CENTAURS AND ICY PLANETARY BODY IMPACTS ON OCEAN VOLUMES AND CHEMISTRY THROUGH TIME Pat WILDE Pangloss Foundation 1735 Highland Pl. #28 Berkeley, California 94709 [email protected]Mary S. QUINBY-HUNT Lawrence Berkeley Laboratory Berkeley, California 94720 [email protected]
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CENTAURS AND ICY PLANETARY BODY IMPACTS ON OCEAN VOLUMES AND CHEMISTRY THROUGH TIME Pat WILDE Pangloss Foundation 1735 Highland Pl. #28 Berkeley, California.
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CENTAURS AND ICY PLANETARY BODY IMPACTS ON OCEAN VOLUMES AND CHEMISTRY
The number of icy bodies reported in the solar system has increased dramatically in the past few years suggesting their potential importance in Earth history via impacts. Wilde (1987) proposed that icy bodies may be a significant source of the oceans during the later stages of accretion. Wilde and Quinby-Hunt (1997) discussed the chemical consequences of impacts of ice-volatile bolides of various compositions. The 'rain' of icy bodies hitting the Earth throughout time suggests implications for the following Earth processes.
Jupiter (orbit)
Mars (orbit)
Earth
Mercury (orbit)
Venus (orbit)
Plot of the Inner Solar SystemThe plot shows the current location of the major planets (Mercury through
Jupiter) and the minor planets that are in the inner region of the solar system. Source: http://cfa-www.harvard.edu/iau/lists/InnerPlot.html
Light Blue: The orbits of the major planets
Large Colored Dots: the current location of the major planets
Green Circles: The locations of the minor planets, including numbered and multiple-apparition/long-arc unnumbered objects
Red Circles Objects with perihelia within 1.3 AU are shown by red circles.
Objects observed at more than one opposition are indicated by filled circles, objects seen at only one opposition are indicated by outline circles.
Deep Blue Circles: The two "clouds" of objects 60° ahead and behind Jupiter (and at or near Jupiter's distance from the sun) are the Jupiter Trojans
PLATE TECTONICS AND THE EVOLUTION OF GRANITIC CRUST
Earliest sediments thus found are greenstones, basically basaltic sediments suggesting lack of a granite source. Without a granite-oceanic basaltic crustal difference, early surface terrains would be limited to a relatively low relief consisting of abyssal plains, seamounts, and the ridge-rise system.
Incrementally the impact of icy objects would provide fluid for the then shallow ocean basins. During subduction at depth the pressure and temperature plus fluids could hydrate the basaltic crust producing granitic compositions. With time the production of granite could produce the continental blocks raising the present freeboard of the continents and the relief of the ocean basins. Chondritic compositions are too water poor to support Rubey's (1951) theory that volatile components such as water largely come from expression from the mantle.
Molecular Weight of Amphibole = 814Molecular Weight of Water = 18
Molar Ratio = 0.022
Continental Crust = 5 e+22 KgOceans = 1.3 e+21 Kg
For 15% Amphibole = 7.5 e+21 Kg
Water needed to produce amphibole: 0.0221 x 7.5 e+21 = 1.658 e+20 Kg
Input Water = 3.77 E10 Kg over 4.4 Billion Years
Amount Water/Yr needed to convert Basalt to Amphibole
0.0377 Km3/Yr
A bolide this big per year is enough to maintain the oceans and granitize the basalt
Amount H2O/MillionYr 37700 Km3/MillionYr
Amount H2O/100 Million Yr 3770000 Km3/100 MillionYr
SEISMIC STRATIGRAPHY AND TIME SCALE OF ICY IMPACTS
Third-order sea level rises of durations of a few million years can not be related to known glacio-eustatic climatic events. These sea level rises may be the result of impacts of icy Centaur-like bodies briefly adding to the ocean volume and eventually being absorbed in the granitizing process of subduction. The frequency of the third-order events could record the timing of icy impacts of significant size.
Centaurs
1
100
10,000
1,000,000
100,000,000
10,000,000,000
1 13 25 37 49 61 73 85 97 109121133145
Number in decreasing volume
Volu
me
in K
m^3
0.00001
0.001
0.1
10
1000
100000
Appa
rent
Sea
Lev
el
rise
in M
eter
s
3rd ORDER SEA LEVEL RISE
3rd ORDER SEA LEVEL RISE
Centaurs
1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000
1 15 29 43 57 71 85 99113127141
Vo
lum
e i
n K
m^
3
1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000
10,000,000,000
Tim
e i
n Y
rs t
o a
bs
orb
by
su
bd
uc
tio
n
Effect of adding the mass of water in impacting objects
Estimated potential maximum sea level rise from the total melting of present-day glaciers
VARIATIONS IN OCEANIC COMPOSITION
Berner (2004) and others have discussed changes in the bulk composition of the oceans during Phanerozoic time. A potential contribution to such variations would be the introduction of icy planetary bodies with the variation a function of bolide composition. Such events may be seen in the delta spike of C and S isotope values against the background of terrestrial isotopic processes.
From: Carbon and Sulfur isotope anomalies across the Permian-Triassic boundary (PTB) in W. Slovenia
Matej Dolenec and Barbara Vokal
Carbon, organic carbon and sulfur isotope variability across the PTB in the Idrijca Calley (W. Slovenia)
Perm
ian
Tria
ssic
CHEMICAL CHANGE
Effect of adding the mass of C in impacting objects
CHEMICAL CHANGE
TESTS OF CONJECTURES
Upcoming missions to analyze the composition of comets and other icy bodies, thought to be remnants of original solar system building blocks, will be useful in discerning the contributions of icy extraterrestrial bodies to on-going Earth processes.
REFERENCES
Berner, R. A., 2004, A model for calcium, magnesium and sulfate in sea water over Phanerozoic Time: American Journal of Science, v. 304, p. 438-453.
Rubey, W. W., 1951, Geologic history of seawater: an attempt to state the problem: Geological Society of America Bulletin, v. 62, p. 1111-1147.
Wilde, P., 1987, Primordial origin of the oceanic Rubey Volatiles as a consequence of accretion of ice-sulfur planetesmals, (abst.): EOS, 68: no. 44, p. 1337.
Wilde, P. and M. S. Quinby-Hunt, 1997, Collisions with ice/volatile objects: Geological implications- A qualitative treatment: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 132, p. 47-63.