venus n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Venus PowerPoint Presentation
Download Presentation
Venus

Loading in 2 Seconds...

play fullscreen
1 / 72

Venus - PowerPoint PPT Presentation


  • 118 Views
  • Uploaded on

Venus. Jewel of the Sky Earth’s Sister Planet. General Information. Brightest object in sky after the Sun & Moon Named after the Roman goddess of love and beauty Once thought to be two different celestial bodies Thus known as the Morning or Evening Star

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Venus' - cyrah


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
venus

Venus

Jewel of the Sky

Earth’s Sister Planet

general information
General Information
  • Brightest object in sky after the Sun & Moon
  • Named after the Roman goddess of love and beauty
    • Once thought to be two different celestial bodies
    • Thus known as the Morning or Evening Star
  • The Sun rises in the west and sets in the east
    • Slow retrograde motion causes this phenomenon
    • Slow rotation makes a Venusian day longer than a Venusian year
  • Features on Venus are named after goddesses of mythology, famous women, and common female first names
  • Atmosphere
    • Thick, dense cloud cover
    • Atmospheric pressure 92 times that of Earth at sea-level (equal to being ~1km beneath the ocean)
    • Clouds composed of CO2, H2O, and sulfuric acid droplets
    • Runaway greenhouse effect
  • Visible to naked eye
    • Always appears close to the Sun
planetary statistics
Planetary Statistics
  • Mean distance from Sun 108,200,000km
    • 0.723 A.U.
  • Orbital Period = 224.7 days
  • Rotational Period = 243 days
  • Axis Tilt = 177.4 degrees (23.5)
  • Diameter = 12,104km (12,756km)
  • Mass = 4.869 x 1024 (5.97 x 1024)
    • (.815 of Earth)
  • Density = 5.25gm/cm3 (5.515gm/cm3)
stats cont d
Stats cont’d
  • Equatorial surface gravity = 8.87m/sec2 (9.78m/sec2)
  • Visual albedo = 0.65 (.37)
  • Moons = none
  • Surface = Rolling plains, volcanoes & lava flows, extensive folding & faulting and very little topographic relief
  • Atmospheric composition
    • CO2 96%
    • Nitrogen 3%
    • Sulfur dioxide, water vapor,carbon monoxide, argon, helium, neon,hydrogen chloride, and hydrogen fluoride
  • Mean surface temperature = 170C (330F)
    • Max temp = 482C (896F)
    • Hot enough to melt Pb
atmosphere
Atmosphere
  • It is thickness not density that hides surface
  • Expected composition formed by secondary processes of differentiation and outgassing
  • Some fluids may have been supplied to inner planets via cometary collisions
    • Venus too hot = water vapor
    • Earth cooler = water fluids
  • Cloud cover extends >50km
    • Main cloud deck betwn/25 & 75km
    • Level @ which H2SO4 (sulfuric acid) can condense
    • Potent acid rain doesn’t reach the surface (virga) because of evaporation ~30km altitude
  • Greenhouse Effect
    • Surface receives less solar radiation than Earth’s
    • Gas and fluid molecules in atmosphere absorb energy
    • Cloud cover traps heat from escaping
    • Heat distributed planet-wide (no cold polar regions)
  • Mass of water 100,000 times less than Earth’s
atmosphere cont d
Atmosphere (cont’d)
  • Carbon cycle
    • Fossilized atmosphere trapped in Earth’s carbonate sedimentary rocks
    • If released the two planets atmos. would be much more similar
    • If carbonate rx existed on Venus temp’s now too hot – gas released back into atmosphere
  • Weathering
    • Varies with elevation (pressure and temperature zones)
      • Consistent boundary elevation
      • Varies by <100m over 100’s of km
      • Cuts across various types of terrain
    • Low temp & hi elev. basalt reacts w/sulfur to form pyrite
      • Bright signatures
    • Hi elev & lo albedo = young lavas not weathered into pyrite
venus atmospheric profile
Venus Atmospheric Profile
  • The first Soviet probe, Venera 4, descended by parachute through the atmosphere
    • Apparently was crushed by the dense atmosphere (~90 atm) and high temperatures
  • Did return info confirming that CO2 makes up about 97% of all gases present (very little water)
  • Detected droplets of sulfuric acid in the outer cloud deck
  • Venera data (refined by later Pioneer data) also lead to a general profile of temp & press distributions in the atmosphere (at right)
venus geologic activity
Venus – Geologic Activity
  • Venus has a silicate (rocky) crust and mantle with a metallic core
  • No detectable magnetic field
    • Slow rotation does not preclude existence of a partial liquid core
  • Volcanism, weathering, aeolian transport tensional and compressional tectonic forces are dominant geologic processes
    • No water so weathering and erosion are very different from Earth
    • Greenhouse may have been process responsible for loss of primal water
  • Accretion, internal differentiation and out-gassing were important early events
geologic activity cont d
Geologic Activity (cont’d)
  • Juvenile water
    • Water as a component of mantle
      • Small fraction lowers melting temps by ~200K (-100F)
      • Increases fluidization and formation of an asthenosphere
  • Mantle processes
    • No water, no asthenosphere, no plate tectonics (as we know it on Earth)
    • No water, no granite, no bimodal crustal composition (i.e. continental & oceanic crust)
major geologic provinces
Major Geologic Provinces
  • Lowlands
    • Cover ~60% of the planet
    • Rolling plains w/little local relief (<500m)
    • No evidence for formation by large impacts
    • Extensive basaltic flows w/few volcanoes
