Venus
description
Transcript of Venus
Venus
VenusEarth’s “sister planet”
0.72 AU from Sun~2x farther from Sun than Mercury
so ~4x less sunlight
~1.4x closer than Earth so sunlight is (1.4)2 times =~2x more intense
Venus approaches closer to Earth than any other planet so we should
know a lot about it.
However, its surface is invisible underneath a thick atmosphere.
“true” color image
Venusglobal properties
albedo = 0.65mass = 0.815 of Earth’sdiameter = 0.95 of Earth'sdensity = 5.3 gm/cm3 surface gravity = 0.91 Earth’saxial tilt = 177.3 deg.ORBIT:
0.72 AU = semi. axis0.0068 = eccentricity3.4 deg = inclination224.7 day = period “false color” image
in UV
1962: Carpenter & Goldstein (US) used radar "echoes“ to study Venus’
surface
"double" inverse square problem
RADAR: “Radio Detection and Ranging”
Arecibo Observatory in Puerto Rico
Mapping the Surface via RadarVenus is the most thoroughly mapped of any
planet
movie98% of the surface has been mapped to 100 meters
resolutionOver 80% of Venus’ surface lies within 1 km of its mean radius
Radar Mapping
Radar Mapping
Radar Map of Venus’ Surface
Surface features shown in artificial colors.
Scattered impact craters
Volcanic regions
Smooth lava flows
Lava Flows
Young, uneven lava flows (shown: Lava flow near Flagstaff, AZ) show up as bright regions on radar maps.
Surface Features on Venus
Smooth lowlands Highland regions:Maxwell Montes are ~ 50 %
higher than Mt. Everest!
Craters on VenusNearly 1000 impact
craters on Venus’ surface:→ Surface not very old.
No water on the surface; thick, dense atmosphere
→ No erosion
Craters appear sharp and fresh
Shield Volcanoes
Found above hot spots:
Fluid magma chamber, from
which lava erupts repeatedly through
surface layers above.
All volcanoes on Venus are shield volcanoes
Volcanism on VenusSapas Mons (radar image)
~ 400 km (250 miles) 2 lava-filled calderasLava flows
Volcanic Features on
Venus
Baltis Vallis: 6800 km long lava flow channel (longest
in the solar system!)
Coronae: Circular bulges formed by volcanic activity
Aine Corona
Lava flowsPancake Domes:
Associated with volcanic activity forming coronae
Some lava flows collapsed after molten lava drained away
Lakshmi Planum and Maxwell Mountains
Radar image
Wrinkled mountain formations indicate compression and wrinkling, though there is no evidence of plate tectonics on Venus.
Surface “Flights” computer generated images from radar data
Alpha RegioVertical scale is exaggerated for
visibility
Impact Craters
About 1000 craters are located randomly around
Venus.
Venus’s atmosphere is a shield
very few craters <35 km diameter
Craters show little modification by
tectonism or volcanism.
Few craters suggests the surface is relatively
young.
~30 km diameter
Largest crater is Mead ~280 km diameter
with a double-ring.
Effects of a Hot SurfaceImpact crater Addams, 90 km diameter.
The surface is so hot that impacts more easily melt the surface than on other planets.
Outflow of lava extends 600 km away.
Volcanoes & Lava Flows over 10,000 small shield volcanoes
Gula Mons3 km tall volcano
Maat Mons 8 km tall volcano with lava flows
extending hundreds of km
1962-1994: Spacecraft to VenusUnmanned Spacecraft
US:Mariner 2, 5, 10 flybys
Pioneer Venus orbiter & probes(1st radar from space)
Magellan (high resolution radar)Galileo (flybys enroute to Jupiter)
Soviet:Venera 4-16 (#7,8; 9,10; 13,14
landed)VEGA 1, 2 (landers & balloons) Surface map from 10
years of radar data
Lava Channels1-2 km wide and at least 100’s of km
long
12 km diameter crater
Baltis Vallis Longest channel in solar system: 6800 km long
and 1.8 km wideLo Chen Vallis
How Does Venus Release Its Heat?
Volcanic plumes instead of plate tectonics?Arachnoids
Circular features with concentric rings & fractures with diameters 50-
230 km
CoronaeCircular troughs around volcanic
plateausCould the troughs be subduction
zones?
Artemis Corona2000 km diameter
6 km from rim to trough528 km across
The Surface as Imaged by Venera 14 Composition: volcanic basalt
These surface probes typically survived about one hour
The Surface of VenusEarly radar images already revealed mountains, plains, craters.
Venera 13 photograph of
surface of Venus:
Colors modified by clouds in Venus’
atmosphere
More details from orbiting and landing spacecraft:
After correction for atmospheric color
effect:
Atmosphere96.5% CO2, 3.5% N2 -- no O2 or H2O
also acids: hydrochloric, hydrofluoric & sulfuric
Dark areas are locations of the sulfuric acid clouds.
Bright areas are gaps between clouds.
Clouds near equator are fluffy but those at higher latitudes are stretched by high winds.
H2SO4 (sulfuric acid) clouds may come from SO2 outgassing
from active volcanoesNighttime side of Venus in
false-color image from a near-infrared camera (2.3mm) on
the Galileo spacecraft
The Atmosphere of Venus
UV image
Extremely inhospitable:96 % carbon dioxide (CO2)3.5 % nitrogen (N2)
Rest: water (H2O), hydrochloric acid (HCl), hydrofluoric acid (HF)
4 thick cloud layers (→ surface invisible to us from Earth).
Very stable circulation patterns with high-speed winds (up to 240 km/h)
Extremely high surface temperature up to 745 K (= 880 oF)
Very efficient “greenhouse”!
“Greenhouse Effect”Venus is the hottest planet and has the densest
atmosphere1950's: radio wave
emissionsurface temperature:
750 K = 900 F
Venus’ thick CO2 atmosphere keeps the surface hot.
Surface pressure is 100x Earth’sHow many pounds per square-
inch?[same as ~3000 feet under
water]
Sulfuric acid clouds“runaway greenhouse
effect”
No Magnetic Field25,000 x weaker than Earth’s
Too slow a rotator to generate an internal dynamo
Perhaps Venus’ lack of crustal plates inhibits internal
convection currents of molten rocks.