Exobiology, or the study of living organisms in space, has certainly evolved steadily in the last few decades. To show you just how serious this business has become since 1995, consider this. NASA now has a formal institute of astrobiology which is being led by a Nobel Prize winner, as the following NASA Press Release says:
NASA selected Dr. Baruch Blumberg, distinguished professor, researcher, biochemist and winner of the 1976 Nobel prize for Physiology or Medicine, as Director of NASA's Astrobiology Institute (NAI), effective today. NAI is an institution without walls, a virtual organization comprising NASA centers, universities and others dedicated to studying the origin, evolution, distribution and destiny of life in the universe. "Dr. Blumberg is a world-renowned scientist and researcher who will bring powerful and committed leadership to the Agency's Astrobiology Institute," said NASA Administrator Daniel S. Goldin. "We are extremely fortunate to have a person of his scholarship, experience and accomplishment. I am delighted that he has joined the NASA team to lead our visionary program in astrobiology."
Astronomers now know from direct observation, that interstellar clouds of gas and dust also are teaming with large molecules based on hydrogen, carbon and oxygen, which are by definition what distinguish organic chemistry from all other processes. This is itself a big step because in the 1950's - 1960's it was presumed that organic chemistry only occurs on planets or in planetary atmospheres.
The next big step was the discovery that stars frequently and naturally pass through a young stage where they are surrounded by accreting disks of gas and dust, and that the conditions could be right for forming planets. Then there have been sporadic 'discoveries' of Jupiter-sized planets around other stars culminating with the discoveries in the 1990's of the planets orbiting many of the nearby stars. By 2000, over 35 Jupiter-sized bodies have been detected. The instruments are only sensitive to really big planets, so presumably there could be many more smaller bodies independently orbiting these stars, or orbiting the larger planets as satellites. These discoveries, beginning in 1995 and accelerating in 1996-1998 have been the watershed event in astronomy that forces us to accept that stars have planets around them and that our solar system is not unique. So, we have organic chemistry in the interstellar medium, and we also have planetary surfaces on which to cook up some really complex molecules if other conditions are favorable.
Then we have the detection of complex organic molecules in the atmospheres of the satellite Titan and the planet Jupiter, so we do not just have to have an Earth-like planet at the 'right' distance from it's star to make really big molecules in large quantities.
Then, on Earth, we discovered in the 1960-70's, fossils of bacteria 3.8 billion years old that now form the Greenland Chert, and these bacteria lived when the crust of the Earth was still settling down. Asteroids had been pummeling the surface relentlessly before this time, and the crust was just now settling down.
Finally, in the 1980's-90's we find new types of bacteria living in the most obscene environments on the Earth, in boiling hot springs, on vents in the ocean floor, and even colonies thriving inside solid rock over a mile below the surface. These 'extremophiles' redefine the entire concept of what life is, by showing that respiration can take many forms beyond the simple oxygen-CO2 cycle, and that all you really seem to need is some source of local environmental energy to keep life going.
So, it doesn't seem that it is such a big deal anymore to at least have living systems in the form of bacteria and viruses. The universe must be filthy with bacteria, living in every nook and cranny. The big step is whether anything more complicated than bacteria and algae are 'inevitable'. Don't forget, since bacteria first appeared on Earth about 3.8 billion years ago, life never got more complex than a single cell until about 570 million years ago. That means that the step from inert organic chemistry to self-replicating bacteria is not only a very quick step in terms of geologic time, but once it establishes itself on a planet, it is very robust. Statistically, if a planet can remain a stable environment long enough (that means a favorable star with a long life span!!) then it can spend the vast majority of its life harboring bacteria.
To prove there are life forms more complex than bacteria, we have only one option. We must establish radio contact, thereby ignoring all the other planets in the Milky Way that may still have the equivalent of dinosaurs, jelly fish, whales and a thriving biosphere. In the 570 million years this planet had complex life, only in the last 50 years have we been able to broadcast radio waves. That's quite a long shot for detecting other civilizations if you ask me!
Copyright 1997 Dr. Sten Odenwald
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