Solar system 05 terrestrial planetsPresentation Transcript
Solar System 05: The Terrestrial Planets
The Terrestrial Planets
Terrestrial means “earthlike”
The terrestrial planets are Mercury, Venus, and Mars
Mercury Data http://www.vegaattractions.com/images/1mercury.gif Surface Gravity if Earth = 1 0.38 Planet Symbol Mass if Earth = 1 0.055 Length of Day 58.65 Earth days Diameter if Earth = 1 0.38 Length of Year (revolution around the sun) 87.97 Earth days Diameter at the Equator 3,031 miles Moons None Mean Distance from the sun 36,000,000 miles 0.4 AU
Mercury is only Slightly Larger than the Moon MERCURY OUR MOON
Discovery : Mercury has been known since prehistoric times.
It was first mentioned in written records of the Sumerians (3000 BC).
Mercury is visible either early in the evening just after sunset or early in the morning just before sunrise.
It is always close to the sun and can be seen for just a few minutes either at sunset or sunrise.
Phases of Mercury
As an inferior planet (between sun and earth), Mercury displays phases that resemble the phases of earth’s moon.
You need a telescope to observe the phases of Mercury.
Galileo first observed the phases of Mercury and Venus. This observation represented proof of the heliocentric (sun-centered), or Copernican solar system
Phases of Inferior Planets http://www.polaris.iastate.edu/EveningStar/Unit1/Graphics/PicES1_6c.gif http://astromm.calstatela.edu/images/planets/larousse/Me_Phases.jpg Telescope sketches of Mercury Orbit of an inferior planet
Mercury’s eccentric orbit brings it close and far from the sun during its revolution.
This means that the orbital shape is much more oval or elliptical in appearance.
Mercury’s orbit is one of the most eccentric in the solar system.
At its closest approach to the sun (perihelion), Mercury lies at a distance of 46 million km
At its farthest approach (aphelion) Mercury lies at a distance of 70 million km.
Planetary Eccentricities Which “planet” is most eccentric?
Impact craters on Mercury have similar features to those on the Moon. CRATERS ON BOTH MERCURY AND THE MOON HAVE RINGS OF MOUNTAINS SURROUNDING THEM MERCURY OUR MOON Jumbled hills surrounding the Caloris Impact Basin
Mercury also has numerous long cliffs, called scarps, believed to have formed when the planet cooled
One huge impact feature on Mercury is named the Caloris Basin, it is about 800 miles in diameter and was created by the impact of a large comet or asteroid.
The Caloris Basin resembles the large impact basins (maria) on earth’s moon.
The impact that created this basin was so large that it created a warped surface area on the area of the planet directly behind the impact.
http://www.record-producer.com/i/capacitor-microphone-sizzle.jpg Hot basin
Features on Mercury have been named for famous writers, musicians, and painters.
For example, there are craters named after Beethoven, Homer, Mark Twain, and Matisse.
There are 297 named features on Mercury
16 Largest Craters on Mercury
Shakespeare quadrangle of Mercury http://www.hollowaypages.com/images/CHANDOS2.jpg
Amazingly, radar observations of Mercury’s north pole from the Aricebo dish in Puerto Rico provide evidence that water ice may exists in the always-shadowed areas of some craters.
These craters exist near the poles of Mercury, where sunlight never reaches. Similar deposits might also be present on our moon.
If true, these deposits could contain a record of much of the solar system’s history.
Ice on Mercury? homepage.smc.edu/.../ MERCURY/polar_ice.jpg White patches in the right image may represent deposits of ice at Mercury’s south pole
Precession of Mercury’s Orbit
Mercury’s orbital path precesses (wobbles) in a manner that could not be explained by the theories of Isaac Newton
The planet’s perihelion position (closest approach to sun) drifts slowly as a result, and the rate of wobble is once per 30,140 years
Explaining Mercury’s orbit was one of the first predicitons of Einstein’s theory of General Relativity
Newton’s Laws break down in the presence of an intense gravitational field, such as that of the sun’s
The warping of space by the sun’s gravity accounts for Mercury’s anomalous precession
Mercury’s Precession http://scholar.uwinnipeg.ca/courses/38/4500.6-001/Cosmology/general_relativity.htm http://antwrp.gsfc.nasa.gov/apod/image/einstein_clerk_big.gif Perihelion position
LeVerrier, who along with Adams predicted the existence of Neptune, proposed that the mysterious precession of Mercury’s revolution was caused by the gravity of an undiscovered planet that lay between Mercury and the sun.
