Astronomy Midterm 2
Uranus and Neptune vs. Jupiter and Saturn
- most probably have an ocean of water, methane, and ammonia covering surface - receive much less solar radiation and have much cooler interiors
Martian Weather
Tilt of axis and elliptical orbit During summer polar cap disappears
Life of Ganymede
Varying bombardment activity and boundaries between new and old surfaces 2 components to magnetic field" own and Jupiter's rotation ocean?
4 Geological Processes that shape Earth's surface
Volcanism, plate tectonics, erosion, impact cratering
Fossils of early life are very difficult to identify in very old rocks because early life
Was very simple and microscopic in size
Erosion
Water and wind erosion result in weathering and transport of solids Given enough time, flattens mountains
How do we know that early Earth could not have had an oxygen atmosphere? Where did the oxygen in our atmosphere come from? How did the introduction of oxygen affect early life?
We know that early Earth could not have had an oxygen atmosphere, because oxygen is a highly reactive gas that would disappear from the atmosphere in just a few million years if it were not continually resupplied by life. The oxygen atmosphere acme from microscopic bacteria known as cyanobacteria. Oxygen levels remained far too low for complex animals until somewhere near the time of the Cambrian explosion, which occurred when Earth was almost 4 billion years old.
Scientists were skeptical about Lowell's claims on Martian canals because
When they pointed their own telescopes toward Mars they couldn't see them
Adaptation
ability to change over a period of time in response to environment
Reproduction
ability to produce more organisms either asexually or sexually
5 kingdoms of organisms
based on appearance Monera (all prokaryoot, later divided into bacteria and archea), Protista, plants, fungi, Animalia
Miller Urey Experiment
can early organic conditions lead to life organic soup from methane and water unrealistic representation of early atmosphere
Saturn's Enceladus
geologically active geysers pf liquid water and ice icy vocalism= reservoir of subsurface liquid
Photoheterotrophs
get carbon from consuming organisms and energy from sunlight; an example of this is chloroflexus bacteria
Growth
growing organism increases in size in all of its parts rather than just getting more matter
Jupiter's mini solar system
only 8 moons in regular orbits- formed along with Jupiter in solar nebula remainder are captured formed in outer solar system where rocky and icy planetismals formed
Martian Sky
pink at sunset and turns violet when clouds of water ice are overhead, or take on a reddish hue if lots of dust in atmosphere
Basic requires of Life: organic molecules
presence of organic molecules, amino acids, etc. resulting from chemical reactions in atmosphere and near deep sea vents, or molecules from space
Response to stimuli
response to environmental inputs, often expressed via motion
Prokaryotes
single cell, no nucleus
Aristotle
species= fixed and independent of each other
Organization
structurally composed of 1 or more cells
Metabolism
transformation of energy by converting chemicals and energy into cellular components
Photoautotrophs
use carbon dioxide and sunlight; an example of this is a plant
If no greenhouse gases, Earth's average surface temp:
-16 degrees
Mass Extinction Events
-Asteroids, supervolcanism- can result in ice age, gamma ray bursts- evenly distributed in space- very rare and caused by final collapse of star and formation of black hole- high luminosity- can sterilize earth and destroy all life
Successful Missions
19, currently 6 spacecrafts in space in orbit and 2 landers
Carboniferous period
360 million years ago amphibians and insects roamed and fed on land bound plants Pile up of dead organic matter led to formation of coral beds
Archean
3x hotter than now, more active plate tectonics
Cambrian Explosion
545 million years ago, span of less than 40 million years, diversity occurred O2 enrichment allowed larger organisms to exist Evolution of genetic complexity Climate change- end of snowball Earth No efficient predators
Habitability Litmus Test
A world can be habitable only if it has a liquid medium, preferably liquid water, but possibly including liquid methane, ammonia, or ethane
Herschel and Mars
All bodies in solar system inhabited
The fact that all cells used in life on Earth are based on the same biochemistry suggests that
All life on Earth shares a common ancestor
Common Origin to Life
Amino acids that compose DNA are all left handed and the same 20 used in all life on Earth
A radioactive isotope is
An unstable nucleus that spontaneously breaks apart
The first person to introduce concept of evolution
Anaximander
AKA Curiosity Rover Findings
Ancient Mars could have had right chemistry to have supported living microbes- curiosity found carbons, hydrogens, oxygen, phosphorus, and sulfur clay minerals and not too much salt, which suggests drinkable water ancient stream-bed: rocks found smooth and rounded and likely rolled downstream for few miles petrified sand dunes at foot of Mt.Sharp radiation could pose risk for humans
Current geological evidence suggests that life
Appeared quite early in Earth's history
Biochemical view of life
Bacteria, archaea, eucarya
Terraforming Mars
Building up atmosphere importing water and releasing water in soil icy asteroids, ammonia, rich aseteroids, or outer solar system bodies rich in methane could be brought to Mars to bolster atmosphere Add cynabacteria Current technology only allows us to use very large nuclear bombs to blast asteroids towards mars
Earth life based on what?
