Re: Snowball Earth at 2.3 gya

This is just my opinion, but with an early-earth atmosphere similar to
Jupiter, methane was likely the primary atmospheric greenhouse gas (25X
as potent as CO2), keeping water in liquid form at this time of lower
sun intensity. Methane and ammonia seem to be stable on Jupiter and
the other gas giants, in spite of the storms on the surface. Free
oxygen, produced (by cyanobacteria like the today's top producer,
Prochlorococcus marinus) would have first rusted iron in surrounding
seas; oxygen was not at all initially abundant. As iron went out of
solution, the oxygen could then be free to act on aqueous sulfates,
atmospheric ammonia and atmospheric methane. Atmospheric nitrogen and
carbon dioxide resulted; had it not been for life locking-up CO2, we
would have a CO2 atmosphere like Mars and Venus. There was likely
insufficient CO2 in the atmosphere to prevent the snowball of 2.3bya.,
once a necessary amount of methane was lost to oxidation (to CO2).
Small amounts of CO2 (O2 from photolysis of H2O) would be necessary for
photosynthesis to produce the oxygen, but todays historical planatary
low CO2 levels provide more than enough CO2 for the process.
Photosynthesis is likely a chemosynthetic bacteria variation of the
following similar processes, one of which is an anaerobic
photosynthetic depletor of atmospheric CO2..
Careful examination at ground level reveals a green bacterial layer at
or just below the moist surface (photosynthesis occurs here). Below
the green layer is a red layer (of sulfate fixing bacteria); this is an
area of sulfate (and nitrate) formation via oxidation. Further below
the red layer is a black layer (of sulfide bacteria); this is an area
of sulfate reduction. Hydrogen sulfide (H2S) production occurs here.
A similar community exists under ponds, lakes and oceans. The
near-surface green layer is in the water column above. Sometimes the
sulfate-fixing cloud of bacteria can be seen floating in oxygenated
water just above the bottom floor. In the bottom black sulfide layer,
smelly, toxic, hydrogen sulfide (H2S) is produced. This black layer
can also contain inorganic carbon as carbon dioxide (CO2) and
anaerobically locked-up carbon as methane (CH4). Sulphur compounds,
mainly hydrogen sulphide (H2S), can serve as sources of electrons for
bacterial chemosynthesis. As in photosynthesis, inorganic carbon (CO2)
is reduced to organic carbon (CH4), while the oxidation of sulphur
serves as the source of energy instead of light. This oxidation may go
all the way to sulphate (SO4=) by the acid-producing (sulphur) bacteria
or may stop at an intermediate oxidation state. In other words,
chemobacteria can create carbohydrates capturing close-by carbon in a
chemosynthetic cousin of the carbon cycle. The sulfate produced can be
reduced once again by sulfate-reducing bacteria, providing additional
energy.
Chemosynthetic bacteria obtain energy by chemical oxidation or
reduction of simple organic compounds. Examples include NH3 to N2 or
(NO2-) or (NO3-), or to (NH4+); H2S to S or (SO3=) or (SO4=), or, vice
versa; and FeS2 to Fe(OH)3, (SO4=) & H+, as well as Fe2O3 and H2S to
FeS2. Oxygen must be present in the environment for oxidation to
occur. There are exceptions. Black sulfide layer activity has been
recently discussed (chemobacteria can create carbohydrates capturing
close-by carbon in a chemosynthetic cousin of the carbon cycle).
Anaerobic photosynthetic sulphide oxidation occurs primarily in
estuaries.
Jannasch, H. W., in Interactions between the Carbon and Sulphur Cycles
in the Marine Environment, has an interesting perspective. Since
hydrogen sulphide is a product of sulphate reduction and that uses
photosynthetically-produced organic matter as reductant, chemosynthesis
by sulphur-oxidizing bacteria could be considered in the flow of energy
as a form of secondary production. Microbial sulphur oxidation appears
twice. It appears 1st as an aerobic and chemosynthetic process. It
appears 2nd as an anaerobic photosynthetic process. In estuaries,
bacterial anaerobic reduction of CO2 requires light as a source of
energy and uses hydrogen sulphide (H2S) as a source of electrons. In a
way, if the above terminology is used, this bacterial photosynthesis
represents (as does the green plant photosynthesis) a form of primary
production. Green plant photosynthesis uses H2O rather than H2S for
the electron source. The distinction between primary and secondary
production of organic carbon is important if the interactions between
the carbon and sulphur cycle are linked to the flow of energy, be it
light or chemical energy.
Mid-ocean rift sea-vent chemobacteria extremophiles mimic activities of
their photosynthetic cousins from above, making carbohydrates from
H/O/C; they can create carbohydrates (e.g. CH4) capturing close-by
carbon in a chemosynthetic cousin of the carbon cycle. Recall that
reduced sulphur compounds, mainly hydrogen sulphide (H2S), can serve as
sources of electrons for bacterial chemosynthesis. As in
photosynthesis, the presence of inorganic carbon permits reduction to
organic carbon while the oxidation of sulphur serves as the source of
energy instead of light. This oxidation may go all the way to sulphate
by the acid-producing (sulphur) bacteria or may stop at an intermediate
oxidation state. Other types of sea vent extremophiles simply use
sulfate reduction (to sulfides) for respiration; both parallel
chemosynthetic activity seen in the bottom of the green-red-black
surface layers.
In addition, chemobacteria extremophiles in sea vents and non-marine
hot springs (both at very high temperature) can use locally-abundant
sulfur (S), rather than oxygen, as an electron acceptor in respiration.
In this case the reduction of sulfur generates hydrogen sulfide (H2S)
rather than water, as a by-product of respiration. This can be used by
other extremophiles (recall the mid-ocean rift, in the area of the
under-water hot water cycle, can contain certain chemobacteria capable
of creating carbohydrates capturing close-by carbon in a chemosynthetic
cousin of the carbon cycle). If the available sulfur is organically
bound, the sea vent / hot spring extremophiles may produce hydrogen
gas, which is of use to still other extremophiles (deep-rock
extremophile discussion follows). Sea-vent/hot-spring extremophiles
are often anaerobic, but can tolerate oxygen to some degree. Their
ability to generate hydrogen from organic waste products, while
tolerating oxygen allows great flexibility.
Chemobacteria extremophiles can have many different pathways for their
very slow respiration. Chemobacteria extremophiles that live deep in
the earth only need water to live in and heat of the earth (energy) to
reduce (or oxidize) rocks and minerals. H2 gas is released as water
seeps through rock (produced from iron oxide reacting with water);
molecular hydrogen can be reacted with carbon, oxygen or sulfur to
sustain deep rock extremophile respiration. In caves, extremophile
(sulfur) bacteria derive their energy from inorganic hydrogen sulfide;
previously discussed, H2S is carbohydrate-convertible when small
amounts of carbon are present (chemobacteria can create carbohydrates
capturing close-by carbon in a chemosynthetic cousin of the carbon
cycle). Limestone extremophiles can reduce the rock and release CO2;
the resultant carbonic acid dissolves limestone, forming caves.
As far as the Pre-cambrian snowballs go, there enough increased sun
intensity for CO2 levels to now play a major role. Unicellular plant
life dropped atmospheric CO2 enough to create the smowballs; there was
likely no total blackout. Anyone that has spent much time diving under
ice realizes that there is only a die-back for plant life, and it is
not that dramatic. There may have even been open water. The dual-role
bacteria have an even greater ecological valance than the
cyanobacteria. Primitive life at the equator was never really
threatened.
I would not date the last universal common ancestor to the 1st
snowball, even though the environment certainly selected for life
changes. Primitive life had endured far greater challenges. It was
not as yet even an oxygenating environment; only small quantities were
released at one time. It seems to me that the Ediacaran biodiversity
following the worldwide last Precambrian (Varangian) glaciation
parallels the planet of the apes situation of 8-10 mya., where there
were many candidates for our ancestor, which were a result of a
previous adaptive radiation.


