Solar System 2019 Earth’s moon and other rocky bodies of our solar system Scott Jackson, Mt. Cuba Astronomical Observatory (and Planetarium) Help session: Sunday afternoon: March 3, 2019 at Mt Cuba Observatory
Test on March 16, 2019 “Two 8.5 x 11 inch two sided sheet” Test will include questions about a series of images projected onto the front of the room. 1
2 EVENT DESCRIPTION demonstrate an understanding and knowledge of the geologic characteristics and evolution of the Earth’s moon and other rocky bodies of the solar system DwarfPlanets: Pluto, Ceres, Haumea, Makemake, Eris . Satellites: Earth’s Moon,Charon, Mimas, Phoebe General Details of Other Small Bodies: Asteroid Belt,Centaurs, Trojans, Trans-Neptunian Objects Specific Details of: ‘Oumuamua and (225088) 2007 OR10 Missions: New Horizons, Dawn, Cassini, Lucy, Voyager 2 History and formation processes Remote sensing, imagery and satellite measurements Kepler’s laws, gravitational effects of the moon and tides Rotation, libration, phases, and eclipses Surface Dating, volcanism & weathering, cratering & impact processes Internal, surface, and Atmospheric compositions
3 Our sun’s evolutionary stages • Gas and dust compress under self gravitation • Any rotation in the gas cloud is conserved (and causes planets to revolve and rotate) •A protostar star is form • As the gas is compressed by gravity, the core of the protostar increased in pressure and temperature until nuclear fusion occurs: Hydrogen Helium
The star becomes stable and stays this way our sun 4 History and Formation of the Solar System
The planets of the Solar System formed from a nebula of gas, dust, and ices coalescing into a dusty disk around the evolving Sun. Within the disk, dust grains and ices coagulated into growing bodies called planetesimals. These then collided and were swept up together to form the planets and their satellites The fact that all planets revolve around the sun in the same direction and most rotate in the same direction shows the left over energy from the initial collapse of the nebula. 5
Early solar system evolution Early in the sun’s life (as the planets were forming), the sun had a very strong solar wind (from flares) Charged particles streaming out of the suns atmosphere This solar wind was produced as the nuclear reactions in the core of the sun started. The sun produces a weaker solar wind today that fluctuates with the sunspot activity of the sun – more sunspots, more solar wind. Solar wind “storms” cause the Northern Lights (auroras) This early strong solar wind and collisions between particles helped to “pushed” much of the material that had not been formed into planets out to the farther reaches of the solar system This helped formed the Kuiper Belt and the Oort Cloud (the source of long period comets)
6 The end of our solar system • The planets form about the same time as the sun. • At the end of our suns normal life, hydrogen is depleted in the core of the sun. Gravity takes over and causes the core to heat up further. • BUT fusion continues in a shell outside the core. Our sun will “bloat” up to a red giant. The earth will be fried • Helium will start to be fused to carbon in the core of our sun. •
•The sun will be convulsed and throw off half its mass as a planetary nebulea -- solar system destroyed • A white dwarf (carbon) star will be left behind 7 Objects of the Solar System: Planets A planet is … in orbit around the Sun, Has sufficient mass to assume a hydrostatic equilibrium (nearly round) shape, and Has “cleared the neighbor-hood” around its orbit.
8 Dwarf Planets A dwarf planet is … Pluto (spherical with 1 moon- Charon) In orbit around the Sun Ceres Has sufficient mass for Ceres is the largest asteroid in the main asteroid its self-gravity to belt. It is a dwarf planet because of its round overcome rigid body shape forces so that it Rocky (high density) assumes a hydrostatic equilibrium (nearly In asteroid belt round) shape, Between Mars & Has not “cleared the Jupiter neighbor-hood” around its orbit, and Is not a satellite of a planet, or other nonstellar body.
