Transcript The Nature of Science

The Search for Life in the
Solar System
HNRS 228 w/Geller
Reviewing Chapter 6
What’s Up
Review Requirements for Life
Elements, Energy, Water, etc.
Searching for Life in Our Solar System
Remote Sensing, Robotics, Human
Exploration, etc.
Biological Tour of the Solar System
Terrestrial Planets, Jovian Planets, other
bodies
Environment for Life?
Source of elements to build
cells
Source of energy
Medium for transporting
molecules
H2O and CO2 Phase Diagrams
(IMPORTANT environmental consideration)
Exploring the Solar System
Observations from Earth
ground or orbit based
Robotic spacecraft
flybys, orbitals
landers
Human exploration
Planet Generalization
Terrestrial planets are closer to sun
Mercury
Venus
Earth
Mars
Jovian planets furthest from sun
Jupiter
Saturn
Uranus
Neptune
Planetary Summary
Major
Constituents
Mass
(Earth=1)
Density
(g/cm3)
Mercury
Venus
Earth
Mars
0.06
0.82
1.00
0.11
5.4
5.2
5.5
3.9
Jupiter
Saturn
318
95
1.3
0.7
H, He
H, He
Uranus
Neptune
14
17
1.3
1.7
Ices, H, He
Ices, H, He
Planet
Rock,
Rock,
Rock,
Rock,
Iron
Iron
Iron
Iron
Some Conclusions
Planets formed at same time as sun
Planetary and satellite/ring systems are
similar to remnants of dusty disks such as
that seen about stars being born (e.g. T
Tauri stars)
Planet composition dependent upon
where it formed in solar system
Nebular Condensation Model
Most remnant heat from collapse retained
near center
After sun ignites, remaining dust reaches
an equilibrium temperature
Different densities of the planets are
explained by condensation temperatures
Nebular dust temperature increases to
center of nebula
Nebular Condensation Physics
Energy absorbed per unit area from sun =
energy emitted as thermal radiator
Solar Flux = Lum (Sun) / 4 x distance2
Flux emitted = constant x T4 [Stefan-Boltzmann]
Concluding from above yields
T = constant / distance0.5
Nebular Condensation
Chemistry
Molecule
H2
H2O
CH4
NH3
FeSO4
SiO4
Freezing Point Distance from
Center
>100 AU
10 K
>10 AU
273 K
>35 AU
35 K
>8 AU
190 K
>1 AU
700 K
>0.5 AU
1000 K
Nebular Condensation
Summary
Solid Particles collide, stick together, sink
toward center
Terrestrials -> rocky
Jovians -> rocky core + ices + light gases
Coolest, most massive collect H and He
More collisions -> heating and
differentiating of interior
Remnants flushed by solar wind
Evolution of atmospheres
Biological Tour of the Solar
System
Consider problems posed for life on each
of the following
Moon
Mercury
Venus
(Mars will be discussed in Chapter 7)
Jovian Planets
Other Moons
Asteroid, comets and other debris
Some References
 The Search for Life (especially in the solar system)
 http://www.scibridge.sdsu.edu/coursemats/introsci/Solarsys/lecture.html
http://www.resa.net/nasa/ocean_hydrothermal.htm
http://www.nationalacademies.org/ssb/lifeoriginsmenu.htm
http://www.phy.syr.edu/courses/modules/SETI/where.html
 Books
Life on Other Worlds (Dick)
Cradle of Life (Schopf)
Life Everywhere (Darling)
Life on Other Worlds and How to Find It (Clark)