1. Life in the Solar System
Where have all the Martians gone?

2. What is Life?
While we can list characteristics of living organisms (and the book does), many non-living systems will exhibit many, if not all, of these characteristics
Is life about reproduction? Is a sterile human alive?
Maybe it's about arising from reproduction? If we took a copy of you by copying all the atoms of your body, would the copy be alive?
The bottom line is: We have no useful definition of life.
This is a seemingly simple question to ask, but a difficult one to answer. Different definitions may be possible, from the strictly scientific ones applied by researches in the biosciences to those of philosophers and, of course, including the ideas expressed in the scriptures of the world's religions.

3. Types of Life on Earth

4. Origin of Life on Earth

5. Life in Extreme Environments: Extremophiles

6. What do we know? We don’t know exactly what life is.
We don’t know exactly how life began.
What do we know?
Where does life live? Almost everywhere on Earth.
What are the requirements for life to exist and thrive?
This isn’t too bad. After all, to find life, we first need to know where to look.
Step 1: Decide what life needs and identify the places that meet these requirements so we know where to look.

7. What is needed for life? The presence of liquid water
The elements needed for metabolism and reproduction (biogenic elements)
A biologically useful source of energy
Suitable environmental conditions

8. Limiting factor
Biogenic elements (CHONSP…) are all over the Solar System (even in asteroids and meteorites)
Sources of energy:
Sunlight (photosynthesis)
Many chemical reactions generated by heat
Others?
Liquid water requires temperatures of K (0-100 C).
Environment
Mainly, no harmful UV rays
Bottom Line: Follow the water

9. Follow the Water What planetary bodies have liquid water?
Water needs warmth ( K), so heat is necessary.
Where does heat come from in the Solar System?
Internal heat
Solar heat
Tidal heat
That lead us to…
Earth (duh)
Mars
Europa

10. Mars

11. Water on Mars

12. Viking mission
The biggest mission to mars were the Viking (1976) missions (1&2), each had a lander and an orbiter. It was decided to send experiments on the lander to look for life. Together these instruments, dubbed the biology experiment, searched for the presence of Martian organisms by looking for metabolic products. Three distinct instruments (pyrolytic release (PR), labeled release (LR), and gas exchange (GEX)) incubated samples of the Martian surface under a number of different environmental conditions. All results were negative. Most scientists believed there was no chance of life on Mars.
In some instances a sample was heat sterilized and reprocessed as a control. The PR, or carbon assimilation, instrument sought to detect the photosynthetic or chemical fixation of CO2 or CO containing C-14. The samples were incubated for several days in the presence of the radioactive gas mixture, some samples with simulated sunlight and some without. Next, each sample was heated to 120 C to remove unreacted CO2 and CO. The soil was pyrolized at 650 C and any organic products were collected in an organic vapor trap (OVT). Finally, the trap was heated to combust the organic material to CO2 and any evolved radioactive gas was measured. The LR experiment sought to detect metabolic processes through radiorespirometry. Liquid nutrients labeled with radioactive carbon were added to the samples and the atmosphere above was continuously monitored to detect any radioactive gases released from these nonvolatile nutrients. The GEX measured the production and/or uptake of CO2, N2, CH4, H2, and O2 during incubation of a soil sample. The sample was sealed and purged by He, then a mixture of He, Kr, and CO2 was introduced as an initial incubation atmosphere. After the addition of a selected quantity of a nutrient solution (saturated with the diagnostic gas, neon), the sample was incubated. At certain intervals, samples of the atmosphere were removed and analyzed by a gas chromatograph with a thermal conductivity detector.

13. ALH84001
In 1996, scientists made a startling announcement, life in a Martian meteorite. Actually, they announced that they found evidence consistent with primitive life on mars, not “proof”. They had 3 major pieces of evidence:
Shapes that resemble bacteria, as shown here.
These images taken with scanning electron microscopy revealed elliptical, ropelike and tubular structures that could be interpreted as possible fossilized bacteria.
2. Microscopic mineral grains similar in size and shape to some produced by bacteria on Earth.
3. Polycyclic Aromatic Hydrocarbons (PAHs), organic molecules containing multiple connected rings of carbon atoms.
Any of these 3 things can have a non-biological source. However, when considered collectively, they are suggestive of ancient Martian life.

14. Missions to Mars 2001 Mars Odyssey 2003 Mars Exploration Rovers
2005 Mars Reconnaissance Orbiter
Beyond 2007
Smart Lander and Long-range Rover – as early as 2007
Sample Return – as early as 2011, likely 2014

15. Europa

16. Missions to Europa?

17. Questions
How important will it be if we discovered other life in our Solar System?
How would we know it wasn’t life from Earth?
Is NASA right in concentrating much of its resources on searching for life? (ie., is Europa more important than Io?)