    • Exhibit compressional tectonic features (ridges, folds and faults)
    • Few impact craters so probably <1by old
    • Atalanta Planitia – largest area
  • Uplands
    • Isolated domes and broad swells (0-2km elev.)
    • Extensional tectonics resulting in broad domes capped by fault-bounded rifts systems and some shield volcanoes
    • Coronae
      • Volcanic and tectonic
      • Concentric horst and graben features
      • Some flow features
      • Beta Regio – largest upland region
major geologic provinces1
Major Geologic Provinces
  • Highlands
    • “Continental” like
    • 3-5km elev.
    • <15% areal extent of planet
    • Compressional folds, ridges and troughs
      • Lateral movement of crust
    • Perhaps different composition
    • Never been sampled
    • Aphrodite Terra – largest area >9500km east to west
venus visible vs radar
Venus Visible vs Radar
  • This picture shows two different perspectives of Venus. On the left is a mosaic of images acquired by the Mariner 10 spacecraft. The image shows the thick cloud coverage that prevents optical observation of the planet's surface. The surface of Venus remained hidden until 1978 when the Pioneer Venus 1 spacecraft arrived and went into orbit about the planet. The spacecraft used radar to map the surface. The right image show a rendering of Venus from the Pioneer Venus and Magellan radar images.
magellan
Magellan
  • In clean room at JPL
  • Primary instrument - multimode Radar Mapper (2.385 Ghz, or 12.6 cm wavelength)
  • SAR imaging mode (18° and 50° off-nadir), res = 360 m and 120 m (1181-394 ft)
  • It first established orbit on August 10, 1990 after 1 1/2 loops around the Sun
  • Altimeter mode achieved vertical accuracy < 50 m (164 ft) within a ground cell of 10 km (6.2 mi) diam.
  • Radiometer mode could sense surface radio-emission, whose signals can be converted to brightness temperatures with an absolute accuracy of ±20° K
venus geologic activity1
Venus – Geologic Activity
  • Relatively young surface - ~complete resurfacing ~300-500mya
    • Small population of craters
    • Extensive volcanoes & lava flows
    • Evidence of crustal movement (vertical & lateral)
  • Topography
    • Vast plains/lava flows
    • Highlands deformed by geologic activity (isostatic or compressional forces)
  • Craters
    • Distributed randomly across surface
    • Numerous but still few by Lunar and Mercury or even Mars standards
    • <2km diameters virtually non-existent
    • Exceptions
      • When large meteorites break up just before impact
      • Secondary impacts propelled from primary impact event
      • Tend to produce linear crater chains
geologic activity cont d1
Geologic Activity (cont’d)
  • Volcanism - >85% of surface is covered by volcanic rock
    • Very numerous –
      • >100,000 small shield volcanoes
      • 100’s of larger features
    • Lava flows
      • Long sinuous channels
      • Some > 7,000km long
      • Flooded lowlands creating vast plains
    • Shield volcanoes
      • Found on all terrain types except tessera
      • Mostly associated w/rifting (African Rift Valley)
      • Largest volcanoes >1000km across isolated
      • Smaller on flanks and in clusters
    • Calderas
      • Summit vents
      • Single and multiple
      • Larger than any similar features on Earth
venus interior
Venus Interior
  • What is known about interior comes primarily from the Venera, Pioneer Venus and Magellan spacecraft
  • Before scientists thought Venus would have tectonic processes similar to that of Earth's mantle convection
  • However, no sign of plate tectonism & appears to have a single plate
  • Venus is differentiated
    • Basaltic crust extracted from mantle
    • Crust appears to be ~25 to 40 kms & more than 50 to 60 kms in some areas
  • Recent volcanism suggests Venus still retains a partially molten core
  • Slow rate of rotation precludes generation of a magnetic field like the Earth’s
venus interior1
Venus Interior
  • Differentiation of planet
    • Crust of lighter silicate mineralogy
    • Mantle of denser iron and magnesium silicates
    • Core, metallic, mostly iron, possibly liquid component
  • Composition of rocks at surface as measured by Venera landers
    • Basalts
      • Different from primordial meteorites
    • Alkali basalts
      • Evidence of extensive differentiation, partial melting
  • Atmospheric composition that expected by outgassing
  • Crustal features expression of deep internal mantle convection
    • Mostly vertical components
    • No evidence of plate tectonics
on the surface
On the Surface
  • Temperatures at surface = mechanical strength of rocks significantly lowered
    • Over time (~1BY) many topographic features would “disappear”
    • Muting of many topographic effects reduces topo extremes
  • High topography (Ishtar Terra) must be young features
on the surface1
On the Surface
  • Seven Soviet landers successfully reached surface and returned information
  • Rocks show evidence of geologic processes
    • Cratering
    • Volcanism
    • Layering
    • Fracturing (tectonics)
    • Chemical and mechanical weathering
    • Aeolian transportation
  • No hydrologic activity
  • Thin regolith compared to Lunar, Earth or Martian surfaces
golubkina crater
Golubkina Crater
  • Magellan radar image of complex crater
    • Named after the Russian sculptor Anna Golubkina
  • 30 km (18 mi) diam. crater characterized by terraced inner walls and a central peak
    • Typical of large impact craters on the Earth, Moon and Mars
  • Terraced inner walls –
    • Take shape late in the formation of an impact crater
