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by Andy Lloyd April 02, 2002 from DarkStar1 Website
My good friend Lee Covino recently sent me an article from 'Science News' (Vol. 161, no 12) about the source of Earth's oceanic water (1).
Written by Ben Harder, the article outlined the latest scientific thinking about where all the water on Earth came from. This is a particular problem for planetary scientists because the Earth simply should not have the amount of water that it does.
The Earth is relatively close to the Sun, and water, a volatile, should have been expelled from the early inner solar system before the Earth formed.
As such, the Earth should really be a much drier planet. So where
did all the water that is so crucial to the biosphere of this planet
originate?
This bombardment occurred over a billion years (and might also explain how life appeared on Earth so early in its geo-history). But according to Ben Harder's article, recent data from comets has overturned this possibility.
The problem is that the isotopic ratios of terrestrial water and cometary ice are quite different.
The comets analyzed thus far contain relatively large quantities of deuterium, yet this isotopic form of water is rare on Earth.
If this composition of known comet ice is representative of solar system comets in general, then very little of the Earth's water can be attributed to cometary impact following the Earth's formation.
Taking this into account, it appears that only half of the Earth's oceans could have been deposited by impacting comets.
As Ben Harder puts it:
Puzzled scientists have tried to patch the flagging 'late-veneer' theory up, topping up the comet contribution with that of water-rich asteroids, but that doesn't explain other problems to do with the Earth's chemical composition.
The Earth is rich in many other volatiles, and these elements (mostly noble gases) are not noted on meteorites.
Topping up comet water deposition with that of water-rich asteroids would not explain the relative abundance of these other volatile chemicals.
For example, recent studies by
scientists at the University of Arizona regarding the relative isotopic
ratios of osmium in carbonaceous chondrites sink the late-veneer theory
still further; the upper limit for deposition of volatiles from space after
the Earth's formation is a meager 15%
(3).
Various new ideas are being floated, in varying degrees of complexity, to explain this contradiction.
It is
so obvious that its absence within Ben Harder's otherwise excellent article
speaks volumes in itself. The Earth has a rich mixture of volatiles,
including water, because our planet originally formed much further away from
the Sun.
He proposes that the Earth formed from the coalescence of Moon-sized embryos derived from various chaotic orbits in the primordial solar system. The 'volatile carriers' would have formed at about 4 Astronomical Units; four times further away from the Sun than the Earth, but still within the orbit of giant Jupiter.
He notes, however, that
the water-bearing carrier from 4 AU would have been geo-chemically unique in
the solar system.
Somehow, it was shunted into the inner solar system
from an orbit originally much closer to that of Jupiter.
Upon translating and interpreting ancient Sumerian cuneiform texts, this scholar proposed that the earliest Mesopotamian myths were describing the solar system to a high degree of accuracy, but with a few additional features.
Interpreting the myths in an
astronomical context suggested to Sitchin that an undiscovered planet exists
among the comets, one that was not an original member of the solar system,
but an interloper wandering in inter-stellar space that blundered into the
planetary zone.
Not wishing to rely too heavily upon that old die-hard 'Occam's Razor', we seem to have a simple solution to a difficult problem.
He proposes that debris from the impact of the primordial Earth and Nibiru, and/or one or two of its moons, was scattered into the solar system forming the asteroid belt, and the comets.
Perhaps the formation of the asteroids may have occurred in this way, but
not the comet. The 'late-veneer' theory itself is in trouble because the
Earth's oceans could not have been wholly derived from comets. So conversely
the solar system's comets could not have been formed from the oceans of the
primordial Earth. If they had then the comet ice isotope ratio would be
consistent with that of Earth.
The lack of a significant iron core within the Moon suggests that this impact took place after the Earth's own iron core had already gravitated to the centre of our planet (7).
It's conceivable that the remainder of the early Earth's scattered debris formed the asteroid belt, given Sitchin's proposal, and this possibility is readily testable by further scientific study of the composition of asteroids within the belt between Mars and Jupiter.
This might have occurred when the Moon formed, or as a result of
later impacts upon the recovering Earth.
Such a massive terrestrial
planet could have readily held onto a vast amount of volatiles at the
original distance of 4 astronomical units. It also would not be so
incongruous that the larger primordial Earth would have hosted such a
massive satellite as our Moon, a point noted by Sitchin when describing the
relationship between the Sumerian Tiamat and 'Kingu'.
