Astrobiology Test 3 Flashcards
Describe Mercury
Smallest planet Very hot during the day, very cold at night Virtually no tilt Possibility very transient liquid water Metallic core with outer shell
Describe Venus
Hottest - greenhouse gases (H2O vapor and CO2)
Sulfuric acid clouds, chloride, iron, sulfur
Spins “backwards”
Iron core, thin surface, active volcanoes
Describe Earth
Evidence of life in radio waves, oxygen and methane in spectral data
Moon formed by impact by Mars-size object, produces tides
Describe Mars
Thin atmosphere Frozen surface water Subsurface briny liquid water No magnetic field Iron regolith Lava tunnels Similar composition to Earth
Describe Ceres
Asteroid belt
Water ice - maybe more than on Earth
Salts of magnesium sulfate
Describe Jupiter’s moons
Io - most volcanically active
Europa - Subsurface ocean, cracks indicate tidal fluxing or other energy input such as volcanic eruptions / deep sea thermal vents, iron core
Ice covered lake in Antarctica studied as analog
Ganymede - iron core, rocky mantle, layer of ice
Describe Saturn’s moons
Enceladus - icy, possibly liquid water / carbon dioxide / methane in jets
Titan - too cold (liquid ethane and methane), nitrogen atmosphere, pressure 50% higher than Earth, subsurface water
Describe the benefit of Moons and atmospheres
Moons and atmospheres help to stabilize the environment, atmospheres protect from UV radiation and solar radiation
What are three general things determining the plausibility of life?
Liquid solvent, energy, ability to form large, complex molecules
Assumptions for life to begin and continue (2)
Stable environment
Reactions for life formation occurring rapidly (geologically)
Category Two Planetary bodies
Past or present liquid water, energy, organic compounds, stable history
Mars, Europa, Enceladus
-could have life
Category Three Planetary bodies
Physically extreme conditions, energy, complex chemistry
Titan, Venus
-could have life as we don’t know it
Category Four Planetary bodies
Past isolated favorable conditions
Triton, Io, Mercury
-may have very isolated life due to past conditions
Category Five Planetary Bodies
All conditions are unfavorable for Life
Saturn, Jupiter, Moon, Sun
Category One Planetary Bodies
Liquid water, energy, organic compounds, atmosphere, biogenic processes
Earth
-do have life
Giordano Bruno
Proposed the existence of exoplanets in the 17th century
Adriaan van Maanen, 1917
Described a “Polluted White Dwarf”, and the image was later found to have first evidence of an exoplanetary system surrounding it
White Dwarf
White dwarfs are the remnants of stars like ours that have become very small, compressed, and hot, usually characterized by hydrogen, helium and oxygen
The Van Maanen dwarf also had calcium
1990 reexamination of the “polluted white dwarf”
Re-examined glass plates of the polluted white dwarf
Found calcium along with other elements associated with rocky planets in a disk around the dwarf
Indicated a planetary body like Jupiter pushing asteroids, comets, and other rocky bodies towards the gravitational pull of the white dwarf but also preventing them from being entirely consumed
Detecting light from planets
Planets only reflect a small amount of their sun’s light and don’t emit any of their own
Methods of detecting planets
Transit, Radial Velocity, Microlensing, Astrometry
Transit method of detection
small dip in light when a planet passes in front of its sun
Size and temperature of planet, maybe atmospheric composition
Discovery of most exoplanets
Radial velocity method of detection
gravity causes star to wobble, shift spectral lines
Microlensing method of detection
planet warps space, creating a gravitational lens magnifying light
two stars aligned with observer, closer star acts like a lens to bend light, exoplanet around closer star results in a spike in brightness levels
Astrometry method of detection
Measures the location of the star and those around it for tiny changes, then use gravitational microlensing
Kepler Telescope
Specifically designed to discover exoplanets using the transit method - Confirmed 200
Spitzer Space Telescope
Decommissioned in 2020
Studied infrared spectra - “the old, the cold, the dusty”
Found 7 exoplanets around TRAPPIST-1 40 light years away -1999
Transiting Exoplanet Survey Satellite
TESS - confirmed 122 exoplanets over 3 years, with 2601 candidates
Nancy Grace Roman Space Telescope
Used both transit and gravitational lensing method
Classification of exoplanets - Gas giants
Jupiter-like or larger
Classification of exoplanets - Neptunian
small gas giants, around the size of Neptune
Classification of exoplanets - Super-earth
rocky planets much larger than Earth
Classification of exoplanets - terrestrial
rocky planets around the size of Earth
Camile Flammarion
Wrote The Planet Mars
Schiaparelli
found straight lines called channels connecting “oceans” on Mars
Cassini
seasonal changes on Mars
Proctor
Named geographical features after scientists
Confirmed vs candidate exoplanets
Candidate - signals seen by one telescope
Confirmed - two lines of evidence
Naming exoplanets
Name of the telescope
Number relating to the order in which its star was catalogued
Lowercase letter indicates planet order
Ex: Kepler-16b was discovered by the Kepler telescope, in the 16th system discovered by Kepler, and is the closest planet to the star(s)
Capital A for star name, Capital B for second star
How many potential planets in Milky Way
100 billion
Types of Stars (3) and Goldilocks zone
G-type → yellow, 6%, hottest, last around 10 billion years, largest Goldilocks zone
K-dwarfs → orange, 13%, last from 15-45 billion years, 5-25x X-ray radiation
Highest likelihood of exoplanets with life
M-dwarfs → red, 73%, last over 100 billion years, 80-500x X-ray radiation, smallest Goldilocks zone
How many confirmed exoplanets? Terrestrial type planets?
