9/29/2020
Why we start with The UNIVERSE
•
This module sets the foundation for those questions.
•
What is the universe?
•
What kinds of objects are in it?
•
How did they get there?
•
Why is Earth so nice?
•
Are there other nice planets like Earth?
•
If there are other nice planets, is there more than one
history of life?
We’ll start with a tour of our solar system
8 planets revolving around Sun (Earth is one of them)
Sun made up of same elements as Earth
Planets move in same direction around sun in a disk (Solar
System)
4 inner planets: small, dense, rocky (silicon) – “terrestrial”
4 outer planets: large, gas/fluid/ice (hydrogen-helium) –
“Jovian” planets
The sun is 93 million miles from Earth (1 A.U.)
Distance from sun to Neptune is > 30 A.U.
1
9/29/2020
Relative sizes (distances not at all accurate)
“My Very Easy
Method Just Speeds Up Names.”
2
9/29/2020
Terrestrial Planets
Orbital speed of the Earth
around the sun averages
about 19 km/s (68,400 kph)
Mercury
Former surface vaporized
Temperature range -300 ºF to 800 ºF
Slow rotation: 1.5 days/yr
No atmosphere to slow asteroids
Largest crater 2300 km across
Earth
Dense cloud cover
Earth’s “sister” planet
Venus
1877 Italian astronomer
Schiaparelli thinks he sees
network of straight lines or
canals. There ARE
channels on Mars.
Mars
3
9/29/2020
September 2020: phosphine (PH3) detected in the atmosphere of our
neighboring planet Venus.
• How is phosphine formed on Earth?
• What is the significance of phosphine on another planet?
• How was phosphine detected on Venus?
Earth
• Geologically active
• Liquid water at the surface
• Not too hot, not too cold
• Diversity of elements and compounds
4
9/29/2020
1877 Italian astronomer Schiaparelli thinks he sees network of straight
lines or canals. There ARE channels on Mars.
There’s no liquid water now.
5
9/29/2020
The Inner “Terrestrial” Planets
Asteroid Belt
6
9/29/2020
Asteroids
Range in size from tens of meters to hundreds of kilometers across
Asteroid 243 Ida is over 53 km long. Its
moon, Dactyl on the right
Ceres, a dwarf planet and largest object
in the asteroid belt. 950 km across
NASA’s Dawn mission
found that Ceres (dwarf
planet like Pluto) has a
vast repository of salty
water hiding below its
surface.
The surface above the salt
water was melted and
fractured by an asteroid
impact about 20 million
years ago (crater).
Salt water flows up to the
surface through the
fractures.
7
9/29/2020
Interior of Ceres
Detection of simple organics on Ceres. Geologists have collected meteorites on Earth with organic
signatures, but until now we haven’t seen such definitive evidence on any asteroid. Unusually high
concentrations of organic matter exist close to a northern-hemisphere crater called Ernute. This finding
suggests that there are hydrothermal processes going on within or below the crust of Ceres creating
these organics that are later exposed on the surface during eruptions.
8
9/29/2020
The Outer “Jovian” Planets (Gas/Ice Giants)
Jupiter
9
9/29/2020
https://solarsystem.nasa.gov/planets/jupiter/exploration/?page=0&per_page=10&order=launch_date+desc%2Ctitle+asc&search=
&tags=Jupiter&category=33
Tracey Drain worked on the Mars Reconnaissance Orbiter, the Kepler mission
to discover exoplanets, and the Juno mission to Jupiter. Her newest role will be
Deputy Project Systems engineer for Psyche, a mission to the metallic asteroid
16 Psyche set to launch in 2022. Find Tracy, click on the “More about” link.
How did Tracy get her start at NASA’s Jet Propulsion Laboratory (JPL)?
What would it be like to fall into Jupiter?
10
9/29/2020
There are two upper cloud decks. The lower one is
orange-brown. The upper one is thinner and white
(ammonia and water).
Thunderstorms form within the planet’s
deep atmosphere, around 50 km (30 miles) below the
visible clouds.
When these storms are powerful enough, they carry
crystals of water-ice into the upper atmosphere.
What would it be like to fall into Jupiter?
11
9/29/2020
What would it be like to fall into Jupiter?
What would it be like to fall into Jupiter?
Galileo probe 1995
Parachuted 150 km
Collected data for 57 minutes
Crushed by 22 times Earth’s atmosphere
Melted and vaporized by >300˚F.
12
9/29/2020
Galileo proble used infrared light to detect and image compounds
in the upper and lower cloud decks. This is the image. Height
variations of clouds are exaggerated by a factor of 25.
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA01192
13
9/29/2020
Above, an artist’s interpretation of high-altitude
electrical storms on Jupiter. Juno’s sensitive
Stellar Reference Unit camera detected unusual
lightning flashes on Jupiter’s dark side during
the spacecraft’s close flybys of the
planet. Credits: NASA/JPLCaltech/SwRI/MSSS/Gerald Eichstädt/Heidi N.
Becker/Koji Kuramura
14
9/29/2020
UPPER CLOUD DECK
LOWER CLOUD DECK
Thunderstorms form within the
planet’s deep atmosphere, around
50 km below the visible clouds,
where the temperature is close to
0 degrees C. When these storms
are powerful enough, they carry
crystals of water-ice into the
upper atmosphere.
SATURN
15
9/29/2020
NASA Cassini Mission
16
9/29/2020
17
9/29/2020
Why are there rings?
SATURN has 82 moons
Some of those moons orbit within the inner rings
18
9/29/2020
19
9/29/2020
Fly-over animation
Spikes of icy ring material, created by gravitational oscillations, rise up to a mile high along the outer edge of #Saturn's B ring and cast shadows in the perpendicular light of spring equinox. Image captured by NASA's #Cassini spacecraft on July 26, 2009. pic.twitter.com/mdgMtUY0c7
— Jason Major (@JPMajor) July 26, 2019
New moonlette
being formed
20
9/29/2020
What does the video say is special about Enceladus, one of Saturn’s moons?
21
9/29/2020
Beyond Saturn are two Ice Giants
•
•
•
•
Both are bluish or bluish-green, with deep atmospheres and icy interior
Both probably impacted by large planets early on
Uranus and moons are tilted 97 degrees, retrograde rotation
Neptune generates much more of its own internal heat
Uranus
Neptune
Rocky core
H-He Ices, mixed with rock
Liquid H-He, ices
Gaseous H2
Visible clouds
Jupiter and Saturn have an
interior layer of metallic
hydrogen that doesn’t
occur in Uranus and
Neptune
22
9/29/2020
Pluto
A dwarf planet (like Ceres)
Pluto (not a planet)
23
9/29/2020
2006-2015
The smoothest part of Pluto’s bright heart raises a riddle: how this lake of frozen nitrogen,
hundreds of kilometers across, got there, and when. The lack of impact craters suggests
the surface is at most 100 million years old, but what goes on beneath it is a mystery.
24
9/29/2020
Polygonal cells
A clue
Heat source
Cell-like terrain results from convection within a layer
of nitrogen/carbon-monoxide ice. Warmer ice flows
toward the surface, and colder ice sinks. Cells are 30
km wide, 3 km thick. Flow rate is about 7 cm/yr
(about twice as fast as fingernails grow). It would
take nearly half a million years for the cell to refresh
its surface, which is why the cells are crater-free.
25
9/29/2020
A clue
Dark, ancient heavily cratered terrain
Bright, smooth geologically young terrain
Mountains
Dark, aligned ridges that resemble dunes
26
9/29/2020
Massive Ice Volcano
27
9/29/2020
Mountains may be the detached crust (water ice) floating like icebergs on a
deep pool of frozen nitrogen. What severed icebergs from the bedrock? At
depth, pressures and temperatures could cause nitrogen ice to melt,
undermining the crustal blocks.
Solid liquid nitrogen
28
9/29/2020
Relative distances (sizes not at all accurate)
Pluto is sometimes closer to the sun than which planet?
Jupiter Saturn Uranus
Neptune
Pluto
Terrestrial
Planets
1 astronomical unit (A.U.) = 93 million miles
If we shrunk the solar system so that Earth was 4 ft away from the sun,
Saturn would be 40 ft (10 AU) away, and Neptune would be 120 ft (30 AU)
Pluto is 30-50 AU.
On February 14, 1990, NASA commanded the Voyager 1 spacecraft, having
completed its primary mission (Jupiter and Saturn) and out near Neptune (40
AU, to turn around to photograph the planets of the Solar System.
Jupiter Saturn Uranus
Neptune
Pluto
Terrestrial
Planets
29
9/29/2020
We succeeded in taking that picture, and, if you look at it, you see a dot. That’s here.
That’s home. That’s us. On it, everyone you ever heard of, every human being who
ever lived, lived out their lives . . .on a mote of dust, suspended in a sunbeam.
[…] To my mind, there is perhaps no better demonstration of the folly of human
conceits than this distant image of our tiny world. To me, it underscores our
responsibility to deal more kindly and compassionately with one another and to
preserve and cherish that pale blue dot, the only home we’ve ever known.
Carl Sagan, speech at Cornell University, October 13, 1994
Definition of a Planet
The object must be in orbit around the Sun.
The object must be massive enough to be a sphere
by its own gravitational force.
It must have cleared the neighborhood around its
orbit.
[Pluto fails to meet the third condition, since its mass was only
0.07 times that of the mass of the other objects in its orbit. Earth,
Mars, Jupiter, and Neptune share their orbits with asteroids.