CARBON- oxygen, carbon, nitrogen, and hydrogen make up 96% of mass of living cells Organic molecules all contain carbon and complex organization rely on ability of carbon based molecules to form complex chains Carbon can bond up to 4 atoms at a time
Martian Wind Patterns
CO2 in winter hemisphere freezes and decreases atmosphere pressure CO2 sublimation increases pressure in summer hemisphere Winds from winter to summer hemisphere Clouds comprised of dust, water, CO2
Components of a cell
Carbohydrates: energy and cellulose Lipids: fats to store energy and signal cells Proteins: chains of amino acids, enzymes= catalysts for all biochemical reactions Nucleaic Acids: DNA and RNA
Sources of Metabolism
Carbon - Heteroytrophs consume and autotrophs create Energy - Self made from photosynthesis/ consumption
Basic requirements of life: elements
Carbon, O2, Nitrogen, Hydrogen Elemental make up of solar system shows all 4 are abundantly available
More than 96% of the mass of living cells are made of
Carbon, hydrogen, oxygen, and nitrogen
What is a reason that early life formed cells?
Cells concentrate molecules together so they can react more easily
Metabolic needs of life
Cells function as mini factories for carrying out complex reactions, specialized enzymes, ATP used for storing energy *need carbon
Chemoautotrophs
Chemoautotrophs use carbon dioxide and inorganic chemicals. They need either organic food or sunlight to survive; an example of this is extremophile bacteria
Chemoheterophs
Chemohetereotrophs get both energy and carbon from food; examples of this are humans and animals
What is the main factor that drives Darwinian evolution
Competition for finite resources
Hadean
Continents starting to form, life began at end
Glaciers on Mars
Cover of rocky debris concealed and may have helped preserve glaciers Hellas plain shows glacial flows of snow and ice covered by debris
Earth's Magnetic Field
Created by currents in molten core, protects atmosphere from bombardment by solar radiation, partly responsible for retention of atmosphere
Empedocles
Creatures poorly adapted perished
Convection
Currents transport heat from hot to cold
Nearly all life on Earth passes on its heredity using
DNA
Eukaryotes
DNA in cell nucleus, multi cellular
RNA world
DNA requires RNA to replicate, RNA requires enzymes to replicate itself "RNA world" is the idea that modern, DNA-based life might have arisen from an earlier "RNA world", in which RNA molecules served both as genes and as chemical catalysts for copying and expressing those genes. RNA is much simpler than DNA because it has only one strand rather than two and the creation of its backbone requires fewer steps. Once the first living organisms of the "RNA world" arose, biological natural selection could take over. The structural similarities between RNA and DNA make it likely that DNA molecules would eventually have evolved within living cells.
