CHZ Flashcards
(31 cards)
Four ways to define a habitable planet?
Liquids
Suitable star
Atmosphere
Suitable gravity
Important factors to produce life
Chemical elements
Liquids
Gravity
Heavy elements
Collision impacts
Presence of nearby planets
Plate tectonics
Of the 92 naturally occuring elements how many play a role in terrestrial life?
21
What are the major biogenic elements?
C, H, O, N, Mg, Ca and Cl
Why are H O N and C most significant?
Able to achieve electronic stability easily
Why are liquids necessary?
Place for molecules to interact
Need polar solvent to establish H bonds
Why does temperature need to be suitable?
Allows reactions to occur and organic bonds to form
What if temperature is too high?
All moisture will evaporate causing greenhouse effect
What if temperatures are too low on planey?
Planet could have permanent ice age
What happened to venus and its temperature?
Greenhouse effect has dried up surface and raised temperatures to 460 degrees due to insulating atmosphere
What is the Circumstellar habitable zone?
The region around a star within which planets can support liquid water at their surfaces
What can massive ice formation lead to on Earth?
Snowball earth where albedo of surface goes up causing even further cooling
Surface temperatures needed to liquid water
273 K to 373K
What will affect the CHZ?
Long-term stellar variability such as sun becoming larger and brighter
Why are lots of liquids needed?
Produce large pools to circulate vital minerals and elements
How does the gravity need to be for life?
High enough to retain an atmospheric pressure large enough to prevent liquids from evaporating.
Moon Atmosphere and Gravity
Gravity is 1/6 Earth so cant hold atmosphere and high day temperatures mean surface water would evaporate in the day
Mars Gravity and Atmosphere
62% lower than earth
Holds a thin Co2 atmosphere so little insulation so surface temp is very low -50 degrees
Why are heavy elements needed?
Needed to form rocky planets
Which type of stars are heavy elements found in?
All Population - 1 type stars
Not in sufficient amounts in Population - 2 stars
What percent heavy elements is needed to form rocky planets?
1-2%
Where are Population 2 stars found?
Centre of the galaxy and unlikely to have few rocky planets
How can impacts influence life?
Kill life
Also maybe key to introduce new ingredients
How can the gas giants influence the impact rate?
- attract most of the loose solar system debris to protect rocky planets
- disrupt debris from stable orbits and send it towards rock planets
