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Astrobiology > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

General features of carbon that make it a good building block for life

A

small, can form four bonds, chiral, gaseous waste products, abundant, found in asteroids/meteorites, can be used in polar solvent

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2
Q

Bond strength in carbon compounds

A

CC bond is highest energy of all non-metal elements, bond strength between CC and CN are similar

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3
Q

Most reduced and oxidized form of carbon

A

Most reduced is methane (CH4), most oxidized is carbon dioxide (CO2)

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4
Q

Most reduced and oxidized form of silicon

A

Most reduced is silane (SiH4), most oxidized is silicate (SiO4)

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5
Q

Major disadvantages of silicon

A

Cannot form multiple (pi) bonds, silicates are very unreactive and silane is very unstable, needs non-polar solvent

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6
Q

Silicon’s use in life

A

Plant cell walls and diatom shells, mix of silicon and carbon may be used on planets with low carbon levels

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7
Q

Need for a liquid solvent

A

Mobility, dissolves some compounds and allows them to react while stabilizing others, temperature buffer

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8
Q

Advantages of a water solvent

A

Dissolve salts and hydrophilic molcules, strong dipole moment and hydrogen bonds, high specific heat, high enthalpy of evaporation, high surface tension?

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9
Q

Advantages of ammonia solvent

A

Common with some carbon-like properties, has a dipole moment and hydrogen bonding

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10
Q

Characteristic of life in a methane solvent

A

Reversed cell membranes

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11
Q

Advantages of subsurface life

A

Protection from temperature swings, no need for an atmosphere, solvents and energy sources may be present, increase in pressure and temperature with depth maintains liquid water

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12
Q

Metabolism and energy sources of subsurface life

A

Auto-chemotrophs use energy in inorganic chemical compounds, radioactive material to provide heat

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13
Q

Evolution in the subsurface

A

Stable environment leads to stabilizing selection and low diversity

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14
Q

Atmosphere-related risks to life

A

Cosmic and UV radiation, temperature swings, extreme weather, meteorite impacts

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15
Q

Characteristics of a planetary atmosphere that would be capable of supporting floating life

A

Dense, stable temperatures, liquid solvent, some surfaces, source of energy

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16
Q

Characteristics of life capable of surviving in a planetary atmosphere

A

Protection from radiation and free radicals, small, density of surroundings, possibly inclusions of oil or gas or special appendages

17
Q

Characteristics of life in space

A

Low temperature, no pressure, cosmic/UV radiation, greatly reduced rates of metabolism, desiccation or formation of protective envelope layers

18
Q

How habitable zones are detemined

A

Type and distance of star

19
Q

Ranking of stars by heat (3)

A

A (hottest) -> G -> M (cooler, more common, our star)

20
Q

Current number of exoplanets

A

3925+

21
Q

Length of the stable period of a star of a certain size

A

Small stars are more abundant and last longer

22
Q

Galaxy-level habitability

A

Presence of rocky planets, heavy elements like carbon/nitrogen/oxygen/metals, few supernovae, low radiation, moderate gravity, suitable host stars

23
Q

Anthropic Principle

A

Our universe is unique and created the conditions that allow for life to occur and evolve

24
Q

Defn of biosignatures

A

Indications of life, signatures that were produced by a living organisms or living organisms themselves

25
Q

Examples of biosignatures

A

Complex molecules like chlorophyll, phospholipids, some proteins; macromolecules bigger than 200 daltons, preference for chirality, biogenic eat

26
Q

Red edge effect

A

Spectral signature of oxygenic photosynthesizing organisms

27
Q

Defn of geosignatures

A

Evidence of life in the geology of an enviroment

28
Q

Geosignatures of life on Earth

A

High levels of oxygen, methane, and hydrogen in an atmosphere that is out of equilibrium

29
Q

Defn of geoindicators

A

Indications that life could be possible

30
Q

Examples of geoindicators

A

Compounds produced in the presence of water, presence of an atmosphere, thermal gradients, chemical disequilibrium, internal differentiation, nutrient recycling, energy sources, liquid medium

31
Q

Signatures of intelligent life

A

Structures, signals

Problem: evidence of a civilization may become less apparent as they develop

32
Q

SETI’s mission

A

Search for ExtraTerrestrial Intelligence by looking for moderately random radio signals

very regular is pulsar, very random is background radiation

33
Q

People: Dr. Benison

A

Lady that is friends with Dr. Mormile, guest lecturer

34
Q

People: Witman

A

The potential biomass of the subsurface may be greater than the biomass of the surface

35
Q

People: T. Onstott

A

Found life in South African mines that were adapted to the high heat, pressure, and salt concentrations like microscopic roundworms and fungi

36
Q

People: Dr. Deamer

A

Phospholipids as biosignatures

37
Q

People: Percival Lowell

A

Claimed canals on Mars were a sign of life

Astrobiology (5 decks)

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