Term
| Why is there no life on Mercury or the Moon (same reasons)? |
|
Definition
| Terrible Extremes of Temperature, No Atmosphere, UV, Cosmic Rays, Little or No Volatiles, No Liquids |
|
|
Term
| Why is there no life on Venus? |
|
Definition
Very High Temperatures, No or Little Water
Young Surface → No Fossil Record |
|
|
Term
| Reasons there is possible life on Mars? |
|
Definition
Evidence for Liquid Water in Past
– Possible Environments for Life to Survive?
– Volatiles and Water Present Now |
|
|
Term
| What type of atmosphere and temperatures exist on Gas and Ice Giant planets? |
|
Definition
| • Atmospheric layers with roughly Earth-like Temperature & Pressure |
|
|
Term
| What type of surfaces exist on Ice and Gas giants? |
|
Definition
| • But no solid surfaces (except ice crystals) and no liquid water (except very deep in Uranus and Neptune), |
|
|
Term
| What 2 factors of Gas and Ice giants would mix any life-bearing gas quickly over extremes of temperature & pressure? |
|
Definition
| Violent winds and convective turbulence |
|
|
Term
| Despite weak sunlight, what type of heat is available for Gas and Ice Giant planets? |
|
Definition
| internal heat due to convection |
|
|
Term
| Reasons there is probably no life on Jupiter? |
|
Definition
• All the basic molecular ingredients are present in the atmospheres
• But convection will ultimately (and quickly) bring any organic molecules down to regions where T~ 700 C (over 1200 F!) where they will be destroyed |
|
|
Term
| Characteristics of medium jovian moons |
|
Definition
• Enough self-gravity to be spherical
• Are, or were, geologically active.
• Have substantial amounts of ice.
• Roughly circular, equatorial orbits in same direction as planet rotation. |
|
|
Term
| Characteristics of small moons of jovian planets |
|
Definition
• Not enough gravity to be spherical: “potato-shaped”
• Captured asteroids, so orbits do not follow patterns.
• Orbits can be tilted, elliptical, and even backwards!
• No atmospheres or liquid water – not suitable for life |
|
|
Term
| Explanation of Tidal forces/Synchronous rotation |
|
Definition
| o Because the gravitational force decreases with (distance)2, the attractive force experienced by one object (e.g., the Earth) due to the gravitational field of a second object (e.g., the Moon) varies with position (closest parts attracted most strongly). |
|
|
Term
| Which moons in the solar system have synchronous rotation? |
|
Definition
|
|
Term
| The 4 inner moons of Jupiter |
|
Definition
|
|
Term
| What do all inner Jovian moons show evidence of? |
|
Definition
| All show evidence of geological activity - indicators of molten interiors. The heat source is tidal heating |
|
|
Term
| Orbital Ellipticity with moons of Jupiter |
|
Definition
| one side always faces Jupiter as Ganymede completes one orbit, Europa completes exactly two orbits, and Io completes exactly four orbits - moons periodically line up - causes orbital ellipticity- Tidal bulges are constantly being flexed in different directions - generates friction inside |
|
|
Term
| What are the rotational effects of tidal interaction with moons of Jupiter? |
|
Definition
– Rotation of moons become synchronized with their orbits.
– They keep the same face toward the planet.
– The rotation of the planet is slowed down |
|
|
Term
| What are the effects of orbit due to tidal interaction? |
|
Definition
| – Orbits of moons mostly evolve outward |
|
|
Term
| How tidal interaction effects internal tidal heating |
|
Definition
– Eccentric orbits lead to periodic flexing of the moon’s shape which heats the interior.
– Orbital resonances with other moons can maintain eccentric orbits and tidal heating |
|
|
Term
| The most volcanically active world in the solar system and why? |
|
Definition
Io
- friction generates heat
- interior of Io is molten
• Volcanoes erupt frequently.
- sulfur in the lava accounts for yellow color
- surface ice vaporizes and jets away |
|
|
Term
| Atmosphere and surface of Io |
|
Definition
• Thin atmosphere made up mainly of sulfur dioxide, produced by volcanic activity and temporarily retained by the moon’s gravity.
• Evidence of tectonics and impact cratering is covered.
