Mars. PHYS Week 4, Part 2

Transcription

1 Mars PHYS Week 4, Part 2 Lowell s Mars Globe One of the remarkable globes of Mars prepared by Percival Lowell, showing a network of dozens of canals, oases, and triangular water reservoirs that he claimed were visible on the red planet. (Lowell Observatory)

2 2 Table 9-1, p.199

3 3 Mars - HST This NASA Hubble Space Telescope view of the planet Mars is the clearest picture ever taken from Earth. The picture was taken on February 25, 1995, when Mars was at a distance of 100 million km from Earth. Because it is spring in Mars' northern hemisphere, much of the carbon dioxide frost around the permanent water-ice cap has sublimated, and the cap has receded to a core of solid water-ice several hundred miles across. Towering 25 km above the surrounding plains, volcano Ascraeus Mons pokes above the cloud deck near the western or limb. This extinct volcano, measuring 402 km across, was discovered in the early 1970s by Mariner 9 spacecraft. Other key geologic features include (lower left) the Valles Marineris, an immense rift valley the length of the continental United States. Near the center of the disk lies the Chryse basin made up of cratered and chaotic terrain. The oval-looking Argyre impact basin (bottom), appears white due to clouds or frost. Seasonal winds carry dust to form striking linear features reminiscent of the legendary martian "canals." Many of these "wind streaks" emanate from the bowl of these craters where dark coarse sand is swept out by winds. Dark areas, once misinterpreted as regions of vegetation by several early Mars watchers, are areas of coarse sand that is less reflective than the finer, lighter dust. Seasonal changes in the surface appearance occur as winds move the dust and sand around.

4 4 Mars - Happy Face Crater The story of the Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) spacecraft began with a proposal to NASA in The first MOC flew on Mars Observer, a spacecraft that was lost before it reached the red planet in Now, after 14 years of effort, a MOC has finally been placed in the desired mapping orbit. The MOC team's happiness is perhaps best expressed by the planet Mars itself. On the first day of the Mapping Phase of the MGS mission--during the second week of March MOC was greeted with this view of "Happy Face Crater" (center right) smiling back at the camera from its location on the east side of Argyre Planitia. This crater is officially known as Galle Crater, and it is about 215 kilometers (134 miles) across. The picture was taken by the MOC's red and blue wide angle cameras. The bluishwhite tone is caused by wintertime frost. Illumination is from the upper left.

5 Mars Globe from Radar These globes are highly precise topographic maps, reconstructed from 5 millions of individual elevation measurements with the Mars Global Surveyor spacecraft. Color is used to indicate elevation. The hemisphere on the left includes Olympus Mons, the highest mountain on Mars, while the hemisphere on the right includes the Hellas basin, which has the lowest elevation on Mars. (JPL/NASA) Fig 9-13, p.206

6 6 Regional Topographic Views of Mars from MOLA With one year of global mapping of the Mars Global Surveyor mission completed, the MOLA dataset has achieved excellent spatial and vertical resolution. This map has been produced from the altimetric observations collected during MOLA's first year of global mapping and provide a variety of regional topographic views of the Martian surface. The maps were compiled from a data base of million laser altimetric measurements collected between March 1, 1999 and February 29, In each map the spatial resolution is approximately 1/16 by 1/32 (where 1 on Mars is about 59 km) and the vertical accuracy is approximately 1 meter. PIA01049

7 7 Olympus Mons - Altimetry

8 Olympus Mons The largest volcano on Mars, and probably in the solar system in a rendering based on data from the Mars Orbiter Laser Altimeter. The caldera, the circular opening at the top, is 65 km 8 across, about the size of Los Angeles. Note the extensive clouds over the lower slopes of the volcano. (Kees Veenenbos) Fig 9-14, p.206

9 9 Elysium Chasm - Altimetry Comparison of the cross-sectional relief of the deepest portion of the Grand Canyon (Arizona) on Earth versus a Mars Orbiter Laser Altimeter (MOLA) view of a common type of chasm on Mars in the western Elysium region. The Grand Canyon topography is shown as a trace with a measurement every 90 m along track, while that from MOLA reflects measurements about every 400 m along track. The slopes of the steep inner canyon wall of the Martian feature exceed the angle of repose, suggesting relative youth and the potential for landslides. The inner wall slopes of the Grand Canyon are less than those of the Martian chasm, reflecting the long period of erosion necessary to form its mile-deep character on Earth.

