The origin of life in other worlds

In a recent article published in the Annals of the National Academy of Sciences of the United States of America, Christopher McKay analyzes the requirements and limits for life in other worlds. Since we have no data at all about any concrete planet outside the Solar System, and very few about the planets and satellites in our system, apart from the Earth, the study focuses on the limits for life in our world and tries to extrapolate the results to the possible existence of extraterrestrial life.

Thus, for instance, he notices that on Earth there are extremophile organisms, able to survive in environments apparently hostile for life: between -15 and 122ºC; in conditions of extreme dryness; in an almost total absence of light (100.000 times less than the solar flux we use to receive); in the presence of ultraviolet rays and ionizing radiation...

The title of the article, Requirements and limits for life in the context of exoplanets, suggests that two different problems must be separated:

·         Which are the minimal conditions (requirements) for the origin of life in an environment where there was no previous life?

·         Which are the minimal conditions (limits) so that life, once originated, can continue existing?

McKay signals in his article that his analysis focuses mainly on the second question. The first has no answer, apart from generalities such as the presence of carbon and liquid water, since we don’t even know how life originated on Earth, therefore cannot extrapolate to other worlds. This is so because it is possible that life requires strict conditions to appear, but once originated it may be able to resist far more unfavorable conditions.

McKay justifies mixing both problems in the title because our understanding of the origin of life is speculative and so we can only assume that planets that have a diversity of habitable environments are also generative of life.

It is good when the conditions of the problem are well stated. When scientific news of this kind appear in global media, where sensationalism takes precedence, the headlines (and sometimes the text itself) usually give a completely mistaken idea.

The same post in Spanish
Thematic thread on Life in other Worlds: Next

Manuel Alfonseca