System Earth Ch 12 Flashcards
(55 cards)
What is the young sun paradox?
the fact that the earth must have been warm enough for liquid water to exist throughout its history but that the sun used to be 30% less bright
why has the sun’s brightness changed over time?
luminosity increase is due to a change in density caused by the conversion of hydrogen into helium.
what does it mean that luminosity change for the sun is a robust model?
does not depend sensitively on the details of the model - the specifics may be different but the core of the issue will not go away.
How well do we understand the sun?
turns out, pretty well. We have found out that it emits neutrinos in a type that went unmeasured for a very long time. This is how the sun produces energy.
how does teh sun loose mass?
solar wind - outflow of charged particles from the sun’s corona. There us also a rapid rotation which with the magnetic field heats up the star’s corona, driving a stellar wind.
Can we calculate the faint young sun paradox mathematically?
yes, you can look at 30% decrease in luminosity -> 22 degrees temperature change and do your maths from there, while including feedback loops.
what are the three possible solutions to the faint young sun paradox?
- planetary albedo was lower in the past.
- larger GHE
- additional heat sources present.
geothermal heat?
heat produced by the decay of radioactive elements in the Earth’s crust and mantle.
what is the problem with the geothermal heat flux?
it is not enough. It would have been enough to keep deep ocean warm but not the top from freezing.
why is albedo not a solution to the faint sun paradox?
the albedo would have had to be near 0 which is impossible.
what is probably the solution to the faint young sun paradox and which options are wrong?
enhanced GHE but it could not have been water vapour alone. Ammonia is also not an option
Why were there more reduced gases in the atmosphere prior to 2.4 By ago?
This was before an oxygenated atmosphere. So ammonia could have been present were it not for ultraviolet radiation.
is CO2 an option for the faint sun paradox?
with the silicate, carbon cycle, it is definitley a possibility. We would have needed 1000 times current levels, but this is quite possible.
serpentinization
serpentine minerals are formed in a reaction with watera nd iron and magnesium- rich basalts. If CO2 is in the water, methane is formed.
early form of bacteria?
methanogenic bacteria
why is the sky blue
scattering of sunlight by N2 and O2 molecules - Rayleigh scattering
What is Rayleigh scattering
when the shorter wavelengths are scattered preferentially to long wave. So we see a blue sky
Mie scattering
scattering particles that are close in size to the wavelength.
thermophile
organisms with optimum temp between 40 and 80
hyperthermophile
organisms with optimum temp above 80 degrees
organic haze effect
the temperature decreases due to the anti greenhouse effect.
deep sea cores
go back 200 My
oxygen isotopes
look at carbonate rocks. but may have been influenced by other processes such as a change in seawater compositon.
tillites
mixtures of cobbles, pebbles, and and mud that have been packed together to form rocks.
