May 19, 2006
the “Habitable Zone”
The mystery of life, how it
arises and how it survives in extreme conditions, may open new
windows to the world of plasma and electricity.
Human beings live on a planet where life
thrives in every
possible niche. Even at the frozen poles, life hangs on. We used to
think that with too much or too little sunlight and without liquid
water, life could not exist. Scientists developed the concept of a “habitable
zone” around the sun—a range of orbits in which a planet would
receive the right amount of energy from the sun to allow
photosynthesis and to keep water liquid.
But then we discovered whole communities of organisms (images above)
that thrive on the heat of underwater volcanoes. Bacteria synthesize
chemicals in the hot water and live on the excess energy. Other life
forms eat the bacteria. Tubeworms (image above) have no mouths or
digestive systems. The chemosynthetic bacteria live inside the worms
and transfer energy directly to the worms’ cells. The entire
community exists without sunlight.
Still, as far as we can tell, life does require liquid water. Some
organisms produce spores that can survive for centuries without
water, but they need water to spring back to life. Others thrive in
the near-boiling water of hot springs, but the water is still
liquid. Nevertheless, the discovery of life that uses energy sources
internal to the Earth undermines the concept of a habitable “zone”:
Life could exist on a planet with a molten core or with tidal
heating regardless of its distance from its sun.
The Electric Universe extends the possible locations for life even
further. The behavior of plasma may provide another source of heat.
Jupiter’s moons, for example, are awash in electrical activity.
Scientists have already postulated that two of the moons, Europa and
possibly Callisto, have liquid water oceans beneath their frozen
surfaces because of tidal heating. The Galileo probe discovered
“rains of electrons” falling onto these moons. Plasma cosmologists
call such “rains” electric currents, and they know the currents must
close in circuits. Those circuits must travel over or through the
moons, and any resistance will convert some of the energy into heat.
This raises the possibility that electricity could heat and melt
subsurface water. The current coursing through Jupiter’s inner moon,
Io, is even greater than that on Europa or Callisto, and it sports
volcanoes that are hot and active. (See “Filamentation of Volcanic
Plumes on the Jovian Satellite Io”
here.) If water exists
anywhere on Io, that may be another place to look for life.
Furthermore, the biological sciences have not considered the
plasma may play in the origin of life and its adaptation to
sudden changes in environment. Just as astronomers are finding that
plasma in space is important to cosmology, biologists may discover
that it’s important to the origins and evolution of life as well.
Biological experiments that try to create life often make use of
electrical discharge as well as chemical reactions. Were these
experiments showing us that the electrical activity is a fundamental
part of the life-forming process?
Catastrophic theory brings up another question. If plasma activity
accompanied the catastrophic mass extinctions of Earth, then could
this activity also stimulate surviving life to adapt to new
conditions in a single generation? This would explain the puzzle
that biologist Stephen Jay Gould noticed: The fossil record doesn’t
show gradual changes in species. Instead, it shows new species
appearing fully formed and then remaining unchanged for all of their
existence. A plasma point of view would see this as a normal life
function: the increased plasma activity of the catastrophic event
would stimulate sudden and mutually responsive
in living forms and in their environment.
And what does this say about the habitable zone? Perhaps we should
be looking for life in places where there has been strong plasma
activity. In addition to moons that orbit close to their active gas
giants, Wallace Thornhill points out that this would include planets
that orbit inside the chromospheric glow discharge of
stars. In fact, conditions inside such a star might be ideal for
life, unaffected by seasons or day/night cycles.
Irving Langmuir chose the term “plasma” to describe the life-like
behavior of electrified gases. That description works the other way
around, too: Life has plasma-like behavior. Could this resemblance
be more than analogy? Is plasma, like liquid water, an essential
component of life? Do we need a new science of plasma biology?
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