HOW DO WE SEARCH FOR

LIFE IN THE UNIVERSE?

The Search for Life

Robotic Emissaries

Remote Detection

Robotic Emissaries Pioneer 10 & 11

(1972/3) Voyager 1 & 2 (1977) Traveling 23,000 –

39,000 mi/hr Essentially no

onboard guidance system

Random encounter with a stellar system in 1019 years

The Search for Life on Mars

Giovanni Schiaparelli (1877)

Percival Lowell (1894 – 1916)

The “Face” on Mars

Martian Meteorites

Nodules of carbonate

Crystals of iron pyrite

PAH’s (organic material)

Fossil bacteria?

Life on Mars?

History of thicker atmosphere

History of water

Probable Earth-like geologic history

Viking I & II(1976)

Viking Biology Experiments

No organic compounds found in soil

Atmosphere: very small amounts of methane and nitrogen

Biological experiments based on Earth-like life (is this realistic?)

Three biological experiments performed on Martian soil

Viking Biology ExperimentsGEX: Gas Exchange – “feed” the soil

Gas chromatograph measured composition of gasses in chamber before/after feeding

LR: Labeled Release – look for respiration

Look for radioactive carbon in gaseous form.

PR: Pyrolitic Release – “Roast” the soil

look for radioactive carbon in atmosphere.

Viking Biological ExperimentsResults:

All 3 gave positive results!

BUT! All positive results can be produced by non-biological chemical reactions.

Pathfinder(1997)

Europa OceanExplorer (2008?) Arrive 2012

The Search for Life:Remote Detection

If it existed we currently couldn’t detect itWhy?

We can detect the presence of extrasolar planets

We cannot image the planets themselves

Light from host star is too overwhelming

What technology is necessary?

Interferometry for high resolution

Space based or ground based

Nulling technology to reduce glare of host star

Nulling Technology

What Do We Look For?

Image extrasolar planets (if not planets maybe their moons)

Look for chemical signatures for life

Make detailed images of extrasolar planets

Planetary Imaging

Interferometric Projects (ground based):

Palomar Testbed Interferometer

Keck Interferometric Array

CHARA (Mt. Wilson) Others…

Space Interferometry Mission(SIM, NASA) Lower mass limit of 5 earth

masses detection out to 10 parsecs (33 LY)

Lower mass limit of 1 earth mass detection out to 16 LY

Terrestrial Planet Finder (TPF, NASA) Detection of 1 earth-mass

planets out to a distance of 50 light years

DARWIN (ESA)

Planetary Imager (PI, NASA)

6000 km baseline

8-m telescopes

Last Week: Chapter 16: 401 – 409 Questions: 5, 6, 7

This Week: Chapter 14: 335 – 357 Questions: 1-7, 11