10 Valles Marineris This high resolution picture (right) of the Martian surface was obtained by the Mars Orbiter Camera (MOC). Seen in this view are a plateau and surrounding steep slopes within the Valles Marineris, the large system of canyons that stretches 4000 km along the equator of Mars. The image covers only 9.8 km by 17.3 km but captures features as small as 6 m across. The highest terrain in the image is the relatively smooth plateau near the center. Slopes descend to the north and south in broad, debris-filled gullies with intervening rocky spurs. Multiple rock layers, varying from a few to a few tens of meters thick, are visible in the steep slopes on the spurs and gullies. Layered rocks on Earth form from sedimentary processes and volcanic processes. Both origins are possible for the Martian layered rocks seen in this image. In either case, the total thickness of the layered rocks seen in this image implies a complex and extremely active early history for geologic processes on Mars. The left and center 'context' images are Viking mosaics. 10

11 Martian Landslides This Viking orbiter image shows one section of the Valles Marineris canyon system. The canyon walls are about 100 km apart here. Look carefully and you can see enormous landslides whose debris is piled up underneath the cliff walls, which tower some 10 km above the canyon floor. (NASA/USGS) 11 Fig 9-15, p.207

12 12 Heavily Eroded Canyonlands on Mars This Viking spacecraft view looks down on a small part of the Valles Marineris canyon complex and shows an area about 60 km across(nasa/usgs, courtesy of Alfred McEwen) Fig 9CO, p.194

13 13 Geologic 'Face on Mars' Formation NASA's Viking 1 Orbiter spacecraft photographed this region in the northern latitudes of Mars on July 25, 1976 while searching for a landing site for the Viking 2 Lander. The speckled appearance of the image is due to missing data, called bit errors, caused by problems in transmission of the photographic data from Mars to Earth. Bit errors comprise part of one of the 'eyes' and 'nostrils' on the eroded rock that resembles a human face near the center of the image. Shadows in the rock formation give the illusion of a nose and mouth. Planetary geologists attribute the origin of the formation to purely natural processes. The feature is 1.5 kilometers across, with the sun angle at approximately 20 degrees. The picture was taken from a range of 1,873 kilometers. PIA01141

14 The Face on Mars is seen here with ten times better resolution from Global Surveyor. The image has been processed to simulate the lighting conditions of the Viking image for easier comparison. (NASA/Malin Space Science Systems) 14 p.215

15 15 Teardrop Islands The water that carved the channels to the north and east of the Valles Marineris canyon system had tremendous erosive power. One consequence of this erosion was the formation of streamlined islands where the water encountered obstacles along its path. This image shows two streamlined islands that formed as the water was diverted by two kilometer-diameter craters lying near the mouth of Ares Vallis in Chryse Planitia. The water flowed from south to north (bottom to top of image). Note that the ejecta blanket of the third large crater (located at the tapered downstream tail of the uppermost island) is uneroded, an indication that this crater formed sometime after the channel was active. The height of the scarp surrounding the upper island is about 400 meters, while the scarp surrounding the southern island is about 600 meters high. (From Mars Digital Image Map, image processing by Brian Fessler, Lunar and Planetary Institute.)

16 16 Flow around Dromore Crater, Chryse Planitia, Mars Viking 1 Orbiter image of Dromore Crater in Chryse Planitia, Mars. Flow from the left (west) appears to have broken through low points on the ridge and eroded the channels as it flowed around the 15 km diameter crater. The image is approximately 50 km across. North is at about 1:30. (Viking Orbiter 020A62)

17 Yuty - Rampart Crater with Fluidized Ejecta (22 N,34 W) The ejecta deposits around the impact crater Yuty (18 km in diameter) consist of many overlapping lobes. Craters with this type of ejecta deposit are known as rampart craters. This type of ejecta morphology is characteristic of many craters at equatorial and midlatitudes on Mars but is unlike that seen around small craters on the Moon. This style of ejecta deposit is believed to form when an impacting object rapidly melts ice in the subsurface. The presence of liquid water in the ejected material allows it to flow along the surface, giving the ejecta blanket its characteristic, fluidized appearance. (Viking Orbiter image 3A07.) 17

18 18 Parana Valles drainage system in Margaritifer Sinus, Mars This Viking 1 Orbiter image shows the Parana Valles, a digitate valley network in the Margaritifer Sinus region of Mars. These networks look similar to river drainage networks on Earth, and were presumably formed by running water sometime in Mars' past. This image is about 250 km across. North is at ~10:30. (Viking Orbiter 084A47)

19 19 Mars - Chaotic Terrain Like many other channels that empty into the northern plains of Mars, Ravi Vallis originates in a region of collapsed and disrupted ("chaotic") terrain within the planet's older, cratered highlands. Structures in these channels indicate that they were carved by liquid water moving at high flow rates. The abrupt beginning of the channel, with no apparent tributaries, suggests that the water that carved the channel was released under great pressure from beneath a confining layer of frozen ground. As this water was released and flowed away, the overlying surface collapsed, producing the disruption and subsidence shown here. Three such regions of chaotic collapsed material are seen in this image, connected by a channel whose floor was scoured by the flowing water. The flow in this channel was from west to east (left to right). This channel ultimately links up with a system of channels that flowed northward into Chryse Basin. (Image processing by Brian Fessler, LPI)

