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Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine [email protected] umass. edu
Course • Course Website: – http: //blogs. umass. edu/astron 101 -tburbine/ • Textbook: – Pathways to Astronomy (2 nd Edition) by Stephen Schneider and Thomas Arny. • You also will need a calculator.
• There is an Astronomy Help Desk that is open Monday -Thursday evenings from 7 -9 pm in Hasbrouck 205. • There is an open house at the Observatory every Thursday when it’s clear. Students should check the observatory website before going since the times may change as the semester progresses and the telescope may be down for repairs at times. The website is http: //www. astro. umass. edu/~orchardhill/index. html.
Exam #3 • The average was 77. 3 and the grades ranged from 97. 5 s to a 35.
HW #16 • Due by April 20 th at 1 pm • I will take the top 20 HWs out of 24 • As of today, HW averages range from 99. 3 s to a 11. 3 (without dropping any scores) • If you want to make up a missing HW, you can write a 10 page paper on a planetary science subject
Types of Planetary Missions • Fly By • Orbiter • Lander – Atmospheric Probe – Rover – Manned • Sample Return
Mercury/Venus • Mercury is the closest planet to the Sun • Venus is next closest
• Both planets will be visible to the naked eye for the next two weeks as bright, starlike objects that will dominate the low western sky shortly after sunset. http: //news. nationalgeographic. com/news/2010/04/100401 -mercury-venus-planets-conjunction-april/
• http: //www. skyandtelescope. com/observing/home /89279827. html
Mercury • • orbit: 0. 38 AU from Sun diameter: 4, 880 km (38. 3% of Earth) mass: 3. 30 x 1023 kg (5. 5% of Earth) temperature: 90 K (minimum) 440 K (average) 700 K (maximum) • Satellites: Zero
Difficult to study Mercury • Because of Mercury's proximity to the Sun – makes reaching it with spacecraft technically challenging – Earth-based observations difficult.
Mercury • Videos • http: //www. gecdsb. on. ca/d&g/astro/html/Mercury. html
Mariner 10 • The first spacecraft to approach Mercury was NASA's Mariner 10 (1974 -1975).
Caloris Basin (Some of the hill are 1, 800 meters tall)
Messenger data Mariner 10 data
Caloris Basin • A basin was defined by Hartmann and Kuiper (1962) as a "large circular depression with distinctive concentric rings and radial lineaments. " • Others consider any crater larger than 200 kilometers a basin. • The Caloris basin is 1, 550 kilometers in diameter, and was probably caused by a projectile larger than 100 kilometers in size. • The impact produced concentric mountain rings three kilometers high and sent ejecta 600 to 800 kilometers across the planet.
Weird Terrain The weird terrain is almost opposite Caloris Basin. It consists of hills, ridges and grooves that cut across craters. The weird terrain my have been formed by shock waves that raced through the center of the planet and outward early in Mercury's history.
Mercury has high density • Its density is 5. 44 g/cm 3 which is comparable to Earth's 5. 52 g/cm 3 density. • In an uncompressed state, Mercury's density is 5. 5 g/cm 3 where Earth's is only 4. 0 g/cm 3.
