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Fictional portrayal of extraterrestrial life
similar to terrestrial life
How we define extraterrestrial life
ongoing challenge, could be single-celled, multicellular, or unknown
What we are looking for
liquid water, possible debris of other civilizations, occurrence of life elsewhere, conditions and context conducive to life
fields of astrobiology
astronomy, biology, planetary science
role of astronomy
reason what is going on in the night sky, figure out humanity’s place in the universe
is the universe a rational place?
astronomy presents evidence that nature acts rationally and uniformly throughout the universe, making terrestrial observations universally applicable
are there worlds beyond the solar system?
yes, astronomy allows planetary data to apply to extrasolar planets, exoplanets
how do we define a habitable world?
has liquid water, energy, and nutrients, can sustain life for a significant period of time
geocentrism
1st scientific model of universe, earth is surrounded by celestial sphere, sun and stars are placed on the sphere moving around the earth in their own spheres
1st model is successful and unsuccessful at
explaining most astrophenomenon, except planets
what does the first model assume?
earth centered, circular orbits, constant/uniform speeds
about how long is the geocentric model accepted for?
1500 years
heliocentrism
if the smaller moon orbits earth, then smaller earth likely orbits the sun. indicated as correct theory by absence of parallax. simpler heliocentric model produced by Aristorchus of Samus
who/what movement revived heliocentricity?
Copernicus, Copernican Revolution
who helped prove heliocentricity and how?
Brahe observed planetary positions, Kepler used Brahe’s data and discovered heliocentric model worked best
What prevented heliocentrism from being quickly accepted?
proponents could not explain why relative positions of stars seemed to remain the same despite Earth’s changing viewpoints as it orbits the sun (parallax?)
pros of geocentrism
successful at explaining everything except planets
cons of geocentrism
planets undergo retrograde motion, which isn’t reflected in the geocentric model
cons of heliocentrism
needs to be explained, difficult to prove as planets undergo retrograde motion, which is not simple
parallax and how it works
the apparent shift in an object’s position when viewed from different angles or positions
Kepler’s Laws (3 laws of planetary motion)
1) planets orbit in ellipses, not circles
2) planet orbital speeds vary
3) larger orbits have slower speeds and therefore longer orbital periods
aphelion
the point in an orbiting body's path when it is farthest from the sun
perihelion
the point in the orbit of a planet, asteroid, or comet at which it is closest to the sun
light speed
distance light will cover in 1 year
lookback time
The time taken for light from a distant object to reach the Earth
atomic number
number of protons in an atoms nucleus
mass number
the total number of protons and neutrons in an atomic nucleus (equal to atomic mass)
element
atoms with the same number of p+
isotope
same number of p+ but different number of n
ion
atom with non zero net charge (gains or loses electrons)
molecule
two or more atoms bonded together
compound
molecule made from atoms of multiple different elements
energy=
mass x speed of light squared
three types of energy: (+ bonus)
kinetic, radiative, potential (and thermal)
kinetic energy
energy of motion
radiative energy
energy carried by “light”
potential energy
stored energy that can become one of the other kinds
thermal energy
kinetic energy of the particles within the matter
light
type of radiative energy called an electromagnetic wave
radiation
energy that moves from one place to another in a form that can be described as waves or particles
frequency
how many waves would pass through an object per second, frequency and wavelength are used to describe electromagnetic waves
three types of spectra
continuous/continuum, absorption, emission
how a continuous spectrum is produced
directly observe a hot, dense object emitting all wavelengths of light
how an absorption spectrum is produced
observe a hot object through a cooler object, emitting specific wavelengths of light
how an emission spectrum is produced
observe a cool object directly, light from a continuous source passes through a cooler gas, causing certain wavelengths to be absorbed by the gas atoms, leaving dark lines in the spectrum
what can spectral features tell us?
the element and its temperature and density (hotter objects give off shorter wavelengths at peak but are overall more intense
characteristics of a planet
orbit around a star (not another planet), be large enough gravity has forced into a spherical shape, cleared setting of debris
characteristics of an asteroid
small, rocky objects that orbit the Sun elliptically
characteristics of a meteor
visible streaks of light that occur when meteoroids burn up as they enter Earth's atmosphere, many contain iron or nickel (a meteoroid is a small piece of an asteroid or comet, and a meteorite is a fragment of a meteoroid that survives its journey and lands on Earth)
How is the universe “moving?”
dark energy is causing universe to expand, “observable universe” possible expanding at light speed
How do stellar lifetimes change vs stellar mass?
