Astrobio 1

Why Carbon (3)

1) makes polymers
2) does not go in rocks
3) becomes atmosphere

Why water

1) large liquid zone (H bonds)
2) volatile
3) abundant (h and O like to bond)

Drake Equation

N = R fp ne fl fl fc L

origin of life heterotrough

cold
eat organic ocean

Autotrophic orign

hydrothermal vent
methanogenesis

metabolism first

cycles of chemical reactions --> metabolism -> genetic molecules

RNA first

Genetic soup -> genetic molecule -> RNA -> DNA/protien

IW redox buffer

Iron Winstite
Fe + O2 --> FeO
Fe2+ --> Fe2+
very reduced
moon/mars

FMQ redox buffer

Faylite Magnetite Quartz
3Fe2SiO4 + O2 --> 2Fe3O4 + 3SiO2
Fe3+ --> Fe3+, Fe2+
middle reduced
Today's Earth

PPM redox buffer

pyrrhotite, Pyrite, Magnetite
6FeS + 2O2 --> 3FeS2 + Fe3O4
oxidized
crust/ocean/hydrothermal vents/early earth

DNA decay

Cytosine --> uracil
The nitrogen carbon bond gets hydrolysed
1/2 life 17,000 years

Nucleic bases

Cytosine
Uracil
Guanine
Thymine
Adenine

Purines

Adenine
Guanine
- 2 CN rings (4N)

Pyrimidine

Cytosine
Uracil
Thymine
(Benzene C6H6)
- 1 CN ring (2N)
(Cut the pyramid)

Purine Formation

(Adenine, Guanine)
spontaneous photochemical hydrolysis of cyanide
Adenine is 5 HCN's

System

Reduction of System

Ammonia

:NH3

alpha hydroxy acid

Cyano-hydrin

Formaldehyde

aldehyde

hydrocyanide

HCN

Aminoacid from striker (look like)

Could be Alanine or Glycine depending on the group

Alanine

amino acid with R group = CH3

Glycine

Amino acid with R group = H

Adenine Structure

A purine (DNA base) made of 5 CNs

Note: guanine is an extra hydration step

Methane

CH4

Pyrimidine synthesis

Harder to make than purine.
One theory is instead of Base + sugar makes base and sugar together.

Chemical Polymerization

Connecting molecules together chemically

Thermal Polymerization

(unlikely)
Drying out and readding water.
150 -180C exposures

Glycerol Nucleic Acid and Threose Nucleic Acid
Pros and Cons

GNA and TNA

- Simpler than RNA, but can be read by the same systems
- Decays faster (Unstable)

Peptide Nucleic Acid

PNA
- simple and easy to make
- but not sugar backbone (v different)

HCN polymer

- HCN is abundant and while spontaniously do it
- too abundant so it's hard to control

Chondrules

Small inclusions in undiffernchaited metiories

Chondrites

Account for 84% of meteorites
undifferentiated rock

Carbonaceous Chondrites

.5-5% carbon
2 - 10% H20

Pallasite Meteorite

Find in 1951. A stony iron, core mantel boundary.

Why is a methane atmosphere not sustainable

Methane photolyzes in UV on a 100 Myr timescale

Ribozome Protein/RNA

Need RNA more. RNA made Ribosome

Strings of Nucleic Bases are hard to make

Poly A is good, rest much worse. If add isomers only really short chains can be made

Uranium 238

Lead 206
4.5 Ga

Uranium 235

Lead 207
0.7 Ga

Stable Lead isotopes

Lead 204

Rubidium 87

48.6 Ga
Strontium 87

Reverse Gyrase

Hydrothermal supercoiling adaptation used in PCR

On Axis circulation

350-370C
24 Km^3/yr
Less and hotter
Near MOR

Off Axis Circulation

150 avg C
560 km^3/yr
More and Cooler
Far from MOR

Magnetite

Fe3O4

Iron Oxide

FeO

Fayalite

Fe2SiO4
Iron Olivine end member

Pyrrhotite

FeS

Pyrite

FeS2