling stories in which everything leads up to or away from being human.

Extinction has the destructive effect of eliminating established lineages from an evolutionary system and the constructive effect of vacating ecospace into which new lineages can evolve. Mass extinctions, which are times of unusually intense extinction, have been consistently followed by major radiations of new lineages. Extraterrestrial impacts associated with extinction events and a periodic recurrence of these events implicates an extraterrestrial forcing mechanism as the ultimate cause of mass extinction. This suggests that the extraplanetary environment has played an important, active role in the development of complex life on Earth.

Periodicity seen in both the mass extinctions and large impact cratering on earth can be explained if one postulates that the sun has a companion star, orbiting in a moderately eccentric orbit with a major axis of 2.8 light-years. No other explanations that have been suggested are compatible with known facts of physics and astronomy. If the companion is a red dwarf star, the most common kind in the galaxy, then no previous astronomical observations would have found it. A search for red objects with large parallax is now underway at Berkeley, and has a good chance of identifying the star in the near future.

In any statement concerning extraterrestrial life one has to present the best amount of information concerning life as we know it here on earth. One way to do this is to put many classes of known objects in the universe on common plots. I call these plots the “Universal Diagrams”. The quantities plotted are mass, luminous output, temperature, size and entropy change. It is interesting to speculate where etraterrestrial life may lie on these diagrams but it seems that it will have to lie in regions more or less occupied by terrestrial life.