20 Evidence of Liquid Water on Mars This intriguing channel, called Nanedi Valles resembles Earth river beds in some (but not all) ways. The tight curves and terraces seen in the channel certainly suggest the sustained flow of a fluid like water. The channel is about 2.5 km across and the entire Global Surveyor image is 10 km wide. (NASA/Malin Space Science Systems) 20 Fig 9-23, p.212

21 Outflow Channels Here we see a region of large outflow channels, photographed by Viking. These features appear to have been formed in the distant past from massive floods of water. The width of this image is about 150 km. (NASA/JPL) 21 Fig 9-24, p.213

22 Runoff Channels These runoff channels in the old martian highlands are interpreted as the valleys of 22 ancient rivers fed either by rain or underground springs. The width of this image is about 200 km.(nasa/from Mars Digital Image Map, processing by Brian Fessler, LPI) Fig 9-22, p.212

23 Recent Gullies on Mars Gullies on the wall of Newton Crater. Each image is about 2 km across. (NASA/JPL/USGS) 23 Fig 9-25b, p.213

24 Stratification in the Martian Crust As many as 100 layers can be seen in this high-resolution photo of a winderoded mesa within the Valles Marineris canyons. Many geologists interpret this photo as evidence for layers of sediment deposited in an ancient martian sea. The width of the image is only 1.5 km. (NASA/JPL/USGS) 24 Fig 9-26, p.213

25 Recent Gullies on Mars Gullies on a cliff near the South Polar Cap. (NASA/JPL/USGS) 25 Fig 9-25a, p.213

26 Sand Dunes on Mars These dark dunes in the interior of Proctor Crater overlay a lighter sandy surface. Each dune in this high-resolution view is about 1 km across. (NASA/JPL/USGS) 26 Fig 9-19, p.209

27 Tracks of Dust Devils This high-resolution photo from Mars Global Surveyor shows the dark tracks of several dust devils that have stripped away a thin coating of lightcolored dust. This view is of an area about 3 km across. Dust devils are one of the most important ways that dust gets redistributed by the martian winds. (NASA/JPL/USGS) 27 Fig 9-18, p.209

28 28 Mars - North Polar Cap These images were created by assembling mosaics of three sets of images taken by HST in October, 1996 and in January and March, 1997 and projecting them to appear as they would if seen from above the pole. The resulting polar maps begin at 50 degrees N latitude and are oriented with 0 degrees longitude at the 12 o'clock position. This series of pictures captures the seasonal retreat of Mars' north polar cap. October 1996 (early spring in the Northern hemisphere): In this map, assembled from images obtained between Oct. 8 and 15, the cap extends down to 60 degrees N latitude, nearly it's maximum winter extent. A thin, comma- shaped cloud of dust can be seen as a salmon-colored crescent at the 7 o'clock position. The cap is actually fairly circular about the pole at this season; the bluish "knobs" where the cap seems to extend further are clouds that occurred near the edges of the sets of images used to make the mosaic.

29 Layers at the Martian North Pole The small inset in the left image shows a map of the residual north polar cap of Mars, which is about 1000 km across and composed of water ice. The small black box in the middle of the map shows the area covered in the tilted Viking orbiter image at left. The box in that image shows the area of the Global Surveyor high-resolution image at right. On the right image, we see a slope on the edge of the permanent north polar cap, with dozens of layers visible some thinner than 10 meters. (NASA/JPL/Malin Space Science Systems) 29 Fig 9-21, p.211

30 Martian Meteorite A fragment of basalt ejected from Mars in a crater-forming impact, that eventually arrived on the Earth s surface. (NASA/JSC) 30 Fig 9-20, p.210

31 Three Martian Landing Sites The Mars landers -- Viking 1 in Chryse, Viking 2 in Utopia, and Pathfinder in Ares Valley -- all photographed their immediate surroundings. It is apparent from the similarity of these three photos that each spacecraft touched down on a flat windswept plain littered with rocks ranging from tiny pebbles up to meter-size boulders. It is probable that most of Mars looks like this on the surface. (NASA/JPL/USGS) 31 Fig 9-16a, p.208

