Lecture 5: Gaia Hypothesis Flashcards
What approach did James Lovelock take to determining whether life on other planets could exist? What aspect of the planets did he devote particular attention toward?
He looked at the different planets alongside our knowledge of how life affects our planet already. One particular area he looked at was the differing atmospheric compositions
Why were Lovelock’s efforts to determine whether life existed on other planets unpopular amongst his peers?
Because it undermined the credibility of their efforts to determine whether life existed on another planets
What was the conclusion of Lovelock’s work looking at whether life existed on other planets, notably Mars?
That it demonstrated no current or previous indications of life
What do low-entropy/living things do?
They produce high-energy waste products
What do the high-energy waste products match with?
The high-energy waste products are of high disorder which matches with the growing disorder present in the universe
What did Schrodinger state in 1944?
life will always change its surroundings by releasing unusual volatiles and other gases that normally react with each other to vanish, but instead they are maintained causing an unusual mixture in the atmosphere.
What is the idea of disequilibrium?
When things coexist which are highly reactive with each other remain abundant in independent forms
Is the earth in disequilibrium and what is this evident from?
Yes - extreme disequilibrium - evident from the unusual mixture of gases that are highly reactive with each other such as Methane and Oxygen and would normally not be separate
Why is the earth’s atmospheric composition in extreme disequilibrium?
Because life generates large fluxes of gases in order to survive which then alters the atmosphere
What did Lovelock hypothesis from looking at the atmospheric composition over time?
That because the composition has been preserved and stable over time, life must be regulating the atmosphere not just inputting new gases
Who produced the knowledge about the Faint Young Sun Puzzle?
Carl Sagan
What theory did Lovelock develop working with Carl Sagan regarding the faint young sun puzzle?
that is the sun was brighter by 30% before why was it not frozen over? It must have been because the greenhouse gas layer was being altered relative to the sun’s brightness. Vegetation must have been responsible for these changes and therefore alters the climate
What was the Gaia hypothesis?
The theory co-produced by Lovelock and Marguilis which outlined how they believed life was altering numerous aspects of earth
Where did the name “Gaia” come from and what controversy did it have around it?
It was the name of a Greek goddess and it received controversy because it combined quasi and religious ideas
What were some of the topics the Gaia hypothesis wanted to explore?
- Atmosphere disequilibrium, yet stable components
- Why are gases perfectly suitable? e.g. oxygen
- Stable climate despite faint young sun puzzle
- Acidity and redox potential of earth’s surface anomalous yet tolerable
What was the mechanism found in the sulphur cycle that enabled it to recycle?
Dimethyl Sulphide - it resupplied sulphur back to the atmosphere and allowed for sulphur to continue precipitating on the land
What was the mechanism that allowed iodine to be replenished in to the ocean?
Methyl Iodide found in the marine biology
What problems was Lovelock experiencing with getting his Gaia hypothesis to the public? How did he overcome it?
No journal would publish his theory. He would publish a book
Who were two notable peers of Lovelock that criticised his theory? What did they critique?
Dawkins and Doolitle - how could unconscious bacteria consciously determine their environment
What was the name of Lovelock’s response to criticism of his work?
Daisyworld
What was “Daisyworld”?
A model that showed how plants (daises as an example) could automatically alter and regulate their envrionment
What were the two types of plant that he included in the Daisyworld model?
Black Daises - absorb more sunlight which warms their surroundings
White daises - absorb less sunlight
What will happen to black daises if luminosity and therefore temperature reaches a suitable level for growth? What subsequent effect will happen?
They will start to grow - meaning there is more black present which increases temperature more (feedback)
What will happen to black daises when they become too many and temperature reaches too much?
If there are too many daises then the temperature will be too hot so they will start to decline, which dampens the feedback and eventually will vanish as all black daises are gone
What will happen to white daises if luminosity and therefore temperature reach a suitable level for growth? What subsequent effect will happen?
They will start to increase but because they are white there is a negative feedback i.e. the more the temperature increases, the slower the daises start to grow.
What will happen to white daises when the luminosity increases too much?
It will be too hot for the daises to continue dampening the effect by cooling their environment. This will reduce albedo and therefore temperatures will increase even more. Once all daises have gone the temperature relationship will normalise.
Which daises will dominate at the lower level and the upper levels of luminosity/temperature? Think about the reason
Lower - black daises (They absorb more heat so can tolerate the cooler temperatures)
Upper - White (They reflect the heat so can tolerate higher temperatures)
What is the transition between the two daises dominance characterised by?
A slight negative temperature line i.e. it decreases from the transition between black and white daisy dominance
What is the daisyworld model a demonstration of?
Planetary-scale self-regulation can happen automatically
What was the second part of the Gaia hypothesis looking at?
Ocean salinity
What is the ocean salinity level suitable for life today and what would be fatal?
Today = 3.4% Fatal = 6%
What did Lovelock propose as the regulating mechanism for ocean salinity that then came to be wrong?
Coral reefs would create lagoons behind them with salt landforms being created to separate it from the ocean
What are the known outputs/regulators of ocean salinity today?
Mid-ocean ridges: these can provide and take material from the ocean to the crust. Assisted by black-smokers.
Subduction: ancient salt sediments taken down and stored below the crust
What are black smokers and how can they help regulate ocean salinity?
They release hot water that depending on its balance with ocean salt can either enter or remain in sea. The salty elements are also assisted by the high reactivity in these areas so then form rocks that cannot interact
What did Alfred Redfield realise in the 1930s and 1950s?
There was a particular balance of nitrogen and phosphorus in the oceans that matched the requirements of organisms.
What was his explanation for the similarity between organism requirements and ocean content of these ocean nutrients?
Life was responsible for setting the ratio in the ocean. Certain organisms can fix nitrogen in to its bioavailable forms so their activity adapts to and regulates the changing level of nitrogen so that it can be used for the organisms
What is the name of the ratio between plant concentrations of phosphorus and nitrogen and the ocean concentrations?
Redfield ratio
Did Redfield’s ideas predate Lovelock’s and what does this suggest?
They predated his ideas which suggested that he was way ahead of his time
