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 122ÂșC; 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
The same post in Spanish
Thematic thread on Life in other Worlds: Next
Manuel Alfonseca
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