32 Viking 2 in Utopia 32 Fig 9-16b, p.208

33 Sojourner on Pathfinder The Sojourner rover and undeployed ramps onboard the Mars Pathfinder spacecraft can be seen in in this image, by the Imager for Mars Pathfinder (IMP) on July 4 (Sol 1). This image has been corrected for the curvature created by parallax. The microrover Sojourner is latched to the petal, and has not yet been deployed. The ramps are a pair of deployable metal reels which will provide a track for the rover as it slowly rolls off the lander, over the spacecraft's deflated airbags, and onto the surface of Mars. Pathfinder scientists will use this image to determine whether it is safe to deploy the ramps. One or both of the ramps will be unfurled, and then scientists will decide whether the rover will use either the forward or backward ramp for its descent. 33

34 34 Sojourner at Yogi In this scene showing the rover deployed at rock Yogi, the colors have been enhanced to bring out differences. Yogi (red arrow), one of the large rocks with a weathered coating, exhibits a fresh face to the northeast, resulting perhaps from scouring or from fracturing off of pieces to expose a fresher surface. Barnacle Bill and Cradle (blue arrows) are typical of the unweathered smaller rocks. During its traverse to Yogi the rover stirred the soil and exposed material from several cm in depth. During one of the turns to deploy Sojourner's Alpha Proton X-Ray Spectrometer (inset and white arrow), the wheels dug particularly deeply and exposed white material. The lander's rear ramp, which Sojourner used to descend to the Martian surface, is at lower left.

35 35 D-Star Panorama by Opportunity NASA's twin Mars Exploration Rovers have been getting smarter as they get older. This view from Opportunity shows the tracks left by a drive executed with more onboard autonomy than has been used on any other drive by a Mars rover. Opportunity made the curving, 15.8-meter (52-foot) drive during its 1,160th Martian day, or sol (April 29, 2007). It was testing a navigational capability called "Field D-star," which enables the rover to plan optimal long-range drives around any obstacles in order to travel the most direct safe route to the drive's designated destination. Field D-Star and several other upgrades were part of new onboard software uploaded from Earth in Victoria Crater is in the background, at the top of the image. The Sol 1,160 drive began at the place near the center of the image where tracks overlap each other. Tracks farther away were left by earlier drives nearer to the northern rim of the crater. For scale, the distance between the parallel tracks left by the rover's wheels is about 1 m from the middle of one track to the middle of the other. The rocks in the center foreground are roughly 7 to 10 cm tall. The rover could actually drive over them easily, but for this test, settings in the onboard hazard-detection software were adjusted to make these smaller rocks be considered dangerous to the rover. The patch of larger rocks to the right was set as a keep-out zone. The location from which this image was taken is where the rover stopped driving to communicate with Earth. A straight line from the starting point to the destination would be 11 m. Opportunity plotted and followed a smoothly curved, efficient path around the rocks, always keeping the rover in safe areas. NASA/JPL-Caltech/Cornell University PIA10213

36 36 Phoenix Mission Lander on Mars, Artist's Concept The Phoenix Mission is the first project in NASA's openly competed program of Mars Scout missions. The mission's plan is to land in icy soils near the north polar permanent ice cap of Mars and explore the history of the water in these soils and any associated rocks, while monitoring polar climate. The spacecraft and its instruments are designed to analyze samples collected from up to a half-meter deep by a robotic arm. The arm extends forward in this artist's concept of the lander on Mars. (NASA/JPL ) PIA07247

37 37 'Snow White' Trench This image was acquired by NASA's Phoenix Mars Lander's Surface Stereo Imager on Sol the 43rd Martian day after landing (July 8, 2008). This image shows the trench informally called "Snow White." Two samples were delivered to the Wet Chemistry Laboratory, which is part of Phoenix's Microscopy, Electrochemistry, and Conductivity Analyzer (MECA). The first sample was taken from the surface area just left of the trench and informally named "Rosy Red." It was delivered to the Wet Chemistry Laboratory on Sol 30 (June 25, 2008). The second sample, informally named "Sorceress," was taken from the center of the "Snow White" trench and delivered to the Wet Chemistry Laboratory on Sol 41 (July 6, 2008). NASA/JPL- Caltech/University of Arizona/Texas A&M University PIA11010:

38 38 Color View of 'Rosy Red' Delivered to TEGA NASA's Phoenix Mars Lander's Surface Stereo Imager took this false color image on Sol 72 (August 7, 2008), the 72nd Martian day after landing. It shows a soil sample from a trench informally called "Rosy Red" after being delivered to a gap between partially opened doors on the lander's Thermal and Evolved-Gas Analyzer, or TEGA. NASA/JPL-Caltech/University of Arizona/Texas A&M University PIA11023

39 39

40 40 Table 9-2, p.203

41 41 The New Solar System ch13

42 42 The New Solar System ch13

43 43

44 44