Venus. Vital Statistics R = 6052 km M = 4.87 x 10 24 kg R orbit = 1.082 x 10 8 km T = 730º K Eccentricity = 0.007 Axial tilt = 177.4 º “day” = -243.0.

Venus

Vital Statistics

• R = 6052 km• M = 4.87 x 1024 kg

• Rorbit = 1.082 x 108 km

• T = 730º K• Eccentricity = 0.007• Axial tilt = 177.4 º• “day” = -243.0 days• “year” = 224.7 days• orbital inclination = 3.39º

• 0.95 R

• 0.82 M

• 0.72 A.U.

A bit of background

• Known since prehistoric times

• Brightest object in the sky except for the Sun and the Moon

• It was often thought to be 2 separate bodies - the morning star and the evening star - but the Greeks knew better

• Galileo observed phases of Venus

Visibility

Claims to fame

• Earth’s sister planet: only slightly smaller than Earth; few craters young surface; densities and chemical comps similar

• Hottest planet in the solar system

• one of the 4 main pieces of evidence Galileo presented to support the helocentric model

• brightest planet in seen from Earth

• rotates “backwards”

Visits

• Mariner 2 - 1962

• Pioneer Venus

• Venera 7 (Soviet) - 1st spacecraft to land

• Venera 9 - returned first photos of the surface

• Magellan - 1st orbiter, produced detailed surface maps using radar

• Venus Express - ESA - now in orbit

• more than 20 total, so far

Mariner 2

• 1st probe to fly by Venus - 1962

• measured temperature of 800 F, now revised to 900 F

• cloud-covered atmosphere composed primarily of carbon dioxide

Pioneer Venus

• Inserted into an elliptical orbit around Venus on Dec. 4, 1978

• flat cylinder 2.5m in diameter and 1.2m high

• All instruments on the forward end

• total mass of 45 kg

• 17 experiments…

• fuel ran out, fell toward Venus, and burned up in atmosphere in August 1992

Pioneer Venus

Pioneer Venus

• a cloud photopolarimeter to measure the vertical distribution of the clouds

• a surface radar mapper to determine topography and surface characteristics

• an infrared radiometer to measure IR emissions from the Venus atmosphere

• an airglow ultraviolet spectrometer to measure scattered and emitted UV light

• a neutral mass spectrometer to determine the composition of the upper atmosphere

Pioneer Venus

• a solar wind plasma analyzer to measure properties of the solar wind

• a magnetometer to characterize the magnetic field at Venus• an electric field detector to study the solar wind and its

interactions• an electron temperature probe to study the thermal

properties of the ionosphere• an ion mass spectrometer to characterize the ionospheric ion

population

Pioneer Venus

• a charged particle retarding potential analyzer to study ionospheric particles

• two radio science experiments to determine the gravity field of Venus

• a radio occultation experiment to characterize the atmosphere

• an atmospheric drag experiment to study the upper atmosphere

• a radio science atmospheric and solar wind turbulence experiment

• a gamma ray burst detector to record gamma ray bursts

Magellan

• May 1989 - Oct 1994 (commanded to plunge into atmosphere)

• very detailed radar maps 98% of surface

• looped around Sun 1.5 times before arriving at Venus Aug 10, 1990

• high-res gravity data

• imaged in strips

• repeat scans of some strips– “look angle” was different in different scans - allowed

construction of 3-d images

Venus Express

• Venus Monioring Camera

• Analyser of Space Plasma and Energetic Atoms

• Planetary Fourier Spectrometer

• V/UV/NIR mapping spectrometer

• Venus Radio Science Experiment

• UV and IR Atmospheric Spectrometer

Atmosphere

• Surface pressure is 90 atmospheres (about the same as the pressure at a depth of 1 km in Earth’s oceans)

• mostly CO2

• Several layers of clouds many km thick composed of sulfuric acid (the acid in acid rain)

• runaway greenhouse effect (temperature at the surface is hot enough to melt lead)

Atmosphere

Atmosphere

Structure

Surface features

• Probably had large amounts of water, but it has since boiled away

• still volcanically active• pancake volcanoes - eruptions of very thick

lava• coronae - collapsed domes over large magma

chambers• large shield volcanos

Surface features

• no small craters - small objects burn up in atmosphere

• craters come in bunches, indicating that meteors break up in atmosphere

• arachnoids - molten rock seeping into surface features?

• “graph paper” - faults or fractures?

Pancake volcanoes

Shield volcanoes

Sif Mons

Selu corona

Arachnoids

Aphrodite TerraRidges indicate repeated compression and buckling. Dark areas represent regions that

have been flooded by lava

Lava flows - cracks in Venus’ surface

“Graph paper”

fainter lines are spaced at about 1km

Photo from surface

3-d maps of

surface(Lakshmi

Ishtar terra)

3-d maps of

surface(Gula Mons and

Eistla Rift)

Terrain map