However, Earth’s mass, by contrast, is 1.7 million times the
remaining mass in its own orbit]
30
9/29/2020
2006. Children protest the reclassification of Pluto as a TransNeptunean Object or Dwarf Planet. Police keep counter-protesters
on different corner.
31
9/29/2020
Eccentric orbit takes Pluto closer to the sun. Part of the Kuiper Belt
(pronounced like ‘viper’) of Trans-Neptunean objects.
Comet
67P/Churyumov–
Gerasimenko
Orbited by the
Rosetta spacecraft
since 2014.
Former Kuiper belt
comet, now orbits
only as far out as
Jupiter
32
9/29/2020
Comet
67P/Churyumov–
Gerasimenko
67P/CG’s surface appears
remarkably uniform in
composition with a
predominance of organic
materials (hydrocarbons)
and minerals (silicates, Fesulfides, ammoniated salts)
33
9/29/2020
34
9/29/2020
The surface of the comet
67P/Churyumov–
Gerasimenko with dust and
visualizations of cosmic rays.
The downward moving
points of light in the
background are stars. Filmed
by the Rosetta spacecraft’s
OSIRIS instrument.
https://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasimenko#/media/File:67P_Churyumov-Gerasimenko_surface.gif
35
9/29/2020
4.65 trillion miles
from the sun
36
9/29/2020
Oort Cloud
•
•
•
•
•
Hypothesized source of long-period comets
Too small to see with telescopes
2 parts: disc and sphere
1000x farther than Kuiper Belt
¼ of distance to next closest star
Kuiper Belt
(comets)
37
10/6/2020
Recap
You live in a planetary system (aka ‘solar system) with a central
star (aka ‘the sun’), around which 8 planets (terrestrial, gas and
ice giants) and several asteroid and comet belts rotate.
The next closest planetary system from ours is 268,770 A.U. away
(4.25 light years). That’s the star Proxima Centauri, which has
two known planets.
To put this in perspective, Earth-Kuiper Belt distance is 30-50 A.U
and the Voyager 1 spacecraft traveled 141 A.U. from Earth (as
of 2020) since its launch in 1977. It would take another 81,000
years to get as far as Proxima Centauri.
What is this module about?
•
How it all came to be.
•
Why is there a universe with stuff (matter)?
•
•
Why is there a periodic table of elements at all?
•
•
Why isn’t the universe empty?
Why not just one simple element like Hydrogen with one proton?
Why is this stuff organized into stars with orbiting planets within galaxies?
1
10/6/2020
Relative sizes (distances not at all accurate)
“My Very Easy
Method Just Speeds Up Names.”
Oort Cloud
•
•
•
•
•
Hypothesized source of long-period comets
Too small to see with telescopes
2 parts: disc and sphere
1000x farther than Kuiper Belt
¼ of distance to next closest star
Kuiper Belt
(comets)
2
10/6/2020
Beyond the Oort Cloud . . .
If the sun was a marble in Tampa, the Earth would be a pin point 4 ft away, and Saturn would be 40 ft away.
Gravitational edge of solar system (Oort Cloud) is 30-50 miles away, Tampa to Sarasota.
Proxima Centauri, the closest star, would be 230 miles away in Key West.
The next closest star would be 7000 miles away at the South Pole.
What’s the point?
We’re describing our galactic neighborhood so we know where we are.
And so we know scale.
From scale, we can begin to understand how many other solar systems there are besides our own.
That helps us contemplate how many “History of Life” experiments may have been
conducted already besides our own experiment on Earth.
3
10/6/2020
.
.
4
10/6/2020
59 trillion miles
45,000 yrs
Traveling 1 light year
would take 4490 yrs at a
rate of 150,000 mph
1 light year (ly)= 5.9 trillion miles
Selected Star Systems
Within 65 Light Years
380+ trillion miles
Traveling this distance at
a rate of 150,000 mph
would take about
291,000 years
5
10/6/2020
The Universe within 5000 Light Years
29,500,000,000,000,000 miles (29.5 quadrillion)
Traveling 5000 light yrs would
take 22.5 million yrs at a rate of
150,000 mph
Would take almost half a billion years to cross the galaxy from end to end
6
10/6/2020
Traveling 5000 light yrs would take 22.5 million yrs at a rate of 150,000 mph
Our galaxy is >100,000 ly across
The Milky Way Galaxy
22.5 myr to
go this far
If we shrunk the Milky
Way down to 80 miles
across, our solar
system would be 2
mm across
7
10/6/2020
Imagine what you could see if you stared from Earth towards
the center of our Milky Way Galaxy
8
10/6/2020
The Milky Way Galaxy
It takes our Solar System
225–250 million years to
complete one orbit of the
galaxy.
That is 20–25 orbits during
the lifetime of the Sun.
The orbital speed of the
Solar System about the
center of the Galaxy is
approximately 137 mi/s.
493,200 mph
10,000 ly
1 light year (ly)= 5.9 trillion miles
Galactic Habitable Zone?
To harbor life, a planet
must be close enough
to the galactic center
that a sufficiently high
level of heavy elements
exist to favor the
formation
of
rocky
planets.
Heavier
elements, which are
the
basis
of
the
complex molecules of
life.
On the other hand, the
planetary system must
be far enough from the
galactic center that it
would not be affected
by dangerous radiation.
10,000 ly
1 light year (ly)= 5.9 trillion miles
9
10/6/2020
http://rqgravity.net/SpiralStructure
Extensive computer simulations show that, at least in galaxies similar to our own Milky Way, stars such as the sun can migrate great distances,
thus challenging the notion that parts of these galaxies are more conducive to supporting life than other areas.
Astrophysical Journal Letters, Volume 684, Number 2. 2008
Our Universe
In the 1920’s, scientists
thought that the Milky Way
Galaxy was the entire universe.
They also thought the universe
was stationary with no
beginning and no end.
10
10/6/2020
Albert Einstein (1879-1955)
Published a new theory of gravitation in
1916.
Gravity is not an attractive force between
objects but a curved field in space-time
created by the presence of mass.
Orbits are the result of objects passing
through curved space.
Isaac Newton (1643-1727)
The force between two objects is proportional to the product of their masses
and inversely proportional to the square of the distance between them.
11
10/6/2020
12
10/6/2020
The most important prediction of Einstein’s Relativity Theory
Albert Einstein had found that his newly developed theory
of general relativity indicated that the universe must be
either expanding or contracting.
A universe cannot exist at dynamic equilibrium.
Einstein was so bothered by these conclusions that he altered the terms of
his equations to force the conclusion of a static, unchanging universe.
13
10/6/2020
Georges Lemaítre (1894 to 1966)
Belgian Catholic priest and professor of
physics and astronomy (cosmology).
In 1925, he wrote that if the universe is
expanding, then it was smaller
yesterday than today, and must have
had a beginning from an initial point –
the primeval atom.
The universe BEGAN.
Idea was criticized sarcastically as the
“Big Bang Theory.”
Einstein commented:
“Your math is correct, but your physics
is abominable.”
Dust in the Milky Way?
14
10/6/2020
Standard Candles
A light source seen from far away
appears dimmer than the same source
viewed from up close.
Standard candles are objects which are
known to have the same absolute
brightness
(luminosity), and their
distance can be determined by
measuring their apparent brightness.
Beyond the Milky Way
By 1925, scientists concluded that there were other galaxies
•
Supernovae that occurred within one of the dust
clouds, the Andromeda Nebula were 10x less
bright than supernovae within the Milky Way.
•
Presence of dark lanes resembling dust
clouds in our own galaxy.
•
Edwin Hubble calculated that these nebulae
were to be too far away to be part of the
Milky Way.
15
10/6/2020
The first photographs of M31 were taken in 1887.
Scale
16
10/6/2020
Andromeda Galaxy (M31)
17
10/6/2020
Whirlpool Galaxy (M51A/B or NGC 5194/5).
18
10/6/2020
Messier 64
19
10/6/2020
Our solar system is
one of millions in the
Milky Way Galaxy.
240 billion galaxies in
our visible universe
Hubble Ultra Deep Field 2004 – Light from 400-700 million years after the Big Bang
Our solar system is
one of millions in the
Milky Way Galaxy.
240 billion galaxies in
our visible universe
Hubble Ultra Deep Field 2004 – 10,000 “Island Universes”
20
10/6/2020
Our solar system is
millions in the
Way Galaxy.
Our solar system is one of >100 billion planetary systems in the Milky WayMilky
Galaxy.
200+ billion galaxies in our visible universe.
one of
240 billion galaxies in
our visible universe
Hubble Ultra Deep Field 2004 – 10,000 “Island Universes”
It takes about 8 minutes and 19 seconds for
light from the sun to reach Earth. What about for light from a
galaxy that is a few hundred quintillion miles from Earth?
21
10/6/2020
Our galaxy is >100,000 light year across.
How long does it take for light to travel from one edge to the other?
How long does it take for light to travel to us from the nearest large galaxy?
22
10/6/2020
Galaxy distances
Our solar system is
Looking DEEP into space means looking back – looking
back inin the
one of millions
Milky Way Galaxy.
time to when the universe was younger.
240 billion galaxies in
our visibleof
universe
Some of these galaxies are so far away that the journey
their
light began more than 13 billion years ago.
That means we’re seeing them as they were when the universe
was just 600 myr old!