Lave Fountain- active lava hot enough to cause "bleeding" in Galileo's camera - overloading of camera by the brightness of the target
• Gas and dust plume- A broad plume of gas and dust about 80 km high above a lava flow |
|
|
Term
| Compare Io and Europa's tidal heating |
|
Definition
| Europa's is much weaker, but still present |
|
|
Term
|
Definition
• Has a young cracked water ice crust perhaps only a few kilometers thick, and
• May have a warm ocean of liquid water below the crust.
• Icy surface - “fresh” - almost no craters |
|
|
Term
| Evidence that there may be an ocean under Europa's crust |
|
Definition
– Gravity measurements: central metallic core surrounded by 80−170 km of water/ice
– Lack of craters → ice tectonics → liquid below (but could be “fluid” ice, like glaciers)
– Chaotic terrain: like arctic ice pack, with separating pieces
– Magnetic field: conducting liquid for internal dynamo & metallic core too cold → brine ocean
– Tidal heating: computations show it can do the job |
|
|
Term
| Estimated size of crust/ocean of Europa? |
|
Definition
– Crust depth: 5−25 km, based on flooded impact crater
– Ocean 50−150 km deep (< 11 km on Earth) |
|
|
Term
| What did tidal flexing cause of Europa's surface? |
|
Definition
| • Jumbled crust with icebergs and surface cracks with double-ridged pattern |
|
|
Term
| Largest moon in the solar system |
|
Definition
|
|
Term
| On the surface of Ganymede, what shows there once may have been an ocean below? |
|
Definition
| Wrinkles due to tectonic movement in ice crust in (distant) past |
|
|
Term
|
Definition
– Dark areas: cratering upon cratering → several byr old
– Bright areas: far fewer craters and grooves
– Explanation: “lava” (i.e., water) eruptions followed by freezing |
|
|
Term
| Possible characteristics of an ocean on Ganymede |
|
Definition
– Magnetic field ==> convecting core
– Part of magnetic field varies with Jupiter’s rotation ==> electrically conducting interior (brine?)
– Salts found on the surface |
|
|
Term
|
Definition
– Less tidal heating than Europa (larger distance from Jupiter)
– Large mass → more radioactivity
– Much less heat than in Europa → thick crust (>150 km?) |
|
|
Term
|
Definition
Classic cratered "ice ball"
• No tidal heating - no orbital resonances |
|
|
Term
| What is unique about Callisto because of the lack of tidal heating and orbital resonances? |
|
Definition
|
|
Term
|
Definition
| Heavily cratered, however, no water is gushing to the surface |
|
|
Term
| Evidence against gravity on Callisto |
|
Definition
| It is Undifferentiated: mix of ice and rock throughout |
|
|
Term
| Possibility of reason for Callisto's magnetic field? |
|
Definition
|
|
Term
| Life in the subsurface ocean of Europa will most likely consist of... |
|
Definition
|
|
Term
| What is the 2nd largest moon in the solar system (most substantial atmosphere) |
|
Definition
|
|
Term
| Composition of Titan's atmosphere |
|
Definition
| • atmosphere denser than Earth’s but very cold (100K) and composed mostly of N2 and methane (CH4) |
|
|
Term
| What does the few amounts of craters on Titan's surface show? |
|
Definition
Surface eroded by liquids
• Methane/Ethane lakes |
|
|
Term
|
Definition
– Almost double that of our Moon
– Density: 1.9 gm/cm3 ==> equal mixture of rock and ice
– Thought to be differentiated: rocky core of silicates with a crust of water ice |
|
|
Term
| Comparison of Ganymede and Titan to Mercury and Earth |
|
Definition
| larger than Mercury but smaller than the Earth |
|
|
Term
| Most likely composition of all small Jovian moons |
|
Definition
| Captured asteroids and comets |
|
|
Term
| Jovian moons are typically composed of... |
|
Definition
|
|
Term
| Like our own moon, many Jovian moons exhibit what is called synchronous rotation. This means that they rotate at the same rate |
|
Definition
| That they orbit their host planet |
|
|
Term
| Even though JupiterÕs moon Io is similar in size to our geologically dead Moon, it is more geologically active than the Earth. How can this be? |
|
Definition
| Io is tidally heated due to its elliptical orbit, which causes the large tidal forces exerted by Jupiter to constantly change, flexing and distorting its interior |
|
|
Term
| What is the internal structure of Europa? |
|
Definition