Recurrent Slope Line
Dark streaks show hydrated salt deposits that form when briny water flows through landscape perchlorates (salts) can keep water from freezing when it's as cold as -70 Celsius
AKA Curiosity Rover Goals
Determine if life ever arose Characterize climate Characterize geology Prepare for human exploration
Martian Methane
Discovery of methane in martian atmosphere by the ESA Maris express mission began a frenzy 4 sources: comet impacts, volcanism, oxidation or iron, microscopic life
Stromatolites
Earliest colonies of microbial life energy from photosynethesis oldest fossils
Impact cratering
Early in solar system, comets brought water to Earth Subsequently responsible for mass extinctions
Mars vs. Earth- Oceans
Earth has robust magnetic field that protects atmosphere from solar winds- lack of field can result in direct access of solar winds to atmosphere atmospheric pressure of Mars decreased to the point where the pressure was too low for liquid water to exist
Planetary CO2 cycle
Earth warms up a bit, carbonate minerals form in oceans and rapid rate pulling CO2 at faster rate, atmospheric CO2 reduced, greenhouse effect weakens and counteracts initial warming so earth cools
Chemical Analysis
Element/molecules of rock Integral part of Mars Science Laboratory mission
Mars Myth Dispelled
Established Mars was canal less, rocky planet with thin atmosphere
Cassini-Hyygens
Everything we know about Saturn is due to this mission Surface lakes and rivers of hydrocarbons and methane Hundreds of times more liquid hydrocarbons than all the natural gas reserves on earth *what's missing for life: surface temp too cold, metabolism and chemical reactions would be slow, no enduring source of heat
Phanerozoic
Evolution of abundant animal life
Current Operational Missions: Landers
Exploration Rovers, Mars Curious Rovers
Volcanism
Flow of molten lava to Earth's surface, creation of new land masses, partly responsible for atmosphere
How are the geological record and the fossil record related?
Fossil record is part of geological record
Orbital Resonance
Ganymede completes one orbit for each 2 europa orbits and 4 Io orbits: all satellites lines up once every 7 days, tugging on one-another Tug distorts Io's and Europa's orbits into ellipses, amplifying tide heating from Jupiter *no sunlight= heat from volcanoes or tidal heating
Tree of life
Genetic studies show common ancestor Organisms near root of tree closest in structure to earliest life forms Most resemble extremophiles First developed near deep sea volcanic vents Biologists map relationships between species by comparing their DNA or the structures of molecules coded for by DNA. By studying these molecules in tens of thousands of species, scientists have mapped out the tree of life. One idea we learn is that all large, multicellular organisms represent just three small branches of the domain of eukarya. Another idea is that the true diversity of life on Earth is therefore found almost entirely within the microscopic realm. The last idea is that the branch lengths in the tree represent the amount of genetic differences between species. The closer we get to the root, the closer we are to finding an organism that resembles a common ancestor of all life on Earth.
Which component of Earth's geology has helped shield the Earth's atmosphere form energetic particles of solar wind from the Sun which would have gradually stripped it away into space?
Global magnetism
Jupiter near polar orbiter (juno) mission
Goals: composition, magnetosphere, rocky core, amount of water present
Sedimentary Rocks
Gradual compression of sediments (fossils can tell us about relative age of living things and past events)
In which eon of Earth's history did the heavy bombardment occur?
Hadean
For microbes to survive the journey in a meteorite from another solar system body to the Earth would have to survive the
Impact that blasted the rock off the surface, high energy radiation in space, entry through our atmosphere
Martian Viking Landers
Inconclusive results on the presence of microbial life and organic molecules
Traits passed from parents to offspring are referred to by biologists as
Inheritance
What drives geologic activity on Earth?
Interior is still partially molten (fluid) and hot Heat from interior drives activity
Tidal heating at Io and elsewhere
Io: proximity to Jupiter and elliptical orbit push and pull on Io, generating internal friction - Europa and Ganymede participate in orbital resonance with I o - Io is rocky, but Europa and Ganynede have icy crush with ice or oceans underneath
Why might we think that silicon would be an obvious alternative to carbon as a building block for biological molecules?
It has similar electronic structure to carbon, forming a maximum of four bonds, and hence, should have a similar chemistry
Which of the following statements about Titan is not true
It is the coldest moon in the solar system
What is the half-life of a radioactive isotope
It is the time for half of the number of radioactive nuclei to decay
Based on current evidence, what locations on Earth seem likely for the origin of life? What locations can we rule out?