Hubble Ultra Deep Field 2004 – 10,000 “Island Universes”
23
10/6/2020
Andromeda Galaxy (M31)
Contains one trillion stars.
141,000 light years across
1 light year = 5.9 trillion miles
2.5 million light-years away.
We observe it as it was 2.5 million years ago.
Speed of light = 186,000 mi/sec
Andromeda Galaxy (M31)
24
10/6/2020
How far away is the Andromeda Galaxy?
2.5 million light years away
1 light year = 5.9 trillion miles
14,750,000,000,000,000,000 miles
14 quintillion, 750 quadrillion
The Andromeda Galaxy is approaching
Milky Way Galaxy (us) at 300,000 mph
Galaxies will collide in 2-3 Gyr
Andromeda Galaxy (M31)
25
10/6/2020
26
10/6/2020
One star with 8
planets
Dozens of stars,
each with planets
(our solar system)
(Planetary systems)
Hundreds of billions
of planetary systems
plus dust and gas
and black holes
(Galaxy)
Would take >11 billion years with fastest rocket to travel from the
Milky Way Galaxy to the Andromeda Galaxy (assuming the distance
between them stays as it is now 2.5 million light years).
27
10/6/2020
VIRGO SUPERCLUSTER
LOCAL GALACTIC GROUP
>50 galaxies, Gravitationally-bound
Superclusters are large groups of smaller galaxy groups
and clusters and are among the largest structures of the
cosmos. They are so large that they are not
gravitationally bound.
350 MILLION LIGHT-YEARS
28
10/6/2020
The Cosmic Web
Coma
Each point of light is a galaxy cluster
Superclusters group into
enormous “filaments” that can
span a billion light-years in
length.
Centaurus
Virgo
Pisces Perseus
Pavo Indus
You are here
The Cosmic Web
A God’s Eye View
http://cosmicweb.kimalbrecht.com/viz/#2
29
10/6/2020
Gravity is definitely responsible for pulling
matter together to form larger and larger
objects (the cosmic web).
However, gravity is weak at such large scales.
The cosmic web is stretching apart even as fine
strands become better defined.
Doppler Effect
Apparent
Lower
frequency
Apparent
Higher
frequency
http://astro.unl.edu/classaction/animations/light/dopplershift.html
30
10/6/2020
http://astro.unl.edu/classaction/animations/light/dopplershift.html
https://www.youtube.com/watch?v=p-hBCcmCUPg
31
10/6/2020
Higher
frequency
Lower
frequency
32
10/6/2020
Moving away
from us
Stationary
Moving towards
us
Edwin Hubble (1889 to 1953)
American astronomer.
First to demonstrate the vast distance
between the Milky Way and other
galaxies.
In 1929, he published the first
observational support for Lemaitre’s Big
Bang Hypothesis.
The degree of redshift observed in light
coming from a galaxy increased in
proportion to the distance of that galaxy
from the Milky Way.
Space is expanding.
33
10/6/2020
Expansion of the Universe
Using precise measurements of red-shifted light, astronomers know that within about 5 million light years from
Earth, the vast majority of galaxies were orbiting the Local Group’s center of gravity, between the Milky Way and
Andromeda. Beyond 5 million light years to the edge of the group, galaxies were moving out from the group.
Each galaxy’s pace varied depending on its distance from the gravitational center of the group; the farther out
they were, the faster they receded.
How fast is this expansion?
The rate of expansion depends on the distance from Earth. Galaxies farther away move faster from us. As of
2018, the estimated rate is somewhere between 68 and 73 km per second per megaparsec (1 megaparsec =
3.26 million light years). In the image below, galaxies near opposite ends of the scale bar would be moving
apart roughly 700 km per second. In one year, they would move apart over 22 billion km, which is much less
than 1% of 1 light year. http://www.pnas.org/content/pnas/115/40/9810.full.pdf
350 MILLION LIGHT-YEARS
34
10/6/2020
What does “Big Bang” mean?
•
•
•
•
The Big Bang was not an explosion that expanded into empty space but the extremely rapid
expansion of space itself.
Imagine the entire grid below being stretched in every direction at once.
Now imagine that the grid itself extends infinitely in every direction. Even the earliest
universe, prior to expansion, was infinitely large.
Because every cube in the grid is expanding, the Big Bang occurred everywhere in the
Universe. There is no center or starting point from which the universe emerged.
What was in the early Universe?
•
•
•
•
The early Universe was very HOT and filled with energy.
As space expanded and cooled, some of that energy underwent a phase transition to become
matter (E=mc2). Matter is just a highly concentrated form of energy.
An analogy is if you have a hot jar of water vapor (a gas). If you rapidly cool the jar (which
appears empty), the water vapor suddenly changes phase from a gas to liquid or solid.
Subatomic particles (building blocks of protons and neutrons) were first.
35
10/6/2020
Other evidence for the Big Bang
Big Bang Theory predicts that the
early universe was very hot and
cooled as it expanded.
If so, the universe should be filled
evenly
and
everywhere
with
remnant heat in the form of
background radiation.
It’s found everywhere because the
Big Bang occurred everywhere.
Like remnant vibrations of a bell.
36
10/6/2020
Light emitted after the Big Bang.
As universe expanded, the gas within it cooled. Today this radiation is
very cold (almost absolute zero). Detectable only as microwaves.
More or less uniform distribution (because the Big Bang occurred
everywhere in the universe)
The rate of cosmic expansion is accelerating. Previously, cosmologists thought that we lived in a
decelerating universe. In an accelerating universe, however, we are surrounded by a boundary
beyond which occur events we will never see – a cosmic event horizon. Light emitted from
galaxies that are now beyond the event horizon will never be able to reach us. In about 100
billion years, all other galaxies will disappear from the Milky Way’s view (future alien civilizations
will never figure out the Big Bang because of this).
37
10/6/2020
Ultimate fate of the Universe?
Assuming ever increasing expansion . . .
Ultimately, dark energy overtakes gravity and galaxy clusters, stars,
planets, atoms, nuclei and matter itself will be torn apart by the everincreasing expansion in a so-called BIG RIP.
When?
In about ?100? billion years from now . . .
About 3 months before the end, Solar System will come apart
In the last minutes, stars and planets torn apart.
In the last instant, atoms will be destroyed.
The Universe
Not a friendly place. It’s going to destroy life eventually. We aren’t the
center of it. Most of it is inaccessible.
38
10/6/2020
CONFORMAL CYCLIC COSMOLOGY
• The early Universe was SMOOTH.
• As the Universe cooled, lumps
formed (e.g., stars, planets, black
holes, galaxies).
• In the Big Rip, all matter is pulled
apart, reduced to pure energy.
• Alternatively, everything will get
sucked into black holes, which
eventually evaporate into pure
energy. No more matter.
• In either case, the future is a
SMOOTH boundary, much like the
Big Bang. If true, the future may
be a new beginning for the next
Big Bang.
Students often ask for further readings on the astrophysics/cosmology topics
covered in this lecture. This ‘extra’ stuff will NOT be on the exam or in extra credit
opportunities. It’s just for fun learning only.
I highly recommend some youtube resources. This first one is a really good lecture
series for the general public about everything in astronomy. My family sometimes
substitutes this for a movie in our Friday pizza-movie night.
https://www.youtube.com/user/SVAstronomyLectures
There is also a good video series on why there is something rather than
nothing. Watch all three parts. Where does matter come from? This is a link to part
1 of 3 and another link to a video with good animations but not as good an
explanation.
Why does the universe have 3 spatial dimensions? We don’t know but here’s a
possible answer.
http://www.spacedaily.com/reports/Filling_the_early_universe_with_knots_can_expl
ain_why_the_world_is_three_dimensional_999.html
This last one is an MIT course (an entire semester online) on Big Bang inflation by the
person who discovered it, Alan Guth. It gets heavy, but it’s worth the effort if you
want to look under the hood of the universe and figure out how it works.
39
10/6/2020
How many changes has the universe seen in its rate of expansion?
How did all this complexity of matter originate?
carbon
gold
platinum
silver
40
10/6/2020
Nucleosynthesis
Intense heat and pressure within stars act as thermonuclear devices to
synthesize heavier elements from initial H and He. Still occurs today.
All heavier elements (incl. C and O) were synthesized this way.
https://helios.gsfc.nasa.gov/nucleo.html
41
10/6/2020
EXOTHERMIC FUSION
Protons are positively charged and repel each other. However, if there is enough energy to push protons
close together, the nuclear force, which is stronger than the repulsive force at very close distances, takes over
and binds neighboring protons together. This happens in stars, where nuclei are densely packed, and the
interior temperature can be 100 million degrees.
ABOVE: The electrostatic force between the
positively charged nuclei is repulsive, but when
the separation is small enough, the quantum
effect will tunnel through the wall. Therefore, the
prerequisite for fusion is that the two nuclei be
brought close enough together for a long enough
time for quantum tunneling to act.
LEFT: Fusion reaction experiments showing which
temperatures and pressures produce fusion
ignition.
https://www.euronuclear.org/info/encyclopedia/f/fusion.htm
EXOTHERMIC FUSION
The second concept to know is “binding energy.” Fusion of protons and neutrons to form a new alpha
particle (the nucleus of the new, heavier element) results in conversion of some of the mass of those protons
and neutrons to an energy (a binding energy) that holds the new nucleus together. That’s the E = mc2
equation, where E stands for binding energy, m stands for mass change.
http://hyperphysics.phy-astr.gsu.edu/hbase/NucEne/nucbin.html
42
10/6/2020
That’s why stars are bright and how part
of the periodic table was formed.
carbon
gold
platinum
silver
Inside a star, the thermal energy released from the fusion process
at the core creates an outward pressure which combats the inward
gravitational pull of the core’s increasing mass.
