After the Moon-forming Impact

Details After the Moon-forming Impact After the Moon-forming Impact

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.v23h..01z&link_type=abstract

American Geophysical Union, Fall Meeting 2006, abstract #V23H-01

Mathematics

Logic

5225 Early Environment Of Earth, 5418 Heat Flow, 5455 Origin And Evolution, 8125 Evolution Of The Earth (0325), 8136 Impact Phenomena (5420, 6022)

Scientific paper

We address the first several hundred million years of Earth's history. The Moon-forming impact left Earth enveloped in a hot silicate atmosphere that cooled and condensed over ~1000 yrs. As it cooled the Earth degassed its volatiles into the atmosphere. It took another ~2 Myrs for the magma ocean to freeze at the surface. The cooling rate was determined by atmospheric thermal blanketing. Tidal heating by the new Moon was a major energy source to the deep mantle. After the mantle solidified geothermal heat became climatologically insignificant, which allowed the steam atmosphere to condense, and left behind a ~100 bar, ~500 K CO2 atmosphere. Thereafter cooling was governed by how quickly CO2 was removed from the atmosphere. If subduction were efficient this could have taken as little as 10 million years. In this case the faint young Sun suggests that a lifeless Earth should have been cold and its oceans white with ice. But if carbonate subduction were inefficient the CO2 would have mostly stayed in the atmosphere, which would have kept the surface near ~500 K for many tens of millions of years. Hydrous minerals are harder to subduct than carbonates and there is a good chance that the Hadean mantle was dry. Hadean heat flow was locally high enough to ensure that a global ice cover was thin (<5 m) in places. Moreover hundreds or thousands of asteroid impacts would have big enough to melt the ice triggering brief impact summers. We suggest that plate tectonics as it works now was inadequate to handle typical Hadean heat flows of 0.2- 0.5 W/m2. In its place we hypothesize a convecting mantle capped by a ~100 km deep basaltic mush that was relatively permeable to heat flow. Recycling and distillation of hydrous basalts produced granitic rocks very early, which is consistent with preserved >4 Ga detrital zircons. Overall, Earth could have been habitable as early as 10-20 Myrs after the Moon-forming impact.

Affiliated with

Also associated with

No associations

Rating

After the Moon-forming Impact does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with After the Moon-forming Impact, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and After the Moon-forming Impact will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-963112