4375
Terrestrial type planets are in the minority
Requirements for life
Bounded local environment with disequilibrium (cell-like structures)
Consume energy to maintain internal order and adjust to the environment
Replicate by passing on hereditary information from one generation to the next
Life based on spin configurations
Gerald Fienberg and Robert Shapiro Orientations of hydrogen atoms Cold environments with solid hydrogen Infrared as a source of energy Issues with bounded local environment
Fred Hoyle’s Black Cloud
Hoyle worked in nucleosynthesis of heavy elements in stars, named Big Bang theory
Thought the universe was static
Book about a dark object blocking out the light from other stars and expanding into our solar system blocking out our sun
Object would communicate using radio waves
Issues with replication with hereditary information
Quantum computers
Store information on molecules that change conformation in response to light
Use qubits that can take on more than two forms
More possible states involve more potential mistakes
Requires extreme stability (cold)
Neutron star
Formed from a collapse of a massive star after a supernova explosion
Possesses masses between 10-25 solar masses
Smallest and densest other than black holes
Electrons and positrons cancel out and become neutrons
Magnetic energy makes life on surrounding planets very unlikely
Detected by infrared telescopes
Types of neutron stars
Pulsars - Energy and light emitted from magnetic poles, stars are rotating very fast
Magnetars - trillion times the magnetic field of Earth, 1000x that of regular neutron stars, release burst of magnetic energy
Brown dwarfs
In between gas giants and stars
Described by Jill Tarter
First evidence in 1995
15-80x mass of Jupiter
Insufficient material to start fusion reactions (some can fuse deuterium)
Orbit other stars around 1000AUs away or are rogue
Discovered by Spitzer / infrared telescopes
Types of brown dwarfs
L brown dwarfs → 1200-2000*C
T brown dwarfs → < 1200*C
Habitability brown dwarfs
No life due to high temperatures and lack of a surface, lack of heavier elements, severe weather
May have their own planets circling them
Very narrow habitable / Goldilocks zone
Forms of energy - magnetic?, light and photosynthetic organisms,
Lack of stable environment
Rogue planets
Billions of trillions in Milky Way, planets without a host star
Formation of Rogue Planets
Collusions while system is forming Gravitational pull or lack thereof Formation of lone brown dwarfs As stars age, can have decrease in gravitational pull Ricochet from multi-star system
Characteristics of Rogue Planets
Most are gas giants, some are rocky planets
Can be detected by microlensing → light from star becomes aura as planet bends space when passing near it
Life on Rogue Planets (energy, water, metabolism)
Sources of energy → geothermal through plate tectonics or radioactive elements, retention of infrared energy through thick atmosphere with N2/CO2/CH4/C2H6
Water → Accretion during formation, outgassing during accretion (certain reactions between early materials during formation)
Life → if so, microbial with chemolithotrophic metabolism
Evolutionary fates of life
Species collapse
Transition
Plateaus
Species collapse
Non-reversible adaptations followed by rapid environmental change and a lack of suitable adaptations
Past evolutionary success no longer providing adaptations (slow environmental change)
Well-adapted organisms displaced by better adapted species (invasive species or other competition)
Species transition
Becoming different species
Punctuated equilibrium model of origin of species
Major transitions on Earth → eukaryotic organisms, photosynthesis (oxygenic esp), calcified exoskeletons, aquatic to land, invertebrates to vertebrates, multicellular life, sexual reproduction
Species plateaus
Stable environment
Bacteria, archaea, some multicellular life
Characteristics of Intelligence
Ability to communicate Utilization of tools, development of technology Remembrance Coordinated activities Mourning / Emotions
Rise and fate of technology
Technology → use of energy, tools, materials, and information to amplify the impact of a species on its environment
Fates of population with advanced technologies:
Custom-designed, genetically engineered organic beings
Totally mechanical forms with artificial intelligence