Exothermic
vs.
Endothermic
reactions
43
10/6/2020
Energy needed to overcome the
repulsive forces (energy input) is
exceeded by the binding energy
released (energy output). Fuels more
fusion.
Energy needed to overcome the
repulsive forces (energy input)
exceeds the binding energy released
(energy output) during fusion.
Formation of iron still happens but it
results in net loss of energy.
THE SWITCH FROM EXOTHERMIC TO ENDOTHERMIC FUSION
Binding energy released per nuclear particle
increases from the fusion of helium (2 protons) to
oxygen (8 protons). That energy keeps a selfsustaining series of reactions going as long as there
is fuel (hydrogen and helium nuclei).
For atoms bigger than oxygen (8 protons), the
alpha particle (the nucleus of the new, bigger
atom) is so big and protons so far apart that the
force that repels every proton from every other
proton starts to catch up in strength with the
nuclear force that binds neighboring protons. In
other words, the amount of energy required to
overcome the repulsive force (energy input)
increases relative to the energy released (output),
but the output is still greater and, thus, the reaction
is still exothermic.
However, during fusion of iron (26 protons), the
energy needed to overcome the repulsive forces
(energy input) exceeds the binding energy
released (energy output) during fusion. Iron is still
formed inside the star because there is, at this point,
a LOT of energy, but it results in the first net loss of
energy (i.e., endothermic). It’s like taking more
money out of a bank account than you put in.
Fusion reactions involving iron are no longer
sustainable, and the core implodes.
44
10/6/2020
When endothermic reactions begin, the core begins to collapse.
Core collapses at 42,000 mi/s (151,200,000 mph). Rebound
produces a shock wave.
Speed of light 186,000 mi/s (669,600,000 mph)
45
10/6/2020
Supernovas
•An exploding star. Aging star
collapses under weight of its own
gravity
creating thermonuclear blast.
•Most energetic explosion in
nature.
•Can outshine its galaxy before
fading over weeks or months.
Supernovas
•Explosion expels much or all of star’s material at a velocity up to 10
million miles per hour creating a shock wave.
•About 20-30 are observed outside of our galaxy each year. About
every 50 years within a galaxy the size of the Milky Way.
46
10/6/2020
Supernovas:
Their role
•Heavier elements synthesized during the explosion.
•Blast enriches interstellar medium with higher mass elements (beyond lead).
•Accumulate as dense molecular clouds (nebulae)
•Expanding shock waves from supernovas can trigger formation of new stars.
47
10/6/2020
Serbian Proverb:
“Be humble, for you are made of dung.
Be noble, for you are made of stars.”
(and supernovas)
Eta Carinae Nebula
48
10/6/2020
High-velocity plasma/gas is ejected from
massive stars, eventually colliding with dense
molecular gas to form rippled clouds
Rippled clouds
49
10/6/2020
At certain points in their
evolution, some stars blow
streams of material from their
surfaces into the space around
them.
When these stellar winds run into
the surrounding molecular gas,
they press it forward, increasing
its density.
The result is to compress regions
of the molecular cloud, which may
create clumps of high density. The
clumps may become so dense that
gravity causes them to collapse,
leading to the formation of a
second generation of stars.
Over tens of millions of years, a
series of star-forming episodes
can gradually eat into a molecular
cloud, and eventually destroy it.
50
10/6/2020
Eagle
Nebula
51
10/6/2020
Protoplanetary disks
52
10/6/2020
Protoplanetary disk (artistic reconstruction)
53
10/6/2020
Chondrites
Chondrites are stony (non-metallic) meteorites.
Have not been modified by melting or differentiation of the parent body.
Formed by accretion of dust and small grains present in the early solar system.
Represent 85% of all meteorites that fall on Earth.
Offer clues for understanding the origin and age of the Solar System, the synthesis of organic.
compounds, the origin of life, and the presence of water on Earth.
Planetesimals grow by continuous collisions. Irregularly-shaped proto-Earth develops.
Interior heats up & becomes soft. Gravity reshapes proto-Earth into sphere.
54
10/6/2020
Planetesimal vs. USF
Gas giant planet cleaning its orbit of debris
55
10/6/2020
Growing rocky planets are probably vaporized multiple times during their formation.
These collisions throw up a cloud of spinning, pulverized material, with an inner region
that rotates at a single rate and an extended structure shaped like a red blood cell (a
synestia) that rotates at orbital velocities. Synestias only last for a short period: hundreds
or thousands of years. VIDEO: https://www.macfound.org/fellows/1024/
http://www.nature.com/news/fleeting-phase-of-planet-formation-discovered-1.22039
56
10/6/2020
July 2018
http://www.eso.org/public/archives/releases/sciencep
apers/eso1821/eso1821b.pdf
Astronomers have captured for the first time an image
of a baby gas giant planet. The planet is clearing a
path through the star’s disk of gas and dust roughly the
same distance in our solar system as Neptune is from
our sun. The host star PDS 70 is 370 light years from
Earth (1 ly is about 6 trillion miles)
57
10/6/2020
Supernova
Nebula
Protoplanetary disk
N AT U R E | VO L 4 8 7 | 5 J U LY 2 0 1 2
58
10/6/2020
The stuff of the universe is characterized by a
long-term tendency towards reduced entropy.
After the Big Bang, stuff organizes itself to
become more complex and organized (e.g.,
carbon, amino acids, planetary systems)
creating all of the necessary conditions for life.
59
10/11/2020
What is this module about?
LAST LECTURE:
•
After the Big Bang, the universe cooled, transforming energy to matter (quarks), then into
•
small atoms (H, He). From there, gravity pulled atoms into masses so dense at hot that they
underwent stellar ignition (became stars).
Nucleosynthesis in stars and exploding stars (supernovas) formed all the elements needed
•
to build planets. Supernova shock waves through nebula create new planetary systems
(i.e., HABITATS). The universe is becoming increasingly complex all by itself.
THIS MODULE:
•
•
WHAT DOES ‘HABITABLE’ MEAN?
•
WHY ARE SOME PLANETS HABITABLE BUT NOT OTHERS?
•
CAN HABITABLE PLANETS BECOME UNINHABITABLE?
What does “habitable” mean?
•
Energy source (sun, geothermal, chemical)
•
Chemical building blocks of life available
nucleic acids (information system)
amino acids (building materials, work)
lipids (cellular units)
sugars (energy currency)
•
Liquid (preferably H2O) so that chemical “supplies”
can flow into cells and waste can move out.
•
Requires just right distance from star, insulating
atmosphere, not tidally locked
•
Protection from solar radiation (magnetic field)
•
Geological cycles to replenish nutrients (C, O, P, N)
1
10/11/2020
What does “habitable” mean?
•
Energy source (sun, geothermal, chemical)
•
Chemical building blocks of life available
nucleic acids (information system)
Easy
Easy
amino acids (building materials, work)
lipids (cellular units)
sugars (energy currency)
•
Liquid (preferably H2O) so that chemical “supplies”
Not easy
can flow into cells and waste can move out.
•
Requires just right distance from star, insulating
atmosphere, not tidally locked
•
Protection from solar radiation (magnetic field)
Not easy
•
Geological cycles to replenish nutrients (C, O, P, N)
Not easy
What makes Earth so special?
2
10/11/2020
•Water vapor.
•Carbon dioxide.
•Methane.
•Ozone
3
10/11/2020
•
•
•
•
CO2 and temperature are strongly correlated over the past 1 myr, but the
relationship is complicated
Temperature cycles were primarily caused by Earth’s orbital cycles
Warming caused CO2 to be released
CO2 release causes additional warming beyond that possible from orbital cycles
alone
https://www.ncdc.noaa.gov/global-warming/temperature-change
4
10/11/2020
Earth if it had much lower
Greenhouse Gas
Concentrations
Mars
Greenhouse Gases Gone
5
10/11/2020
Venus
Runaway
Greenhouse
Effect
The Greenhouse Effect
works on Earth
For now
How?
6
10/11/2020
1. Rainwater and carbon dioxide gas mix to make acid
CO2 (carbon dioxide) + H2O (water)
=
H2CO3 (carbonic
acid)
2. Acidic rain weathers rocks, releasing Ca and CO3
H2CO3 (acid) + CaSiO3 (rock) = SiO2 (silica) + Ca + CO3 (carbonate) + H2O
7
10/11/2020
3. These ions combine in the ocean to form limestone
Ca + CO3 (carbonate) = CaCO3 (calcium carbonate)
8
10/11/2020
CO2 (carbon dioxide) + H2O (water)
H2CO3 (acid) + CaSiO3 (rock) = SiO2 (silica) + Ca + CO3 (carbonate) + H2O
Ca + CO3 (carbonate) = CaCO3 (calcium carbonate)
=
H2CO3 (carbonic
acid)
9
10/11/2020
A volcanic planet can stabilize concentrations of greenhouse
gases in its atmosphere, but ONLY IF THERE IS WATER
The tropopause
10
10/11/2020
Without the tropopause, the Earth
would lose its water
TROPOPAUSE
The tropopause
11
10/11/2020
Tropopause
Plate tectonics recycles greenhouse gases back into the atmosphere.
