Transcript Lecture27

Lecture 27. Habitability of Bodies in the Solar
System. Voyager and Venus Landers.
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reading: Chapters 6,7
Missions to Venus
Spa cecraft
Mariner 2
Venera 4
Mariner 5
Venera 5
Venera 6
Venera 7
Venera 8
Mariner 10
Venera 9
Venera 10
Pioneer-Venus 1
Pioneer-Venus 2
Venera 11
Venera 12
Venera 13
Venera 14
Venera 15
Venera 16
Vega 1
Vega 2
Magellan
Laun ch DateTyp e of Mission
1962
Flyby; first flyby of Ve nus
1967
Hard-lander; first to descend through atmosph ere
1967
Flyby
1969
Hard-lander
1969
Hard-lander
1970
Soft-lander; first to soft land on surface
1972
Soft-lander
1973
Flyby en route to Mercury
1975
Orbiter, soft-lander; first to return photos o f surface
1975
Orbiter, soft-lander
1978
Orbiter with radar altimeter; first detailed radar mapping of surface
1978
Four hard-landers
1978
Flyby , soft-lander
1978
Flyby , soft-lander
1981
Orbiter, soft-lander; first color images of surface
1981
Orbiter, soft-lander
1983
Orbiter with radar mapper
1983
Orbiter with radar mapper
1984
Flyby , atmosph eric balloon probe
1984
Flyby , atmosph eric balloon probe
1989
Orbiter with radar mapper; first high-resolution glob al map o f Venus
+ 4 missions that failed completely
Mariner 2
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Flyby in 1962
Scanned surface with infrared and microwave radiometers
Showed surface to be 425˚C/800˚F
Venera 4
Atmospheric Probe in 1967
Showed atmosphere was 90-95% CO2
Didn’t detect N2
Surface T reading was 500˚C, P reading 75 bar
Crushed by the pressure before reaching the surface
Mariner 5
Flyby in 1967
Studied magnetic field
Found atmosphere was 85-99% CO2
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Venera 5 & 6
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Atmospheric Probe in 1969
Atmosphere 93-97% CO2, 2-5% N2, <4% O2
Probe also crushed by the P
Venera 7
Lander in 1970
First successful landing on another planet
External cooling device to send back 23 minutes of data
Surface T 475˚C, Surface P 90 bar
Venera 8
Venus Lander 1972
Measured wind speed variations as it descended
Winds of 100 m/sec in high atmosphere,
~40 m/s below 48km, 1 m/s by the surface
Returned data for 50 minutes after landing
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Mariner 10
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Mercury and Venus Flyby in 1974
First dual planet mission, first to have an imaging system
Recorded circulation in the Venus atmosphere, showed T of the
cloud tops to be 23˚C
Venera 9 & 10
Orbiter and Lander in 1975.
Photographed clouds and
analyzed upper atmosphere
Different cloud layers found
Lander survived 53 minutes, transmitted first black & white images
Showed flat rocks and basaltic terrain.
Pioneer Venus 1
Orbiter, 1978-1992.
Used radar to map surface.
Electron field detected radio bursts from lightning.
No magnetic field detected.
1978-1988 amount of SO2 in the atmosphere decreased 10%
Pioneer Venus 2
4 atmospheric probes, 1978
Found haze layers at 70-90 km
Cloud layers 10-50 km
Clear atmosphere below 30 km
Venera 11
Lander, 1978
Returned data for 95 minutes
Imaging systems failed
Venera 12
Lander, 1978
Returned data for 110 minutes
Recorded lightning
Venera 13 & 14
Flybys/Landers, 1981
Returned first color panoramic views
Conducted soil analysis, found leucitic and tholeiitic basalts
Venera 15 & 16
Orbiters, 1983
High resolution imaging of the surface
Found hot spots, probably volcanic activity
Vega 1 & 2
Flyby in 1985, dropped of a lander and a balloon
Vega 1 Lander’s soil experiment failed, Vega 2 found soil like lunar
highlands (anorthosite-troctolite)
Balloon floated in the atmosphere for 48 hours
Found downward gusts of 1 m/sec, velocities of 240 km/hr
Magellan
Orbiter, 1989-1994
Mapped using synthetic aperture radar
Produced detailed images of the surface, mapped 99% of the surface.
Interesting facts about the surface of Venus:
Has few craters globally.
Resurfacing of the planet 300-500 Ma??
There are lots of volcanoes!
More volcanoes than any other planet in the solar system!
1600 major volcanoes
perhaps over 100,000 smaller ones (no one’s ever counted)
No evidence of plate tectonics.