This hypothetical planet was named Vulcan.
Some astronomers in the 1800’s claimed to have observed this planet using telescopes, but these observations have never been confirmed, and it is unlikely that anything like Vulcan exists.
Live long and prosper
Transits of Mercury
A transit is the passage of an inferior planet (Venus or Mercury) across the face of the sun
On average, there are 13 transits of Mercury visible each century
In contrast, Venus transits are much rarer, they occur in pairs over a century apart
The last Mercury transit occur in November 2006
May 2003 Transit of Mercury
Nov 2006 Transit of Mercury Where’s Mercury?
November 2006 Mercury Transit
Lore of Mercury
Clay tablets written by the Sumerians show that these people kept very accurate records of the appearances of Mercury in the night sky. The Sumerians flourished around 5000 years ago in modern day Iraq
Wednesday, or Woden’s Day, is named for the planet Mercury
According to legend, Copernicus never was able to see Mercury. It’s not difficult, you just need to know when and where to look
Lore of Mercury, Cont.
The Greeks named the evening appearance of the planet Apollo, they named the morning appearance Hermes
In Roman mythology, Mercury is the god of commerce, travel, and thievery, the Roman counterpart of the Greek god Hermes, the messenger of the gods
The planet probably received this name because it moves so quickly in the sky from night to night
Cuneiform Mercury Tablet, Roman Statue of Mercury www.gwydir.demon.co.uk
Venus Data http://www.vegaattractions.com/images/1venus.gif Surface Gravity if Earth = 1 0.91 Planet Symbol Mass if Earth = 1 0.815 Length of Day 243.01 Earth days Diameter if Earth = 1 0.95 Length of Year (revolution around the sun) 224.70 Earth days Diameter at the Equator 7,521 miles Moons 0 Mean Distance from the sun 67,200,000 miles 0.72 AU
Venus : The Roman goddess Venus was the goddess of love and beauty
Venus is the brightest planets seen from earth
Discovery of Venus
Discovery : Venus has been known since prehistoric times. It is the brightest object in the sky except for the sun and the moon.
The appearances of Venus are described in the mythology of many peoples including the Sumerians and Mayans.
Evening and Morning Star
Venus is visible either early in the evening just after sunset (evening star), or early in the morning just before sunrise (morning star)
Although always near the sun, Venus can extend about 45º to the east or west of the sun
On any particular evening or morning, Venus stays in the sky much longer than Mercury
Venus often pairs with the crescent moon for pretty scenes
Venus as Evening Star Venus as an evening star in the western sky after sunset
Venus as Morning Star Venus as a morning star in the eastern sky before sunrise
Changing Positions of Venus, Mercury http://www.nmm.ac.uk/upload/img/mv-orbit.jpg
Evening Star: Venus and Moon http://www.russellsastronomy.com/sky/April-June%20Planets.htm
Phases of Venus
As an inferior planet (between sun and earth), Venus displays phases that resemble the phases of earth’s moon
You need a telescope to observe the phases of Venus
Galileo first observed the phases of Venus in the early 1600s
Phases of Venus, cont.
Galileo’s observation of the phases of Venus provided important evidence in favor of Copernicus’s heliocentric (sun-centered) theory of the solar system.
The Ptolemaic, or earth-centered solar system would only allow Venus to have crescent phases
The Copernican model allows a nearly “full” Venus, which is what Galileo observed.
The Clouds of Venus Venus is covered with a dense layer of clouds that hides its surface. Unlike the benign water vapor clouds on Earth, these clouds contain large amounts of sulfur dust and sulfur compounds, giving them a yellow-orange color. The clouds on Venus are made of concentrated sulfuric acid.
