Astrobiology

Astrobiology or Exobiology (also knows as Bioastronomy) is the study of life in the universe. More precisely, it is the study of the origins, evolution and distribution of life in the universe and of the structures and processes associated with life itself

When NASA started the Apollo program, with the project of sending men to the Moon and bringing lunar samples to the Earth, the question of the possible presence of (indigenous) life on our natural satellite arose logically. The problem was in fact double: if there were life forms on the Moon, it was essential to avoid any biological contamination of our satellite by terrestrial organisms, and—even more important—of the Earth by hypothetical lunar organisms present in the lunar samples carried back to our planet. Thus, in the 1960s, planetologists and microbiologists alike started to work together to tackle this question. This was the time when the recipient of the Nobel Prize Award (1958) in Medicine and Physiology, Joshua Lederberg, invented the word ‘Exobiology’. It then became a fully recognized scientific field, spanning many classical domains, including astrophysics, astronomy, planetology, physics, chemistry, biochemistry and biology, as well as human sciences and even mathematics.

The more logical and direct way is to search for life on extraterrestrial planetary objects. This can be done by remote sensing measurements or even, with the availability of space technologies, by in situ exploration. It can also be carried out by studies of extraterrestrial samples transferred to the Earth through natural processes (Meteorites, micrometeorites, cosmic dust particles and cometary materials) or collected in space by robots or manned missions. Remote sensing techniques can even be applied to search for biological activity on extra-solar planets, when techniques become powerful enough to detect Earth-like objects and the presence of molecular oxygen and ozone in large amounts in their atmosphere (assuming that this is an unambiguous signature of life).

The other approach is to assume that what happened on Earth is a common event in the universe and that there are numerous places in our Galaxy where life arose and evolved toward intelligent and technologically developed living systems. Then, by listening to the universe in the right direction and at the right frequency (presumably radio waves) and at the right time, one should be able to detect signals from extraterrestrial civilizations. This is the SETI (search for extraterrestrial intelligence) approach mainly based on radio observations. There is a less direct approach but fully logical: the study of the terrestrial example, and, first of all, of the origin of life on Earth. By putting together the pieces of the puzzle of the origins of the first living system on our planet, one should be able to put some constraints in the conditions necessary for the emergence of life, in general, on a planetary body.

Many objects of the solar system are of exobiological interest: not only Earth, but also comets, Mars, Europa, and even the giant planets and some of their satellites, such as Titan and Triton, because of the very complex organic chemistry which is involved in their environments. Thus far, the two planetary objects seem to be the most promising for a direct search for extraterrestrial life in the solar system. The first is the planet Mars and the second is Europa, one of the Galilean satellites of Jupiter.

Questions to Ponder:

• What are the vital conditions for the existence of life in a planet?
• What is the goal of the SETI Program?