TIDAL HEATING OF THE MOON
1. Strong gravitational pull from parent planet = Fg
2. Tidal force = difference between Fg on/near far sides of the moon.
3. If the moon has slightly elliptical orbit the magnitude and direction of tidal force keep changing.
4. Moon is constantly flexed ▯ warmth!
External Sources of Water for Earth
• Volcanic water vapour
⋅ One of the ~60 moons of Saturn
⋅ Has methane lakes
⋅ Thick atmosphere – 200km high (denser than Earth’s atmosphere). Protects surface against radiation.
⋅ 90% N2, CH4 1.4%, Ar, C2H6, and other hydrocarbons.
Cassini Huygens Mission
⋅ Sent to study Saturn.
⋅ Attached Huygens probe to spacecraft. Cassin performed flybys (mapped surface)
2005: Huygens probe dropped on Titan. It gave aerial views of hills and forking channels, carved by liquid methane and ethane
• Rocks on Titan= frozen liquid water
• Smoggy, chemically active atmosphere, produced by outgassing (perhaps) from Titan’s interior [internal pressure causing
Methane & Ethane lakes Water
Ice rocks (water) Rocks (made of minerals)
Slushy mix of water ice/ammonia (volcanoes) Lava (volcanoes)
Hydrocarbon particles on surface/in rain/in atmosphere ▯smog Soil
Dunes of hydrocarbons Sand/snow dunes
Atmosphere: 90% N2 Atmosphere: 78% N2
Photochemical haze Ozone UV Light from sun: Dissociates methane in upper atmosphere
⋅ An organic smog of complex hydrocarbons such as C2H2 (Acetylene)
⋅ And tholins = large, complex, N2 rich organic molecules
Continued presence of methane in Titan’s atmosphere:
A surface source of methane renewal. Probably evaporation from methane lakes
OR Methanogens? : organisms that produce methane
(Biochemical process in life forms)
Earth Animal Metabolism:
⋅ Glucose + Oxygen ▯ Carbon dioxide + Water
C H 6 12 O 6 + 2 6O ▯2 2 6CO + 6H O
Earth Methanogen Metabolism:
⋅ Carbon dioxide + Hydrogen ▯ Methane + Water
CO 4H 2 2 ▯ 4 2 CH + 2H O
Titan Life Chemistry:
Might Titanians use H2 as Earthlings use O2, Methanogenic life on Titan is plausible using the following as an energy source for
⋅ Acetylene + Hydrogen ▯ Methane OR Ethane
+6 2 2 2 4 Hydrogen ▯ 2 2 4 Methane
C H + 3H ▯ 2CH C H + H ▯ 2CH
Photochemical (nonlife) models predict that Titan would have a surface layer of many meters of ethane. Therefore, if there exists
depletion of ethane (and acetylene), there would be strong support for uptake by surface methanogens.
Cassini Huygens Mission 2010
June 2010: Cassini Mission did NOT find a thick layer of ethane predicted by photochemical models.
⋅ It found less acetylene, ethane and hydrogen than expected: depleted by metabolism of methanogenic life.
⋅ A biological cause for depletion? Microbial extraterrestrial life?
⋅ Huygens was not equipped to detect life forms: panspermia? Microbeladen rocks from Earth to Titan?
Suitable Conditions for Life on Titan
• Many organic molecules in atmosphere
• Surface is cold (180 degrees Celsius) ▯ slow metabolism life forms; could use catalysts to speed up biochemical
Hypothetical Titan Life forms SILICON CREATURES:
⋅ Might breathe in O2 of H2 but 02 is rare and CO2 is frozen on Titan
⋅ Releases Si 02 or Si H2: would be rigid and slowmoving and slender because of lowgravity.
SUITABLE CONDITIONS FOR LIFE ON TITAN:
• Icy volcanism= cryovalcanism ▯ eruption of water, ammonia, methane.
• Energy to melt subsurface ice comes from tidal fraction?
• Maybe a warmer subsurface? Allowing water/ammonia slush which melts at 95degrees Celsius.
• Titan could have an alien chemistry of life.
• Methanogen microbes = microscopic life. H2 can combine with gaseous hydrocarbons, C2H2 or C2H6 and release methane
• Low gravity and dense atmosphere [only moon with one] could support heavy birdlike life forms which might breathe in H2
and releases CH4
⋅ One of the ~ 60 moons of Saturn
Atmosphere: 91% water vapour, 4% N2, 3.2% CO2, 1.7% CH4. Low mass of Enceladus ▯atmosphere must be replenished.
