/
Astrobiology: the origin, evolution, Astrobiology: the origin, evolution,

Astrobiology: the origin, evolution, - PowerPoint Presentation

nullitiva
nullitiva . @nullitiva
Follow
347 views
Uploaded On 2020-08-27

Astrobiology: the origin, evolution, - PPT Presentation

distribution and future of life in the universe Reminder No class this Wednesday Happy Thanksgiving Next Monday primarily review Next Wed YOU each do class presentation 30 of your final ID: 806018

stars life water earth life stars earth water surface planets liquid seti jupiter europa galaxy number 000 intelligent moon

Share:

Link:

Embed:

Download Presentation from below link

Download The PPT/PDF document "Astrobiology: the origin, evolution," is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.


Presentation Transcript

Slide1

Astrobiology: the origin, evolution, distribution, and future of life in the universe

Reminder:No class this Wednesday, Happy Thanksgiving!Next Monday: primarily reviewNext Wed: YOU each do class presentation (30 % of your final)Mon, Dec 9 Final exam. Would you all like to follow this with a potluck supper? (Colette and I will contribute major items!) No need to cook something!

Outline of this class:

Life, extreme life on earth

Where else in solar system could life exist? Mars, Titan&

Europa

,

Habitable zone (review), difficulty with estimating probability of life,

Drake equation for estimating likelihood

SETI: Search for Extraterrestrial Intelligence

Slide2

What defines life?

the capacity to grow, metabolize (convert food to energy)respond (to stimuli), adapt reproduceWhat is necessary? Recent discoveries of life under extreme conditions on earth (extremophiles) show that neither sunlight nor oxygen are required

Slide3

yellowstone

Yellowstone National Park: microbes live in boiling water (90 C). Other pools are extremely acidic, yet microbes and bacteria thrive there

Slide4

Life in extreme conditions 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 ft long)

Slide5

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 radiation. They can go without food or water for more than 10

years and then revive.

Bacteria up to a mile underground: water seeps in, and bacteria generates energy from chemical reactions

(Less than 1 mm long)

Slide6

Are there other places in our solar system that might harbor life?

We discussed the Goldilocks idea for Venus (too hot), Mars (too cold), Earth (just right)Temperatures that allow liquid water may be very important

Slide7

Could there have been life on Mars in the distant past?

1996: Martian meteorite found on earth, could it be possible fossil life from Mars? Current thinking is that this is not a fossil, but it raises interesting questions

Slide8

What about other places? The moons of gas

giants

Slide9

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 iceTitan: has atmosphere, and liquid surface (but not water…)

Slide10

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 relatively close to JupiterNASA Galileo mission, launched 1989, reached Jupiter 1995, orbited

with

flybys of moons

until 2003

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

tides

from Jupiter)

Liquid water: raises possibility of primitive life?

Next, an Aside on tides:

Slide11

Aside on tides:

Earth- moon: ocean tides caused by gravity ( force = mass, inverse distance)Tides consume energy (friction): lead to tidal locking

Example of tidal locking: moon keeps one face to the earth all the time)

Slide12

Surface of Europa, from the Galileo mission, showing “ice rafts”

A t

heoretical

model of possible

ocean on

Europa

.

(Rick Greenberg, UA)

Scale: This image is 20

by 50 miles

Slide13

NASA Cassini mission to Saturn:Launched 1997, arrived

2004Cassini made multiple flybys of Venus, Earth and Jupiter to gain the required energy to reach SaturnIt carried a probe, named Huygens, that parachuted to the surface of the moon Titan in 2005, sending back images of the descent

Cassini is still orbiting Saturn, sending back data

Slide14

Saturn’s largest moon:

TitanView of surface from Huygens probe, which parachuted to the surface

atmosphere

Surface:

Surface from about 30 km

Slide15

Titan: further exploration suggest lakes of liquid methane, ethane: a “water cycle” than involves no water!

While these are interesting places, we have no evidence of any form of life on them. Let’s turn to the stars.

Slide16

Is extrasolar intelligent life likely? Let’s start with a statistical estimate exercise:

how many left-handed, 8 year old boys are there is the US right now?

Slide17

how many left-handed, 8 year old boys are there is the US right now?Population of the US, P:Fraction of males, FmFraction of people who are left handed Fl

Fraction of population who are 8 years old F

8

Answer = P * F

m

* F

l

* F

8

Slide18

Scientific Notation: or handling big numbers

scientific notation: 1,000 = 103 = one thousand1,000,000 = 106 = one million1,000,000 = 109 = one billion 100 = 102 1000 = 103 , 102 x 10

3

= 10

5

(add the exponents)

(2 x 10

2

) x (3 x 10

3)

= 6 x 10

5

10

5

/ 10

3

= 10

2

(subtract

the exponents)

Our CCD at 0.9m was 4

x

10

3

by 4

x

10

3

pixels. How many pixels total?

Slide19

The Drake Equation: statistical estimate of the number of intelligent, communicating civilizations in our galaxy right now

Number of stars in our galaxyFraction of stars that have planets around themNumber of planets per star that are capable of supporting life (see habitable zone)Fraction of planets where life evolvesFraction of these planets where intelligent life evolvesFraction of intelligent life that communicatesFraction of a planet’s lifetime during which the civilizations communicate

N equals the product of all these factors!

Slide20

1. How can we measure the number of stars in our galaxy?

(This isn’t an actual picture of our galaxy. Why?)

Slide21

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 galactic orbit.

V

c

= velocity of sun around galactic center

r = distance from sun to galactic center

We divide this mass by the average mass per star to get the number of stars

Current best number:

2-4x10

11

stars

(200 to 400 billion)

Slide22

2. What is the fraction of stars that have planets?

Kepler Project: indicates that practically all sun-like stars have planetsAlthough Kepler looks at a very small fraction of the Milky Way galaxy, it should be representative of most

Slide23

Is is appearing that the majority of planets are more earth-like

than Jupiter-like

Slide24

http://astro.unl.edu/naap/habitablezones/animations/stellarHabitableZone.html

Slide25

Recall the habitable zone concept – warm enough for liquid waterNOV 4 2013: KEPLER PRESS RELEASE:

“one in five stars like the sun is home to a planet up to twice the size of Earth, orbiting in a temperate environment. “3. What number of planets are able to support life?

Slide26

The other factors ( 4 through 7 ) are up to you:

Note that this ONLY addresses our galaxy: there are about as many galaxies in the known universe as there are stars in our galaxy!Values you get?

Slide27

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)

Slide28

Listening for intelligence: from Project Ozma (1960) to SETI (today)

Slide29

SETI Project: search for intelligent signals

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

Small percent of time devoted to this search,

Slide30

SETI Project: the Allen Telescope array

Need for more telescope time: proposal to build up to 350 small radio telescopes, supported by Paul Allen (Microsoft 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 galactic plane for very powerful transmitters

Slide31

What sort of signal is SETI looking for?

The Arecebo telescope does not track the sky, so a exterrestrial signal will drift 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 information, it will be pulsed

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

pulses

If we detect a signal, how will we decode it?

Slide32

Needless to say, we haven’t heard anything…

do you think we will? How will we decode it?

Slide33

Slide34