Spacecraft to Venus
Spacecraft : The first spacecraft to visit Venus was Mariner 2 in 1962
Venus was visited next by many others (more than 20 so far), including Pioneer Venus and Soviet Venera 7, the first spacecraft to land on another planet, and Venera 9, which returned the first photographs of the surface
The orbiting US spacecraft Magellan has produced detailed maps of Venus’s surface using radar. Magellan entered Venus’s orbit in 1990
Venus’s Surface, courtesy of Venera Edge of Venera Lander
This image of the Venusian surface from the Soviet spacecraft Venera 13 shows rock plates which are possibly fractured lava. Unfortunately, this craft was destroyed by the intense pressure and extreme temperatures on the Venusian surface.
The Magellan spacecraft, in an orbit around Venus, was able to “see through” the thick clouds using radar, giving us the best view of our sister planet.
This false color map of Venus, equivalent to a topographical map of Earth, shows the large-scale surface features of the planet.
A global view of Venus using radar images from the Magellan spacecraft The craters found on Venus tend to be in clusters. This suggests that they were formed from a large single piece of falling debris that was broken up by the Venusian atmosphere.
Most of Venus’ surface consists of gently rolling planes with little height differences
There are very few surviving impact craters on Venus
There are several large, low areas (depressions) such as the Atalanta Planitia
There are two large plateaus or highland areas, one is named the Ishtar Terra and the other is named the Aphrodite Terra
Venus’s Surface Features, cont.
Data from Magellan suggests that the surface is covered largely by lava flows.
There are several large volcanoes such as the Sif Mons .
Recent findings suggest that Venus still has active volcanism, but only in a few areas.
Venus also exhibits some unique landforms such as pancake volcanoes, spider-like “arachnoids,” and coronae.
The pancake volcanoes seem to be eruptions of very thick lava and the coronae seem to be collapsed lava domes.
3D Venus Map http://masa-p3-rw.hp.infoseek.co.jp/planet/venus_3dmap02.jpg Terras
Magellan Global Views http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-venus.html
Maya Venus “Observatory” at Chichen Itza http://centros.edu.aytolacoruna.es/sfxabier/world_links/mexico_observatory.jpg
This famous structure is also named the Caracol
Chichen Itza is located near Cancun, Mexido
Lore of Venus: Paradise Lost
Milton : The movement of Venus in the sky was used by Milton as a metaphor of the fallen angel Lucifer and forms the central theme of his epic poem Paradise Lost.
Paradise Lost is a long poem that was first published in 1674, the poem deals directly with ideas from the Bible.
Paradise Lost http://www.clt.astate.edu/wnarey/Honors%20Seminars_files/Horror/summar3.jpg http://users.ox.ac.uk/~lina0897/emwo/images/big/PARADISE_LOST.jpg
Mars Data http://www.vegaattractions.com/astrology/symbols.html Surface Gravity if Earth = 1 0.38 Planet Symbol (draw) Mass if Earth = 1 0.107 Length of Day 24 hr. 37 min. 22.6 sec. Diameter if Earth = 1 0.53 Length of Year (revolution around the sun) 686.98 Earth days Diameter at the Equator 4,217 miles Moons 2 Mean Distance from the sun 141,500,000 miles AU
God of War : Mars was the Roman god of war.
The planet probably got this name due to its red color.
Mars is also referred to as the Red Planet.