2005: Found fresh icy material exiting from long cracks in the southern atmosphere, the make patterns called “TIGER STRIPES:”
⋅ ~130 km long, 2km wide, 500km deep
⋅ Higher surface temperature at ~93 degrees C, than other regioTs encelad ~200
⋅ Active tectonics
⋅ Absence of impact, craters, therefore the stripes are “young”
Full of Geysers, which means it’s warm inside & has water (this is potential for life)
Icy volcanism ▯ geysers of ice, water vapour, methane, CO2, nitrogen, organic molecules, salts (subsurface salty liquid water),
SUITABLE CONDITIONS FOR LIFE OF ENCELADUS
Cryovalcanism ▯ surface heat and liquid water could support microscopic life forms
Heat energy to melt interior ice from: tidal friction? Radioactive decay? Unknown process?
Geysers, hundreds of km high, replenish atmosphere and eject water ice vapour and organic compounds
We should send a probe to fly through the geysers to collect plume sample to return to Earth and examine for life. (No digging or
landing necessary). Problem with this is: organisms on craft could be a result of probe contamination on Earth. Gravitational Force
⋅ The more neutrons, the stronger the pull of gravity.
The Fg of a 60kg spacecraft, sitting on the surface of Enceladus.
R= the radius of Enceladus (from core to the spacecraft on the surface)
Fg= (6.37 x 10 ) 3 2 (60) (1.2 x 10 )
(249 x 10 )
Fg= 7.75N (7.4)
⋅ One of the ~63 moons of Jupiter
Atmosphere: ~100% oxygen, extends 200km high.
Earth’s oxygen is produced by life. On Europa it is produced when charged particles hit icy surface and vaporizes ice.
Water vapour splits into oxygen and hydrogen escapes into the atmosphere.
Oxygen remains in atmosphere continually replenished
SUITABLE CONDITIONS FOR LIFE
Subsurface oceans indicated by:
1. Lack of impact craters. (Young surface from oozing slush below?)
2. Surface broken into huge moving ice blocks ▯ churned by sloshy water below?
3. Salt exists on the surface, salty ocean (good place for extremophiles
4. A salty ocean (creates a magnetic field if moving pull of Jupiter conducts currents) melted Europa’s interior. 20 25 km of thick
ice. Ocean ~100km deep
ENERGY TO SUPPRT LIFE:
1. From chemical reactions near deepocean floor vents may not exist. (hypothesis only)
2. From potassium decay? Potassium (K) is in rocks on the ocean floor of Earth. 40K ▯ 40Ca + e + V + energy [V= neutrino, almost O mass, moves at almost the speed of light
Cannot get energy from the sun
1. Heat (O2 goes into the atmosphere, Hydrogen goes into space)
2. Radioactive decay – H2O2 (Hydrogen peroxide remains and smaller amounts of other molecules)
If these molecules filter into the subsurface ocean, they could provide energy for oceanic life forms ▯ into vents & down into oceans
3. Not much energy is available to support macrolife, but maybe microbes exist. We need to send a lander to determine whether
an ocean exists and to search for organic molecules, amino acids and microbes.
The V escfrom earth is 11.2 km/s
What is the V escfor a 100kg spacecraft on Europa?
V esc= 2Gm m= mass of the object you are trying to escape and radius of the same
-11 27 1/2
= 2(6.67 x 10 ) (4.97 x 10 kg)
1.565 x 10 m
= 2058m/s = 2.06km/s Life in Our Galaxy
Birth of Stars
Consider: they are giant, interstellar and cold, molecular H2 cloud
⋅ ~tens of light years across
⋅ Can contain (104 – 106)times the mass of the sun
⋅ Gravitational force is proportional to mass
Fg= ((G M1M2) / R2))
⋅ Random particle fluctuations in the cloud act as gravitational force to attract more material
⋅ Contracting condensates in cloud, dissipate their gravitational energy, as heat (infrared radiation longer wavelength). Any
particle around will be in the pull of its gravity.
Sun’s name is Sol, hence solar wind
Stuff from another star= stellar wind, stella = star
Material falling onto a condensate
Internal heat and shock waves
H2 molecules dissociate
This contracting object is a PROTOSTAR. The core of a protostar = the central 10%15%
▯Core reaches 10 million K.
=10 x 10 to the 6 K
= 1 x 10 to the 7 K
Hydrogen based nuclear reactions begin in core: A star is born
The strong nuclear force particles with same change coming 10 to the 15m of each other they will.
A Main Sequence Star has:
⋅ H based nuclear reactions in the core
⋅ 4H ▯ He + energy
⋅ The entire birth process for an average star takes 10 to the 6 – 10 to the 9 years.
⋅ The process is faster for a massive star ~10 to the 5 years
Tcore > 10 x 10 (to the 6) K ▯ Hydrogen fusion nuclear reactions in the core, Helium build up in core. ⋅ A star spends its life in a delicate balance between outward radiation pressure and inward gravitational pull. Hydrostatic
equilibrium if reactions stop, star collapses.