| thin icy crust, subsurface ocean of water, thick rocky mantle, central iron core |
|
|
Term
| Stars spend 90% of their lives.. |
|
Definition
| fusing hydrogen into helium in their cores and slowly brightening (Main Sequence) |
|
|
Term
| If life exists in the Europan oceans, it most likely originated |
|
Definition
| Close to volcanic vents on its ocean floor |
|
|
Term
| The complexity of any life present in EuropaÕs subsurface ocean is mainly limited by the |
|
Definition
| The amount of energy to sustain it |
|
|
Term
| What is believed to have been the main source of TitanÕs atmosphere? |
|
Definition
| Outgassing from the interior |
|
|
Term
| How is Titan similar to Earth? |
|
Definition
| like the Earth, Titan has an atmosphere made mostly of molecular nitrogen |
|
|
Term
| Which moon has fountains of ice particles and water vapor spraying out from its surface |
|
Definition
| Saturn's icy moon Enceladus |
|
|
Term
| Even though Titan has liquid methane on its surface, some internal heat, and plenty of carbon-containing compounds, it is not a suitable place for life as we know it because |
|
Definition
| it is far too cold, and methane is not a very good biological solvent |
|
|
Term
| What is the definition of a starÕs habitable zone? |
|
Definition
| the range of distances from the star where liquid water can be stable on the surface of a suitable planet |
|
|
Term
| Europa is located outside the SunÕs habitable zone and yet may be habitable. How can this be? |
|
Definition
| Europa is tidally heated, allowing liquid water to exist beneath its icy surface |
|
|
Term
| The fact that the strength of gravity decreases with distance means the force of gravity exerted by one object on another (e.g., the Earth and Moon) is greater on the near side than the far side. This effect is commonly referred to as a |
|
Definition
|
|
Term
| Although Titan is roughly the same size as Mercury, Titan has an atmosphere while Mercury does not. How can this be? |
|
Definition
| Even though Titans gravity is weak, it is much colder, allowing molecules to be trapped in its atmosphere |
|
|
Term
| What is able to provide internal heat on Titan? |
|
Definition
| • Tidal heating together with radioactive decay are enough to provide the internal heat needed to keep water liquid. |
|
|
Term
|
Definition
– 30 km volcano observed on Titan, including caldera inside
– Magma would be mainly CH4 & H2O
– Energy?: tidal heating & radioactivity |
|
|
Term
|
Definition
– Huygens saw round ice pebbles
– Sinuous channels: liquids
– East-west dunes near equator with sharp western boundaries: super-rotating winds |
|
|
Term
| Possible Earthlike Processes on Titan |
|
Definition
• Tectonics
• Weather, including rain (methane)
• Erosion by winds and liquids
• Formation of complex organic compounds
• Greenhouse effect
• Volcanism (molten water, not rock
(ALL AT MUCH LOWER TEMPERATURE) |
|
|
Term
| Atmospheric details of Titan |
|
Definition
• Pressure: 1.5 bar
• Surface temperature: -180°C (-290°F)
• Composition: 92−98% N2 + 2−6% methane (CH4)
• Constantly smoggy: UV breaking up CH4 into radicals
Create Hydrocarbons |
|
|
Term
| Why does Titan have an atmosphere but the larger Ganymede does not |
|
Definition
• At Saturn’s distance from the Sun, the protosolar nebula was much colder that at Jupiter.
• Ammonia (NH3), methane (CH4) & ethane (C2H6) ices could condense at Saturn’s distance, but not at Jupiter, where only water ices condensed.
• Moons formed at Saturn could have significant amount of methane, ethane, ammonia - this provided molecules for UV interactions to form atmosphere
• Comets and asteroids hit at a smaller velocity (~ half the energy), so collisional losses were smaller. |
|
|
Term
| Largest lake discovered on Titan |
|
Definition
Ontarius Lacus
- Composed primarily of Methane, Ethane and propane |
|
|
Term
| Why liquid methane is not as effective as liquid water |
|
Definition
– Chemical reaction rates orders of magnitude slower
– Poorer solvents than water
– No density anomaly: liquids freeze completely |
|
|
Term
| Process which makes life possible due to organic life on titan |
|
Definition
– UV forms organic molecules in the upper atmosphere, which sink to the CH4−C2H6 lakes and the surface
– Comet or asteroid impacts can create pockets of water lasting thousands of years?