    • Due to the collapse of the initial cavity created by the meteorite impact
  • The central peak –
    • Forms due to the rebound of the inner crater floor
golubkina crater1
Golubkina Crater
  • This is a computer generated, 3D perspective view of Golubkina crater
    • Complex crater form w/central peak
    • Flat-floored crater interior (possible melt)
    • Vertical exaggeration in this image is about 20 x
crater mead
Crater Mead
  • Largest known crater on Venus
    • named after Margaret Mead, the American anthropologist
    • measures 280 km (168 mi) in diameter and is located north of Aphrodite Terra and east of Eistla Regio
  • Classified as a multi-ring crater
    • innermost ring is thought to be the rim of the original crater cavity
    • irregular, radar-bright crater ejecta crossing the radar-dark floor terrace and adjacent outer radar-bright ring suggests that the terrace floor region is likely down-dropped and tilted outward, forming a concentric ring-fault
balch crater
Balch Crater
  • This remarkable half crater is located in the rift between Rhea and Theia Montes in Beta Regio.
    • (Radar illumination is from the left)
    • ~37 km (23 mi) in diam.
  • Cut by many fractures or faults since it was formed
    • eastern portion was partially destroyed during the formation of a fault-valley
    • measures up to 20 km (12 mi) wide
    • north-south profile through the center of this crater resulted from the downdropping and removal of most of the eastern half of the crater
  • Rifting shows evidence of vertical movement but no horizontal component indicative of tectonic forces
wanda crater akna mountains
Wanda CraterAkna Mountains
  • Mtns. form the western edge of Lakshmi Planum
  • Wanda crater, upper right
    • Diameter of 18 km (11 mi)
    • Doesn't appear deformed by tectonics but material from the Akna Mountains appears to have collapsed into it
    • Area of image is about 200 km (124 mi) long x 125 km (78 mi) wide
alcott crater
Alcott Crater
  • Magellan detected few impact craters in the process of being resurfaced by volcanism
    • Alcott is the largest of these craters with a diam. of 63 km (39 mi)
    • The trough-like depression (lower left) is a rille through which lava once flowed
    • Open lava tube
    • Remnants of rough radial ejecta is preserved outside the crater's southeast rim
  • Important to our understanding of resurfacing rates on Venus by volcanism
  • Note older, rougher terrain in upper right of image
barton crater
Barton Crater
  • 54-km (32-mi) diam. crater
    • size at which craters on Venus begin to possess peak-rings instead of a single central peak
  • The floor is flat and radar-dark
    • indicates possible infilling by lava flows sometime following the impact
    • central peak-ring is discontinuous and appears to have been disrupted or separated during or following the cratering process
    • name has been proposed by the Magellan Science Team, after Clara Barton, founder of the U. S. Red Cross; the name is tentative pending approval by the IAU
carson crater
Carson Crater
  • Venusian impact craters are frequently surrounded by radar-dark halos
    • Several of these special craters have halos that are parabolic in shape, and are very long, extending hundreds of kms
  • The darkness of the emissivity data indicates a smooth surface
    • halos may be thick, smooth sediment deposits formed when incoming projectiles crashed into the surface
  • The black strips represent missing data
atmospheric effects on ejecta distribution
Atmospheric Effects on Ejecta Distribution
  • Large impact crater about 30 km (19 mi) in diam. surrounded by a fresh ejecta blanket
  • Extreme brightness of the blanket is due to its roughness and its ability to scatter the radar signals that are used to collect these images
  • Missing section of the ejecta blanket (NW) is due to atmospheric blast that followed the impactor as it crashed through the Venusian atmosphere
crater cluster
Crater Cluster
  • A small projectile broke up in the atmosphere to form four smaller impactors that struck nearly simultaneously to form this crater cluster. Illumination is from the left at an incidence angle of 38 degrees
  • Note overlying ejecta blankets and broken, irregular rims.
sapas mons
Sapas Mons
  • Large volcano ~400 kms diam & 1.5 kms
  • Located on a topo rise in Atla Regio
  • Summit has 2 mesas w/flat to slightly convex tops and smooth surfaces (radar-dark)
  • Sides of volcano show bright overlapping flows
  • Many of the flows appear to be flank eruptions
  • Radial fractures transect the flows to the east and south
  • Darker flows in the southeast quadrant are smoother flows.
cinder pyroclastic cones
Cinder (Pyroclastic) Cones
  • The cone volcanoes in this cluster are about 2 kms (1.2 mi) in diam, 200 m (660 ft) high, with 12° steep slopes overlying a fracture network in NiobePlanitia
  • Some cones are cut by younger, more widely spaced, north-striking fractures with curvilinear outlines
  • Figure at right shows cinder cone field in a corona structure with associated linear faulting
lava flows
Lava Flows
  • A) Lakshmi Planum light and dark surfaces equivalent to basalt flow types known as pahoehoe (smooth lavas; somewhat specular surfaces) and aa (chunky lavas, better backscatterers)
  • B) Series of Lava flows emanate from the Sils Mons volcanic source
  • C) A long channel filled with volcanic flow material, over which a younger flow has straddled is the Ammavaru flow sequence in the Lada region
    • The scene's dimensions are 450 by 630 km

