Starry Monday at Otterbein : Starry Monday at Otterbein
Astronomy Lecture Series
-every first Monday of the month-
March 5, 2007
Dr. Uwe Trittmann Welcome to
Today’s Topics : Today’s Topics Life in the Universe
The Night Sky in March
On the Web : On the Web
To learn more about astronomy and physics at Otterbein, please visit
http://www.otterbein.edu/dept/PHYS/weitkamp.asp (Observatory)
http://www.otterbein.edu/dept/PHYS/ (Physics Dept.)
Life in the Universe – Some Questions : Life in the Universe – Some Questions What is life?
What are the prerequisites for life?
Where can it exit?
How can we find it?
What is Life? : What is Life? Common features:
reacts to environment
metabolism (draws energy from environment)
reproduction
Life on Earth
Based on complex chemistry of carbon
Fundamental building blocks are amino acids
Small compounds containing C, O, H, N, S
It seems unlikely that life can be based on significantly different chemistry
The “evolution” towards life : The “evolution” towards life Evolution is not just biological evolution!
Quasars : Quasars Cosmic Evolution:
the universe gets organized
Cosmic Evolution : Cosmic Evolution
The prerequisites for life : The prerequisites for life Need the right “stuff”
Liquid water
Atmosphere is a plus!
Stable energy source (star)
Hot stars die fast!
Right temperature range
…
Habitable Zones : Habitable Zones
1 A.U. = average Earth-Sun distance
Major Epochs of Life Development : Major Epochs of Life Development Cosmic evolution of biogenic compounds
prebiotic evolution
early evolution of life
development of advanced life
“The stuff”: Biogenic Elements : “The stuff”: Biogenic Elements Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Sulfur
all but hydrogen come from exploded stars!
Cosmic evolution of biogenic compounds : Cosmic evolution of biogenic compounds nucleo-synthesis and ejection into the interstellar medium
chemical evolution in the interstellar medium
protostellar collapse
chemical evolution in the solar nebula
growth of planetesimals from dust
6) accumulation and thermal processing of planetoids
From “dead stuff” to life : From “dead stuff” to life Organic material
Protocell
Last common ancestor
Eukarya Procarya Archea
“Creating life”: Miller-Urey Experiment : “Creating life”: Miller-Urey Experiment Idea: build complex biochemical molecules from simple chemicals plus electric discharges
Simulates early Earth conditions:
lightning
primordial oceans
Successful experiment!
Life in hostile environments : Life in hostile environments “One current theory is that life originated deep beneath the surface of the ocean at deep sea hydrothermal vents. These hydrothermal vents were first discovered in 1979. Soon after, scientists made an exciting discovery. These vents release hot gaseous substances from the center of the earth at temperatures in excess of 572 °F.”
Life from Meteors: Panspermia : Life from Meteors: Panspermia “In the early twentieth century, a Swedish chemist named Svente Arrhenius developed a theory called panspermia. Arrhenius' theory accounted for life's origins by simply stating that life did not originate on the Earth, but originated elsewhere in the universe. He believed that cellular life reached the Earth hiding inside a meteor which hit the Earth long ago. Newly uncovered evidence suggests that this might be possible.”
Life in frozen oceans? : Life in frozen oceans? “Three billion years ago, the Sun which lights our solar system was thirty percent less luminous than it is today. Mant people believe that if the Earth's atmosphere was the same then as it is today, the oceans would be frozen. But recently, Jeffrey Bada of the Scripps Institution of Oceanography has proposed that the oceans would not completely freeze. Instead, he calculates that only the top 300 meters of the ocean would freeze over.“
Evidence for Panspermia: Meteor ALH84001 : Evidence for Panspermia: Meteor ALH84001 “In 1996, a meteor was found in Allan Hills, Antarctica. Upon examination, it was discovered that this meteor, which is 4.5 billion years old, fell to the earth 13,000 years ago, and possibly contained evidence of life on Mars. Inside the meteor, along tiny cracks, scientists found evidence of what many believe to be ancient bacteria.“
Reverse Panspermia : Reverse Panspermia There is life on Earth, maybe it was “exported” to other parts of the solar system (Mars, Europa, Titan)
See Sky & Telescope January 2007: Is Earth Contagious?
Is Life on Earth… : Is Life on Earth… a) A miracle?
b) An accident?
c) More-or-less inevitable given the laws of physics and chemistry, and suitable conditions?
Principle of Mediocrity: There’s nothing special about the astronomical, geological, physical and chemical circumstances on Earth; most likely nothing special about biology either
Life in the Solar System? : Life in the Solar System? Planets
Moons
“The face on Mars”
Life cares about (Atmospheric) History : Life cares about (Atmospheric) History Primary atmosphere: hydrogen, helium, methane, ammonia
Too light to “stick” to a planet unless it’s very big Jovian Planets
Secondary atmosphere: water, CO2, SO2, …
Outgassed from planet interiors, a result of volcanic activity
Atmospheric Histories : Atmospheric Histories Earth: Temperature allowed water to liquify; CO2 dissolved in oceans; early life contributes oxygen
Venus: run-away Greenhouse effect; CO2 could not be absorbed by water, rocks because of higher temperature closer to sun
Mars: CO2 dissolves in liquid water; temperature drops below freezing point (reverse greenhouse effect!); permafrost forms with CO2 locked away
Hothouse Venus: 850 °F : Hothouse Venus: 850 °F
Water on Mars? : Water on Mars? Mars Louisiana
Life on Mars? : Life on Mars? Giovanni Schiaparelli (1877) – observed “canali” (channels) on Martian surface
Interpreted by Percival Lowell (and others) as irrigation canals – a sign of intelligent life
Lowell built a large observatory near Flagstaff, AZ
(Incidentally, this enabled C. Tombaugh to find Pluto in 1930)
Speculation became more and more fanciful
A desert world with a planet-wide irrigation system to carry water from the polar ice caps?