– Underground water ocean? |
|
|
Term
| Description of Saturn's Enceladus |
|
Definition
➢ Small icy moon (500 km) in diameter
➢ Young, crater-free surface regions with like those on Europa
➢ Orbit resonance with Dione
➢ South polar hot spot and ice plumes
➢ Thin “atmosphere” of water vapor |
|
|
Term
| Characteristic of ice plumes that make it possible for ocean on Enceladus |
|
Definition
| Area of plumes is much warmer than surroundings - evidence of subsurface reservoir of liquid water |
|
|
Term
| What do the names of all the moons of Uranus have in common |
|
Definition
| They are all characters from the works of Shakespeare & Alexander Pope |
|
|
Term
| Only moon of interest from Neptune |
|
Definition
|
|
Term
| Atmosphere and surface of Triton |
|
Definition
– Extremely cold (< 40K) objects made from volatile materials produce icy volcanism.
– Huge geysers of nitrogen! |
|
|
Term
| What is the main factor of the decline of probability of life beyond Saturn |
|
Definition
|
|
Term
| Pluto and the remaining moons |
|
Definition
– Too cold and too small
– But, amino acids seen in meteorites
• Most likely, there is subsurface liquid water, simple organics, and water vapor welling up from below. |
|
|
Term
|
Definition
| • A mass of gas held together by gravity in which the central temperatures and densities are sufficient for steady nuclear fusion reactions to occur. |
|
|
Term
| What is indicative of a star's wavelength? |
|
Definition
|
|
Term
| Where does nuclear fusion occur? |
|
Definition
|
|
Term
| What is the nuclear process functioning over most of a star's lifetime? |
|
Definition
| Fusion of hydrogen to helium (Main Sequence) |
|
|
Term
| A plot of temperature of stars against their brightness |
|
Definition
| Hertzsprung-Russell Diagram |
|
|
Term
| Where do hot stars (bluer) fall in the HR diagram |
|
Definition
| at the upper left hand end of the Main Sequence while cooler (redder) stars are found to the lower right. |
|
|
Term
| The Hottest and coolest types of stars |
|
Definition
|
|
Term
| What is more common, hotter main sequence stars or cooler ones? |
|
Definition
|
|
Term
| Hotter stars have ____ Main Sequence lifetimes than cooler stars |
|
Definition
|
|
Term
| How does location play a role in life on the surface of a planet?? |
|
Definition
| It must fall in a star's habitable zone |
|
|
Term
| Why is size important for a planet to be suitable for life? |
|
Definition
Large enough to retain an atmosphere substantial enough for liquid water
– Large enough to retain internal heat and have plate tectonics for climate stabilization |
|
|
Term
| Definition of the habitable zone |
|
Definition
| • An imaginary spherical shell surrounding a star throughout which the surface temperatures of any planets present might be conducive to the origin and development of life as we know it |
|
|
Term
| Essentially, what does the habitable zone provide? |
|
Definition
| A place where liquid water can survive |
|
|
Term
| Which has the larger habitable zone, cooler or hotter stars? |
|
Definition
|
|
Term
| What hurts the chances of life forming on a planet in the HZ? |
|
Definition
| if planets exist too close to its parent star, the development of life might be made problematic because the tidal friction would have led to synchronous rotation |
|
|
Term
| Do brighter or dimmer stars have wider HZ's? |
|
Definition
| Brighter, but their main sequence lives are short-lived |
|
|
Term
| Given the rate of evolution of life on Earth, it is possible that microorganisms might have time to develop on worlds around which stars? |
|
Definition
|
|
Term
| In the search for extraterrestrial intelligence, the HZs around |
|
Definition
|
|
Term
| What do planets and stars orbit? |
|
Definition
|
|
Term
| What tells us the extent of the star's movement about this center of mass induced by a planet's gravitational tug. |
|
Definition
| Velocity or change of position |
|
|
Term
| From what info can a planet's mass and orbit can be deduced |
|
Definition
| the extent of the star's movement about this center of mass induced by a planet's gravitational tug. |
|
|
Term
| How the doppler shift can detect planets |
|
Definition
| The larger the planet and the closer it is to the host star, the faster the star moves about the center of mass, causing a larger Doppler shift in the spectrum of starlight. That's why many of the first planets discovered are Jupiter-class (300 times as massive as Earth), with orbits very close to their parent stars |
|
|
Term
| Radial velocity planet detection |
|
Definition
| this methods depends on the slight motion of the star caused by the orbiting planet. In this case, however, astronomers are searching for the tiny displacements of the stars on the sky. |
|
|
Term
|
Definition
If a planet passes directly between a star and an observer's line of sight, it blocks out a tiny portion of the star's light, thus reducing its apparent brightness.