The two processes, rinsing and release, balance greenhouse gases in
the atmosphere like a planetary thermostat.
H2CO2
CO2
CaCO3
12
10/11/2020
13
10/11/2020
Venus
Runaway
Greenhouse
Effect
•Similar in size to Earth
•Venus year is 224 days
•A little closer to the
•sun than Earth
•Known as Earth’s
“sister planet”
•Broken thermostat
VENUS
•Unmanned missions to Venus began in early 1960’s
•Probes initially designed to land on Venus’ oceans
14
10/11/2020
•Mariner 2 (American) mission , 1962.
•Orbited Venus with infrared radiometer.
•Cloud tops were cool, but surface was
HOT 500ºC (932ºF) = hot enough to melt
lead.
VENUS
•Venera 4 (Soviet) mission into
atmosphere, crushed, and melted.
•Atmosphere = sulfuric acid clouds
and lots of carbon dioxide
•Venera 5 and 6 launched in 1969,
built to withstand crushing
temperatures but only made it 20 km
above surface.
15
10/11/2020
VENUS
Venera 7, 8, 9, 10, 11,
and 12
Soviet landers precooled and reinforced
to withstand crushing atmospheres of 180 bar
Lasted for 1 hour on surface
First pictures from surface of another planet
There are no oceans. There is no water.
16
10/11/2020
Shield Volcanoes on Venus
Venus is geologically active
On Earth
https://www.youtube.com/watch?v
=5v5prMW3AzA 1:45-4:10
17
10/11/2020
The Carbon Cycle on Venus
It’s too hot for a tropopause, so water is lost to space
That also means there’s no way to rinse CO2 gas from the
atmosphere and stored as carbonate rock
However, there IS volcanism on Venus, so carbon dioxide gas
builds up and triggers a “runaway greenhouse effect”
Billions of years ago, the sun was only 70% luminescent as
today. So Venus may once have been more Earth-like.
In the future, the sun will be more luminous (about 10%
increase every 1 billion years). As Earth’s surface temperature
rises, it will eventually become Venus like.
18
10/11/2020
19
10/11/2020
Venus is still
geologically active
Few impact craters.
No plate tectonics because no
water
Without plate tectonics,
tremendous heat builds up
in the planet’s interior.
Catastrophic overturn and subduction of crust over a
period of 100 myr every 0.5 to 1 billion years
https://www.nature.com/articles/s41598-018-30174-6.pdf
https://www.youtube.co
m/watch?v=iZPIk8-ABvM
https://www.youtube.co
m/watch?v=qKU8NBCdlZ
Q
20
10/11/2020
Davaille, A., S. E. Smrekar, and S. Tomlinson. 2017. Experimental and observational evidence for plume-induced subduction on Venus. Nature Geo
21
10/11/2020
The surface of Venus has been previously suggested to undergo short, intermittent and dramatic global resurfacing events. Subduction on
Venus happens locally, with slowly sinking plates but no significant plate motion at the surface. As such, it can explain both Venus’s old
surface and the presence of sinking plate fragments.
Mobile-lid mantle convection on Earth (a) involves most surface plates (black), which are recycled by sinking back into the deep mantle.
The ongoing plate destruction causes a more heterogeneous mantle and a surface of variable age, with young and thin oceanic plates
and old and thick continental plates that remain at the surface. Mantle plumes (red) tend to occur far away from sinking plates. By contrast,
the mode of mantle convection on Venus (b) — as suggested by Davaille and colleagues — consists of a nearly immobile, mostly stagnant
lid, and only localized, short sinking plate portions that are formed by (and thus spatially coincide with) hot mantle upwelling (red). The
resulting surface deformation matches observations from coronae on Venus. The short sinking portions do not, in contrast to Earth,
significantly move their tail ends at the surface, which explains the uniformly aged, relatively thick surface plate (black).
Crameri, Fabio. “Planetary Tectonics: Sinking plates on Venus.” Nature Geoscience (2017).
Mars
22
10/11/2020
Grand
Canyon
Mars
Grand Canyon
Groundwater sapping
23
10/11/2020
Mars
Groundwater sapping
Groundwater sapping
24
10/11/2020
https://vimeo.com/81095090
25
10/11/2020
26
10/11/2020
27
10/11/2020
Conglomerate
Rock
28
10/11/2020
29
10/11/2020
A vast ocean covered the northern hemisphere of
Mars 3.5 billion years ago.
30
10/11/2020
How did Mars
‘break’?
31
10/11/2020
Mars Environment
•Mars lost liquid water when it lost its atmosphere
•Atmosphere of 0.006 Bar (1 Bar = Earth’s atmospheric pressure)
•No chance for liquid water at surface! (would require higher atm pressure)
32
10/11/2020
How did Mars lose its atmosphere?
Internal heating (which creates magnetic field) on Mars ceased. Without the
protection of an active magnetic field, the solar wind blasts Mars’ atmosphere,
causing gas molecules to be swept away and water to break into free oxygen and
hydrogen. Free oxygen may explain rusted soil on Mars.
If we were to infuse Mars, today, with an Earth-like atmosphere, the solar wind
would whittle it back down to its present density in a mere few tens of millions of
years.
33
10/11/2020
Mars is relatively small
Earth
Mars
The phase transition from brittle to ductile mantle material
happens close to the core boundary in Mars, where it
suppresses rising mantle plumes. Only one hot (red) plume
is left in the right hemisphere and reaches up to the cold
(blue) crust.
34
10/11/2020
As planetary mass increases,
more heat is produced within.
This causes the shear stress
within the crust to increase (due
to heat trying to escape) and
plate thickness to decrease (due
to melting at depth).
Because thin plates are weaker,
plate
tectonics
becomes
“inevitable” on massive rocky
planets.
Our own planet seems to lie at
the threshold. If it were any less
massive, it would probably not
be geologically active.
Greenhouse gases may also have
been removed by the carbon cycle
How would you test this
hypothesis?
35
10/11/2020
Testable Prediction:
There should be a thick layer of
carbonate buried below the
surface of Mars
MARS
CO2
CO2
CO2
36
10/11/2020
Landed in 2005. On May 19, 2010, Opportunity reached 2246 sols of operation, making it the
longest Mars surface mission in history, breaking the record of 2245 sols set by Viking 1.
37
10/11/2020
38
10/11/2020
39
10/11/2020
40
10/11/2020
41
10/11/2020
Sedimentary Layers
42
10/11/2020
43
10/11/2020
pH
scale
CaCO3 + 2HCl => H20 + CaCl2 + CO2
Evidence for past CO2 on Mars
CaCO3 + 2HCl => H20 + CaCl2 + CO2
•Calcium carbonate (3 to 5%) in soils around the Phoenix landing site.
•pH of soil did not change when acid was added (must be buffered by carbonate)
•CO2 gas released when soil was heated
44
10/11/2020
Samples from two different drill sites on an ancient lakebed have yielded 3-billion year old, complex organic
macromolecules that look strikingly similar to kerogen, the goopy fossilized building blocks of oil and gas on Earth. At a
few dozen parts per million, the detected levels are 100 times higher than previous finds, but scientists still cannot say
whether they have origins in biology or geology. The discovery positions scientists to begin searching for direct evidence
of past life on Mars and bolsters the case for returning rock samples from the planet, an effort that begins with the Mars
2020 rover.
45
10/11/2020
The ‘Goldilocks Zone’
To maintain stable concentrations of greenhouse gases, a
planet must be big enough to sustain long-term volcanic
outgassing. (unlike Mars)
Planet must also not be too close to the sun or a runaway
greenhouse effect will cause water to ‘leak’ into space.
(Unlike Venus)
Planet must be close enough to the sun for water to be in
liquid form (Unlike outer planets).
Is Earth ‘just right’?
Some review questions to
consider
•What are greenhouse gases?
•How does Earth self-regulate CO2 greenhouse gases?
•And last, describe the steps that would happen to
Earth’s climate if either one of those regulatory
processes stopped working.
46
10/20/2020
Astrobiology
Module
RECAP
Matter in the universe has become increasingly organized since
the Big Bang (formation of atoms led to stars, which led to
nucleosynthesis, which led to planets, which are potential
habitats for life)
•
Astrobiology
Module
•
The universe is made up of H>He>O>C>N
Sawtooth pattern due to greater stability of atoms with even numbers of protons
1
10/20/2020
Astrobiology
Module
The universe is made up of H>He>O>C>N
•The most abundant atom in your body is hydrogen (H). Next is
oxygen (O), which combines with H to make water (H2O), then
carbon (C), then nitrogen (N). The only difference is He, which
is chemically inert.
•We are made of the same raw materials as the universe in the
same order of abundance.
Astrobiology
Module
•
Amino acids (part of proteins), nucleic acids and ribose (part
of DNA), and fatty acids (part of cell membranes) have all
been detected by telescopes in space or inside meteorites
and comets.
•
Formed from chemical reactions triggered by protons from
solar wind. http://www.pnas.org/content/112/23/7109.short
2
10/20/2020
Glowing protoplanetary disks (“proplyds”) are chemical reactors for
amino acids, nucleic acids, ribose, and fatty acids, seeding new
planets with the ingredients for life from the very start.
Life should be everywhere.
Astrobiology
Module
•CONCLUSION
•Life is an expression of the universe’s natural chemistry and physics.
•Given the billions of planetary systems just in our own galaxy, it is
unlikely that Earth is unique.