It is unlikely that life arose on land, because the early atmosphere contained practically no molecular oxygen, so our planet could not have had a protective layer of ozone. Organic compounds may have formed spontaneously in shallow ponds. However, shallow water would not have offered much protection against ultraviolent radiation. Volcanic hot springs may also have offered energy to support an origin of life. The best possibility is deep-sea or underground environments, which were protected from high-energy radiation.
Which is the MOST important property of the element carbon that makes it ideal as a fundamental building block of biological molecules?
It readily forms chemical bonds with itself and other elements, allowing a wide variety of complex molecules to form
If earth formed in the inner solar system, how did it get atmosphere and oceans
Jovian planets knocked many icy planetesimals into inner solar system Some planetesimals were incorporated into formation of the Earth, trapping gases in interior - Repeated comet impacts are thought to have supplied the water for oceans - Volcanism supplied atmosphere - Life consumed carbon dioxide/ created oxygen
Jupiter's Rotation and Storms
Jupiter rotates 10 hours fast rotation stretches storms into colorful bands surrounding entire planet red spot rotation: Coriolis force causes deflection of winds (shrinking) Magnetosphere enormous compared to earth, particles supplied by volcanic eruption on Io Aurora: electrical currents and particles raining down footprints of Galiean moons
Which approach is currently proving to be the most promising way of how life on Earth originated?
Laboratory simulations of condition present on the early Earth
Why haven't we colonized solar system
Lack liquid water, breathable O2 atmosphere, atmosphere that can block UV radiation, food exploration has to be self contained and self sufficient
Rover Mission
Lands on planet's surface and examines
Lander/probe Mission
Lands or impacts a surface and descends into atmosphere
Valles Mariners is:
Large canyon on Mars
Saturn's Titan
Larger than Mercury Has atmosphere- nitrogen with some methane and hydrocarbons *moon and mercury don't have atmospheres, but titan does because it's much colder at titan, so gases don't move as fast **atmosphere formed: ammonia was broken down by solar radiation to give nitrogen, breakdown of methane gives hydrocarbons, clouds of ethane can form, and a methane cycle seems to exist on the moon
Mars Phoenix Lander Mission
Last communication March 2010
AKA Curiosity Rover Overview
Launched 2011, laser spectrometer can analyze chemical makeup of rocks at distance of 13 m
Anaximander
Life arose in water and evolved
Briefly discuss the possibility that life migrated to Earth. Also discuss the possibility that Earth life might have migrated to other worlds, and the implications of possible migration to the search for life elsewhere.
Life could have migrated to Earth via meteorites, we know that they can and do travel from one world to another. Careful chemical analysis has so far revealed dozens with compositions that clearly suggest that they came from Mars and the Moon. Some suggest that life does not form as easily as we have imagined on the conditions present on early Earth, so it must have come from somewhere else. Others argue that life forms so easily that we should expect to find life originating on any planet with suitable conditions. It seems almost certain that microbes from Earth have many times gone to Mercury, the Moon, Venus, and Mars, as Earth has suffered plenty of impacts large enough to blast rock into space during its long history.
Why can studies of carbon isotopes be used to detect the presence of past biological activity in rocks?
Living organisms absorb certain carbon isotopes more easily than others
Lowell and Mars
Map of canals - objections= Maris was too cold for liquid water to flow and polar caps must be CO2 dry ice; canals ran straight from thousands of miles, instead of following terrain
Schiaparelli and Mars
Map of surface with channels
Carbon isotopes
Microorganisms alter ratio of carbon 13 to carbon 12 in rocks rocks older than 3.85 billion years contain organic carbon 13 Life on earth originated within 100-400 years of formation of planet
Igneous Rocks
Molten that has cooled and solidified
Synchronous Rotation
Moon always keeps same face towards parent planet Moon executes one rotation around its axis during each revolution around the planet Tidal friction slows down planet's rotation, planet's gravity slows down moon's rotation
Silicon
Most similar to carbon- bonds are weaker and doesn't last long in water, solid so limited mobility
Liquid Water on Mars
Multiple locations where channels and gullies have formed from flow of liquid water Gusev Crater rocks contain iron rich hematite which forms in water Hematite blueberries and popcorn give us clues to water
Jupiter's Interior
No solid surface Bizarre and unusual liquid and metallic phases of hydrogen and helium
Current Operational Missions: Orbiters
Odyssey, Mars Express, Reconnaissance, MAVEN, Orbiter, Mangalyaan , ExoMars
Zircons
Oldest rocks, embedded in sedimentary, have been formed 4.4 billion yrs ago
Martian Geology of Extremes
Olympus Mons= highest mountain in solar system= Martian gravity weaker so mountains higher deepest canyon= values marineris
Is liquid the choice fluid?