Haumea Dwarf planet beyond Neptune, About the size of Pluto with 2 moons, fast rotation rate Collision likely caused it to rotate so fast and to form its 2 moons – Kuiper belt object Ceres 9 Pluto Dwarf Planets Remarkably complex geology – Surface is 98% frozen nitrogen plus a little methane and carbon monoxide New (No craters) and old (cratered) surfaces next to each other Nitrogen ice glaciers Ice water mountains Possible cryovolcanoes Water ice glacier on Earth Nitrogen ice glacier on Pluto
Ceres 10 11 12 Atmosphere on Pluto – very thin ~ 0.00001 atmosphere Nitrogen, methane, particles (causes haze),
13 Dwarf Planets
Makemake Dwarf plant beyond Pluto It and Haumea and Eris are responsible for demoting Pluto to a dwarf planet No close up pictures 870 miles in diameter, no atmosphere Takes 310 years to go around the sun, in the Kuiper belt Frozen layer of methane and possibly ethane and nitrogen One moon Eris About the same size as Pluto No close up pictures 1400 miles in diameter – a little smaller than our moon. Takes ~5 hours for sunlight to reach Eris. 557 years to orbit the sun In the Kuiper belt One very small moon – allows astronomers to determine the mass of Eris
Ceres 14 Some 7000 asteroids Asteroids have been identified so far. Most are in a belt or band between the orbits of Jupiter and Mars Jupiter probably stopped planetisimals asteroid Gaspra formed at the birth of the solar system from Why is Gaspra not a dwarf planet and Ceres coalescing into a
is ? planet. 15 The Kuiper Belt is made up of Kuiper Belt & Oort cloud millions of icy and rocky objects that orbit our Sun beyond the orbits of Neptune and Pluto. These are planetesimals that did not combine to make planets. It is the source of short period comets Oort Cloud is spherical and is at the outer edge of our solar system It was pushed out there at the start of the solar system by strong solar winds and by the gravity of the large gas giant planets The Oort cloud acts as a reservoir for the long-period comets
16 Charon Biggest moon of Pluto. Half the size of Pluto double dwarf system New Horizon’s fly by Orbits Pluto every 6.4 days
Mimas -- moon of Saturn Cassini space craft image. 246 miles in diameter – smallest spherical body known Mostly water ice (same density as water) Giant impact crater Not as big as Titan, the largest moon of Saturn
Tidally locked like the Earth’s moon. 17
Phoebe another moon of Saturn Cassini probe took this close up Picture Roughly 120 miles in diameter Orbits Saturn every 18 months Likely a “captured” object May be a captured Centaur asteroid – material from the beginning of the solar system
Centaur asteroids
18 Centaur A cross between asteroids and comets Across the orbit of Neptune Considered very old and likely composed of material from the beginning of our solar system
19 Asteroid Belt The heaviest concentration of asteroids is in a region lying between the orbits of Mars and Jupiter called the asteroid belt.
20 Facts about the Asteroid Belt Traveling through the The total weight of all asteroid belt in a space the asteroids in the ship would not be like asteroid belt is about what you see in a 1/35th of that of our science fiction film. moon! In addition to the belt Ceres, the largest asteroids, there are asteroid (a dwarf others classes of planet), is about 1/3 the asteroids based upon total weight of all the their location and orbit asteroids! in the solar system: Even though there are Apollo (Earth crossing), a lot of asteroids, the Amors, Atons, Trojan asteroid belt is mostly (along the orbit of empty space. Jupitor) and Centaurs.
21 Oumuamua
The first and only interstellar object that travel through our solar system in 2017 Its very high speed proved it came from outside our solar system Its changing light output indicates that it is very long like a cigar.
22 225088 2007 OR10
Binary object (a dwarf planet with a moon) beyond the orbit of Neptune (Trans Neptunian) 780 miles in diameter Largest unnamed object in our solar system Slightly larger than Charon Discovered in 2007
23 Missions New Horizons • Interplanetary space probe. • Launched in 2006 • Primary mission: Flyby Pluto and later a Kuiper belt object (Ultimate Thule) • Detected “hydrogen wall” (a region of hot hydrogen at the edge of the solar system where the solar wind Hits the interstellar wind)
24 Missions -- Dawn • Ion propulsion used to go to the asteroid belt and observe Ceres (a dwarf planet) and Vesta • First to orbit two different targets • Current in a uncontrolled orbit around Ceres. • It ran out of fuel
25 Missions:Cassini -Huygens • Probe sent to study Saturn • Huygens probe attached to Cassini was dropped to the surface of Titan • Many crossings of the ring system • Purposely flown into Saturn to burn up to avoid any possibility of contaminating Saturn’s moons
26 Missions -Lucy • To be launched in about 3 years • Explore the Trojan asteroids • Trojans believed to be remnants of the early solar system that became locked into Jupiter’s orbit and low energy points.
27 Missions:Voyager 2 • Launched in 1977 • Only probe to fly by Uranus and Neptune • Crossed the heliopause into interstellar space • Remains an active mission to measure the interstellar media.
28 Accepted theory of the Origin of our moon… • A small planet named “Theia” slammed into earth • It may have side swiped the earth, created the moon, and Theia was thrown out of the solar system • OR it blew apart the earth making the combined Earth+Theia into the Earth- moon system.