A

C

B

basaltic flows
Basaltic Flows
  • A flow field south of Ozza Mons in Atla Regio consists of numerous adjacent and overlapping flows with varying degrees of brightness
    • Brightness in radar images is related to several factors such as surface roughness and emissivity
  • Approximately 300-500mya tremendous outpourings of lava like this resurfaced Venus creating topographically flat plains and burying evidence of previous impact record
myletta fluctus flow
Myletta Fluctus Flow
  • One of the longest flows in SS occurs in Lavinia Planitia
    • ~1000km long
    • Must be low silica, low viscosity
    • Mafic basaltic composition
    • Infilling of crater between arrows
anemones
Anemones
  • Scientists have named this type of volcano "anemone" because of its petallike lava flows and radiating radar-bright patterns
  • Normally occur in association with fissure type eruptions
    • 40 by 60 kms (25 by 37 mi) in size
    • Dark central edifice with bright central flows
    • Elongated summit pits and an arcuate graben along the southern summit
pancakes

This cluster of four overlapping domes is located on the eastern edge of Alpha Regio. The domes average about 25kms (16 mi) in diam with max heights of 750m (2,460ft)

Pancakes
  • These features can be interpreted as viscous or thick eruptions of lava coming from a vent on the relatively level ground allowing the lava to flow in an even lateral pattern.
calderas
Calderas
  • Sacajawea Patera
  • Elliptical caldera 260 by 175 kms that forms a depression about 2 kms deep
  • Depression is enclosed by a zone of concentric troughs that show radar-bright outlines
  • Floor covered with smooth mottled plains
  • Brightest deposits occur around the periphery and near the center of the caldera floor
domes
Domes
  • This 17.4km dome in Navka Planitia shows collapsed margins and landslide deposits in both the NW and & NE quadrants
  • Landslide deposits show hummocky surfaces extending up to 10km out on the plains
  • Dome is ~1.86 km high & has a slope of about 23°
  • In general, the scale of lava domes and collapse features on Venus is orders of magnitude larger than that on Earth
volcanic dome in aino planitia
Volcanic Dome in Aino Planitia
  • Central dome ~100 km across
  • 1 km high
  • Note thick, fan-shaped lava flows and larger flow w/banded surface
  • Fan-shaped flow lobes are thick & vary between 120 and 540 m
  • Shape suggests the lavas had a hard time flowing away from the volcano
  • The banded flow looks like those produced by viscous lavas on Earth
  • Rarely basalts
  • Such lavas need water to form, however, water is scarce on Venus
mantle melting and convection
Mantle melting and convection
  • Different scales produce different features
  • Large shield volcanoes = large bodies of magma
  • Coronae = significant melt with slightly larger but more short-lived upwellings
    • Larger plumes also yield larger collapse features
  • Volcanic rises = very large-scale mantle upwelling
arachnids
Arachnids
  • Arachnoids are one of the more remarkable features found on Venus
  • They are seen on radar-dark plains
  • Arachnoids are circular to ovoid features with concentric rings and a complex network of fractures extending outward
  • Arachnoids range in size from ~50 kms (29.9 mi) to 230 kms (137.7 mi) in diam
arachnids1
Arachnids
  • Believed to be igneous related
  • Buoyant plume rises causing crust to stretch and thin
  • Crust may not be pierced and plume widens, flattens and spreads
  • As plume cools it sinks causing secondary tensional deformation
  • Result is uplifted circular mountain ring surrounding central depression
coronae
Coronae
  • Unlike Earth, Venus shows no evidence of plate tectonics
    • Process that helps release interior heat
  • One way Venus releases heat is by the formation of a large number of features called coronae
    • Circular patterns of fractures thought to form when hot material beneath the crust pushes up, warping the surface
    • Often accompanied by vast lava flows
    • Width of image area: 528 km (328 mi)
fotla corona
Fotla Corona
  • Named after the Celtic fertility goddess. It is located in a vast plain to the south of Aphrodite Terra
  • Just north (top) of this corona is a flat-topped pancake dome, about 35km in diameter
  • Another pancake dome is located inside the western (left) part of the corona
  • There is also a smooth, flat region in the center of the corona, probably a relatively young lava flow
  • Complex fracture patterns like the one in the north-east (top-right) of the image are often observed in association with coronae
novae
Novae
