Exobiology

Question 1

What is the Fermi Paradox?

Answer 1

the Fermi Paradox states that there should be a great many space-faring civilisations out there in the Universe – so why don’t we see them?

Question 2

What two questions must be asked to figure out if we are alone in the universe?

Answer 2

1) is there life elsewhere in the solar system?
- Mars, Europa, Titan, Enceladus
2) is there life elsewhere in the Universe
- Extrasolar planets.

Question 3

At present…

Answer 3

…n = 1

Question 4

What is The Drake Equation used to figure out?

Answer 4

no. of civilisations in Milky Way whose transmissions are detectable

Question 5

What is life?

Answer 5

1 – life has energy flow through it – it transforms energy into useable energy enabling it to:

move
respond to the environment
grow
reproduce

2 – life is characterised by the flow of information which enables it to:

move
respond to the environment
grow
reproduce

3 – characterised by bounded compartments in thermodynamic disequilibrium with the environment

Question 6

Life is a chemical system that:

Answer 6

1 - Is in disequilibrium with its surroundings

2 – Has the property of replicating itself

3 – Undergoes evolutionary change over time

Question 7

What two reactions are coupled in lifes chemical system?

Answer 7

Exergonic and endergonic reactions.

Question 8

What do exergonic reactions release?

Answer 8

generates ATP

Question 9

What do endergonic reactions use up?

Answer 9

uses ATP.

Question 10

What codon is always the start codon?

Answer 10

The start codon is always AUG, which also codes for methionine. This means all amino acid sequences will contain methionine as its first amino acid.

Question 11

What does the STOP codon do?

Answer 11

signals the end of translation

Question 12

How do you translate using the genetic code grid?

Answer 12

1) Scan for start codon (AUG)
2) Use grid to convert codon (3 bases) into amino acids until a stop codon is reached.

Question 13

What happens to codons that come before the START codon or after the STOP codon?

Answer 13

They do not get translated.

Question 14

Is life inevitable?

Answer 14

1) even with all of these conditions life is improbable and the origin of life is not likely

2) if these conditions are met life is likely to begin

Question 15

What has the rover opportunity found evidence of on Mars?

Answer 15

found evidence of past running water. Pebbles were found which were likely too large to have been carried by wind and resemble fossil stream beds from Earth.

outlines of what look like channels created by water flow which look very similar to dry river valleys on Earth

Question 16

Where on mars does water exist?

Answer 16

water exists on the Martian surface at the poles but it is in the form of ice mixed with dust and frozen CO2

there is also evidence of water ice in impact craters

Question 17

What happens during seasonal changes on Mars?

Answer 17

seasonal changes show channels forming, and widening before ‘drying up’ again.
one possible explanation is the presence of very salty water.

Question 18

What globules were found on Mars?

Answer 18

presence of 300 micrometere carbonaceous globules – suggested that they could only develop in water

Question 19

Were what found in the globules?

Answer 19

Within the globules were worm-like structure.

Question 20

What were detected due to the globules?

Answer 20

Large organic molecules.

Question 21

Does organic molecules = life?

Answer 21

now known to be alternative ways that the organic molecules could arise without the need for life

Question 22

What is magnetite used for on earth?

Answer 22

on earth some bacteria use magnetite as a means of determining their aspect in terms of the earth’s magnetic field (i.e. which way is down)

Question 23

Why is life beyond Mars unpromising?

Answer 23

solar flux is much lower so any energy from the sun at the orbit of Jupiter and Saturn is weak

Question 24

What may be under the surface of Europa?

Answer 24

possibility of a liquid ocean beneath the surface of Europa

Question 25

What are the lakes made of on Titan?

Answer 25

there are liquid lakes on titan but not of water

these are lakes of liquid hydrocarbons (ethane, methane)

Question 26

What does Titan atmosphere made up of?

Answer 26

thick atmosphere consists mostly of nitrogen and methane but also containing complex carbon compounds

suggests that plenty of organic material exists in the outer solar system

Question 27

How are we able to detect extrasolar planets?

Answer 27

using either changes in Doppler shift of stars or detecting changes in brightness due to transits of planets

refinement of these techniques has led to the discovery of earth-sized planets

Question 28

Why are the discovered earth sized planets uninhabitable?

Answer 28

the vast majority of earth-sized planets so far discovered have been close to their star

i.e. outside the habitable zone

Question 29

Where does the search for life bearing planets cocnentrate?

Answer 29

the search for extrasolar planets that are potentially life-bearing concentrates on those that surround their star’s habitable zone

Question 30

What does the size of the habitable zone depend on?

Answer 30

the size of the star itself.

Question 31

Where is Proxima Centauri b ?

Answer 31

A planet orbiting the nearest star which lies in the Goldilocks zone.

Question 32

What does life leave behind?

Answer 32

Chemical signatures. For instance the presence of molecular oxygen in the Earth’s atmosphere is due to photosynthesis (plants, algae, cyanobacteria). Likewise the presence of methane (CH4) is due to its production by Archaeans. Currently this is difficult but with better telescopes and an increased number of known exoplanets this may be possible

Question 33

What happens when oxygen molecules appear in the atmosphere in significant quanitities?

Answer 33

once oxygen molecules (O2) appear in the atmosphere in significant quantities we get conversion of a proportion of these molecules into ozone (O3)

Question 34

What does ozone do?

Answer 34

the important thing about the presence of ozone is that it blocks short wave UV radiation which damages DNA

Question 35

Why is the ozone layer described as dynamic?

Answer 35

the ozone layer is dynamic – ozone is continually being built up and broken down by the action of UV radiation

Question 36

What suggestions have been made as to why life developed on earth?

Answer 36

1) the presence of Jupiter in the outer solar system
- acts as a gravitational attractant for comets, meteorites and asteroids (e.g. Comet Shoemaker-Levy)

2) the presence of the Moon
- the moon has a stabilising effect on the Earth’s rotation. It is by far the biggest satellite in comparison to it’s mother planet