From: Andy Soos, ENN
Published April 5, 2013 10:48 AM
Origin of the Primordial Soup of Life
Researchers at the University of Leeds may have solved a key puzzle
about how objects from space could have kindled life on Earth. While it
is generally accepted that some important ingredients for life came from
meteorites bombarding the early Earth, scientists have not been able to
explain how that inanimate rock transformed into the building blocks of
life. There have been many theories. There is no standard model of the
origin of life on Earth. This new study shows how a chemical, similar to
one now found in all living cells and vital for generating the energy
that makes something alive, could have been created when meteorites
containing phosphorus minerals landed in hot, acidic pools of liquids
around volcanoes, which were likely to have been common across the early
Earth.
Abiogenesis or biopoiesis is the natural process by which life arises
from inorganic matter. The earliest known life on Earth existed between
3.9 and 3.5 billion years ago, during the Eoarchean Era when sufficient
crust had solidified following the molten Hadean Eon.
"The mystery of how living organisms sprung out of lifeless rock has
long puzzled scientists, but we think that the unusual phosphorus
chemicals we found could be a precursor to the batteries that now power
all life on Earth. But the fact that it developed simply, in conditions
similar to the early Earth, suggests this could be the missing link
between geology and biology," said Dr Terry Kee, from the University’s
School of Chemistry, who led the research.
All life on Earth is powered by a process called chemiosmosis, where the
chemical adenosine triphosphate (ATP), the rechargeable chemical battery
for life, is both broken down and re-formed during respiration to
release energy used to drive the reactions of life, or metabolism. The
complex enzymes required for both the creation and break down of ATP are
unlikely to have existed on the Earth during the period when life first
developed. This led scientists to look for a more basic chemical with
similar properties to ATP, but that does not require enzymes to transfer
energy.
Phosphorus is the key element in ATP, and other fundamental building
blocks of life like DNA, but the form it commonly takes on Earth,
phosphorus (V), is largely insoluble in water and has a low chemical
reactivity. The early Earth, however, was regularly bombarded by
meteorites and interstellar dust rich in exotic minerals, including the
far more reactive form of phosphorus, the iron-nickel-phosphorus mineral
schreibersite.
The scientists simulated the impact of such a meteorite with the hot,
volcanically-active, early Earth by placing samples of the Sikhote-Alin
meteorite, an iron meteorite which fell in Siberia in 1947, in acid
taken from the Hveradalur geothermal area in Iceland. The rock was left
to react with the acidic fluid in test tubes incubated by the
surrounding hot spring for four days, followed by a further 30 days at
room temperature.
In their analysis of the resulting solution the scientists found the
compound pyrophosphite, a molecular cousin of pyrophosphate — the part
of ATP responsible for energy transfer. The scientists believe this
compound could have acted as an earlier form of ATP in what they have
dubbed chemical life.
Adenosine-5'-triphosphate (ATP) is a nucleoside triphosphate used in
cells as a coenzyme. It is often called the "molecular unit of currency"
of intracellular energy transfer. ATP transports chemical energy within
cells for metabolism. It is one of the end products of
photophosphorylation, cellular respiration, and fermentation and used by
enzymes and structural proteins in many cellular processes, including
biosynthetic reactions, motility, and cell division.
"Chemical life would have been the intermediary step between inorganic
rock and the very first living biological cell. You could think of
chemical life as a machine —a robot, for example, is capable of moving
and reacting to surroundings, but it is not alive. With the aid of these
primitive batteries, chemicals became organized in such a way as to be
capable of more complex behavior and would have eventually developed
into the living biological structures we see today," said Dr Terry Kee.
The team from NASA’s Jet Propulsion Laboratory (JPL-Caltech) working on
the Curiosity rover, which landed on Mars in August last year, has
recently reported the presence of phosphorus on the Red Planet.
"If Curiosity has found phosphorus in one of the forms we produced in
Iceland, this may indicate that conditions on Mars were at one point
suitable for the development of life in much the same way we now believe
it developed on Earth," added Dr Kee.
For further information see
Primordial Soup.
Stromatolites image via Wikipedia.
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