: the origin, evoluon, distribuon, and future of life in the

Outline of this class: Life, extreme life on earth Where else in solar system could life exist? Mars, & , Habitable zone (review), difficulty with esmang probability of life, Drake equaon for esmang likelihood SETI: Search for Extraterrestrial Intelligence

Reminder: • No class this Wednesday, Happy Thanksgiving! • Next Monday: primarily review • Next Wed: YOU each do class presentaon (30 % of your final)

• Mon, Dec 9 Final exam. Would you all like to follow this with a potluck supper? (Colee and I will contribute major items!) No need to cook something! What defines life?

• the capacity to grow, • metabolize (convert food to energy) • respond (to smuli), • adapt • reproduce

What is necessary? Recent discoveries of life under extreme condions on earth () show that neither sunlight nor oxygen are required yellowstone

Yellowstone Naonal Park: microbes live in boiling water (90 C). Other pools are extremely acidic, yet microbes and bacteria thrive there Life in extreme condions on earth

Black smoker, deep in the ocean: an example of life that has no need of sunlight: From vents deep in the ocean hydrogen sulfide provide energy for bacteria, which in turn feed clams, tube worms (up to 10 long) Bacteria up to a mile underground: water seeps in, and bacteria generates energy from chemical reacons

A NASA favorite: Tardigrade (water bear) that survive at temps from absolute zero to above boiling, pressures up to 6x that of deepest ocean trenches, ionizing radiaon. They can go without food or water for more than 10 years and then revive.

(Less than 1 mm long) Are there other places in our solar system that might harbor life?

Temperatures that allow liquid water may be very important

We discussed the Goldilocks idea for (too hot), Mars (too cold), Earth (just right) Could there have been in the distant past?

1996: Maran meteorite found on earth, could it be possible fossil life from Mars? Current thinking is that this is not a fossil, but it raises interesng quesons What about other places? The moons of gas giants Moons of Jupiter (Ganymede, Europa) and Saturn (Titan)

NASA missions in past 20 years have revealed a great deal:

Europa: covered with ice, possibly liquid beneath the ice Titan: has atmosphere, and liquid surface (but not water…) Europa: One of 4 Jupiter moons easily seen with small telescope - About the size of earth’s moon - Orbits Jupiter in about 4 days – so relavely close to Jupiter

NASA Galileo mission, launched 1989, reached Jupiter 1995, orbited with flybys of moons unl 2003

Found the surface of Europa is covered in ice, long fractures – suggests liquid water underneath ( heated by strong des from Jupiter)

Liquid water: raises possibility of primive life? Next, an Aside on des: Aside on des:

Earth- moon: ocean des caused by gravity ( force = mass, inverse distance)

Tides consume energy (fricon): lead to dal locking

Example of dal locking: moon keeps one face to the earth all the me) Surface of Europa, from the Galileo mission, showing “ice ras”

Scale: This image is 20 by 50 miles

A theorecal model of possible ocean on Europa. (Rick Greenberg, UA) NASA Cassini mission to Saturn:

Launched 1997, arrived 2004 Cassini made mulple flybys of Venus, Earth and Jupiter to gain the required energy to reach Saturn

It carried a probe, named Huygens, that parachuted to the surface of the moon Titan in 2005, sending back images of the descent

Cassini is sll orbing Saturn, sending back data Saturn’s largest moon: Titan View of surface from Huygens probe, which parachuted to the surface

atmosphere

Surface from about 30 km Surface: Titan: further exploraon suggest lakes of liquid methane, ethane: a “water cycle” than involves no water!

While these are interesng places, we have no evidence of any form of life on them. Let’s turn to the . Is extrasolar intelligent life likely? Let’s start with a stascal esmate exercise: how many le-handed, 8 year old boys are there is the US right now? how many le-handed, 8 year old boys are there is the US right now?

1. Populaon of the US, P:

2. Fracon of males, Fm

3. Fracon of people who are le handed Fl

4. Fracon of populaon who are 8 years old F8

•Answer = P * F m* Fl* F8 Scienfic Notaon: or handling big numbers scienfic notaon: 1,000 = 103 = one thousand 1,000,000 = 106 = one million 1,000,000 = 109 = one billion

100 = 102 1000 = 103 , 102 x 103 = 105 (add the exponents) (2 x 102) x (3 x 103) = 6 x 105 105 / 103= 102 (subtract the exponents)

Our CCD at 0.9m was 4 x 103 by 4 x 103 pixels. How many pixels total? The Drake Equaon: stascal esmate of the number of intelligent, communicang civilizaons in our right now

1. Number of stars in our galaxy 2. Fracon of stars that have planets around them 3. Number of planets per that are capable of supporng life (see habitable zone)

4. Fracon of planets where life evolves 5. Fracon of these planets where intelligent life evolves 6. Fracon of intelligent life that communicates 7. Fracon of a planet’s lifeme during which the civilizaons communicate

N equals the product of all these factors! 1. How can we measure the number of stars in our galaxy?

(This isn’t an actual picture of our galaxy. Why?) How do we measure the number of stars in our galaxy?

We can use the law of gravity to measure how much mass is within our galacc orbit.

Vc = velocity of sun around galacc center r = distance from sun to galacc center

We divide this mass by the average mass per star to get the number of stars Current best number: 2-4x1011 stars (200 to 400 billion) 2. What is the fracon of stars that have planets?

Kepler Project: indicates that praccally all sun-like stars have planets

Although Kepler looks at a very small fracon of the galaxy, it should be representave of most Is is appearing that the majority of planets are more earth-like than Jupiter-like hp://astro.unl.edu/naap/habitablezones/animaons/ stellarHabitableZone.html 3. What number of planets are able to support life?

• Recall the habitable zone concept – warm enough for liquid water

• NOV 4 2013: KEPLER PRESS RELEASE: “one in five stars like the sun is home to a planet up to twice the size of Earth, orbing in a temperate environment. “ The other factors ( 4 through 7 ) are up to you:

Values you get?

Note that this ONLY addresses our galaxy: there are about as many in the known universe as there are stars in our galaxy! So, how far might the nearest earth-like planet be?

If there is intelligent life there, do they know about us? (the “I Love Lucy” effect) Listening for intelligence: from (1960) to SETI (today) SETI Project: search for intelligent signals

SETI@home: 1998, cizen science program, using personal computers to help with data reducon, also support from Planetary Society (private group)

Small percent of me devoted to this search, SETI Project: the Allen Telescope array

• Need for more telescope me: proposal to build up to 350 small telescopes,

• supported by Paul Allen (Microso founder), located at Hat Creek Obs, CA

• Went on line in 2007, only 3 telescopes in place

Survey 1,000,000 “nearby”stars for SETI emission

Survey the galacc plane for very powerful transmiers What sort of signal is SETI looking for?

•The Arecebo telescope does not track the sky, so a exterrestrial signal will dri through its beam.

•We might expect an intelligent exterrestrial signal to be narrow in frequency, rather than covering a broad range

•If the signal contains informaon, it will be pulsed

•Since planets (like us) probably rotate, it may show a Doppler shi , or change in frequency – and this would include pulses

•If we detect a signal, how will we decode it? Needless to say, we haven’t heard anything… do you think we will? How will we decode it?