  • Nova - radial network of grabens
    • Radiate from central point
    • Extentional faulting
    • Upward pressure on crust by ascending magmatic plumes stretches overlying crust causing normal faulting
  • There have been about 50 novae identified on Venus
    • This Magellan radar image is from the Themis Regio
    • 250 km in diameter
corona and nova
Corona and Nova
  • 3D view of Yavine Corona
    • superposed 100km wide nova
    • nova are circular hills with star-shaped fractures
  • Yavine corona contains 2 novae; The view is a close-up of the southern nova showing its fractures to be grabens or fault bound depressions
  • Novae may represent an intermediate stage in coronae formation
corona and volcano
Corona and Volcano
  • 3D oblique view of Nagavonyi Corona in the foreground (200 km wide)
  • A 2-km high shield volcano behind the corona partly buries the Phoebo Regio highlands (shown as radar-bright mounds)
ridge belts
Ridge Belts
  • Belts of compressional folding and faulting
    • Sinuous and overlapping nature suggest low-angle thrust faulting senario
  • Compose ridges and mountain chains
  • Common in lowland areas of Venus
  • Found in absence of volcanic features or tensional fracturing
ridge belts ovda regio
Ridge BeltsOvda Regio
  • Common in lowland areas
    • Young volcanic features and extensional fractures are absent
    • Tectonic rather than volcanic in nature
    • Km’s high, 10’s of km’s wide, and 1,000’s km long
  • Compressional features suggesting crustal shortening
    • Large-scale downwelling in mantle
    • Return flow for cooling mantle material
    • Drag crust resulting in compressional crumpling
  • Some of the ridges have been cut at right angles by extension fractures
  • Dark material, either lava or windblown dirt, fills the region between the ridges
fracture belts
Fracture Belts
  • Belts of extensional faulting
  • Common in equatorial region of Venus
  • Occur in areas with lithospheric domes and abundant volcanic features
  • Narrow grabens imply shallow depth of deformation
tesserae graph paper terrain
Tesserae(Graph Paper Terrain)
  • Orderly association of perpendicular lineaments
    • Two groups of parallel features that intersect almost at right angles are visible
  • The fainter lineations are spaced at intervals of about 1 km and extend beyond the boundaries of the image
  • The brighter, more dominant lineations are less regular and often appear to begin and end where they intersect the fainter lineations
  • It is not yet clear whether the two sets of lineations represent faults or fractures, but in areas outside the image, the bright lineations are associated with pit craters and other volcanic features
highland tesserae
Highland Tesserae
  • More complicated version of tessera
    • Complex pattern of ridges and valleys probably formed by several episodes of faulting, folding, shearing, compression and extension
    • Largest ridges and troughs are about 10 km wide and less than 70 km long
  • Chaotic tessera terrain is often found at relatively high elevations
    • up to 3 thousand meters above the surrounding plains
bright streaks
Bright Streaks
  • Adivar Crater is surrounded by a streamlined, horseshoe or parabolic shapes (top and bottom right) and a bright, jet-like streak (center left) that extend over the surrounding plains
  • These unusual features, seen only on Venus, are believed to result from the interaction of ejected debris and high-speed winds in the upper atmosphere, blowing from the east (right)
  • The crater is 30km in diameter
  • Named for the Turkish educator and author Halide Adivar
dunes
Dunes
  • The tight pattern of bright and dark ripples in the center of this image is an area where loose material was sculpted by the gentle surface winds into dunes
  • The bright streaks of material curve away from small hills, revealing which way the winds were blowing
  • Stronger winds caused by meteorite impacts may also help create such features
  • Width of image area: 172 km (107 mi.)
wind streaks
Wind Streaks
  • The comet-like tail trends northeast from this volcanic edifice
  • The volcano, whose basal diameter is 5 km, is a local topographic high that has slowed down northeast trending winds enough to cause deposition of this material
  • The streak is 35 km long and 10 km wide
  • Not dust so why so bright?
    • Large vs small grain sizes
fracture network
Fracture Network
  • Magellan radar image covering a 105- km (63-mile) by 45-km (27-mile) region near Hestia Rupes on the northwestern corner of Aphrodite Terra
  • The complex network of narrow (<1 km) fractures in the center of the image extends for approximately 50 km