•The history of life has probably happened many times.
3
10/20/2020
Astrobiology
Module
THIS MODULE
• Astrobiology
• Exoplanets and exomoons: discovery, types, habitability factors
• How likely are we to discover intelligent life beyond Earth?
• Properties of living systems – basic requirements anywhere
• Different approaches to studying how life started here
What is astrobiology?
NASA Astrobiology profiles the career path of up and coming astrobiologists from all
around the world. This episode showcases Dr. Betul Kacar, an Assistant Professor at the
University of Arizona, and a prominent member of the NASA Astrobiology community.
4
10/20/2020
Astrobiology
Module
• Exoplanets and exomoons: discovery, types, habitability factors
In 1992, astronomers confirmed the
existence of the first extrasolar planet
“That makes the coincidences
of our planetary conditions –
the single sun, the lucky
combination of Earth-sun
distance and solar mass – far
less remarkable, and far less
compelling as evidence that
the earth was carefully
designed just to please us
human beings,” Hawking
writes.
5
10/20/2020
Exoplanets are very difficult to
detect because they don’t emit any
light of their own and are
completely obscured by their
extremely bright parent stars.
Normal telescope observation
techniques cannot be used.
Instead of trying to image/detect
exoplanets directly we look for the
physical effects they have on their
parent star such as shifts in
position or changes in brightness.
6
10/20/2020
Mercury passing
in front of the sun
7
10/20/2020
Radial Velocity Method
Transit Method
Even with the most powerful telescopes, we can’t see planets orbiting distant stars.
But when we see a star that blinks at regular intervals, a planet may be orbiting and
blocking a bit of light each time it crosses in front of the star. Knowing the interval
and how long and deeply they make the star fade, scientists can determine how big
the planet is and how long it takes to orbit the star.
8
10/20/2020
Infrared
Direct
Imaging
Method
This infrared image of 3 faint bodies orbiting star HR 8799 (2008 Science 322 1348)
is the first direct image of a triple-planet system. The center area is the residual light
from the host star, while the red dots at 2, 5 and 10 o’clock are the orbiting planets.
The planets’ estimated masses range from 7 to 10 times the mass of Jupiter; with
orbital distances of 24, 38 and 68 astronomical units (AU), this cluster of alien
worlds resembles a larger version of the outer solar system.
(Neptune is 30 AU from the sun)
Microlensing method
Works for planets thousands of light years away. The lensing star (white) and planet (blue)
in the inset diagram move in front of the source star (orange) magnifying the source star’s
image and creating a microlensing event.
Us
Source
Star
Lensing
Star
9
10/20/2020
10
10/20/2020
What kinds of planets have been discovered?
Alien planets are a diverse bunch. Astronomers have found
•
•
•
•
•
A planet as light and airy as styrofoam,
A planet made out of diamond,
A planet as dense as iron.
Planets that orbit two suns and one that has four suns.
And planets with such high temperatures and pressures that they
would form exotic materials like ‘hot ice’ or ‘superfluid water,’
substances that are completely alien to our everyday experience.
Exoplanets detected by various methods. Horizontal lines mark the sizes of Jupiter, Neptune and Earth,
all of which are displayed on the right side of the diagram. The shaded gray triangle at the lower right
marks the exoplanet frontier that will be explored by future exoplanet surveys.
https://www.nasa.gov/image-feature/ames/kepler/exoplanet-populations
11
10/20/2020
Earth is BARELY within the habitable zone
The dark green area represents an optimistic estimate for the habitable zone, while the brighter green
area represents a more conservative estimate for the habitable zone.
https://www.nasa.gov/image-feature/ames/kepler/kepler-habitable-zone-planets
12
10/20/2020
(Oct. 2012)
WASP-18b
1.9 million miles from its star (about 1/50 distance from Earth to sun)
Surface temperature is about 3800° F. 10 times bigger than Jupiter
(puffed up because of heat)
Clouds of rock dust, possibly metals due to high temperatures (not
ammonia and methane ice clouds as on Jupiter – can’t condense
at high temperatures). Orbital period is less than one day!!! Will likely
spiral into its star in less than a million years
13
10/20/2020
Alien planets are a diverse bunch. Astronomers have found one planet as light and
airy as Styrofoam, some made out of diamond, and another as dense as iron. They’ve
discovered several alien worlds that orbit two suns, like Luke Skywalker’s home
planet of Tatooine in the “Star Wars” films, and one that has four suns.
GJ 1214b, a super-Earth, is about 2.7 times Earth’s diameter. It orbits a red-dwarf
star at a distance of 1.2 million miles, giving it an estimated surface temperature of
446 F — too hot to host life.
Since astronomers know GJ 1241b’s mass and size, they’re able to calculate its
density, which turns out to be just 2 grams per cubic centimeter (g/cc). Earth’s
density is 5.5 g/cc, while that of water is 1 g/cc. GJ 1214b thus appears to have much
more water than Earth does, and much less rock. The alien planet’s interior structure
is likely quite different from that of our world.
The high temperatures and pressures would form exotic materials like ‘hot ice’ or
‘superfluid water,’ substances that are completely alien to our everyday experience.
Super Earths are bigger than Earth but smaller than ice giants Uranus and Neptune
14
10/20/2020
15
10/20/2020
How exoplanets are studied
Join Dr. Aomawa Shields, an astronomer and astrophysicist at UCLA in California, as she hunts for
exoplanets and extraterrestrial life in the universe.
16
10/20/2020
Exomoons?
The 5 billion origins of life in the Milky Way estimated from
the Drake Equation only considered life on planets.
What are the basic geological requirements
for a moon to have complex life?
17
10/20/2020
Jupiter’s moon Io
18
10/20/2020
Europa
Bluish-white = pure water ice. Orange = water ice mixed with salts, magnesium
sulfate or sulfuric acid. It is possible that these surface features may have
communicated with a global subsurface ocean layer during or after their formation.
19
10/20/2020
Europa flyover (scale: one pixel = 55 m)
https://www.youtube.com/watch?v=QDo3em6pqv4&feature=youtu.be
20
10/20/2020
21
10/20/2020
NASA’s Europa Clipper
orbiter will be launched
in 2024, and a lander
mission may follow after
that.
Survey mapping needs
to be done first.
Surface is too chaotic
to attempt a lander
without knowing where
to land safely.
22
10/20/2020
Saturn’s moon Enceladus
Saturn’s moon Enceladus
Deep, canyon-size, curvilinear faults cutting across the landscape through impact basins
and formed as a response of the crust to stress from Saturn’s gravitational pull.
23
10/20/2020
Convection
24
10/20/2020
Enceladus’ Geysers
Enceladus’ Geysers
25
10/20/2020
This illustration shows NASA’s Cassini spacecraft diving through the
plume of Saturn’s moon Enceladus, in 2015.
Astronomers will be looking for a universal molecular signature of water-based life. That
biomarker would likely be a large molecule composed of many repeating subunits with
an electrical charge, because that’s the only molecule type that can support
Darwinian evolution. Astronomers will also be looking for isotopic signatures of life, and
long carbon chain molecules that could serve as cell membranes.
http://www.astrobio.net/news-exclusive/big-repeating-molecule-may-defines-life/
Deep in Enceladus, water reacts with rocks containing reduced iron-bearing minerals,
which react with H2O to produce molecular hydrogen (H2). This molecular hydrogen has
been detected in the plumes.
H2 is important because microorganisms at deep ocean vents on Earth obtain energy
when they use it to convert CO2 (carbon dioxide) to CH4 (methane). The conditions for
simple bacterial life therefore DO exist in Enceladus’ oceans.
26
10/20/2020
Saturn’s moon Titan
Cassini-Huygens NASA/ESA/ASI
robotic spacecraft mission to
Saturn and its moons. Probe was
launched in 1997 and entered
Saturn orbit in 2004. Huygens
probe landed on Titan Jan. 2005
(first landing in the outer solar
system).
https://www.youtube.com/watch?v=jiEycgFtPcM
27
10/20/2020
https://www.nasa.gov/image-feature/jpl/working-toward-seamless-infrared-maps-of-titan
28
10/20/2020
January 2005, by ESA’s
Huygens probe during its
successful descent to
land on Titan.
It shows the boundary
between the lightercoloured uplifted terrain,
marked with what
appear to be drainage
channels, and darker
lower areas.
These images were taken
from an altitude of about
8 kilometres .
29
10/20/2020
Altitude of approximately
10 miles.
Shows short
drainage channels leading
to a shoreline.
Feb. 22, 2007, lake on Titan.
Island is 62 by 93 miles across.
30
10/20/2020
And what if liquid water is not the only possible
medium of life? Temperature ranges for some solvent
candidates to occur in the liquid state (at 1 bar)
Titan
Methyl nitrate
Earth
31
10/20/2020
Results from the Huygens
probe to Saturn’s moon Titan
1.Only known moon with a thick
atmosphere. UV converts to hydrogen
cyanide, an amino acid building block
essential for life.
2.Only body known to have surface liquid
besides Earth. River channels cut into the ice
(ice =“bedrock” on Titan ).
3.Liquid lakes, but the surface is -178 C!
Liquid cannot be water, but is ethane.
Ethane is what happens to methane in the
upper atmosphere after contact with UV.
Freezing point = -183 C.
4.The lakes are a low-temperature, nonpolar
solvent (very different from water), but are
still potential chemical reactors. Only small
molecular weight organic molecules are
soluble in liquid methane.