⋅ ~ 90% 95% of stars are Main Sequence: including our Sun.
END OF STAR FORMATION
⋅ Stars form a vast interstellar H and He clouds. As the Universe ages Hydrogen is being transformed into heavier elements
inside the stars.
⋅ Hydrogen component of the Universe is always decreasing while the abundance of heavier elements are increasing.
⋅ Eventually new stars will cease to form and the stelliferous era will end.
Core Accretion Theory
1. Protostellar cloud contracts ▯ star and disk of gas and dust
2. Some atoms in disk bond= condensation ▯ “seeds” of planets
3. “Seeds” gently collide and stick together via forces: electrostatic and / gravity.
4. Process continues until a planetary mass
Extra Solar Planets
1992: first two exoplanets discovered in orbit around a pulsar (PSR B1257 +12). Massive stars leave behind neutron star (pulsar) or
black hole when it dies in a supernova explosion.
1995: 51 Pegasi b = first exoplanet in orbit around a main sequence star.
Discovered via radial velocity method. It is a “hot Jupiter” gas giant. Not like Earth
Today: >850 confirmed exoplanets ▯ they are plentiful BUT most discoveries are hot Jupiters because they’re easy to see. They have
high surface temperatures because it orbits close to parent star (0.015 to 0.5 AU).
Our Jupiter is 5.2AU from the Sun
Detection of Extra solar Planets
Radio Velocity: star would just move without any gravitational pull from a planet
Star moves away red shifted, moves towards us blue shifted
Shifting ▯ star is moving alternately toward and then away ▯ gravitational pull of an unseen planet. Most planets are several times the
mass of the earth
In lab, H gamma has wavelength = 434nm. In spectrum of a star, this same line has wavelength of 434.03nm.
Detection of extra solar Planets 1. Transit Method: Planet passes in front of star; we observe changes in star’s brightness. Three periodic light dips confirm the
planet is present.
Red dwarf stars are good search candidates because you can see dip in the light as planet passes
2. Direct imaging ▯ host star and exoplanet are spatially resolved
Glare of parent star makes it extremely difficult to see the planet. We have images of a few exoplanets
Red Dwarf Stars
⋅ They are main sequence star (fusing hydrogen to helium in core): 4H He + energy
⋅ Small and lightweight (0.1 to 0.5 the mass of the sun)
⋅ Live for ~100 billion years
⋅ Cool (2000K 3000K on surface)
⋅ Most abundant type of star, more search targets
⋅ Dimmer than larger stars ▯ easier to detect reflected light from nearby planets
⋅ Nearby exoplanet ▯ many transits over a short time
⋅ Habitable zone would be ~1/50 AU
Kepler Space Telescope
⋅ Launched in 2009 into heliocentric orbit (Helios Greek name for sun). Keeps a fix on 170 000 stars simultaneously seeks
Earthlike planets in Goldilocks zone.
James Webb Telescope
⋅ To be launched in 2018
⋅ Infrared optimized (too much dust in the galaxy)▯ can see through the dusty clouds in space
⋅ Observe star/planet formation
Able to detect oxygen, ozone, water and CO2 on exoplanets
Parent star’s light passes through exoplanets’ atmosphere.
Take spectrum of light of star and again when planet passes star. Atmosphere will let light pass through it. Subtract the 2 and
left with planet’s atmosphere
Gliese (multiplanetary system) 581g
⋅ Orbits the red dwarf star, Gliese 581
⋅ 20.3 ly from us
⋅ Mass ~ 3 4 times the mass of the Earth
⋅ Radius ~1.5 the radius of the earth
⋅ Year = 37 days
⋅ Found by radial Velocity
⋅ Rocky planet
⋅ In the center of its habitable zone
⋅ Gravity sufficient to retain an atmosphere
⋅ Not properly aligned for transit method – no info on atmosphere.
⋅ Orbits a Gtype star (like our Sun),
⋅ Host star is G5 ▯ sunlike (G2)… but a bit cooler
⋅ 600 ly from us ⋅ Mass ~6.4 times the mass of the earth (perhaps?)
⋅ Radius ~ 2.1 R earth
⋅ Year = 290 days
o Detection method: Transit (Kepler telescope)
⋅ In the habitable zone
⋅ Type of planet is unknown. (Rocky? Gaseous? Liquid?)
⋅ No info on atmosphere
⋅ [email protected]
⋅ Detection method: Transit
⋅ 42 ly from us
⋅ T surface ~520 K
⋅ Mass = 6.36 times the mass of Earth
⋅ Density = p ~ 1870kg /m cubed
⋅ Mostly wate