  • This network exhibits tributary-like branches similar to those observed in river systems on Earth called trellis drainage patterns
  • The angular intersections of tributaries suggest tectonic control
  • These features appear to be due to drainage of lava along preexisting fractures and subsequent collapse of the surface
channels
Channels
  • 200 kilometer (124 mile) segment of a sinuous channel on Venus
    • 2 km (1.2 miles) wide
  • Common on the plains
  • In some places they appear to have been formed by lava which may have melted or thermally eroded a path over the plains' surface
  • Similar to rivers in some respects, with meanders, cutoff oxbows, and abandoned channel segments
  • Channels appear to be older than other channel types on Venus, as they are crossed by fractures and wrinkle ridges, and are often buried by other volcanic materials
  • In addition, they appear to run both upslope and downslope, suggesting that the plains were warped by regional tectonism after channel formation
weathering on venus
Weathering on Venus
  • Type of weathering differs with altitude
  • Hi alt, lo temp
    • Sulfur in atmosphere reacts w/mafic lavas to form pyrite (FeS2)
    • Pyrite is highly reflective at radar wavelengths
    • May be why highlands and mtn. peaks are bright
  • Lo alt, hi temp
    • Magnetite and anhydrite are more stable and less reflective
summary
Summary
  • Earth and Venus formed at approx. same distance from Sun during SS formation
    • Should be of similar composition & planetary evolution
    • Cratering, volcanism and vertical tectonics in common
    • Bulk density and composition in common
  • Contrast of two planets
    • Water
    • Silicic volcanism
    • Plate tectonics
  • Young surface
    • ~0.5 BY
    • Few impacts scattered evenly across surface
    • Resurfacing by volcanic events
    • Catastrophic vs gradual resurfacing
  • Lack of water
    • Outgassed early on
    • No carbonate rx
    • Thick, dense atmosphere rids Venus of water to space
    • No lowering of melting temps in mantle
    • Lack of large volume of granitic rx
    • No formation of asthenosphere no plate tectonics
    • Buoyant crust resists subduction
    • Up- and downwelling dominate
  • No magnetic field
    • Rate of rotation
    • Possibly still some liquid core material
venera 13
Venera 13
  • On March 1, 1982 the Venera 13 lander touched down on the Venusian surface east of Phoebe Regio. It was the first Venera mission to include a color TV camera. Venera 13 survived on the surface for 2 hours, 7 minutes, long enough to obtain 14 images. This color panorama was produced using dark blue, green and red filters. Part of the spacecraft is seen at the bottom of the image. Flat rock slabs and soil are visible. The true color is difficult to judge because the Venerian atmosphere filters out blue light. The surface composition is similar to terrestrial basalt. On the ground in the foreground is a camera lens cover.
venus exploration chronology
Venus Exploration Chronology
  • Venera 1 - USSR Venus Flyby - 643.5 kg - (February 12, 1961)
    • Now in a solar orbit.
  • Mariner 2 - USA Venus Flyby - 201 kg - (August 27, 1962 - January 3, 1963)
    • On December 14, 1962, Mariner 2 arrived at Venus at a distance of 34,800 kilometers and scanned its surface with infrared and microwave radiometers, capturing data that showed Venus's surface to be about 425°C (800°F). Three weeks after the Venus flyby Mariner 2 went off the air on January 3, 1963. It is now in a solar orbit.
  • Zond 1 - USSR Venus Flyby - 890 kg - (April 2, 1964)
    • Communication lost en route; now in a solar orbit.
  • Venera 2 - USSR Venus Flyby - 962 kg - (November 12, 1965 - 1966)
    • Communications failed just before arrival. Now in solar orbit.
  • Venera 3 - USSR Venus Atmospheric Probe - 958 kg - (November 16, 1965 - 1966)
    • Communications failed just before atmosphere entry. Crashed on Venus.
  • Venera 4 - USSR Venus Atmospheric Probe - 1,104 kg - (June 12, 1967)
    • Venera 4 arrived at Venus on October 18, 1967. This was the first probe to be placed directly into the atmosphere and to return atmospheric data. It showed that the atmosphere was 90-95% carbon dioxide. It detected no nitrogen. The surface temperature reading was 500°C and pressure reading was 75 bar. It was crushed by the pressure on Venus before it reached the surface.
venus exploration chronology1
Venus Exploration Chronology
  • 26 different missions have visited Venus
    • More than any other planet
    • Many failed due to loss of communications and/or extreme environmental conditions