Virtual (non-material) entities
Destroy itself
SETI
Search for Extraterrestrial Intelligence
SETI was started by NASA, switched to private donations in 1993
Philip Morrison and Giuseppe Concori
can receive radio signals from light years away
False Positives in SETI
pulsars, terrestrial origin, rotating neutron stars (ideally would have 3 confirmations)
WOW signal
Neither very regular nor very random signals are indications of possible life
Big Ear Telescope in Delaware, Ohio
72 seconds and not detected again
Sagittarius part of Milky Way
Too short to be get confirmation by other telescopes
SETA
Search for Extraterrestrial Artifacts (SETA)
Space structures - dyson sphere
Drake equation
Number of possible civilizations that could make contact
N = R* times FP times NE times FL times FI times FC times L
Rate of star formation, fraction of stars with planets, number of planets capable of supporting life, fraction that do sustain life, fraction with intelligent life, fraction with communication, length of time for signals
We would be able to get good guesses with the first three, and estimate the rest
L involves the development of the alien society beyond signals we can detect as well as the length of time it takes them to send whatever signal
(stars, planets, possible life + life, intelligent, communicate, signals)
Fermi’s Paradox / Great Silence
Lots of stars → lots of exoplanets → no evidence for life?
Reasons → right form of life is very uncommon / we are not looking hard enough, space is big
Robots vs Humans space exploration
Humans need radiation protection / food / oxygen, some observations are better in person, can guide rovers on Mars themselves, long transit times
Robots have their own instruments
Rovers vs Orbitals space exploration
Orbitals have a global view
Rovers have better detail
InSight Lander Mission
Lander with two small orbiters
Orbiters allow better communication between lander and Earth
Focus on geology and interior of Mars, weather on Mars
Measure seismology, 480 Marsquakes
Geological activity due to past volcanic activity
Perseverance and Ingenuity Missions
Astrobiology and previous evidence for life
Sample caching
Preparing for the arrival of humans
Radioactive plutonium
Weather conditions
X-ray fluorescence spectrometer to determine minerals
Ground-penetrating radar that can see subsurface water
UV laser for mineralogy and organic compounds
MOXIE demonstrates the feasibility of producing oxygen
Ingenuity
Helicopter associated with a rover
Helicopter helps determine where the rover should travel next
Humans to Mars logistics
Oxygen - MOXIE
Nutrients - essential elements
Water - frozen/ice on Mars, use Antarctica analogs
Shelter - temperature, weather, space suits, UV radiation / space radiation / ionizing radiation (damage to DNA, cells), lava tubes?
Moon travel 2024
Ejecta from early Earth impacts preserved in the lunar surface
Preserve conditions in early Earth
Similar requirements for humans as Mars, expect for the lack of CO2 and the ice limited to the South pole
Use as a stopover for Mars missions
International Space Station height
250 miles (250,000 to moon)
Five Categories of target bodies (with respect to planetary protection concerns)
Category One - no worries about life
Category Two - process of chemical evolution and the origin of life, worry about false positives
Category Three - flyby or orbiter mission (possible life)
Category Four - probe, lander, rover (possible life)
IVa - does not have proper instruments
IVb - intended to investigate extant life
IVc - Martian Special Regions, extant life and possibility for replication of terrestrial life
Category Five - something returns to Earth
Terraforming Mars
Factors Oxygen/Atmosphere - retain heat, dense enough, greenhouse gases May not be enough resources there Liquid water Asteroids Soil/Plants Soil is not super renewable
Notes from Gravity Assist
Heat shock swab samples so they only look at the stuff that would survive launch
500,000 spores or <300 per square meter
Hydrogen peroxide, 70% isopropyl alcohol
Missions on the Moon will help plan to prevent contamination on Mars
Pulses of elevated methane that disappear (not explained by abiotic)
James Webb Telescope
infrared to study the beginning of the universe and the atmospheres of exoplanets using star magnification and transits
