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Cosmos > Life in the Cosmos > Flashcards

Life in the Cosmos Flashcards

1
Q

All chemical elements except from hydrogen, helium and lithium were formed by what?

A

Nucleosynthesis in the cores of previous generations of stars and ejected into supernova

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2
Q

Where does star and planet formation take place?

A

Molecular clouds

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3
Q

3 steps of protoplanet formation

A
  1. Condensation into dust molecules
  2. Accretion into planetesimals
  3. Coalescence into protoplanets.
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4
Q

First Earth Area

A

Hadean Era

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5
Q

What was earth like during the Hadean Era

A

Hot, volcanic and under constant bombardment by meteorites/ planetesimals

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6
Q

Atmosphere in the Hadean Era

A

Mainly N2, CO2, H2O, CH4, H2

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7
Q

What era were the first ambiguous signs of life?

A

Archean Era

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8
Q

What is life on earth based on?

A

Proteins and amino acids

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9
Q

Where have amino acids been detected?

A

Space, meteorites

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10
Q

What experiment have amino acids been formed in

A

Miller-Urey

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11
Q

What is outgassing?

A

Heating and melting of the earths surface drove volatile gases into the atmosphere.

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12
Q

What was the Hadean atmosphere rich in?

A

CO2

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13
Q

What did the Hadean CO2 rich atmosphere cause?

A

Greenhouse effect

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14
Q

How did CO2 leave earths atmosphere?

A

Mainly precipitated out,
Some was returned to atmosphere by plate tectonics

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15
Q

How did the fraction of oxygen in Earths atmosphere start to rise?

A

Oxygen is produced by photosynthesising organisms

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16
Q

Increase in oxygen conc. marks the start of what era?

A

Proterozoic era

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17
Q

What is the Pre-Cambrian Era made up of?

A

Archaean Aeon and Proterozoic Aeon

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18
Q

What does the Pre-Cambrian Era constitute?

A

The vast majority of the time for which life has existed on Earth

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19
Q

Why is oxygen a better element for us to have in our atmosphere?

A

Its much more reactive than CO2, easier for living organisms to extract energy using aerobic reactions than anaerobic

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20
Q

What is ozone?

A

A form of oxygen that protects life on earth by screening out the suns UV radiation

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21
Q

What was the Cambrian Explosion?

A

Huge growth in the number and variety of multi-cellular creaturesW

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22
Q

When was the Cambrian Explosion?

A

540 Million Years ago

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23
Q

Factors for the growth of diversity?

A

Oxygen, Genetic complexity, absence of predators

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24
Q

What is the geological year

A

Representation of the development of life by imagining the lifetime of the Earth compressed into a single year.

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25
Q

What is the K-Pg extinction?

A

The extinction that killed the dinosaurs

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26
Q

What do scientists think the K-Pg extinction was caused by?

A

Impact of a 10 km meteorite

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27
Q

Evidence for the K-Pg extinction being caused by a large meteorite?

A

Large crater of the right age, and a high iridium abundance at the K-Pg boundary, consistent with that found in meteorite material

28
Q

Fossil record provides evidence for how many mass extinctions?

A

20

29
Q

Which events have a much higher probability of occuring than large, energetic events

A

Small, less energetic events

30
Q

The bigger an impacting meteorite, the bigger the ______

A

BANG

31
Q

Do meteorites always leave a crater?

A

No not always

32
Q

If a meteorite doesnt leave a crater, can it still cause damage?

A

Yes - considerable amounts of damage

33
Q

What was the Tunguska airburst?

A

A meterorite or comet exploded in the earths atmosphere, about 8 km above the ground

34
Q

How does an explosion above the ground happen?

A

Rapid heating due to friction with molecules in the atmosphere

35
Q

Effects of the Tunguska airburst

A
  1. Shock wave flattened a 2000 km area
  2. Forest fires that burned for weeks
  3. Ash and debris sent to atmosphere, carried around the world m
36
Q

When did the most extreme extinction occur?

A

Between the Permian and Triassic Eras

37
Q

What percentage of organisms were lost in the Permian-Triassic extinction?

A

90% of ocean species

70% of all land vertebrate species

38
Q

What is life defined as?

A

A material system which as the ability to self-replicate, mutate and evolve in response to changing environments

39
Q

What must a system do in terms of energy and raw materials to repair itself?

A

Must be able to draw energy and process raw materials to repair itself.

40
Q

What are optimal conditions

A

Conditions we would look for to maximise our chances of finding extra-terrestrial life

41
Q

Carbon forms bonds with itself, creating _____ bonds

A

Covalent

42
Q

Are carbon-carbon covalent bonds strong?

A

Yes, take a lot of energy to break therefore can withstand high levels of heat.

43
Q

Where does carbon place in terms of how abundant it is in the universe?

A

4th most abundant element in the universe

44
Q

Why is carbon such a succesful element?

A

Forms a greater variety of chemical compounds than any other element, Has the greatest ability of any element to bond with itself, can form long chain molecules that encode information

45
Q

Why is silicon not as likely to be the basis of alien life than carbon?

A

Bonds arent as strong
Cant form double bonds
Silicon more likely to bond with oxygen into a small molecule than form long chain molecules

46
Q

What is a deep-sea smoker?

A

Deep sea geothermal which is expelling extremely hot mineral rich water from within the Earths Crust.

47
Q

What element were the ecosystems found around deep sea-smokers based on

A

Sulphur

48
Q

What word describes bacterial colonies that live around the deep sea smokers and metabolise sulphur compounds?

A

Anaerobic

49
Q

When colonies live deep down in the sea with no sunlight, where do they get energy from?

A

Sulphur chemistry

50
Q

Where do many scientists believe life orginated?

A

Deep sea smokers, due to chemical reactions in the mineral-rich waters.

51
Q

What factors make up the overall environment of a planet?

A

Temperature, mass, age and atmospheric composition

52
Q

What are the compounds that if present are hopeful signs of life?

A

Water, oxygen and carbon

53
Q

What other conditions are necessary to protect life?

A

Protection from radiation, Moderate and stable temperatures, atmospheric recycling mechanisms

54
Q

What is the electromagnetic spectrum?

A

A continuous spectrum of energy-carrying waves of electric and magnetic fields

55
Q

The shorter the wavelength, …

A

The greater the energy

56
Q

Is short or long wavelength radiation more dangerous?

A

Short

57
Q

Why are shorter wavelengths more dangerous?

A

They have enough energy to break bonds in carbon chemistry

58
Q

How are we (carbon life) protected from radiation?

A

Ozone layer

59
Q

For liquid water to survive on a planetary surface, the planet must lie within the _______

A

Habitable Zone

60
Q

What is the habitable zone?

A

The range in distance from the central star in which water can exist as a solid

61
Q

What happens if a planet is too close to its central star?

A

It will recieve a lot of heat radiation, overheating. Water will evaporate.

62
Q

If planet lies outside of habitable zone?

A

Planet too cold, water will freeze.

63
Q

What makes Venus and Mars interesting candidates for the search of extra-terrestrial life?

A

They are both very near the edge of the habitable.

64
Q

A star hotter than ours will have a more _____ zone

A

Distant

65
Q

A star cooler than ours will have a _____ zone

A

Closer

66
Q
A

Cosmos (3 decks)

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