Why is Venus So Interesting for Astrobiology?
On Earth, most of the atmosphere
Is in the top 10 km.
On Venus, it is in the top ~50 km.
The T drops rapidly with altitude.
Clouds appear up to 70 km.
No clouds below 30 km.
Are distinctive cloud “decks”.
Windy Clouds
Strong winds blow the clouds around the planet.
Keep temperatures equilibrated on day and night side.
V-shaped clouds: winds at the poles cause clouds to overtake the
Equatorial clouds.
The Venusian Atmosphere
96.5% CO2
3.5% N2
Traces of water vapor, CO, SO2, Ar
Very dry atmosphere.
Venus has probably lost most of its water.
So hot, turned any liquid water into water vapor.
Photochemical reactions break it down.
Why is Venus So Interesting for Astrobiology?
Clouds contain droplets of sulfuric acid.
There is H2S and SO2 in the atmosphere.
Remember the 5 things you need to have life?
Venus Express
Arriving on April 11
Goal: to study the atmosphere and its history
In more detail
Mechanism driving circulation of the clouds
Composition and chemistry of the lower atmosphere and clouds
Past and present water in the atmosphere
How sunlight and greenhouse effect drives past and present
atmosphere.
Is there current volcanic activity or tectonic activity on the planet?
Voyager Mission Trivia
Approved in 1972
Total cost from May 1972 until Neptune encounter $865M
(including launch, RTGs, DSN tracking support)
$0.20/US resident/year
11,000 workyears
5 trillion bits of data (5 Terabits)
Voyager signal is 10-16 watts in strength
Designed and protected to withstand radiation from Jupiter’s belt
Tape recorder records digital images that are later sent back to Earth
Each carried 11 cameras/instruments.
Computer memory has 80 kilobytes.
Nuclear-powered generators fueled by the heat of decay of
plutonium generate electricity.
Needs 400 watts of power to operate instruments.
Original 5 year missions: Jupiter and Saturn
V1 and V2 are identical
Voyager Instruments
Flight Data Subsystem - single eight-track digital tape recorder
configures instruments, controls instrument operations
collects data formats it for transmission.
Data played back every 6 months
Attitude and Articulation Control Subsystem - controls spacecraft
orientation, points High Gain Antenna towards the Earth, controls
attitude maneuvers
Wide angle and narrow angle camera. Television-like cameras.
Infrared and ultraviolet spectrometers
Magnetometers
Plasma detectors
Cosmic-ray and charged-particle sensors
Radio for conducting experiments
Major Discoveries
Explored the 4 gas giants, 48 moons, and rings
Discovered 22 new moons
Jupiter: complicated atmospheric dynamics, lightning, auroras, rings!
Io (Jupiter): Exploding, sulfurous volcanoes
Saturn: 1000 ringlets, shepherd satellites that keep the
rings stable, weather, and braids, kinks, spokes in the rings.
Titan (Saturn): smog
Mimas (Saturn): looked like the Death Star
Major Discoveries, cont.
Uranus: highly monochromatic,
magnetic axis skewed from tilt axis
Miranda (Uranus): Huge fault canyons, bizarre patchwork of terrains
Ariel (Uranus): icy channels
Major Discoveries, cont.
Neptune: active weather, numerous clouds,
several rings, skewed magnetic
axis
Triton (Neptune): Geysers (liquid at 38˚K?),
cantaloupe appearance
Voyager 1
Launched 1977
Flew past Jupiter in 1979, Saturn in 1980
Could have done a flyby of Pluto, but JPL chose to get a close-up of Titan
Voyager 2
Launched 1977
Flew by Jupiter in 1979, Saturn in 1981, Uranus in 1986, Neptune in 1989
Rare planetary alignment allowed it to visit all 4.
Uranus and Neptune flybys not originally planned.
Voyager Golden Record & Its Cover
Gramophone record, attached to the spacecraft.
Contains sounds and images to portray the life and culture on Earth.
Surf, wind, thunder, animal sounds, songs of birds and whales, music.
Contents selected by committee chaired by Carl Sagan.
40,000 years away from another star.
To communicate with ETs
The Voyager Mission Today
Costs $4.2M/year to run - 10 full-time staff members.
2005 President Bush proposed to shut the program down.
At edge of the solar system- virtually nothing none about this boundary.
V1 and V2 should provide data well into 2020.
V1:
9 billion miles away
46,000 mph
V2:
7 billion miles away
63,000 mph
Lecture 28. The Viking Lander Missions.
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