Lecture 29: Habitability

Question 1

what is habitability and what are some problems in defining the idea?

Answer 1

an environment that can support the activity of atleast one known organism- activity being maintenance, growth, or reproduction

habitability often defined by life as we know it; hard to branch out when so unknown

Question 2

give and elaborate on arguments and data for and against habitable conditions on mars

Answer 2

for:
- CHNOPS: contains elements required
- physical conditions: radiation low below surface, pressure good for growth particularly underground, no known toxins to prevent life

against:
- energy: anoxygenic photosynthesis but no water today on surface; very energy limited

Question 3

what is the ‘habitable zone’ and what are some of its simplifications?

Answer 3

region around a star where conditions might be just right for liquid water to exist on a planets surface

simplifications
- ignores subsurface oceans that may be habitable, assuming we need surface water
- often assumes earth like greenhouse gases

Question 4

how might stellar type influence habitability?

Answer 4

luminosity and habitable zone location:
- hotter, more massive stars are very luminous, so habitable zones are farther out but often short lived

stellar lifespan
- massive stars burn out quickly, often too short for life to evolve

Question 5

what is the galactic habitable zone?

Answer 5

the region in a galaxy where conditions are most favourable for the formation and long-term survival of life-supporting planetary systems

-enough heavy elements to form rocky planets
- stable enough for life to develop and persist over billions of years

Question 6

how are being habitable and being inhabited not necessarily the same?

Answer 6

environment can be habitable but life just hasn’t originated there

life could have gone extinct

life could be undetectable