32
10/20/2020
Astrobiology
Module
• How likely are we to discover intelligent life beyond Earth?
How common is life outside our solar system?
What chance do we have of discovering intelligent life
outside of our solar system?
33
10/20/2020
The ‘Goldilocks Zone’
To have conditions necessary for life, a planet must
be big enough to sustain long-term volcanic
outgassing (Mars)
Planet must also not be too close to its star or a
runaway greenhouse effect will cause water to ‘leak’
into space (Venus)
How many extrasolar planets have these Earth-like
properties?
The Drake Equation
In 1960, Frank Drake conducted the first search for radio signals from
extraterrestrial civilizations at the National Radio Astronomy Observatory
in West Virginia.
Soon thereafter, the National Academy of Sciences asked Drake to
convene a 1961 meeting on detecting extraterrestrial intelligence. The
equation that bears Drake’s name arose out of his preparations for the
meeting.
“As I planned the meeting, I realized a few days ahead of time we
needed an agenda. And so I wrote down all the things you needed to
know to predict how hard it’s going to be to detect extraterrestrial life.
And looking at them it became pretty evident that if you multiplied all
these together, you got a number, N, which is the number of
detectable civilizations in our galaxy.”
34
10/20/2020
The Drake Equation
Probability of life evolving = N* x FP x NE x FL
Where:
N*
FP
NE
FL
200 billion X 0.50 X 0.10 X 0.50 = 5 billion planets with life in Milky Way
= number of stars in the Milky Way Galaxy (about 200 billion)
= fraction of stars that have planets around them (50%)
= fraction of planets capable of sustaining life (10%)
= fraction of planets in ne where life evolves (50%)
What is the probability of CONTACTING
intelligent life beyond our solar system?
N = (N* x FP x NE x FL) x FI x FC x FS
Where:
(N* x FP x NE x FL) = 5 billion (# of planets with life in Milky Way)
FI = fraction of planets where intelligent life evolves (1%)
= 50 million planets with intelligent life in our galaxy
35
10/20/2020
Intelligent life beyond Earth?
Stephen J. Gould
Consciousness at
our level
of
language
and
conceptual
abstraction has evolved but once on
Earth — in a small lineage of primates
(some 200 species), within a small
lineage of mammals (some 4,000
species), while the more successful
beetles now number more than half a
million … If complex consciousness has
evolved but once … how can anyone
defend
the
inevitability
of
its
convergent evolution?
Natural History, December 1998
What is the probability of CONTACTING
intelligent life beyond our solar system?
N = (N* x FP x NE x FL) x FI x FC x FS
Where:
(N* x FP x NE x FL) = 5 billion (# of planets with life in Milky Way)
FI = fraction of planets where intelligent life evolves (1%)
FC = fraction of fi that try to communicate (10 %)
FS = fraction of the planet’s life during which the
communicating civilizations live (could be 0.001%)
5 billion X 0.01 X 0.10 X 0.00001 = 50 planets in the Milky Way
with intelligent life capable of communication and alive during
our civilization
36
10/20/2020
FERMI PARADOX:
“Where is everyone?
Since the number of stars in the universe far surpasses the
number of sand grains on every beach on Earth, why
haven’t we found aliens yet?
The Great Filter?
• Humanity seems to be on track to expanding way beyond Earth,
potentially filling the universe with life.
• The fact that space near us seems dead tells us that there could
be a great filter.
• If so, how far along the filter are we?
THE GREAT FILTER?
1. The right star system (including organics)
2. Reproductive something (RNA, DNA)
3. Simple (single-cell life)
4. Complex (eukaryotic) single-cell life
5. Sexual reproduction
6. Multi-cellular life
7. Tool-using animals with big brains
8. Where we are now
9. Colonization explosion
Life on Earth has passed from stages 1-8. Humanity filling the universe
with life seems inevitable. Competition should encourage population
expansion, as those who travel too slow, linger too long, or choose
not to replicate become outnumbered by others. Increasingly fast
and high risk colonization probes may be sent on increasingly long
journeys, all for a chance at being the first to colonize vast virgin
territory. The Great Silence implies that one or more of these steps
are very improbable; there is a “Great Filter” along the path to
explosive life that destroys life or resets the stages.
http://mason.gmu.edu/~rhanson/greatfilter.html
37
10/20/2020
Recent updates
• Alien supercivilizations absent from 100,000 nearby
galaxies
• Dyson Spheres: energy-hungry futuristic civilizations might
dismantle a few planets to produce star-enveloping solar collector
• Prediction: optically dim but hot (mid-infrared)
http://www.scientificamerican.com/article/alien-supercivilizations-absent-from-100-000-nearby-galaxies
Recent updates
• Alien nuclear wars might be visible from Earth
• If there were many explosions, it might generate enough heat and
life to be seen from nearby stars.
• Assumption: Intelligent species are likely to stumble upon nuclear
technology . . . and use it.
http://www.theatlantic.com/technology/archive/2015/09/alien-nuclear-wars-might-be-visible-from-earth/404176/
38
10/20/2020
Recent updates
• Did life spread like an epidemic across galaxies?
• Panspermia: Idea that life can spread between planets or
between star systems, either by gravitational slingshotting of
asteroids or travel by intelligent life.
• Prediction: Should have a pattern similar to outbreak of an
epidemic. Should find infected pockets of life.
http://www.dailygalaxy.com/my_weblog/2015/08/cosmic-oases-did-life-cross-the-vast-gulf-of-interstellar-space-long-ago.html
Astrobiology
Module
THIS MODULE
• Properties of living systems – basic requirements anywhere
• Different approaches to studying how life started here
39
10/20/2020
Properties of Living Systems
Self-organizing. Living systems use energy from light and chemical
bonds to produce and maintain organized structures over time. This is
also called metabolism.
Information control. All organisms must maintain, grow, and replicate
efficiently. To do so requires storage and management of cellular
instructions.
Carbon-based. All living systems we know require a carbon-based
chemistry.
Compartmentalization. Life needs membranes that surround cells
and compartmentalize internal components because organizing
molecules is key to getting them to work together at the right time
and place. Some molecules also need to be kept apart.
Why Carbon?
Abundance. Carbon is very abundant due to
nucleogenesis in stars. Requires simultaneous
collision of 3 helium nuclei.
40
10/20/2020
Why Carbon?
Carbon is very flexible in its bonding. It readily forms
single, double, and triple bonds.
Why Carbon?
Carbon-based molecules can exist as gases and
liquids, gels, and solids.
Carbon works very well in water.
A major element in DNA, cell membranes, and
proteins
41
10/20/2020
Carbon-based life
Carbon-based life
Amino Acids
42
10/20/2020
Carbon-based life
Carbon can be linked to itself in long chains.
Why Cells?
All life requires a boundary layer (a membrane)
that separates internal contents from an external
environment.
This helps regulate the flow of nutrients in and
keep waste products out. It also keeps out toxins
and keeps in structures necessary for functioning.
The cell is the smallest unit of life that can
perpetuate itself.
Carbon liposomes form cells spontaneously.
43
10/20/2020
Phospholipids (necessary for cells)
Phosphate end likes water
Carbon chain end ‘hates’ water
Organic molecules with two sides – one attracts water and one repels water.
https://www.youtube.com/watch?v=IPM8OR6W6WE (hydrophobic concept)
Lipids self-assemble
in a sheet (lipid
bilayer) with the two
sides
facing
opposite directions.
One side attracts
water,
one
side
repels it.
44
10/20/2020
If the sheet folds on itself, it
forms a waterproof ‘cell’
around whatever contents it
has trapped.
These cells are called
‘liposomes’
and
form
spontaneously in nature.
Liposomes
45
10/20/2020
https://www.youtube.
com/watch?v=lmdAvbl330
46
10/20/2020
Lipids
If DNA is present in the solution, it may be
trapped inside the liposome in high
concentrations.
47
10/20/2020
Life is Made from Organic Molecules
Carbon-based
Include:
Proteins and amino acids
Lipids (fats)
Carbohydrates (sugars)
Called ‘organic’ because they are synthesized by living
organisms.
The Origin of Life
There is no direct fossil evidence of progression from
non-living to living things.
Bacteria-grade cells just appear in the Archean.
But we can make an educated guess how it happened
(origin of organic molecules, transition to life)
48
10/20/2020
Origin of Life Problems
There are 2 ways to study these problems:
1. Top-down
Start with primitive life that still exists today. Scientists look for
primitive modern cells for clues. How simple can a cell be
and still be a fully-functioning cell?
2. Bottom-up:
Scientists try to make a self-replicating cell (or building
blocks)in the lab. Can we recreate early Earth conditions
and ‘make’ life happen?
Stanley Miller
experiments (1953)
Mixed methane, ammonia, and
hydrogen with water and
electricity.
Assumed these were abundant
on early Earth.
Concluded that the complex
organic molecules for life were
abundant on early Earth.
49
10/20/2020
50
10/20/2020
Stanley Miller
experiments (1953)
Problem: It is controversial
whether there was methane in
the early atmosphere.
It is unlikely that organic
molecules could have been
synthesized in this manner.
Update
51
10/20/2020
The Bottom up Approach
Jack Szostak
Research on molecular
precursors to DNA
“RNA World” hypothesis
The Bottom up Approach
52
10/20/2020
Protoplanetary disks in the Orion Nebula
Attempts to find building
blocks of life in space are
also ‘bottom up’
An infrared spectrum from the
European Space Agency’s
Infrared Space Observator
superimposed on an image of
the Orion nebula, where
complex organics were found.