29 Evidence that Theia is part of the Earth – moon system • Ratio of oxygen isotopes provides a unique signature to each planet in our solar system – Oxygen normally has 8 protons and 8 neutrons That is called 16O – Some oxygen has 8 protons plus 9 neutrons or 10 neutrons –Called 17O to 18O – Ratio of 16O to 17O to 18O is the same in the earth and the moon – Indicates that they were made from the same material = Theia+ the original Earth 30 More Evidence for the impact origin of our moon • Earth has a iron core – source of our magnetic field • Moon does not – any iron in Theia merged with earth’s iron core. – The material thrown off during the collision would have been less dense. • The moon is the largest moon relative to the planet it is orbiting – A substantial amount of material would have been thrown off from the collision – making a large moon. 31
Estimating apparent age of surfaces
• Crater density • Which is older?
32 Tidal effects on Earth (and our moon) Tidal Effects The gravity of our sun and our moon yanks the near side of the oceans to form a high tide. Gravity also tugs at the (solid) earth away from the oceans on the far side. Hence high tides on the far side! Our moon "solid ground" also has tides – very small Tides also occur in the crust – causing frictional heating like IO
33 Tidal effects on Earth (and our moon) 1. A long time ago… The tidal forces of Earth on the Moon slowed down the rotation of the Moon (while speeding up the rotation of the Earth). 2. The Moon eventually keeps the same face toward the Earth, becoming tidally locked (as it is now) 3. The tidal forces of the Moon on the Earth slow down the rotation of the Earth, while speeding up the orbital motion of the Moon 4. The Moon spirals away from the Earth, increasing its angular momentum, compensating for the lost angular momentum of the Earth rotation. 5. The Earth eventually keeps the same face toward the Moon, becoming tidally locked. 6. The system stops evolving and remains in this configuration
forever (except as influenced by external forces). 34
Tidal effects on Tidal Effects The gravity of Jupiter and satellites its large moons yank its satellite Io every which way. Io’s "solid ground" tides are more than five times as high as Earth’s highest ocean tides! This causes a lot of friction and heating of the crust of Io This causes sulfur volcanoes across the face of Io
35 Lava (Basalt) filled ancient craters to form the Mare (Seas)
Our Moon
Lots of craters –most from impacts36 But mare on the moon not like volcanoes on Earth • Mare mostly caused by the process that formed the moon • There are volcanoes on the moon that likely formed like that on Earth (next slide) • All now extinct
37 Cross section of our moon Essentially dead – no plate techtonics (like the earth). No strong magnetic field (no large molten iron inner core)
38 We all know about solar eclipses (yes?) • The moon completely blocks out the sun’s light in a very small spot on Earth.
• August 21st
39 • Here is what it looks like if you were standing near the sun (HOT!!) and looking through a telescope.
40 41 42 Partial Solar Eclipses
If the penumbra passes over you, only part of the Sun's surface will be blocked out. You will see a partial solar eclipse, and the sky may dim slightly depending upon how much of the Sun's disc is covered.
Partial Solar Eclipse
43 In some cases, the moon is far enough away in its orbit that the umbra never reaches the Earth at all. In this case, there is no region of totality, and what you see is an annular solar eclipse. In an annular eclipse, only a small, ring-like sliver of light of the Sun’s disk is visible. ("annular" means "of a ring").
Annular Solar Eclipse
44 Lunar Phases
45 But… did you know that you can “see” (barely) the “dark” side of the moon during a total solar eclipse • But how can that be???!! • The earth reflects a lot of light back to the moon – like ~10x that of a full moon. • So there is enough sunlight reflected off the earth to illuminate the “dark”
side of the moon!!!46
We all know about Lunar eclipses (yes?)
• The Earth completely blocks out the sun’s light falling on the moon. • BUT – the whole moon can be darkened – why? • Jan 31, 2018 • Jan 20/21, 2019
47 What does a lunar eclipse look like from the surface of the moon? • Like this!!!! • The size of the earth, appears to be much larger than the sun as viewed from the moon… • So… it completely blocks the sun out when there is a lunar eclipse.
48 From the surface of the moon, the Earth appears to go through phases… just like the moon…
• So… What phase is the moon when the Earth is “full”????
49 We always see the same face of the moon… But actually can see more than half of the moon… Libration – or apparent wobble of the moon.
The moon appears to “wobble” up and down and left to right a little
50 We always see the same face of the moon… What do you think the earth looks like from the moon?
Click here
51 After a really long time, a rectangle is formed…
This is due to the Moon’s rotation rate is slightly out of sync with its orbital rate around the earth This is due to the Moon’s tilt of its axis
This is also the wobble from before
52 Mars
53 Mars • Gigantic volcanoes – Olympus Mons is the largest found in the solar system – Would cover the state of Arizona – Similar composition to volcanoes on Earth – None active
– No current magnetic field on Mars means no molten core to drive active volcanoes. – But Mars had a molten core in the past that produced these volcanoes 54 Global Mars mosaic from Mars surveyor (http://www.msss.com/mars_images/moc/7_19_99_f ifthMars/01_daymap/moc2_143_msss_2.jpg)
North polar cap at top, Volcanoes to left, Enormous rift valley left of center, clouds, craters at bottom
55 Olympus Mons (http://www.solarviews.com/raw/mars/olympus.gif)
Huge shield volcano
The largest in the solar system But no clear evidence of plate techtonics 56 Mars North Polar Cap from Mars surveyor
(http://www.msss.com/mars_images/moc/may_2000/n_pole/npole_50.jpg) Extremely cold temperature, The white stuff is frozen carbon dioxide not water but ….
