L14 : Prospect of Life Habitability in Solar System

Question 1

What is the working definition of life?

Answer 1

Life is a self-sustaining chemical system capable of undergoing Darwinian evolution
Gerald Joyce

Question 2

What are the 4 key requirements for life?

Answer 2

• Raw materials
• Source of energy
• Liquid medium (probably water)
• Other environmental conditions

Question 3

What must life be capable of to fit the definition?

Answer 3

Mainting itself through metabolism and internal chemical processes
Replicating and evolving through natural selection

Question 4

Examples of raw materials needed for life?

Answer 4

Organic molecules or simpler substances from which these can be built

Question 5

Name three possible energy sources for life

Answer 5

Sunlight
Redox reactions
Serpentinisation

Question 6

Why is water considered the best medium for lfie?

Answer 6

Supports chemical reactions needed for life due to solvent properties and wide temperature range

Question 7

What other environmental conditions are important for biochemical processes?

Answer 7

Temperature, pH, trace elements

Question 8

What is the difference between abiogenesis and habitability?

Answer 8

Abiogenesis is the origin of life from non living matter

Habitability is the ability of an environment to support existing life

Question 9

What is shown by the 3D life parameters grap?

Answer 9

Potentially habitable conditions from combination of temperature, pH, salinity

Based upon life on Earth

Question 10

Was early Mars likely habitable?

Answer 10

Yes
Thicker atmosphere
- trap heat
Liquid water on surface
- stable environment for life

Question 11

What is significant about Jezero crater?

Answer 11

Ancient lakebed and well-preserved river delta
Indicates Mars once had long-standing surface water

Question 12

What are the 3 main possibilities of life on Mars?

Answer 12

Extant near-surface microbial life
Extant subsurface microbial life
Extinct fossil life

Question 13

What challenges face near surface life on Mars?

Answer 13

High UV radiation
- thin atmosphere
Oxidising surface environment

Question 14

Why is subsurface Mars most promising for life today?

Answer 14

Offers protection from radiation
May host aquifers with liquid water
Geothermal heat

Question 15

What did the Viking biology experiments attempt to detect ?

Answer 15

1976
Signs of metabolism in Martian soil
Results were ambiguous

Question 16

Why is Europa a strong candidate for life?

Answer 16

Likely has subsurface ocean beneath icy crust, heated by tidal forces

Question 17

What do few impact craters on Europa suggest?

Answer 17

Surface is young and may have been resurfaced recently by upwelling water

Question 18

How does Europa’s interaction with Jupiter’s magnetic field support ocean evidence?

Answer 18

Induced currents imply a conductive, salty ocean beneath the ice

Question 19

What makes Ganymede less habitable than Eurpoa?

Answer 19

Liquid water may be isolated by dense, high-pressure ice layers (Ice VI)
Limits interaction with rock and possibility for serpentinisation

Question 20

What is unique about Ganymede?

Answer 20

Largest moon in Solar System
Only moon known to have magnetic field
- likely due to molten iron core

Question 21

What are layers within Ganymede’s internal structure?

Answer 21

Ice shell, rocky mantle, molten core

Question 22

Why is Callisto a low potential candidate for life?

Answer 22

Similar to Ganymede
- Less geologically active
- Much less resurfacing
- No magnetic field

Question 23

Briefly describe key features of Enceladus?

Answer 23

Very active
Very small (only 500 km diameter)
Plumes observed at South Pole

Question 24

What does Enceladus’s plumes contain?

Answer 24

Water, ice crystals, sodium, hydrogen, and possible organic material

Question 25

What is the internal structure of Enceladus?

Answer 25

Rocky core, possible internal ocean, icy crust with cracks

Question 26

Why does Enceladus still need further study to confirm habitability

Answer 26

Lacks confirmed carbon source essential for Earth-like life

Question 27

Key features of Titan?

Answer 27

Saturn's largest moon Earth-like but much colder

Question 28

What is unique about Titan's atmosphere?

Answer 28

Thick and nitrogen-rich, with methane instead of oxygen

Question 29

What causes Titans orange atmospheric haze?

Answer 29

May be due to organic molecules from photodissociation of methane Possible prebiotic chem?

Question 30

What are Titan's rivers made of? Why not water?

Answer 30

Methane and ethane Surface temperature ~90 K, far too cold for liquid water

Question 31

What are 2 possible habitats for life on Titan?

Answer 31

Surface liquid methane Subsurface liquid water ocean

Question 32

What is Titan's internal structure?

Answer 32

Organic rich surface Global subsurface ocean High-pressure ice layer Hydrous silicate core

Question 33

Where has atmospheric life been hypothesised in Solar System?

Answer 33

Upper atmospheres of Venus and gas giants

Question 34

What are the main challenges to atmospheric life on other planets?

Answer 34

Extreme radiation, pressure, acidity Lack of complex chemistry

Question 35

Is atmopsheric life currently considered likely?

Answer 35

No, remains speculative due to harsh conditions

Question 36

Why is atmospheric life valid enquiry?

Answer 36

Regarding thick and dynamic atmospheres

Question 37

What must be considered about conditions for emerging and sustaining life?

Answer 37

Conditions for origin of life may be very different from those required to sustain it for millions or billions of years

Question 38

Which locations are considered most promising for life (descending)?

Answer 38

Early Mars Martian aquifers Europa and Enceladus Other icy moons Ganymede/Callisto/Titan Present day Mars surface Giant planet/Venus atmospheres