A star's lifetime is inversely proportional to its mass, meaning that more massive stars have shorter lifespans
3 rock types
igneous, sedimentary, metamorphic
igneous
solidified lava
sedimentary
compressed silt
metamorphic
things that have changed into something else based on heat and pressure
how can rocks change types?
the rock cycle, driven by heat, pressure, and tectonic activity
radiometric dating
radioactive parents try to decay themselves down into stable daughters, decay rates are known for many isotopes
half-life
time for half of parent to decay into daughter
age of the oldest intact earth rocks
4.02 Gyr (earth’s crust has been formed by this time)
age of the oldest meteorites, also considered the age of the solar system
4.57 Gyr
age of oldest earth rock fragments and what they are
4.38 Gyr old zircon crystals
characteristics of the Hadean Earth
constant volcanic eruptions, Earth’s crust being opened and re-opened, atmosphere arises from volcanic out-gassing of trapped gas, surface undergoing bombardment by leftover planetesimals
atmosphere of the Hadean Earth
many of the gases released from eruptions are greenhouse gases, and Earth’s atmosphere allows it to hold onto heat and provides surface pressure, allowing for liquids to exist, atmosphere starts to build up and water vapor condenses and rains down to the surface, filling the lakes and oceans
gases released from eruptions during Hadean Earth
H20, CO2, N2, H2S, SO2
surface of the earth was constantly changing, being reshaped by____, driven by _____
volcanism, plate tectonics, erosion, driven by the planet’s internal heat
relative ages of regions such as continents vs ocean floor
continental crust (granite) is much older than the “young” material of the seafloor crust (igneous basalt)
how the magnetic field is made
the rotating, electrically-conducting, convecting liquid outer core of Earth generates magnetic field (powered by solidification of planet’s liquid iron core, creating powerful electric currents that extend 1000s, of miles into space
what does the magnetic field do for us and the planet?
forms a protective barrier, protecting the atmosphere from erosion by solar wind particles, and the surface against bombardment by high energy particles
Solar wind stripping
the process by which the sun's solar wind removes gas from a planet's atmosphere, earth doesn’t experience solar wind stripping due to our strong magnetic field, which deflects most of the sun’s charged particles (northern lights are charged particles hitting earth’s magnetic field)
Different lunar surface regions and what they tell us
-highlands= lighter colored, heavily cratered, older than maria
-maria= dark-colored areas are impact basins that were filled with lava, lower in altitude, younger, have fewer craters
original heat sources
gravitational energy, radioactivity, impacts (impart extra energy to Earth)
ongoing heat sources
radioactivity, good insulation (residual heat drives geological activity)
thermal escape
gas molecules become too hot to be held onto by the planet's gravitational pull, causing them to escape into the vacuum of space— ^ temperatures, ^ evaporation, ^ precipitation, v CO2 in atmosphere, v greenhouse effect, v temperatures
how does the Earth keep its atmosphere?
the Earth keeps its atmosphere due to the force of gravity, which pulls the gasses that comprise the earths atmosphere toward the planet’s surface, more planet’s mass>stronger gravity, atmospheric pressure
does the earth experience thermal escape? why or why not?
yes, thermal escape helps earth to maintain a stable temperature. when temperatures increase too much, evaporation increases, precipitation increases, more CO2 is removed from the atmosphere, the greenhouse effect weakens, and temperatures drop