http: //www. psrd. hawaii. edu/Web. Img/Mercury. Core. gif
Magnetic Field • Despite its small size and slow 59 -day-long rotation, Mercury has a significant, and apparently global, magnetic field. • It is about 1. 1% as strong as the Earth’s. • Particularly strong tidal effects caused by the planet's high orbital eccentricity would serve to keep the core in the liquid state so it could have a dynamo
Messenger • Mission to Mercury • Launched August 3, 2004 • Flew by Mercury in 2008 and 2009 • Will orbit Mercury in 2011
Messenger video • A set of five 11 -band images was captured by MESSENGER just after the spacecraft crossed the night/day line (the “terminator”), which are the highest-resolution color images ever obtained of Mercury’s surface. • At the beginning of this movie, it is dawn in that region of Mercury, and the Sun is just off the horizon. The long shadows that are cast by crater walls exaggerate the ruggedness of the terrain and highlight variations in topography. • Though Mercury’s true colors are subtle, the 11 color bands of MDIS were combined in a statistical method used to highlight differences in color units. Older, low-reflectance, and relatively blue material is encroached by younger, relatively red smooth plains. Several lobate scarps or cliffs are observed, which are places where compressional stresses caused Mercury’s crust to fracture and shorten. http: //messenger. jhuapl. edu/news_room/presscon 5_images/Robinson%20 Image%205. 7. mov
Mercury Much of the image to the right of the Kuiper crater (in the centre here) had never been imaged by a spacecraft before. Researchers were surprised to see long crater rays that extend thousands of kilometers from a crater at the planet's north pole http: //space. newscientist. com/data/images/ns/cms/dn 14893 -1_450. jpg
Mercury Dark material, shown in deep blue in the enhanced colour image at right (a composite of visible and near-infrared images), was kicked up by impacts. The material seems to be widespread but patchy, suggesting the planet's interior is not homogenous. http: //space. newscientist. com/data/images/ns/cms/dn 15077 -1_600. jpg
Mercury • Double ringed basin • 290 km in diameter • Appears young (few craters on it) • ~ 1 billion years old • Lava may have covered up the central part of the basin http: //messenger. jhuapl. edu/gallery/science. Photos/pics/presscon 6_img 4_5_lg. jpg
• 160 km in diameter http: //en. wikipedia. org/wiki/File: Mercury_Double-Ring_Impact_Basin. png
Spectra of Mercury Weak to absent absorption features – no iron in the silicates
Mercury’s Surface • Possibly made of Enstatite (Mg. Si. O 3) – Mg-rich pyroxene • Possibly made of material like the Lunar Highlands – Plagioclase feldspar - Ca. Al 2 Si 2 O 8
Questions: • Why does Mercury have such a large iron core?
One possibility • Mercury may have been struck by a planetesimal of approximately 1/6 its mass and several hundred kilometers across. • The impact would have stripped away much of the original crust and mantle, leaving the core behind as a relatively major component.
Venus • orbit: 0. 72 AU from Sun • diameter: 12, 103. 6 km (94. 9% of Earth) (called Earth‘s twin) • mass: 4. 869 x 1024 kg (81. 5% of Earth) • Temperature on surface: 726 K(average) • Satellites: Zero
Venus’ atmosphere • Atmospheric pressure at surface is 92 times the pressure on the Earth’s surface • • • Atmospheric content: Carbon dioxide 96. 5 % Nitrogen 3. 5 % Sulfur dioxide 150 ppm Argon 70 ppm Water vapor 20 ppm
Venus’ clouds • Venusian clouds are thick and are composed of sulfur dioxide and droplets of sulfuric acid. • These clouds reflect about 75% of the sunlight that falls on them,
Greenhouse Effect • The greenhouse effect is the rise in temperature that a planet experiences because certain gases in the atmosphere (H 2 O, CO 2, CH 4) trap energy emitted from the surface. • Visble light hits the surface • Surface warms and emits infrared radiation • Atmospheric gases absorb some of the infrared light • Surface and Atmosphere heat up
Stefan-Boltzman Law Emitted power (per square meter of surface) = σT 4 λ·Tmax = 2, 900, 00 nm
Runaway Greenhouse Effect • Runaway greenhouse effect to describe the effect as it occurs on Venus • Venus is sufficiently strongly heated by the Sun that water is vaporized and so carbon dioxide is not reabsorbed by the planetary crust
Why does Venus has such a thick atmosphere? • The luminosity of the Sun has increased by 25% from 3. 8 billion years ago • The atmosphere of Venus up to around 4 billion years ago maybe was more like that of Earth with liquid water on the surface. • The runaway greenhouse effect may have been caused by the evaporation of the surface water and the rise of the levels of greenhouse gases that followed.
Surface • Mapped by Magellan spacecraft (1990 -1994) • How was it mapped if it has a dense atmosphere?