Ice water is under this
57 Reflected Radar mapping of what is under the pole
Ice layers Base rock
Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter for mapping underground ice-rich layers of the north polar layered terrain on Mars The penetrating radar reveals icy layered deposits overlying a base rock.
58 Mars South Polar cap
• Photos from Mars Global Surveyor • The bottom photo was taken during summer. This is essentially “permafrost” that is, it does not go away.
• CO2 frost grows much larger during winter.
• Picture taken by Mars Global Surveyor
http://www.nasa.gov/centers/ames/multimedia/images/2005/marscap.html 59 Evidence for glaciers on Mars • Glaciers are largely restricted to latitudes above 30° latitude. Based on models of the Martian atmosphere, ice should not be stable at the surface near the equator. Glaciers near the equator must be covered with a layer of rubble or dust preventing the sublimation of the ice into the atmosphere. A terminal moraine is in the rectangle.
http://en.wikipedia.org/wiki/File:Wide_view_of_glacier_showing_image_field.JPG 60 More evidence for glaciers on Mars
• http://en.wikipedia.org/wiki/File:ESP_028352_2245glacier.jpg
61 Valles Marineris
A gigantic rift valley 62 Mars interior – was molten iron – had a magnetic field that has since disappeared when solidified
63 Mars moons • Geologically inactive. Captured asteroids. • Not large enough to have enough gravity to make them spherical.
64 Venus • Dense atmosphere / completely clouded over – Run away greenhouse heating – very hot surface temperatures
– Can’t easily “see” the surface but…. Radar used to “see” the surface. • Radar has seen evidence of lava flows and
volcanism 65 • Radar images of Maat Venus Mons • Unclear if it is an active volcano • Probably formed like those on Earth & Mars • No craters
• But no clear evidence of plate techtonics 66
No magnetic field –very slow rotation rate and lack of internal movement of conductive material that can create a magnetic field
67 Mercury
• No air • First satellite pictures showed a surface a lot like the moon • Very hot on the sun side (melts lead) • Very cold on the shady side • “Inferior” planet • Show phases like the moon • But very difficult to see – always close to the sun • BUT recent satellite images suggest…. Extinct Volcanoes! 68 Tectonic activity on Mercury
• Over thrust faults caused by contraction of mercury when cooled
69 Cross section of Mercury Molten core should create a strong magnetic field There is a magnetic field but 200x weaker than Earths..
70 Jupiter Largest planet Rotates every 6 hours, appears “flattened” Gas giant, would “float” on water Visible in a pair of binoculars Four major moons The closest to Jupiter is Io Many sulfur volcanoes Caused by the friction heating from the strong tides produced from Jupiter’s gravity. Totally different than Earth, Moon, Mars, Venus or Mercury 71 Io and sulfur volcanoes Tidal Effects Io shows the same face to Jupiter – gravitationally locked (like our moon)
72 Structure of Io • Determined using Galileo spacecraft. • Low density crust 20-30 miles (grey) • Molten magma “ocean” -- red brown & orange(source of volcanoes) • Io’s magma ocean is very conductive and deflects the Jupiters strong magnetic field lines (blue) • Iron and iron sulfide core (silver)
73 Ceres: • the largest asteroid and the only dwarf planet in the inner Solar System, orbiting in the asteroid belt between the orbits of Mars and Jupiter. It is a rock–ice body 950 km (590 mi) in diameter and the smallest identified dwarf planet. It surface is probably a mixture of water ice and various hydrated minerals such as carbonates and clay minerals. It appears to be differentiated into a rocky core and icy mantle, and may harbor an ocean of liquid water under its surface,
Hubble space telescope image 74 Planetary Motions: Rotation
A planet or dwarf planet or asteroid will rotate on an axis. Its rate of rotation gives the length of a “day” on the object.
75 Kepler’s First Law of Planetary Motion
The path of the planets about the sun are elliptical in shape, with the center of the sun being located at one focus. (The Law of Ellipses)
76 Kepler’s Second Law of Planetary Motion The line joining a planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse.
77 Kepler’s Third Law of Planetary Motion The square of the total time period (T) of the orbit is proportional to the cube of the average distance of the planet to the Sun (R). (The Law of Harmonies)
78