[Sonia]

Some scientific questions are of immediate and widespread interest, and they stir out imaginations. The subejct being is there is life beyond the Earth? The question for years and years has been pondered, but it is only in the last 50 years or so that we have made significant progress towards answering it. But yet today the question is still unanswered with still much uncertainty. A few people believe life is out there and claim to be visited by aliens. It is easy for us to laugh at the idea of us being visited by them, but in fact it is a serious question to ask whether it happened or not, with the serious answer being there is no scientific evidence for it. They lack objective facts. The important word in all of the "is there life beyond earth?" is unexplained, and that alien visitation is just a belief. There could always be tomorrow of alien visitation, but not happened yet.

We know that on Earth there is life. But for searching for life elsewhere we have to look at some key features, and the essential conditions.

All organisms are fundamental sense rather than similar. Familiar ones being large ones - from elephants, blue whales and trees, down to spiders and fleas, and consist of a large number of cells. Others could just be single. It is these substances in the cell that we discover and are essential for all life on Earth.

In search of for potential habitats for life beyond the Earth we should restrict ourselves to places where huge, complex compounds can exist. The availability of carbon is no problem, it is failry common and widespread element. But only under conditions of temperatures.

All life on Earth has some other requirements, but there is one more requirement that will be great importance in aiding our search for life elsewhere. Itis chemical compound found in cells.

With planets around other stars we should be able to establish whether liquid water existed at the surface, and therefore whether the surface conditions were suitable for carbon water life. If there was an ozone absorption feature we would fairly confident that life was present. We would be confident if other absorption featues were present, through space and time restrictions do not permit details to be given here.

Unfortunately, ozone could be below detectable limits even if life were present. This could happen under 3 conditions.

Local lifeforms do not photosynthesize.
Local lifeforms do photosynthesize but oxygen is not released.
The rate of release of oxygen is s slow that the atmosphere abundance, in the face of removal processes, remains low.

This took me ages to type, so would like your opinions..
Thanks! Sonia..