.

Relevant Pages

  • Re: Snowball Earth at 2.3 gya
    ... > as potent as CO2), keeping water in liquid form at this time of lower ... But that first primary Earth atmosphere of H2, methane, and ammonia ... Oxygenic photosynthesis probably did not arise ... > carbon dioxide resulted; had it not been for life locking-up CO2, ...
    (sci.bio.evolution)
  • Re: comments guys
    ... carbon dioxide is a greenhouse gas - a minor one. ... every 100,000 molecules of atmosphere, every five years. ... routinely transfers 40 times as much CO2, and 24,000 times as much water ... the human source represents only 3% the size of the ...
    (uk.sci.weather)
  • comments guys
    ... carbon dioxide is a greenhouse gas - a minor one. ... every 100,000 molecules of atmosphere, every five years. ... routinely transfers 40 times as much CO2, and 24,000 times as much water ... the human source represents only 3% the size of the ...
    (uk.sci.weather)
  • Re: Solar Activity Reaches 1,000 Year Peak
    ... of the currents are the controlling factors in climate over the long ... CO2 via volcanic action back into the atmosphere. ... The atmospheric concentrations of carbon dioxide in the Early ...
    (soc.retirement)
  • Re: Money manking idea
    ... power to farms, ... We never know what bacteria out there are capable of. ... further break down to carbon and oxygen. ... discover a bacteria which can cover the CO2 into hydrocarbon ...
    (soc.culture.singapore)