|Origin of Life -
Was it an astrobiological event
or chemical evolution ?
Minerals play a Role
in Chemical Evolution?
work of Robert Hazen at Carnegie Institute (Geophysical Lab)
evidence favors a chemical evolutionary origin of life
"simple chemical self-assembly has lead to self-replicating systems"
Earth forms 4.5 billion years ago
from 4.5 to 4.0 bya - Asteroids bombard & sterilize planet surface
4.0 bya - first fossil evidence of microscopic life
Initial event may have been evolution of
Carbon based molecules
ancient atmosphere (was reducing) with single carbon gases
carbon monoxide, carbon dioxide, methane
1953 - Miller & Urey @ U Chicago
recreate ancient atmosphere [ammonia,
methane, water, &
produce amino acids, which many assume can now link into complex polymers
rocky surfaces allow concentration via evaporations
§ Origin of Life research is no longer philosophical, but rather experimental
- discovery of deep hydrothermal vents
suggests that origin of life organic reactions
may have occurred in intense
heat & pressure of
Hazen's lab designed experiments to
mimic high temp/pressure of
& look at the role minerals may have played in producing
ROLE of MINERALS -
may have fostered organic chemistry of early life.
1998 - began in
Robert Hazen's lab
[Carnegie Institute, Washington]:
showed that amino acids decompose at 200
oC under pressure,
but when FeS
(iron-sulfur) minerals are added, amino acids
the idea is one of SCAFFOLDING SUPPORT
by the minerals...
an easy way to assemble molecules in dilute solution is to
concentrate the molecules
on a flat surface,
which is exactly what minerals may have helped provide:
that houses microscopic pits that could shelter life's precursor
molecules from UV radiation and destruction...
and greater chemical reactivity
magnetite* (iron oxide) - triggers combination of nitrogen & hydrogen
ammonia (NH3), a reduction reaction essential for organic life
clay* - layered clays can
trap organics [help concentrate
them] between clay sheets;
held close together molecules can
then form more complex molecules...
montmorillonite clays can sharply accelerate the formation of
these vesicles can grow and undergo a simple form of division, giving them
properties akin to primitive cells & might be a mechanism that helped create
enclosed in a membrane?
Minerals may provide some possible answers to
the selection of only 1 specific optical isomer [ L-amino acids ]
out of 2 (D & L)
in the making
of cellular proteins... today's proteins contain only L-amino acids.
Miller's experiments produces
50-50 mix of
the 2 isomers, the D & L amino acids...
Could the Earth's minerals have help select one
isomer over the other isomer?
carbonate mineral that attracts D & L- amino acids to
different crystal faces, thus in the origin of life
amino acid isomer could have been selected over the other.
origin of life was
not a single event...
it was most likely a gradual sequence of modest chemical
which added a degree of
order and complexity to molecular structure.
1st step -
abiotic formation of building blocks...
Miller & Urey or hydrothermal vents
or via 'space debris'
2nd step -
minerals provide structural basis for
confining, ordering, & selecting molecules;
may have lead to first
primitive self-replicating systems
next step - competition for limited
chemical resources leads to
MOLECULAR NATURAL SELECTION