Lots of sci-fi, including H.G. Wells, Bradbury, …
All an illusion! There are no canals…
Viking Lander Experiments (1976) : Viking Lander Experiments (1976) Search for bacteria-like forms of life
Results inconclusive at best
Jupiter’s Galilean Moons : Jupiter’s Galilean Moons
Europa : Europa Europa might have liquid water oceans under the surface Life?
Titan : Titan Titan is the only moon in the solar system known to have an atmosphere
Life on Titan would be
methane-based
Is There Life Elsewhere in the Solar System? : Is There Life Elsewhere in the Solar System? Moon and Mercury lack liquid water, atmosphere
Venus is too hot, lacks water
Titan has methane/ammonia/nitrogen atmosphere, but is probably too cold
Europa, Ganymede, and Callisto may have liquid water
Perhaps the most likely sites for other life in Solar System
Mars is too cold and lacks liquid water
But formerly had more atmosphere, higher temperatures, and running water
Viking lander tests were at best inconclusive
1996 claim of evidence of fossils in Martian meteorite
Is there life FAR out there? : Is there life FAR out there? Depends on a lot of unknown factors
Cannot probe it to find out (takes “forever” to get there)
Need to look for “signals” of life
Do we have a chance of finding life?
Green Bank (or Drake) Equation : Green Bank (or Drake) Equation Estimated number of technological civilizations present in the Milky Way galaxy is given by
the average rate of star formation
fraction of stars having planetary systems
average number of planets within the habitable zone for various types of star and star system
fraction of habitable planets that develop life
fraction of life-bearing planets on which intelligence appears
fraction of intelligent life forms that develop technology
average lifetime of a technological civilization
Could be 100 to 1 billion (?)
Illustration of Drake Equation : Illustration of Drake Equation
Time is of the Essence : Time is of the Essence A lot of things can go wrong in “cosmic instances” like a few thousand years
It is “guesstimated” that a technological civilization might last about 3000 years
Extinction of the Dinosaurs : Extinction of the Dinosaurs Possibly caused by impact of
a large meteorite
Large amount of dust thrown into atmosphere, causing global cooling, disruption of the food chain
Evidence:
Iridium layer found in fossil record at about time of extinction of dinosaurs
Large numbers of species become extinct at about the same time
Crater in Yucatan may be “the one”
Are extinctions periodic?
SETI : SETI If average lifetime is 1 million years, then the average distance between civilizations in the galaxy is 150 ly
Thus 300 years for messages to go back and forth
Communications via radio signal
Earth has been broadcasting in RF range for most of this century
Earth is brighter than the Sun in radio
18–21 cm wavelength range good for interstellar communication
SETI search is ongoing
SETI@Home: http://setiathome.ssl.berkeley.edu
If they exist, should we contact them?
SETI with Radio Telescopes : SETI with Radio Telescopes Radio frequencies are used because
Civilizations are likely to use these frequencies
We can observe them from the ground
Biggest radio telescope is in Arecibo, Puerto Rico
Our Message to the Aliens : Our Message to the Aliens Golden plate with essential info on humans
On board Pioneer 10 space probe
Started in the 70’s
past solar system
The Night Sky in March : The Night Sky in March Long nights, early observing!
Winter constellations are up early: Orion, Taurus, Gemini, Auriga, Canis Major & Minor, the spring constellations come up: Cancer, Leo, Big Dipper
Saturn dominates the evening, Jupiter early morning.
Moon Phases : Moon Phases Today (Waning gibbous, 96%)
3 / 11 (Last Quarter Moon)
3 / 18 (New Moon)
3/ 25 (First Quarter Moon)
Today at Noon : Today at Noon Sun at meridian, i.e. exactly south
10 PM : 10 PM Typical observing hour, early March
Moon
Saturn
South-West : South-West Plejades
Hyades
Zenith : Zenith Big Dipper points to the north pole
West : West High in the sky:
Perseus and
Auriga
with Plejades and the Double Cluster
South-West : South-West The Winter Constellations
Orion
Taurus
Canis Major
Gemini
Canis Minor
The Winter Hexagon : The Winter Hexagon Sirius
Procyon
Pollux
Capella
Aldebaran
Rigel
South : South M44, Praesepe, an open star cluster
East : East Saturn in Leo
Mark your Calendars! : Mark your Calendars!
Next Starry Monday: April 2, 2007, 8 (!!!) pm
(this is a Monday )
Observing at Prairie Oaks Metro Park:
Friday, April 27, 8:30 pm
Web pages:
http://www.otterbein.edu/dept/PHYS/weitkamp.asp (Obs.)
http://www.otterbein.edu/dept/PHYS/ (Physics Dept.)
Mark your Calendars II : Mark your Calendars II
Physics Coffee is every Wednesday, 3:30 pm
Open to the public, everyone welcome!
Location: across the hall, Science 256
Free coffee, cookies, etc.