Transcript Venus - AstroArts

Venus
• 68
million
miles
from
Sun
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 reradiates 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
Lava domes
The “Tick”
Typical corona
A portion of Alpha Regio,
showing tesserated
terrain
Basaltic Surface
Photos taken by Soviet (Russian) lander late 70s
No American spacecraft has ever landed on Venus
Photo from surface (USSR)
This is what it saw: a hazy,
sullen sulfur sky and slabs
of basalt, everywhere.
The Soviet
Venera lander
c.1980
Comparison of Plate Activity for Earth & Venus
Cool crust
Warm crust
Water lubricates tectonic
motion
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.
Venus by the book
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!
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.