And so they might have remained had the solar system not been disturbed by an interloper.
Nibiru, a wandering giant planet or small brown dwarf (9,10), entered the planetary zone, bringing with it a ready made contingent of comets and moons.
This latter action may have been the 'late, great bombardment' that occurred 3.9 billion years ago, when thousands of killer impactors bombarded our planet.
Nibiru itself
became captured by the Sun, but remains loosely bound and possibly erratic
still, a condition that prevents the known planets from harmonizing their
resonances.
Without the action of a passing intruder planet of vast proportions (and I consider Nibiru to be no less than a sub-brown dwarf), the Earth would be a much colder place than it is now. More like 'Snowball Earth'.
Life relies upon liquid water…would the current
bio-diversity on this planet have arisen if Earth was still at 4 AU? One
suspects not.
The presence of abundant liquid
water on the cooled planet becomes a paradox, because heat and water do not
appear to mix when terrestrial planets form. So this paradoxical situation
we currently find on Earth is solved either by considering the possibility
that the Earth has moved significantly closer to the Sun since its
formation, or by rethinking how planets form.
The Earth's abundance of liquid water may be very rare if the action of an intruder planet is required to explain its shunting into a closer inner orbit. (Saying that, some of the extra-solar planets found so far have odd orbits; particularly gas giants that whizz around the parent stars at very close proximity (11).
Why was the constituent gas not blown away by the star before the planet
formed? Does this imply that planetary orbits can change radically, possibly
as a result of outside interference? More planets, please, Dr Marcy!
We always assume that our average boring old Sun is the blue-print for other star systems that might harbor the conditions for life. Perhaps this assumption is correct, and the search for Extra-Terrestrial Intelligence should remain targeted at similar stars to our own Sun.
But if Earth's acquisition of abundant water is truly an anomaly given the local heat generated by our Sun upon its formation, then perhaps we should be looking for life on star systems whose primordial fires aren't so hot.
After all, the spectrum of stellar characteristics does not
begin with our own Sun.
These relatively cool stars
might have allowed watery worlds to form more readily around them, and
bombard them with less harmful radiation to boot. SETI may have been
searching in the wrong place all this time.
It was not so long ago that Tom van Flandern heavily criticized Zecharia Sitchin's '12th Planet Theory' on the basis that Earth could not have migrated into the inner solar system from the asteroid belt. Van Flandern argued that Earth's orbit should still be highly elliptical if that was the case, and the orbit should still cross through the asteroid belt.
These arguments were sufficient to swing Alan Alford away from the idea of
the existence of a substantial Planet X body
(12).
These bizarre giant planets are
too close to their stars to have formed where they currently lie (according
to existing theoretical models of planet formation, anyway), so the concept
of 'migration' is increasingly mooted to help planetary scientists sleep at
night. If such a model can be widely applied elsewhere, then surely it could
have happened in our solar system too? Possibly even to the Earth?
This class of planets, called the 'Water Worlds', are still theoretical, but this looks like a very exciting development for those interested in Tiamat's transformation into the Earth:
There is so much that we don't understand about the formation of planetary systems.
This can be only one of a myriad of possibilities, but its early introduction to scientific speculation would indicate its potential. If such Water Worlds are found to exist then they would provide a huge lift for Sitchin's theories. Because one of them may have formed between Mars and Jupiter and, through interaction with Nibiru, migrated into towards the Sun 3.9 billion years ago, thereby losing substantial quantities of that water into the solar system.
The result, as they say, is history. Earth's History!
It can be easily argued that the conditions on that moon would be warm enough for liquid water, but some have offered a counter-argument that there still would be insufficient light for photosynthesis to take place in the outer solar system.
Such light as there is would have to come from Nibiru, an old
and small sub-brown dwarf: a class of failed stars about which we have
little knowledge. Astronomers argue about whether such bodies can even emit
light, but there does seem to be a good possibility that they do, through
chemical reactions in the substantial outer layers of atmosphere. This would
result in 'flaring' of light rather than constant brightness.
I suggest that it is.
The scientist Chris McKay has studied eco-systems that depend upon the dimmest of light emerging through the ice to trigger photosynthesis:
When you add in the warming and local lighting effect of the dark star Nibiru, then conditions on its moons would be more favorable still for the emergence of complex ecosystems in the outer solar system.
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