Discovery : Mars has been known since prehistoric times
It is still a favorite location for science fiction stories
Mars becomes very bright about every two years, sometimes even brighter than Jupiter and Sirius
Spacecraft : The first spacecraft to visit Mars was Mariner 4 in 1965
Several others followed including Mars 2, the first spacecraft to land on Mars and the two Viking landers in 1976
After 20 years, the Mars Pathfinder landed successfully on Mars on July 4, 1997
In 2004 the Mars Expedition Rovers "Spirit" and "Opportunity" landed on Mars sending back geologic data and many pictures
Spirit and Opportunity are still operating after more than three years (2007) on Mars
Below: The crater Endurance, photographed by the Martian rover Opportunity
Mariner 4 : No Canals (1965) http://mpfwww.jpl.nasa.gov/MPF/martianchronicle/martianchron2/issue2images/mariner4photo.jpeg
Viking (1976) http://www.hypography.com/bilder/viking_on_mars.jpg Viking’s robotic arm (below) collected soil samples to test for life
Pathfinder (Mars or Arizona?) http://anw.com/mars/images/widescene.jpg
Spirit & Opportunity
Climate : Temperatures on Mars range from –207ºF at the winter pole to 80ºF on the day side during summer
The average temperature is –67ºF
Despite being cold, Mars has the most earthlike climate of any of the planets
Atmosphere : Mars has a very thin atmosphere composed mostly of carbon dioxide (95.3%) plus nitrogen (2.7%) and various other gases
Mars displays strong winds and immense dust storms that can cover most of the planet and last for many months
Dust devils, small tornadoes, have been sighted on Mars
Mars Dust Storm
Although it is sometimes blue, the Martian sky generally takes on a rust color because of dust particles blown into the atmosphere by strong winds. Sunset on Mars
One earthlike feature of Mars are the ice caps which grow and shrink with the seasons on Mars
The ice caps are composed mainly of frozen carbon dioxide (dry ice) and water ice
Mars is tilted on its axis by 25.19 (nearly the same as Earth) and has seasons. Martian Seasons Large ice cap made mostly of frozen carbon dioxide (dry ice) The dry ice melts, leaving a much smaller polar cap
High winds create dust devils on the Martian surface. A DUST DEVIL FROM ABOVE DARK STREAKS SHOW THE PATH OF DUST DEVILS
Surface : Although Mars diameter is less than earth, its surface area is about the same as the land area of earth’s continents
Much of Mars’ surface is old and cratered and resembles the highlands on earth’s moon, but there are also younger features such as rift valleys, ridges, hills, and plains.
Mars has some unique features and probably has the most interesting terrain of any world besides earth.
Mars Tour Guide
Olympus Mons : A volcano, the largest mountain in the solar system (78,000 ft, about 22 mi). Its base is more than 310 mi in diameter
Valles Marineris : A system of canyons 3,750 mi long and from 2-7 mi deep
The Martian terrain includes broad towering volcanoes, vast windswept plains, and enormous canyons. Valles Marineris is a vast canyon stretchimg over about one-fifth the circumference of Mars.
Vallis Marineris (Viking)
Mars also has volcanoes. The largest of these is Olympus Mons. It covers an area the size of Missouri and rises three times higher than Mount Everest.
Tharsis Region Olympus Mons & clouds
Olympus Mons http://www.physast.uga.edu/~jss/1010/ch10/mtoly.jpg
No Plate Tectonics : Mars appears to lack plate tectonics
This seems to have helped in the development of the huge volcanoes such as Olympus Mons
Plate motions wouldn’t allow such large piles of lava to build up
No active volcanism has been observed on Mars
Impact Craters on Mars Most of these craters are found in the Southern Hemisphere, suggesting that the northern vastness has been resurfaced.
Liquid Water : There is much evidence of past running water on Mars’ surface including large floods and small river systems.
Some large lakes or oceans may also have existed.
Ice Caps : Mars has permanent ice caps at its north and south poles.
This ice is mainly composed of frozen carbon dioxide (dry ice) with a small amount of frozen water ice.
The winding canyons found on the Martian surface are similar to those found in river beds on Earth, suggesting that liquid water once flowed on Mars. Martian winding canyon, photographed by the Viking orbiter The Yangtze River in China has similar features
Surface features believed to be ancient waterways An ancient lake A dried riverbed Sedimentation
Layers of rock laid down by water Hemetite black rocks, usually formed in water Gullies in crater walls
Nirgal Vallis, possible river valley http://science.nasa.gov/headlines/y2001/ast05jan_1.htm
Sedimentary Layers from Water http://science.nasa.gov/headlines/images/mars_water/sediments.jpg
Chyrse, “Teardrop” Islands
The teardrop islands represent an erosional feature created by past running water
Mars has been the Center of Speculation about Extraterrestrial Life Early telescope images showed features which were perceived as irrigation canals. People feared an attack from Mars, like this one portrayed in “The War of the Worlds.”
Canals on Mars?