On colder worlds, ammonia, methane, and Ethane may be found in liquid at much lower temps over a small range of temps reactions are slower in colder environments water freezes top to bottom, unlike any other substance electrical properties of water also make it deal for life
Fly By Mission
One shot chance at capturing data and flying on
Early life, step by step
Organic soup formed on Earth or carried by meteors, self replicating RNA molecules form in presence of silicate clay, natural selection favors stronger replicating RNA molecules, pre cells with RNA enclosed in simple membranes arise, enclosed RNA molecules can hold on to their enzymes, early cell forms evolve into primitive cells with RNA genomes, cells with DNA genomes evolve, resembled today's simples prokaryotic cells, anaerobic, chemoautotrophs obtained carbon from dissolved CO2
Which of the following processes is believed to have been an important source of the Earth's atmosphere?
Outgassing by volcanoes on the Earth's surface
Proterozoic
Oxygen, glaciers, multicellular organisms
Milankovitch Cycles
Periodic changes in Earth's orbit
What is orbital resonance?
Periodic gravitational interaction of two orbiting bodies on one another resulting in changes in the orbits
Orbitor Mission
Placed in orbit around planet- long term
Co2 Cycle
Plants absorb atmospheric CO2, animals consume plants and absorb CO2, animal and plant decay brings it into the ground, eventually becoming fossil fuels, animals exhale CO2, burning fossil fuels returns it to atmosphere
Mineralogical Analysis
Present minerals Conditions of formation Routinely used to identify suitable landing spots on Mars
Human evolution
Primates evolved from common ancestor 60 million years ago Incorrect. to say man evolved from chimps Wasn't linear- Homo sapiens and neadertals co existed
Greenhouse gases
Reflect/ trap radiated heat, stabilizing climate
Homeostatis
Regulation of internal environment to maintain constant state
The most basic definition of life which takes account of the relative importance of the six fundamental properties of living things is that life is something that can
Reproduce and evolve through natural selection
Plate tectonics
Reshaping of continents (continental drift), formation of mountains, motion of rocky plates in lithosphere floating on mantle, surface broken into 12 plates Ring of fire, Himalayas, Red Sea= boundaries Mid Ocean Ridges- flow of magma fills mid ocean fissures (when magma cools, magnetized along direction of magnetic field) - new seafloor carried away by tectonic motion, with several of Earth's magnetic field every several hundred thousand years, successor bands of seafloor have opposite polarity
Venus vs. Earth
Runaway greenhouse effect has raised average temp on Venus, slow rotation means no wind or circulation *Carbon dioxide on Earth trapped into carbonate rocks and removed from atmosphere
Basic requires of Life: energy
Saturn receives 1/100th of the sunlight light that Earth does (1%) *need atmosphere or liquid to allow chemical processes to proceed
Rocks are found on the surface of another planet which appear to have been formed at the bottom of an ancient ocean. Given this, they are classified as:
Sedimentary
How do studies of DNA sequences allow us to reconstruct the evolutionary history of life? What living organisms appear to be most closely related to the common ancestor of all present life?
Since living species have evolved from common ancestors, the base sequence in DNA of living organisms provides a sort of map of the genetic changes that have occurred though time. By compared the genomes of organisms, we can reconstruct the evolutionary history of life on Earth. For instance, two species that have similar DNA sequences probably diverged relatively recently in history, while two species with drastically different sequences most likely diverged much longer ago. Initially, scientists believed that most of the organisms closest to the root were extremophiles, but more recently scientists have found non-extreme living archaea that are genetically similar.