    • The few that successfully landed lasted for only a few minutes to hours
    • Some successful sample experiments giving us compositional information
    • Magellan has mapped >70% of the surface using radar instruments
venus exploration chronology2
Venus Exploration Chronology
  • Venera 5 - USSR Venus Atmosphere Probe - 1,128 kg - (January 5, 1969)
    • Venera 5 arrived at Venus on May 16, 1969. Along with Venera 6, atmospheric data was returned indicating an atmosphere composed of 93-97% carbon dioxide, 2-5% nitrogen, and less than 4% oxygen. The probe returned data down to within 26 kilometers of surface and was then lost - crushed by the pressure on Venus.
  • Venera 6 - USSR Venus Atmosphere Probe - 1,128 kg - (January 10, 1969)
    • Venera 6 arrived at Venus on May 17, 1969. Along with Venera 5, atmospheric data was returned indicating an atmosphere composed of 93-97% carbon dioxide, 2-5% nitrogen, and less than 4% oxygen. The probe returned data down to within 11 kilometers of surface and was then lost - crushed by the pressure on Venus.
  • Venera 7 - USSR Venus Lander - 1180 kg - (August 17, 1970)
    • Venera 7 arrived at Venus on December 15, 1970 and was the first successful landing of a spacecraft on another planet. It used an external cooling device which allowed it to send back 23 minutes of data. The surface temperature was 475°C, and surface pressure was 90 bar.
  • Venera 8 - USSR Venus Lander - 1,180 kg - (March 27, 1972)
    • Venera 8 arrived at Venus on July 22, 1972. It measure wind speed variations as it descended through the atmosphere: 100 meters/second above 48 kilometers, 40-47 meters/second at 42-48 kilometers, and 1 meter/second below 10 kilometers. It returned data for 50 minutes after it landed.
  • Mariner 10 - USA Mercury/Venus Flyby - 526 kg - (November 3, 1973 - March 24, 1975)
    • Mariner 10 was the first dual planet mission. It flew past Venus on February 5, 1974 for a gravity assist to the planet Mercury. Mariner 10 was the first spacecraft to have an imaging system. It recorded circulation in the Venusian atmosphere and showed the temperature of the cloud tops to be -23°C. It is now in a solar orbit.
venus exploration chronology3
Venus Exploration Chronology
  • Venera 9 - USSR Venus Orbiter and Lander - 4,936 kg (June 8, 1975)
    • Venera 9 arrived at Venus on October 22, 1975, three days before the arrival of its sister spacecraft, Venera 10. Both orbiters photographed the clouds and looked at the upper atmosphere. Differences in cloud layers were discovered at 57-70 kilometers, 52-57 kilometers and 49-52 kilometers from the surface. The lander arrived on the Venusian surface on November 22, 1975. During a period of 53 minutes, it transmitted the first black and white images of the planets surface. It showed sharp-edged flat rocks and a basaltic terrain. The probe in now in a Venus orbit.
  • Venera 10 - USSR Venus Orbiter and Lander - 5,033 kg - (June 14, 1975)
    • Venera 10 arrived at Venus on October 25, 1975, three days after the arrival of its sister spacecraft Venera 9. Both orbiters photographed the clouds and looked at the upper atmosphere. Differences in cloud layers were discovered at 57-70 kilometers, 52-57 kilometers and 49-52 kilometers from the surface. The lander arrived on the Venusian surface on November 25, 1975. During a period of 65 minutes, it transmitted black and white images of the planets surface. The terrain was more eroded than at the Venera 9 landing site.
  • Pioneer Venus 1 - USA Venus Orbiter - 582 kg - (May 20, 1978 - 1992)
    • Pioneer Venus 1 (also known as Pioneer 12) arrived at Venus on December 4, 1978. It operated continuously from 1978 until October 8, 1992, when contact was lost with the spacecraft. It was expected to burn up in the Venusian atmosphere 6 days later. The orbiter was the first spacecraft to use radar in mapping the planet's surface. The electron field experiment detected radio bursts presumably caused by lightening. No magnetic field was detected. From 1978 to 1988 the amount of sulfur dioxide in the atmosphere decreased by 10%. The reason for this decrease is unknown. Perhaps a large volcano erupted just before the orbiter arrived and the amount of sulfur dioxide slowly declined.
venus exploration chronology4
Venus Exploration Chronology
  • Pioneer Venus 2 - USA Venus Atmosphere Probe - 904 kg - (August 8, 1978)
    • Pioneer Venus 2 (also know as Pioneer 13) carried four atmospheric probes. One large and three smaller ones. They arrived at Venus on December 9, 1978 and plunged into the atmosphere. The four probes descended through the atmosphere by parachute while the spacecraft burned up high in the atmosphere. At a height of 70-90 kilometers the probes encountered a fine haze layer. Between 10-50 kilometers there was little atmospheric convection and below 30 kilometers the atmosphere was clear.
