Life outside earth

Life outside Earth

First of all dismiss any thoughts of UFO’s , visitors from another universe etc. The evidence is zero and all the speculation is bunkum. There are two main threads to serious investigation. The first is to search for microscopic, bacteria like life within our solar system and the second is the search for extra-terrestrial intelligent life( often abbreviated to SETI).

There are no little green men on Mars or anywhere else in the solar system. We have explored enough to be very confident about this. What there may be is bacterial life. Much of the exploration of Mars is presently driven by the search for bacterial life. These bacteria may well be dead, certainly the surface of Mars is too hostile for bacteria to survive. However there could be live bacteria underground.

The interest has been triggered by investigation of so called extremophiles on Earth. Over recent decades ideas about the conditions for bacterial survival has expanded a lot. High temperatures ( or low ), acidity and alkalinity, radiation, vacuum and many other environments once thought too hostile have in fact shown bacteria surviving and living. In fact the one thing thought necessary is liquid water.

It is the discovery that Mars once had water and maybe still has which has encouraged scientists to keep looking. It isn’t just Mars which is of interest. The moons of Jupiter and Saturn may also repay investigation. Enceladus, a small moon of Saturn, with a frozen surface is thought to have liquid water seas underneath an icy exterior. It shows monstrous plumes of geyser type which contain mainly water and a variety of other chemicals necessary for life. The energy driving this geological activity is thought to arise from tidal effects.

Exploration of life on Earth is not yet complete. Biologists have been fascinated by primitive eel like creatures around undersea hydrogen sulphide plumes. These are hot and tube worms use symbiotic bacteria to extract energy from the vented gas and derive nutrients from trace chemicals in the water

The SETI search is totally different. Essentially this looks for signals over astronomical distances typically using radio telescopes. The search was triggered by the now famous Drake equation. Essentially Drake put a guesstimate on the probability of life by multiplying up the number of galaxies, stars, planets, of planets containing liquid water  etc.. The numbers involved are so large that even if the probability is low for each factor life is likely.  Many billions of stars exist. Personally I’m very unconvinced as the unknowns are simply too large.

At any rate the SETI search has been going on for about 50 years. While some anomalies have been seen there is nothing consistent. Partly the problem is what to look for. While certain constants like the ratio of the radius of a circle to its circumference ( pi ) should be universal we don’t know how information may be encoded.

There is a more fundamental issue. Space is big, very big with distance often measured in light years( the distance light travels in a year, nothing travels faster than light ). This means that radio signals travelling at the speed of light would still take many years to reach us. The nearest star is just over 4 light years away and most stars are much, much further. It is likely that any signal would take hundreds of years to reach us. This means a two way conversation would be impossible unless some presently unknown physics is found. We would need to be content knowing we were not alone.