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Orbital Characteristics
• Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. It is the brightest object in the night sky, except for the Moon, reaching an apparent magnitude of −4.6.
Sister Worlds?
• Venus, a terrestrial planet, is sometimes called Earth's "sister planet", as the two are similar in size, gravity, and bulk composition.
Mystery Planet
• The planet is covered with an opaque layer of highly reflective clouds, preventing its surface from being seen from space in visible light, and which made it a subject of great speculation until some of its secrets were revealed by planetary science in the twentieth century.
Venus in SciFi
• For over a century prior to space exploration, we assumed Venus to be much like the Earth.
• Same size, covered in clouds…maybe, just maybe it is our twin sister planet!
Early Scientific (not fictional) Speculations - limited by cloud-covered surface
See original paintings by Charles Knight (C .1930’s)
Needless to say, Venus like Mars, has loomed large in the human imagination
• Why do you think that is?
People have wondered since the caves, why are we here, where did we come from and what’s for dinner.
And so on…
We study Venus and the other planets in order to understand our own
• Aside from fueling the fervent imaginations of many a young science geek, the exploration of Venus has revealed a twin, indeed.
• Only, a twin world that sometime in the distant past, went wrong and Venus is now locked in a runaway Greenhouse Effect and permanent acid rain.
• Perhaps we should say, the Earth no longer wishes to be Venus’ twin. What can we learn from her?
Heavy Air
• Venus has the densest atmosphere of the terrestrial planets, consisting mostly of carbon dioxide, and the atmospheric pressure at the planet's surface is 90 times that of the Earth.
•96% CO2, 3% N2
•Psurface = 90 bars
•Clouds: Mostly
Droplets of
concentrated
sulfuric
acid (H2SO4)
Hot or Not?
• That is the question we are asking about Earth these days.
Turns out, Venus’ CO2 –rich atmosphere and subsequent high planetary temps tipped off Earth climatologists decades ago that if our atmospheric carbon concentration got higher, so would our temperatures.
No, not her
Why so different? - Greenhouse Effect
1. Visible light, to which atmosphere is transparent, absorbed by ground - heats it
2. Ground re-radiates energy as infrared light, to which the atmosphere is opaque
3. Warmed atmosphere re-radiates some of the IR back to the ground, keeping everything warmer
Facts & Mistakes
Earth:
Major Greenhouse Gases: Water Vapor & Carbon Dioxide
Other greenhouse Gases: Methane, Ozone, Nitrous Oxide
Venus: Carbon Dioxide - a LOT of it!!
COMMON MISCONCEPTION: greenhouse effect is NOT synonymous with the ozone layer!!!! Ozone is a (minor) greenhouse gas, but that is all.
Why Different Greenhouse Effects?
Earth’s water removes CO2 and sequesters (stores) it in rocks so, we have a small, but necessary Greenhouse. If we didn’t, we would likely be too far from our star to support complex life.
“Big Idea”: if all the CO2 in rocks were released, we would have an atmosphere similar to that of Venus! (and we would all die…)
Venus is like Earth in Size & Mass, but little else
3 faces of Venus
Visible Light (Mariner 10)
Radar map (Magellan) color as seen from surface
Radar map color-coded for elevation
Craters
The black & white images to follow are all radar images converted to visual pictures
Lava channel
Sif Mons: colorized radar image
The “Tick”Lava domes
Typical corona
A portion of Alpha Regio, showing tesserated terrain
Basaltic SurfacePhotos taken by Soviet (Russian) lander late 70s
No American spacecraft has ever landed on Venus
Photo from surface (USSR)
The Soviet Venera lander
c.1980
This is what it saw: a hazy, sullen sulfur sky and slabs of basalt, everywhere.
Comparison of Plate Activity for Earth & Venus
Cool crust
Water lubricates tectonic motion
Warm crust
No water
The next two slides will be a summary of Venus—by the book. You can find out more from http://www.windows.ucar.edu/tour/venus/venus.html
Venus is the second planet from the Sun, and is Earth's closest neighbor in the solar system. Venus is the brightest object in the sky after the Sun and the Moon, and sometimes looks like a bright star in the morning or evening sky.
The planet is slightly smaller than Earth, and its interior is similar to Earth. We can't see the surface of Venus from Earth, because it is covered with thick clouds that strongly reflect sunlight. However, space missions to Venus have shown us that its surface is covered with craters, over 1600 major volcanoes, mountains, large highland terrains, and vast lava plains. The surface of Venus is not where you'd like to be, with temperatures reaching more than 450C (approaching 900F - high enough to melt lead), an atmosphere 90 times heavier than our own, and clouds of sulfuric acid floating around to top it off!
Venus by the book
The atmosphere of Venus is very hot and thick. You would not survive a visit to the surface of the planet - you couldn't breathe the air, you would be crushed on by the enormous weight of the atmosphere, and you would burn up in surface temperatures high enough to melt lead.
The atmosphere of Venus is made up mainly of carbon dioxide, and thick clouds of sulfuric acid completely cover the planet. The atmosphere traps the small amount of energy from the sun that does reach the surface along with the heat the planet itself releases. This greenhouse effect has made the surface and lower atmosphere of Venus one of the hottest places in the solar system! If you were on the surface of the planet, the air above you would be about 90 times heavier than the Earth's atmosphere. This is like what a submarine experiences at 3000 ft below the surface of the Earth's ocean. The atmosphere is composed mainly of carbon dioxide (96%), 3.5% nitrogen, and less than 1% is made up of carbon monoxide, argon, sulfur dioxide, and water vapor.
Why should Venus and not the Earth have a hot and thick atmosphere? Some scientists call it the Goldilocks phenomenon.
Measurements made by probes which travelled through the atmosphere have shown that the atmospheric temperature remains nearly constant through the long dark night. Thus there are neither significant seasons, nor daily temperature changes in the atmosphere.
