Atmospheric composition Flashcards
what are reducing and oxidising atmospheres
reducing: abundunt in hydrogen. hydrogen reacts with other molecules to for things like methane and ammonia
oxidising: lack of hydrogen. things like methane and ammonia will react to form hydrogen.
why is earths atmosphere so different from mars and venus
CO₂ removal via weathering. the similarity between mars and venus atmosphere suggests it is the primordial atmosphere
what can cause isotopic variations
the H/D ratio changes as more hydrogen escapes than deuterium since deuterium is heavier. Venus has a very high ratio due to a runaway greenhouse effect and loss of water
how do clouds form
when water vapour exceeds the saturation pressure limit, the excess condenses out to form clouds
what are clouds made of on all planets
Earth: water
Venus: sulphuric acid
Mars: ice and dry ice clouds only no liquids
gas giants: methane, ammonia, water
how do we determine the atmospheric composition of distant planets
when the planet transits in front of a star the spectra of light that passes through the planet is different. The wavelengths of light absorbed correlate to different elements and compounds.
what caused the end of the last glacial period
- increase in insolation due to the Milankovitch cycles
- triggers the melting of northern ice sheets
- increase in north Atlantic water upsets ocean circulation
- this backs up heat that would have gone to the northern hemisphere, pushing it into the southern hemisphere.
- this causes the southern ocean to release CO₂
- CO₂ release causes global temperatures to rise
are we entering an ice age
yes: (evidenced since 8000 BC)
glacial growth
Canada snow cover
Sahara drying
No: (recent)
The industrial revolution caused a massive increase in the greenhouse effect.
How does the Greenhouse effect work
Sun emits light at ~ 0.5 micron wavelengths (shown with Wein’s law at 6000k). Earth’s atmosphere is transparent at these wavelengths. The earth’s surface is 290k which emits ~10 micron wavelengths. Earth’s atmosphere is opaque at these wavelengths. Hence the heat can pass through the ground and is then trapped.