How did it do it? • Used Radar (radio waves)
• Most of Venus' surface consists of gently rolling plains with little relief. • Data from Magellan's imaging radar shows that much of the surface of Venus is covered by lava flows. • Lava flows stopped ~300 -500 million years ago • Very few craters
• Most volcanoes on Venus are shield volcanoes • Low viscosity lava
Maat Mons • • Highest volcano on Venus 8 km high Shield Volcano Could be active
Volcanoes • ~170 giant volcanoes over 100 km across • On Earth, only the Big Island of Hawaii is this large • This is due to Venus’ crust being older • Earth’s crust is continually being recycled by subduction
Craters • Venusian craters range from 3 km to 280 km in diameter. • There are no craters smaller than 3 km because the dense atmosphere stops small incoming objects.
• 200 km long channel • 2 km wide http: //hyperphysics. phy-astr. gsu. edu/hbase/Solar/venusurf. html
Pancakes Domes • Flattened lava domes are attributed to upwellings of molten rock which then subsided. • The solid crust left behind then flattened and cracked.
Coronae • Corona is an oval-shaped feature. • hot rising bodies of magma reach the crust and cause it to partially melt and collapse • Generates volcanic flows and fault patterns that radiate from the central structure. 100 km in diameter http: //pds. jpl. nasa. gov/planets/captions/venus/vencor. htm
Arachnoids • concentric ovals surrounded by a complex network of fractures, and can span 200 kilometers
• Almost all Venusian surface features are named after historical and mythological women. • The only exceptions are Maxwell Montes, named after James Clerk Maxwell, and two highland regions, Alpha Regio and Beta Regio
Venera • Venera probes were launched by the Soviet Union and enter Venus’ atmosphere • 1961 -1984 • Venera 3 -16 • 10 probes landed on surface
Venera 9 and 10 pictures
Pioneer • Pioneer Venus 1 or Pioneer Venus Orbiter was launched in 1978 and studied the planet for more than a decade after orbital insertion in 1978. • Pioneer Venus 2 or Pioneer Venus Multiprobe sent four small probes into the Venusian atmosphere.
Pioneer 2 bus • The Pioneer Venus bus portion of the spacecraft was targeted to enter the Venusian atmosphere at a shallow entry angle and transmit data until destruction by the heat of atmospheric friction. • The objective was to study the structure and composition of the atmosphere down to the surface, the nature and composition of the clouds, etc. • With no heat shield or parachute, the bus made upper atmospheric measurements down to an altitude of about 165 km before disintegrating on December 9, 1978.
• • Pioneer 2 Large Probe that entered the atmosphere Had parachute a neutral mass spectrometer to measure the atmospheric composition a gas chromatograph to measure the atmospheric composition a solar flux radiometer to measure solar flux penetration in the atmosphere an infrared radiometer to measure distribution of infrared radiation a cloud particle size spectrometer to measure particle size and shape a nephelometer to search for cloud particles temperature, pressure, and acceleration sensors
3 small probes • No parachute
Venus Express • Launched November 9, 2005 (Soyuz-Fregat from Baikonur, Kazakhstan) • First global monitoring of composition of lower atmosphere in near-infrared transparency ‘windows’ • First coherent study of atmospheric temperature and dynamics at different levels of atmosphere, from surface up to ~200 km • First measurements from orbit of global surface temperature distribution
Mostly spare parts from Mars Express or Rosetta • ASPERA-4 - Neutral and ionised plasma analysis - Mars Express • MAG - Magnetic field measurements - Rosetta Lander • PFS - Atmospheric vertical sounding by infrared Fourier spectroscopy - Mars Express • SPICAV - Atmospheric spectrometry by star or Sun occultation - Mars Express • Ve. Ra - Radio sounding of atmosphere. France)Ve. Radio sounding of atmosphere - Rosetta • VIRTIS - Spectrographic mapping of atmosphere and surface - Rosetta • VMC - Ultraviolet and visible imaging Mars Express and Rosetta
• http: //www. hulu. com/watch/94012/the-universemercury-and-venus---the-inner-planets