Life on Mars ? In the early 1900s, Percival Lowell claimed to have observed canals on Mars’ surface
He created maps and theories concerning the canals, but we know that they do not exist
Lowell believed that the canals were the efforts of a dying civilization on Mars to capture water from the frozen poles for survival
Martian Nomenclature : The main features on Mars were named by the astronomer Schiaparelli
He selected geographical and imaginary names from Greek and Roman literature such as Solis Lacus (Lake of the Sun), Aurorae Sinus (Bay of Dawn), Margaritifer Sinus (coast of India), Syrtis Major (Gulf of Sidra), Mare Tyrrhenum (Tyrrhenian Sea)
The names of dark areas were those of bodies of water, and those of bright areas, of lands
Gulliver’s Travels : Jonathan Swift, in his 1726 book Gulliver’s Travels , described how the astronomers of Lilliput had discovered “two lesser stars, or satellites, which revolve around Mars”
Swift gives their periods of revolution as 21 and 10 hours (quite close to the true values)
These conjectures seem to have been lucky guesses
Mars in the Night Sky : Every two years, Mars gets very bright and easily visible
These events are named oppositions, they occur when earth and Mars reach a minimum distance apart
Opposition occurs when a superior planet is opposite of the sun in earth’s sky
At opposition, the planet rises in the east as the sun sets in the west.
Only superior planets can reach opposition
Oppositions of Mars
7 Nov 2005
24 Dec 2007
29 Jan 2010
3 Mar 2012
8 April 2014
22 May 2016
27 July 2018
13 Oct 2020
Face on Mars
“ Face on Mars ”: Images from the Viking Orbiter 1 show what appears to be a large, human face located in the Cydonia region of Mars.
Some writers have claimed that this shape was artificially sculpted, Richard Hoagland, for example, created elaborate systems of alignments linking the Face to the Egyptian Pyramids and Sphinx on earth
Images returned from the Mars Global Surveyor reveal that the “face” is little more than a pile of rocks.
Viking’s Face on Mars (1976) http://mcadams.posc.mu.edu/images%5Cface_mars.jpg
Mars Global Surveyor Face (2001) http://mars.jpl.nasa.gov/mgs/msss/camera/images/moc_5_24_01/face/ “ Face” the truth, Mr. Hoagland http://www.sg.hu/kep/2004_03/0322mars1.jpg
War of the Worlds Scare
War of the Worlds Scare : In 1938, Orson Welles broadcast a radio play based upon H.G. Wells’ novel The War of the Worlds
The realistic nature of the broadcast convinced many listeners that a Martian invasion was really taking place
Hysterical listeners called the police and newspapers, fled from their homes, and gazed at the sky in terror
About 28% of listeners thought that the invasion was real
In 1938, Orson Welles broadcast a radio play based upon H.G. Wells’ novel The War of the Worlds
The realistic nature of the broadcast convinced many listeners that a Martian invasion was really taking place
About 28% of listeners thought that the invasion was real
Orson Welles as a broadcaster
Science Fiction: War of the Worlds
Science Fiction : Many science fiction works take place on Mars (here is your summer reading list):
Herbert G. Wells, The War of the Worlds (1898).
This novel describes an invasion of the earth by technologically advanced Martians.
“ Yet across the gulfs of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us. ”
A Princess of Mars
Edgar Rice Burroughs, A Princess of Mars (1911)
Burroughs, best known as the creator of Tarzan, wrote a series of novels placed on Mars
The hero, Civil War veteran John Carter, is transported to Mars where has various adventures, and marries an egg-laying Martian Princess
The term “little green men” came from these books.
“ I opened my eyes upon a strange and weird landscape. I knew that I was on Mars; not once did I question my sanity or wakefulness .”
Ray Bradbury, The Martian Chronicles (1951).
This book is a series of loosely connected stories which relate the story of humanity’s conquest of Mars.
The Martians in these stories are often seen as the “good guys.”
“ The Men of Earth came to Mars. They came because they were afraid or unafraid, because they were happy or unhappy, because they felt like Pilgrims or did not feel like Pilgrims. There was a reason for each man .”
Stranger in a Strange Land
Robert Heinlein’s, Stranger in a Strange Land (1961), was a favorite counterculture novel of the 1960’s
It is the story of Valentine Michael Smith, the sole survivor of the first manned expedition to Mars who was raised and educated by Martians.
Stranger introduced the term “Grok” to pop culture
“ Smith is not a man. He is an intelligent creature with the genes and ancestry of a man, but he is not a man. He's more a Martian than a man. Until we came along he had never laid eyes on a human being. He thinks like a Martian, he feels like a Martian. He's been brought up by a race which has nothing in common with us. “
“ This had been a very short word. Smith still felt that he had grokked rightly the human word "God"... “