MUFOB ARCHIVE/01 Extraterrestrial Life

Alan W. Sharp

Merseyside UFO Bulletin, volume 1, number 4. July-August 1968.  

In considering the possibility of indigenous extraterrestrial life the only reasonable starting point is life as we know it on Earth. Hence we must also limit discussion to environments which are not too dissimilar from those which obtain on the earth at present or have obtained here in the past.

It may, as some people have suggested, be possible to visualise life-forms based on elements such as silicon rather than on carbon, but the fact is that the basic building materials for terrestrial life are the elements carbon, hydrogen, oxygen and nitrogen and it is for combinations of these substances rather than for other more exotic compounds that one must look in the search for life in other parts of the Solar System.

It is, of course, tempting to speculate about the existence of suitable planets and their satellites revolving about other suns than ours where life may exist outside the Solar System, but such theorizing is at present in the realms of science-fiction and is likely to remain so for a long time in the future. Thus it can play no part in any rational discussion of possible extraterrestrial living forms based on premises which stand a reasonable chance of verification or disproof.

In addition to the four main elements mentioned above, there are many others whose presence in small amounts is vital to the continuation of life in all except the simplest of organisrns. Nevertheless, it is to oxygen and hydrogen, in combination as liquid water that we must look for the imposition of stringent conditions when assessing external environments. This is because the complex electro-cher1ical reactions which are involved in active life processes depends in part at least, on aqueous solutions, thus restricting suitable sites to those whose temperatures lie approximately within the range 0 degrees to 100 degrees Celsius.

• • Atmospheres**

The existence of a suitable, reasonably dense atmosphere is another decisive prerequisite for the existence of self-replicating organic systems, for without a properly constituted and dense atmosphere there will be insufficient protection against the impact of energetic particles from space and unbearable extremes of ambient temperature on the surface.

This consideration implies that the Earth, for instance, has always possessed an atmosphere of some sort, though possibly of different composition in the past from that which it has at present when carbon dioxide, oxygen and ozone are indispensible.

It is here that initial planetary mass is so important, since by this is largely decided the composition of any residual atmosphere. For earth, with an escape velocity of 7.1 miles per second, there can be considerable retention, whereas for less massive bodies the ability to retain important gases may be lacking. The Moon, for example, has virtually no atmosphere and offers a stark habitat quite unsuitable for organic development, whereas the major planets are so encased by atmosphere that their surfaces must be inhospitable ineed.

Mercury and Titan may have very tenuous gaseous envelopes; Mars has some atmosphere and that of Venus is in some respects similar to that of Earth but is so hot and dense at the planetary surface that it precludes the existence of life. The spectroscoic identification of substantial atmospheric constituents at great distances offers no particular problem, but small amounts are far less amenable to current techniques. Even now that an instrumented probe has actually descended through the Cytherean atmosphere there is still some uncertainty about its exact constitution.

• • The Moon**

On a large scale the surface consists of dark areas (maria) and light areas (terrae or highlands). The surface material itself was but poorly understood before the advent of recent space probes and is still the subject of speculation. The "soil" is now known to be reasonably cohesive and able to bear substantial loads.

Certain features show that there has been some volcanic activity but comparison with known terrestrial meteorite craters indicates that many of the lunar craters are the result of impact. It is now reallsed that both impact and volcanic features occur but no definitive means of identification seems yet to have been found. It is possible that there may be some subsurface water which may harbour life, but on balance there does not seem to be much hope of finding life there.

• • Planets**

Due to the enormous variations in their distances from the Sun there are corresponding variations in planetary radiation temperatures.

_Jupiter_ has a dense atmosphere composed mainly of hydrogen, methane and ammonia and presents one of the most fascinating problems in physics. The "surface" temperature is a chilly -150 degrees Celsius but the true surface is unknown. The clouds appear to be composed of methane and ammonia crystals but the suggestion that the Great Red Spot is a sort of hydrogen "berg" is quite fantastic. It has not even been possible to decide between rival theories of the centre, e.g, a rocky core or a core composed of highly compressed hydrogen. Jupiter is too small to be considered a dull star since the conversion of hydrogen into helium is ruled out by insufficient pressure.

_Saturn_ is essentially similar to Jupiter apart from the rings which are of high luminosity and may be composed of ice particles.

The distant planets are a poor prospect for life.

_Mercury_: Very little is known about this body but it seems to possess little if any atmosphere although clouds are alleged to have been seen from time to time, The surface temperature is very high and the "clouds" may be volcanic dust. Surface features can not be distinguished but the prospect for life on this planet seems to be negligible.

_Venus_: The latest news is disappointing for the enthusiasts of indigenous Cytherean life. The planet possesses a featureless photosphere consisting of clouds composed of carbon dioxide crystals. Oxygen and water together amount to some 3% of the atmosphere which is mostly carbon dioxide under high pressure at the planet's sauface. The temperature measurements are not of very high accuracy but imply that any surface water would boil off into the atmosphere. Speculations that native life may exist in the atmosphere in the absence of a suitable surface' environment do not merit serious consideration.

_Mars_: The atmosphere exerts a maximum pressure of only a few millibars, equivalent to that at a height of 100,000 feet on Earth, and is seemingly composed in the main of carbon dioxide. There is a surface temperature variation of 90 Celsius degrees, from -70 degrees C to +20 degrees C, with an average value of considerably less than the freezing point of water.

The latest information shows conditions to be a good deal less favorable to the development of life than some people once thought was the case. The thin atmosphere is but poor protection from solar radiation and the famous colour changes are probably not after all due to vegetation. It is not even known whether the dark areas are lowlands or elevated terrain and if anything the latter hypothesis is currently more in vogue than the former.

The Mariner close-up photographs showed no signs of the infamous "canali" despite assertions to the contrary in some quarters, although their did depict a number of craters similar in general outline to those on the Moon though presurn.ably more worn down by erosion.

It is, however, possible that in the past there have been water courses on the Martian surface although no rivers appeared on the photographs.

If surface water has at one time been present - and there seems to be no reason why this may not have been the case -- it is quite possible that indigenous life-forms may have spontaneously arisen, but the present Martian environment would seem to provide a habitat inimical to the preservation of life. Nevertheless, of all the planets in the Solar System apart from Earth this one offers the best hope of finding independent life forms.

The fact that the chances even here must be rated very poorly is indicative of the extraordinarily privileged position of the Earth in this matter.

It is however, more than likely that two bodies in the Solar System, namely the Moon and Venus, have already been contaminated by self-replicating organisms carried from Earth, in which case it may never be possible to answer the question whether these bodies evolved independent life of their own.