Lamarck
Slowly adapt to perform successfully (generations develop new traits)
Life on Europa
Smooth icy surface with fractures Very few impact craters Regions that have rafted across Magnetic field, medium within moon Plumes of water
Earth's Magnetosphere
Solar wind is steady steam of particles from the sun streaming out and carrying with it sun's magnetic field Earth's magnetic field creates protective cocoon called magnetosphere against solar win particles
Earth's interior
Solid inner core, molten outer core Mantle= highly viscous layer Crust of igneous, metamorphic, sedimentary rocks Crust and upper mantle comprise lithosphere (where life exists)
Basic requires of Life: liquid water
Some sort of fluid is necessary for life - formation of complex organic chains requires a medium in which they can travel and interact Water dissolved organic molecules, allows transport of chemicals in and out of cells, and is directly involved in many metabolic reactions
Landing on Mars and Failures lead to drought
Soviet Mars 2 and 3 landers stopped transmitting after reaching surface, Viking 1 transmitted first image in 1976, failures led to drought: failures to reach, lost
Sample Return Mission
Spacecraft returns with samples
Metamorphic Rocks
Structurally and chemically transformed
Which is not evidence for the existence of water on the Martian surface in the past or today
Sublimation of the Martian polar caps
What was the K-T impact, and how is it thought to have led to the demise of the dinosaurs? What evidence supports this scenario? How did this event pave the way for our existence?
The K-T impact was an asteroid strike some 65 million years ago that drastically changed Earth's environment. Evidence for this scenario is the thin layer of sediments that marks the Cretaceous-Tertiary boundary, called the K-T boundary for shot, is unusually rich in iridium, an element that is rare on Earth's surface. The later contains other unusual features as well" high abundances of other metals including gold and platinum, grains of shocked quartz that indicate they experienced high temperature and high pressure conditions of an impact, spherical rock droplets that are known to form when drops of molten rock cool and solidify in the air, and soot that appears to have been produced by widespread forest fires. When the asteroid slammed into Mexico, there was a force of a hundred million hydrogen bombs, which would explain how it led to the demise of dinosaurs. The event paved way for our existence, as among the survivors of the impact were a few small mammals, who may be survived because they lived underground in burrows and managed to store enough food to outlast the global winter that followed the impact. These mammals could have been our ancestors.
What do we mean by the oxygen crisis in relation to the evolution of life on Earth
The extinction of older anaerobic life as oxygen builds up in the atmosphere
What are the three lines of fossil evidence that point to an early origin of life on Earth? Discuss each line and what it tells us about when life arose. What are the implications of an early origin for the possibility of life elsewhere?
The first line comes from stromatolites, which are rocks that are characterized by a distinctive, layered structure. Ancient stromatolites look virtually identical to sections of modern day "living stromatolites" in terms of size, shape, and interior structure. This similarity in structure suggests a similar origin, implying that stromatolites are fossil remnants of early life. This line suggests that life might have begun nearly 3.5 billion years ago. The second line comes from individual fossilized cells. Finding ancient microfossils is quite challenging due to the fact that rocks before rare with age and the oldest rocks are altered by geological processes in ways that destroy the microfossils in them. In addition, it is difficult to determine whether a microscopic structure is biological or mineral in origin. Therefore, this line of evidence often generates significant scientific controversy. The third line is isotopic evidence of some of the most ancient rocks on Earth. Living organisms change the ratios of isotopes from their background, nonliving values. Isotopic evidence has been used on an island off the coast of Greenland, where scientific debate is swaying that the rocks indicate that life already existed by 3.85 billion years ago. This is due to the fact that other rocks dating to some 3.8 billion years ago have been found to show similar carbon isotope ratios. The early origin of life on Earth suggests that what happened on this planet might be typical of what happened elsewhere. We might expect life to begin rapidly on any other world with similar conditions.
What is geology
The study of worlds with solid surfaces, study of the earth, study of the processes, and features that shape worlds
Mineralogical analysis of a rock can tell us
The temperature and pressure conditions under which it formed
Life probably not originate on the land surface because
There was no ozone layer to shield out harmful UV rays
Different species of finches found on the Galapagos islands are evidence of Darwin's theory of natural selection because
They have all evolved adaptations form a common ancestor to suit the environmental conditions found on different islands