Sensitive instruments can detect this periodic dip in brightness. From the period and depth of the transits, the orbit and size of the planetary companions can be calculated. Smaller planets will produce a smaller effect, and vice-versa |
|
|
Term
| How many earth-sized planets have been discovered since kepler's launch |
|
Definition
|
|
Term
| How many planets were found in the habitable zone? |
|
Definition
|
|
Term
| Gravitational Microlensing |
|
Definition
| When a planet happens to pass in front of a star along our line of sight, the planet's gravity will behave like a lens. This focuses the light rays and causes a temporary sharp increase in brightness and change of the apparent position of the star. |
|
|
Term
| Direct Imaging and its difficulties |
|
Definition
| While the parent star is the source of light that will make any planet visible, its glare is between a million and 10 billion times brighter than the faint little speck we are looking for. Therefore, any direct imaging of extrasolar planets requires methods to cover up or otherwise control the glare of the parent star. |
|
|
Term
| How many known planets has the Kepler spacecraft discovered as of 11-27-2011 |
|
Definition
704
- 1200 more candidates, probably 50% planets |
|
|
Term
| # of radial velocity discoveries |
|
Definition
|
|
Term
|
Definition
|
|
Term
| # microlensing discoveries |
|
Definition
|
|
Term
|
Definition
|
|
Term
| # Transit planet discoveries |
|
Definition
|
|
Term
| # of known habitable zone planets |
|
Definition
|
|
Term
| On what part of the HR diagram do most stars fall? |
|
Definition
|
|
Term
| Where do less that 1% of stars fall on the HR diagram |
|
Definition
|
|
Term
| All stars on the main sequence |
|
Definition
| are mature stars that are fusing hydrogen into helium in their cores |
|
|
Term
| Which of the following types of stars is NOT suitable for ADVANCED life |
|
Definition
|
|
Term
| Which type of stars have too short of lifetimes for planet formation |
|
Definition
|
|
Term
| Where are most stars found on the HR? |
|
Definition
|
|
Term
| The total amount of energy that a star radiates out into space is referred to as its |
|
Definition
|
|
Term
| Main Sequence stars much less luminous than the Sun have |
|
Definition
| narrower habitable zones, decreasing the odds of finding habitable planets but much longer lifetimes allowing life to appear and evolve |
|
|
Term
| Most of the extrasolar planetary systems discovered to date are |
|
Definition
| very different than our own solar system having Jovian-sized planets close to their parent stars |
|
|
Term
| In an extrasolar planetary system containing a single planet, the parent star is measured to move about its center of mass every 24 years. Given this, what is the orbital period of the planet? |
|
Definition
|
|
Term
| The wavelengths of radiation coming from a star that is moving toward us |
|
Definition
| are shorter than if the star were not moving |
|
|
Term
| Compared to today, in the future, the Sun's habitable zone will be |
|
Definition
| Wider and farther from the sun |
|
|
Term
| The range of distances that has remained habitable for the entire duration of the SunÕs lifetime is referred to as the |
|
Definition
| continuously habitable zone |
|
|
Term
| What is the spectral type of the Sun? |
|
Definition
|
|
Term
| B-type stars have lifetimes... |
|
Definition
| long enough for planets to form but not for life to appear |
|
|
Term
|
Definition
| have lifetimes long enough for planets to form and for simple life to appear, but not long enough for advanced life to develop |
|
|
Term
|
Definition
| have lifetimes long enough for advanced life to evolve |
|
|
Term
| One of the fundamental principles of stellar evolution is that the more massive a star is |
|
Definition
|
|
