Transcript The Search for Extraterrestrial Life

The Search for exoplanets and
Extraterrestrial Life
• http://www.jpl.nasa.gov/news/news.cfm?releas
e=2011-373
• Kepler mission
• Are we alone?
http://www.jpl.nasa.gov/videos/phoenix/phx20070724/phx-20070723-1280.m4v
• How did life start on Earth?
• Where can we find potentially life supporting
conditions in our solar system?
• SETI
• Video
• Habitable zone
Kepler mission
• Kepler mission is
looking for earth like
planets.
http://www.youtube.com
/watch?v=q1qqJ3AwaB
k
CURRENT PLANET COUNT: 687
stars with planets: 474
Earthlike planets: 0 ?
As of 12/5/11
http://planetquest.jpl.nasa.gov/missions/
missions_chart6.html
http://www.youtube.com/watch?v=q1qqJ3AwaBk
1. What is habitable zone?
2. What is the primary science goal of
Kepler mission?
3. How is that goal achieved?
4. How big is Kepler’s field of view?
5. How does Kepler see? (What is Kepler’s
sensors?)
6. In What direction (constellation) do
Kepler look at?
7. What is photometry?
NASA's Kepler Confirms Its First
Planet In Habitable Zone
Are we alone?
Planet Quest : NASA JPL
http://planetquest.jpl.nasa.gov/science
How did life start on earth?
• An Updated Miller-Urey
Experiment
• exposed a mixture of gaseous
hydrogen, ammonia, methane and
water to an electrical arc for a
week. At the end of the
experiment, the reaction chamber
was coated with a reddish-brown
rich in amino acids and other
compounds essential to life.
• Chemosynthesis : evolved here &
panspermia: evolved elsewhere
Extremophiles
• thermophiles: exist in hot environments
Thermus aquaticus, discovered in hot springs in Yellowstone
National Park (70+oC).
Pyrolobus fumarii, grows on the walls of black smokers (113oC).
• acidophiles: exist in acidic environments
Sulfolobus acidocaldarius inhabits hot (85C) and sulphurous thermal
springs (in Yellowstone national park)
• psychrophiles: exist in cold
environments
Polaromonas vacuolata, which lives in antarctic sea ice.
Ice worms fround at sea floor @ 0oC.
• halophiles: exist in salty environments
These cyanobacteria survive until @ Shark bay, which
is far too salty for any predators to exist in it.
The Search for Life on Mars
• It appears that Mars at
some point in its history
was very much wetter and
warmer than it is today
• Scientists have been
looking for life there
• The Viking landers (1970’s)
tested for the presence of
average distance of 1.52 AU from the Sun
microbes, but returned
rotation period = 24 hours 37 minutes
inconclusive results
orbital period is 687 days.
rotation axis is tilted at 25 degrees: seasons • We are still looking!
Mars's radius ~ half of Earth's, mass is only
10%
Remember Phoenix Lander?
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Environment
CO2 thin atmosphere
Erosion due to flash floods
Erosion due to sustained water flow,
Features around the boundaries of the northern lowlands
which may be the shores of an early liquid-water ocean
or group of lakes. This would explain why the lowlands
appear so smooth.
• Signatures of minerals which can only form in the
presence of liquid water, such as sedimentary deposits of
crystalline haematite(iron ore).
evidence for ancient Martian life:
* tiny, elongated tubular structures around 100
nanometres long, which resemble fossilized microbial
life.
* pure crystals of iron sulphide and magnetite, which
are rarely found together, but can be formed by certain
types of bacteria.
* polycyclic aromatic hydrocarbons (PAHs), organic
molecules which result from the decay of
microorganisms.
Europa of Jupiter
http://www.jpl.nasa.gov/video/index.cfm?all_videos&id=649
orbits Jupiter: every3.5 days @ d= 670,000km
density of about 60%: mostly rocky materials
radius of 1,500km: surface gravity=0.14 Earth’s.
Europa's frozen surface with ocean of liquid
water (tidal heating)
Europa most likely has organic compounds containing
oxygen, carbon, sulphur, hydrogen and nitrogen.
Potential life near geothermal underwater vents
investigation of Europa shall include:
cryobot, to melt through the surface ice,
and a hydrobot, to explore the
underlying ocean and look for signs of
life.
Possible Europa
Life
Cracks with freshly
frozen water and
long faults make it
clear that Europa's
ice is no more than
100 miles thick.
The ocean below
surges up through
cracks with tidal
frequency, water
that is likely at 32°
Fahrenheit — just
at freezing — a
tolerable
temperature for
life.
Titan of Saturn
http://saturn.jpl.nasa.gov/multimedia/flash/Tit
an/index.html
- Titan is the largest of Saturn's satellites
significant atmosphere (nitrogen, ammonia,
methane and hydrocarbons such as ethane and
propane. similar to smog on earth!)
- Orbit Saturn every 20.3 days @ d=1.2 million km
- mixture of ices (methane & ethane) and rocky
compounds, diameter ~5,000 km, (larger than
Mercury)
- Surface temperatures ~ -180C
The present-day prospects for life on Titan
are poor, due to the low temperatures.
Titan’s atmosphere and surface are rich in
the prebiotic compounds which eventually
produced life on Earth.
SETI
• SETI: Search for Extra-Terrestrial
Intelligence
• Listens for electromagnetic evidence
of intelligence elsewhere in the
universe
• To date, evidence has been sparse.
Water hole
This graph shows the background
noise level from the sky at various
radio and microwave frequencies.
The so-called water hole is a range of
radio frequencies from about 103 to
104 megahertz (MHz) in which there
is little noise and little absorption by
the Earth’s atmosphere. Some
scientists suggest that this noise-free
region would be well suited for
interstellar communication. Within
the water hole itself, the principal
source of noise is the afterglow of
the Big Bang, called the cosmic
microwave background. To put this
graph in perspective, a frequency of
100 MHz corresponds to “100” on a
FM radio, and 103 MHz is a
frequency used for various types of
radar.
Since 1995 the SETI Institute in California has been carrying out Project Phoenix. When
complete, this project will have surveyed a thousand Sunlike stars within 200 light-years at
millions of radio frequencies. At Harvard University, BETA (the Billion-channel ExtraTerrestrial
Assay) is scanning the sky at even more individual frequencies within the water hole.
Drake equation
N = R* fp ne fl fi fc L
• N = number of technologically advanced civilizations
in the Galaxy whose messages we might be able to detect
• R* = the rate at which solar-type stars form in the Galaxy(=1)
• fp = the fraction of stars that have planets (=1)
• ne = the number of planets per solar system that are Earthlike
(that is, suitable for life) (~0.25)
• fl = the fraction of those Earthlike planets on which life
actually arises (=1)
• fi = the fraction of those life-forms that evolve into intelligent
species (=1)
• fc = the fraction of those species that develop adequate
technology and then choose to send messages out into space
(=1)
• L = the lifetime of a technologically advanced civilization
(=200 years?)
The Drake Equation : Putting it all
together
* R* is well-known
* fp is reasonably well-known
* ne is uncertain
* fl is highly uncertain
* fi is extremely uncertain
* fc is extremely uncertain
* L is extremely uncertain
Based on the above estimates of each term in the Drake
Equation, the expected number N of civilizations in the Galaxy
which are currently producing electromagnetic signals is 50.
Taking the radius of the galactic disk as 15 kiloparsecs, and
assuming that stars are spread evenly throughout this disk,
then on average we can expect to find one communicating
civilization in each 14 square kiloparsecs of the disk (i.e., in
each 120 by 120 parsec region, or about 400 light year).