  • Venera 11 - USSR Venus Flyby/Lander - 4,940 kg - (September 9, 1978)
    • Venera 11 landed on Venus on December 25, 1978, and returned data for 95 minutes. The imaging systems failed.
  • Venera 12 - USSR Venus Flyby/Lander - 4,940 kg - (September 14, 1978)
    • Venera 12 landed on December 21, 1978 and returned data for 110 minutes. Electrical discharges, probably from lightning, were recorded.
  • Venera 13 - USSR Venus Flyby/Lander - 5,000 kg - (October 30, 1981)
    • Venera 13 landed on Venus on March 1, 1982. It returned black and white, and the first color panoramic views of the Venusian surface. It also conducted soil analysis using an x-ray fluorescence spectrometer. The sample was determined to be leucite basalt, a rare rock type on the Earth.
  • Venera 14 - USSR Venus Flyby/Lander - 5,000 kg - (November 4, 1981)
    • Venera 14 landed on Venus on March 5, 1982. It returned black and white, and color panoramic views of the Venusian surface. It also conducted soil analysis using an x-ray fluorescence spectrometer. The sample was determined to be tholeiitic basalt similar to that found at mid-ocean ridges on the Earth.
venus exploration chronology5
Venus Exploration Chronology
  • Venera 15 - USSR Venus Orbiter - 5,000 kg - (June 2, 1983)
    • Venera 15 arrived at Venus on October 10, 1983. Its high-resolution imaging system produced images at 1-2 kilometers in resolution. Venera 15 and 16 produced a map of the northern hemisphere from the pole to 30°N. They found several hot spots, possibly caused from volcanic activity.
  • Venera 16 - USSR Venus Orbiter - 5,000 kg - (June 7, 1983)
    • Venera 16 arrived at Venus on October 14, 1983. Its high-resolution imaging system produced images at 1-2 kilometers in resolution. Venera 15 and 16 produced a map of the northern hemisphere from the pole to 30°N. They found several hot spots, possibly caused from volcanic activity.
  • Vega 1 - USSR Venus/Comet Halley Flyby - 4,000 kg - (December 15, 1984)
    • Vega 1 flew past Venus on June 11, 1985 on its way for a flyby with comet Halley. It dropped off a Venera style lander and a balloon to investigate the Venusian middle cloud layer. The lander's soil experiment failed. The balloon floated in the atmosphere for about 48 hours at an altitude of 54 kilometers. Between Vega 1 and 2, downward gusts of 1 meter/second were encountered and wind velocities of up to 240 kilometers/hour. The Comet Halley flyby took place on March 6, 1986. The Vega 1 probe is now in a solar orbit.
  • Vega 2 - USSR Venus/Comet Halley Probe - 4,000 kg - (December 21, 1984)
    • Vega 2 flew past Venus on June 15, 1985 on its way for a flyby with comet Halley. It dropped off a Venera style lander and a balloon to investigate the Venusian middle cloud layer. The lander's soil experiment sampled anorthosite-troctolite which is found in the lunar highlands but is rare on Earth. The balloon floated in the atmosphere for about 48 hours at an altitude of 54 kilometers. Between Vega 1 and 2, downward gusts of 1 meter/second were encountered and wind velocities of up to 240 kilometers/hour. The Comet Halley flyby took place on March 9, 1986. The Vega 2 probe is now in a solar orbit.
venus exploration chronology6
Venus Exploration Chronology
  • Galileo - USA & Europe Jupiter Orbiter/Atmospheric Probe - (October 18, 1989)
    • Galileo was designed to study Jupiter's atmosphere, satellites and surrounding magnetosphere for 2 years. In order to get there, it used gravity assist techniques to pick up speed by flying past Venus on February 10, 1990. It then flew past the Earth & Moon on December 8, 1990 and then again on December 8, 1992. It has made encounters asteroid 951 Gaspra on October 29, 1991, and asteroid 243 Ida on August 28, 1993.
  • Magellan - USA Venus Orbiter - (May 4, 1989 - 1994)
    • Magellan was released into Earth's orbit from a space shuttle and then injected into a transfer orbit to Venus by an upper stage. Its primary mission was to map Venus using synthetic aperture radar. The surface of Venus is obscured by thick clouds of carbon dioxide that makes the surface invisible to optical instruments. Magellan arrived at Venus on August 10, 1990. Its radar imaging system was able to produce images at 300 meters/pixel resolution. The spacecraft mapped 99 percent of the planet's surface. In 1994, controllers directed the orbiter into the atmosphere, where it burned up.