Opposition and Conjunction

Transcription

1 Opposition and Conjunction Summary 1. Mars is 52% further the Sun having an orbital period of nearly 2 Earth years 2. Mars is much smaller than the Earth being roughly 53% the size, 11% the mass of the Earth 3. Its density is lower indicating it does not have a larger iron core 4. Mars has a very similar rotation period (about 40 mins longer) and axis tilt to the Earth Opposition occurs every 2 years Best opposition at perihelion 1

2 Percival Lowell Canals on Mars? Martians? Orson Welle s Broadcast (1938) The War of the Worlds H G Wells (1898) 2

3 Science Fiction Mars Attacks (1996) Seasons on Earth The Day on Mars 1 mean terrestrial solar day = 24 hrs 1 mean Martian solar day = 24 hrs 39 mins = 1 sol Low eccentricity ellipse seasons of equal duration and intensity! Seasons on Mars What season was it in the northern hemisphere of Mars when this image was taken? Seasons last twice as long! Vary in duration and intensity due to elliptical orbit! 3

4 Mariner 4 Flyby (1965) Modern View of Mars Much of the surface of Mars is old and heavily cratered No sign of artificial canals! Topography of Mars The northern plains of Mars which cover 40 % of the planet s surface are 4-5 km below the mean radius of the planet and may have been carved out by a giant impact No sign of plate tectonics planet is small and cooled quickly crust too thick The Southern Highlands of Mars Many craters are filled in and eroded with rounded rims Small craters are absent 4

5 10/27/2010 Hubble Space Telescope (2001) The Tharsis Region Massive uplift in Martian crust with huge shield volcanoes Olympus Mons: the solar system s largest volcano! Olympus Mons is huge! Formation of Tharsis The Mariner Valley 2500 miles long! 5

6 Liquid Water once flowed on Mars Layers of Sedimentary Rock on Mars? Recently, ancient lakes found on the Martian equator which are considerably younger (3 bya) Most of the channels are located on the ancient highlands suggesting they were carved out billions of years ago soon after Mars formed Why no water on the surface of Mars today? Atmospheric Composition 95.3% CO 2 High temperatures due to runaway greenhouse like on Venus? 6

7 Average Surface Temperature 220 K = -63 ºF That s 60 K or 111 ºF colder! Why? Atmospheric Pressure at Surface P = atm 1/150 th the pressure on the Earth s surface So thin it cannot retain much heat! Where is the water today? Fluidized Ejecta: Mud Flows around Craters Most is frozen out beneath surface as permafrost! 7

8 Gullies in Santa Monica! Martian Gullies Zack West (Astro 5, Spring 07) Bluffs below Sunset Park overlooking PCH Mars Odyssey Orbiter Water Map The Polar Caps have two layers Some is locked up in the Martian polar caps! 8

9 Seasonal Variations in the Martian Polar Caps Residual North Polar Cap of Water Ice Martian Clouds A small amount remains in the atmosphere forming clouds! What happened to the Martian atmosphere? 9

10 Other factors Viking Orbiter Viking Landers searched for Life in Martian soil Martian Surface from Viking 1 Landing Site CO 2 Frost at the Viking 2 Landing Site Earth: blue skies, red sunsets 10

11 Mars: red skies, blue sunsets! Taking soil samples Mars Pathfinder (1997) Overall Conclusions The Martian soil appears to be very reactive chemically but not biologically! Pathfinder landed on surface using airbags! Sojourner micro-rover on Mars 11

12 Mars Exploration Rovers Sojourner and Opportunity Mer-A (Spirit) Landing Site: Gusev Crater latitude 14.6º S, longitude 175 º E Scientific Goal Search for direct evidence of sedimentary rocks exposed to water on Mars! An impact crater which was once believed to have been filled with water Mer-B (Opportunity) Landing Site: Meridani Planum latitude 2º S, longitude 354º E Grey Hematite A flat plain where remote sensing orbiting satellites indicate there are abundant quantities of the mineral, gray hematite which most commonly forms in the presence of water An mineral of iron and oxygen which most commonly forms in water 12

13 First Image from Spirit Jan 4 th 2004 (Sol 1) Launch on Delta II Rocket from Cape Canaveral, FL Spirit: June 10 th 2003 Opportunity: July 7 th 2003 First Color Image from Spirit Spirit s Landing Site Close-up First Images from Opportunity Jan 25 th 2004 (Sol 1) First Color Image from Opportunity Lander rolls into a small, 65ft diameter impact crater! 13

14 Opportunity's Landing Site from Orbit Analyzing Rocks on the Martian Surface Opportunity seen from orbit! Mars Reconnaissance Orbiter Image of Victoria Crater ALH The Martian Meteorite Meteorites Rocks from space which fall to Earth 14

15 How did it get here? How do we know it came from Mars? it has an unusual oxygen isotope ratio that is not found in rocks on Earth it is an extrusive igneous rock indicating it originated from a planet large enough to have volcanism contains trapped gases with a composition identical to the Martian atmosphere! Where was it found? Antarctic Meteorites Where did it come from? Recent observations by orbiters suggest it could have been blasted from a 20 km diameter impact crater in a branch of the Mariner Valley! May be a good location for a future sample return mission! Eos Chasma 15

16 Fossilized Bacteria? Could Life have been transplanted from Mars to Earth? Evidence: 1 in 10,000 meteorites may travel from Mars to earth in a decade or less terrestrial bacteria have been shown to survive at least 6 years in space Nila Fossae The Moons of Mars Phobos and Deimos Carbonate rocks seen which are similar to those formed by fossilized stromatolites in western Australia Most likely captured asteroids Viking 1 Orbiter (1976) Cydonia Region 16

17 Old Man of the Mountain, NH Mars Global Surveyor Orbiter (2001) Mars Global Surveyor Orbiter Happy Face Crater! Phoenix Lander (2008) Powered Landing Scientific Goals 1. Study the history of water in the Martian arctic 2. Search for evidence of a habitability and assess the biological potential of the icesoil boundary 17

18 Phoenix Instruments Launch Aug 4 th 2007 Martian Landing Sites Corresponding Landing Site on Earth Polygon Patterned Terrain Phoenix Landing Ellipse 18

19 Mars Reconnaissance Orbiter (MRO) Image of Phoenix Descent First image of surface under lander Solar Power Grid First Color Image of Landing Site May 25 th 2008 MRO Image of Phoenix Landing Site Close-up of Polygonal Pattern on Mars 19

20 Landing Site Panorama Ice uncovered beneath lander? Sample Trenches Soil Sample inside robotic arm scoop Soil sample about to be placed in TEGA cell 20

21 Wet chemistry lab animation Disappearing ice? Microscope image of soil sample Sample being deposited into the wet chemistry lab A Martian Dust Devil Results Soil is very alkaline (ph = 8-9) and contains salts suggesting it has been in contact with water in the past. Composition is similar to samples found in the Antarctic Dry Valleys Snow detected falling from sky although vaporized before reaching ground Calcium carbonate (CaCO3) a sedimentary mineral formed in water found in soil samples 21

22 Attempts to contact lander in 2010 failed due to damage to solar panels suffered during winter Mars Science Laboratory (2011) 22