Since wet chemists on Earth have not reinvented life from scratch—not
one self-reproducing living critter, nor even a self-serving prion–we
can probably assume that it’s not easy. A watery planet or moon has to
be quite lucky, for a long time, to get life of any kind going.
It helps a lot to have liquid water around for a while, but that is not
the problem. Water is found in many places and on many objects in our
solar system, and now it’s thought that it wasn’t delivered to Earth by
asteroids or comets. In November 2015 the journal Science reported the
work of Lydia Hallis, who provided evidence that Earth’s water probably
came with the primary dust that circled the sun and gradually congealed
to become our watery planet.
She and her colleagues found a low ratio of two isotopes of hydrogen
(D/H) in lava that came from deep within Earth’s mantle. The lava was
thought to be from an “isolated region of the heterogeneous mantle”
preserved since Earth’s beginnings. A low ratio of D to H “…strongly
indicates that Earth’s water came from the solar nebula…” the dust that
formed our sun’s planets. Similar watery dust would also have become our
neighbors, Venus and Mars.
Hallis’s results depended on her confirming that the original D/H of
Earth’s water was lower than that found in meteorites, comets or
chondrites, once thought to be the source of Earth’s water.
When solar winds are too strong and too close to a planet, they can
strip gas away from a planet at 100grams per second. Protons and
electrons travel at 1 million miles per second, an electric field
shooting ions into space and stripping the planet of any water and
atmosphere it might have had. Though Earth does lose water and hydrogen,
its thick atmosphere and magnetic field helped slow the atmospheric
erosion that dried out our neighbors. Early watery Mars lost its
“…protective magnetic field and atmosphere” and became cold and dry.
Venus’s heat released hydrogen as its water broke up.
Research continues, but the prospects for life are not good on planets
too close to their sun, like TRAPPIST-1. Though that exoplanet’s sun is
half as bright as ours and one-ninth the size of our sun, its four
Earth-sized planets are probably too close to hold a useful atmosphere.
The outer three planets may be just right for watery life to thrive.
Hopefully, the James Webb space Telescope will be able to detect
biological signatures (methane, ozone and carbon dioxide) in their
planetary atmospheres in a few years.
A nice warm planet must face many other challenges before life can begin
and thrive there. Does it have any plate tectonics to shift around and
nudge evolutionary invention? And if it does have active plates like
Earth, will they stay apart and not form a Ring of Fire? The problem
could be too many volcanoes putting out excess heat. Plants could find
that problematic if that happens to earth in 250 million years.
Ward and Brownlee’s book Rare Earth: Why Complex Life is Uncommon in the
Universe makes the case that Earth lucked out, not only with plate
tectonics, but by perching on a remote arm in the outskirts of the Milky
Way with a high metal content, having a moon to provide tides, and a
nearby Jupiter to help sweep up errant asteroids. It also has a
comfortable tilt to provide seasons, and lots of time to tinker with
bioexperiment, bioenergy, and available water.
Its extremeophiles make a case for life’s resilience, but the right
conditions need to be present on a planet or moon long enough for
critical energy reactions to stabilize and find shelter and devise a way
to reproduce. Central hot rocks help, as do cracks in ocean floors.
Hydrothermal vents could have played a large in role getting life
The mystery of where and how life begins continues as we explore more
and more interesting features in the exoplanets we know are so common in
our galaxy. Meanwhile, we can appreciate more and more, how lucky we are
and how much we need to do to protect and restore what we have here on
Author of The Archives of Varok
The View Beyond Earth (Book 1.)
The Webs of Varok (Book 2.)
Nautilus Silver Award 2013 YA
ForeWord IBPA finalist 2012 adult SF
The Alien Effect (Book 3.)
An Alien’s Quest (Book 4. Released Nov.21, 2016)
Excerpts, Synopses, Reviews, On Writing, Characters and More-
Reviews of significant books- http://www.goodreads.com/Cary_Neeper
How the Hen House Turns- http://www.ladailypost.com
Complexity, Bio, Bibliography and Links- http://caryneeper.com
Astrobiology- https://astronaut.com search:Who’s Out There