Stars
produce
organic
molecules and eject them into
space.
Emissions start at
protoplanetary nebula stage
and grow stronger as stars
mature into planetary nebula
phase.
This study proposes the
hypothesis
that
organic
materials found in meteorites
were likely inherited from
interstellar sources.
Sun Kwok and Yong Zhang. 2011.
Mixed aromatic–aliphatic organic
nanoparticles as carriers of
unidentified infrared emission
features. Nature
53
10/20/2020
In the 1960’s,
meteorites
found to
contain
amino acids
54
10/20/2020
Stardust passed through dense gas and dust surrounding the icy nucleus of Wild 2 (pronounced “Vilt-2”) on
January 2, 2004. As the spacecraft flew through this material, a special collection grid filled with aerogel – a
novel sponge-like material that’s more than 99 percent empty space – gently captured samples of the
comet’s gas and dust. The grid was stowed in a capsule which detached from the spacecraft and parachuted
to Earth on January 15, 2006. Since then, scientists around the world have been busy analyzing the samples
to learn the secrets of comet formation and our solar system’s history. So far, a diverse suite of organic
compounds has been identified.
Silicon-based solid
99.8 percent empty space (slightly heavier than air)
Particles bury in the material, creating a track
Brings the sample to a gradual stop (from 13,000 mph)
Tracks used to find and extract the tiny particles.
55
10/20/2020
What evidence suggests that amino
acids on Earth (that gave rise to life)
originated from amino acids in outer
space (and not from Earth)?
E. H. Man, J. L. Bada, 1987. Dietary D-amino acids. Ann. Rev. Nutr. 7:209-225.
Proteins are the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that
speed up or regulate chemical reactions. Just as the 26 letters of the alphabet are arranged in limitless combinations to
make words, life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins.
Amino acid molecules can be built in two ways that are mirror images of each other, like your hands. Life uses only the
left-handed form during protein synthesis. The right-handed form is excreted. Conversion of amino acids back to lefthanded from may occur in kidney and liver but not efficiently. They are not easily transported and not easily catabolized.
If you eat food with the right-handed form, it will be either nutritionally useless or possibly toxic. Some food processing
practices that involve heating for extended periods (e.g., pasteurization of milk, heat sterilization and drying of infant milk
formulas) and exposure to alkaline substances (e.g., processing corn with lime, ash, or caustic soda to make corn chips
and tortillas) can convert left-handed amino acids to right-handed. Significant amounts of right-handed AAs in texturized
soy protein, yogurt, fake bacon, nondairy creamer, wheat crackers, cereal, cooked aspartame.
Benefits of right-handed AAs: some may inhibit pain and others may have anti-biotic properties.
56
10/20/2020
NASA researchers analyzed samples of meteorites with an abundance of carbon and looked for amino acids. Three types of
meteorites had more of the left-handed version than the right-handed variety – as much as a record 18 percent more in
the often-studied Murchison meteorite. That suggests that early life ‘chose’ the left-handed form because it was selecting
from amino acids brought to the early Earth by asteroids and comets. The amino acids weren’t necessarily being formed
from scratch right here on Earth.
Different types of meteorites had different amounts of water, as determined by the clays and water-bearing minerals found
in the meteorites. The researchers discovered that meteorites with more water also had greater amounts of left-handed
isovaline. In other words, the creation of extra left-handed amino acids had something to do with alteration by water.
http://www.nasa.gov/centers/goddard/news/topstory/2009/left_hand_life.html
57
10/20/2020
Origin of Life Problems
There are 2 ways to study these problems:
1. Top-down
Start with primitive life that still exists today. Scientists look for
primitive modern cells for clues. How simple can a cell be
and still be a fully-functioning cell?
2. Bottom-up:
Scientists try to make a self-replicating cell (or building
blocks) in the lab. Can we recreate early Earth conditions
and ‘make’ life happen?
The Top Down Approach
Top-Down Approach:
Carsonella genome has
160kb of DNA.
This is the smallest
amount of DNA ever
discovered in a live cell.
58
10/20/2020
The Top Down Approach
DNA tells us the last universal common ancestor was a
heat-loving chemical eater (extremophiles)
Hydrothermal Vents
59
10/20/2020
Hydrothermal Vents
60
10/20/2020
Hydrothermal Vents
Hydrothermal vents are places in the deep
ocean which spew super-heated gases.
Communities of animals live off of (and
with) symbiotic archaebacteria.
These bacteria convert the carbon-rich
inorganic gases into food, which other
animals can then use.
CO2 + O2 + 4H2S → CH2O + 4S + 3H2O
Deep–Sea Hydrothermal Vents
Until the discovery of these vent systems in
1977, all known ecosystems on Earth had
photosynthetic organisms at the base of
their food chain.
Hydrothermal
vent
ecosystems
are
dependent on chemosynthetic bacteria
that generate energy from eating
hydrogen sulfide.
These
bacteria
exist
in
symbiotic
relationships with other members of the
ecosystem including mussels and 8 foot
long tubeworms.
Tubeworms have no mouth, gut or anus.
Instead, they have a giant organ in the
center of their body that is filled with
symbiotic bacteria that take on all the
digestive and excretory functions of the
worms.
61
10/20/2020
PYRITE
FeS2 (iron(II) disulfide)
Hydrothermal
Vent
One of the key-principles of the
iron-sulphur world theory is to
bring organic molecules close
enough to interact with each
other, using the surface of
pyrite as a substrate in a
hydrothermal setting.
In hydrothermal environments,
organic matter is accumulated
as coatings around, and
through, pyrite grains.
Pyrite crystals (white
green)
Carbon (black and red)
and
Pyrite crystals coated with organic matter. A) Backscattered SEM micrographs of pyrite crystals coated with organic matter in
hydrothermal calcite veins from Mullaghwornia. The pyrite crystals appear white, the organic matter is black, and the calcite is
grey. B) ED X-ray maps for sulphur (green) and carbon (red), with corresponding micrograph of pyrite and carbon.
http://geochemicaltransactions.springeropen.com/articles/10.1186/1467-4866-12-3
62
10/20/2020
Hydrothermal Vent Origins
Energy released during pyrite formation
provides a regular mesh of electrical
charges at the crystal surface that
attracts reactants and arranges them for
synthesis of organic molecules
Hydrothermal Vent Origins
Energy released during pyrite formation
provides a regular mesh of electrical
charges at the crystal surface that
attracts reactants and arranges them for
synthesis of organic molecules
63
10/20/2020
Hydrothermal Vent Origins
Energy released during pyrite formation
provides a regular mesh of electrical
charges at the crystal surface that
attracts reactants and arranges them for
synthesis of organic molecules
Crystals consist of highly ordered,
repeating units of atoms, which gives rise
to
precise
electrical
patterns
Micro-caverns act like cells, concentrate
newly synthesized molecules to form
chains
Steep temperature gradients inside
black smokers allow optimum zones for
reactions
Thermal gradients in millimeter-sized pores can cause extreme buildups of
organic molecules.
64
10/20/2020
Iron-Sulfur World Hypothesis.
The hypothetical “pioneer organism” lived in
hydrothermal flow at high temperatures and
pressures and had metabolism without DNA, cells,
or ability to reproduce.
It had a “composite structure” that included a
mineral base that provided electrons needed to
grow proteins from inorganic gases (CO, CO2 H2S).
The big challenge to this early life was detaching or
decomposing too early. Organic compound variants
that randomly had an ability to stick to mineral base
and/or speed up further mineral formation would
have out-reproduced other variants. This process
mimics inheritance and natural selection. Only
metal-organic composites that stick around are
available for later chemical reactions.
Eventually, natural selection would favor
increasingly complex organic compounds that drive
and speed up self-replication (i.e., genetics).
65
10/20/2020
Last
universal
common
ancestor may have lived inside
a black smoker
Last evolutionary step would be
synthesis of cell so organism
could
leave
micro-cavern
system
Archaebacteria and Eubacteria
have completely different types
of
membrane
lipids
but
common physiology and DNA.
Life evolved BEFORE
membranes???
cell
66
10/20/2020
Quick review
1. What is a liposome
spontaneously?
and
how
does
it
form
2. What are the building blocks of life? Where did they
form?
3. Why does all life on Earth use left-handed amino acids?
4. What is the difference between bottom-up and topdown approaches to understanding the origin of life?
5. What is a chemical cluster/mineral library? How might
natural selection be involved?
The origin of life was a major threshold-crossing event
representing an increase in the degree of organization of the
universe (decreased entropy).
The origin of life was not the first event of this nature.
67
10/20/2020
Our lecture covers the origin of life beyond an introductory level, but if you’re still
curious (and not afraid to skim around, through, under some chemistry jargon) you
might find these two links of interest.
One paper is about self-replicating proteins called prions. They act like viruses and
are actually a cause of disease today.
http://www.sciencedirect.com/science/article/pii/S0306987706003355
The other is about self-assembly of amino acid chains (precursors to proteins) on
mineral surfaces, similar to the iron-sulfur world hypothesis.
http://www.nature.com/nature/journal/v381/n6577/pdf/381059a0.pdf
http://astrobio.net
https://astrobiology.nasa.gov/
68
10/20/2020
http://exploringorigins.org/
69