Transcript Foundation 1 - Discovering Astronomy

Innri Reikistjörnur
Hvað heldur þú?
• Er hitastig á Merkúr, reikistjörnunni sem er
næst sól, hærra en á jörðinni?
• Hver er samsetning skýja sem umlykja
Venus?
• Er fljótandi vant á Mars í dag?
• Er líf á Mars í dag?
Myndir frá
Mariner 10
sýna hve líkt
yfirborð
Merkúr er því
sem er á
Tunglinu
Mercury
Moon
Caloris Basin
Note the edge of
a huge crater on
the left, mostly
in shadow.
Unusual, Hilly
Terrain
The tiny, fine-grained
wrinkles are actually
closely spaced hills.
Mercury has an iron core and a
magnetic field like Earth
Mercury rotates in
176 Earth days,
barely enough to have
a dynamo created
magnetic field -- yet,
Mercury still has a
magnetic field. Its
source is a great
mystery.
Mercury’s temperature range is the
most extreme in the solar system
• Mercury’s slow 176 day rotation and the lack of an
appreciable atmosphere means temperatures vary
enormously from one side of the planet to the other.
• Daytime with the Sun overhead reaches 700K (or
800°F)
• Midnight with the Sun completely obscured is 100K
(or -280°F)
• Earth typically has temperature differences between
day and night of about 11K (or 20°F)
The surface of
Venus is
completely
hidden beneath
permanent cloud
cover
Venus
• Atmosphere is 96% CO2
• Temperature is 750K
– much higher than Mercury
– daytime AND nightime
– caused by the greenhouse effect
The greenhouse effect heats Venus’s surface
Venus is covered with gently rolling hills, two
“continents,” and numerous volcanoes
The Venusian Surface
Impact
Craters
on Venus
Mars as viewed
from Earth
Like Earth,
Mars has polar
ice caps that
grow and
shrink with the
changing
seasons.
Enormous
shield
volcanoes
Valles Marineris is many times larger than the Grand Canyon
Olympus Mons - the largest volcano in the solar
system has a base larger than the state of Colorado
Early space probes to Mars found
no canals but did find some
controversial features
Surface features indicate that
water once flowed on Mars
Ohio
River
valley
on Earth
River
channels
on Mars
Viking I Lander Picture from 1976
1999 Picture
from the Mars
Pathfinder
Lander - Sagan
Station
Note the remotecontrol rover,
Sojourner, next to
a Martian rock
Martian air is thin and often filled
with dust
• Mars’ thin atmosphere is 95% CO2
• Mars’ atmospheric pressure is about 1% as
high as Earth’s
• Mars’ coldest temperatures occur at the
poles at about 160K (-170°F)
• Typical Mars temperatures range between
50°F and -80°F
The Martian meteorite found
in Antarctica has not
provided conclusive evidence
about life on Mars
Mars’ two moons, Phobos and Deimos,
look more like potatoes than spheres
What did you think?
• Is the temperature on Mercury, the closest planet to the
Sun, higher than the temperature on Earth?
The temperature on the daytime side of Mercury is much higher
than on Earth, but the temperature on the nighttime side of
Mercury is much lower than on Earth because Mercury rotates so
slowly and has little atmosphere to retain heat.
• What is the composition of the clouds surrounding Venus?
The clouds are composed primarily of sulfuric acid.
• Does Mars have surface liquid water today?
No, but there are strong indications that it had liquid water in the
distant past.
• Is life known to exist on Mars today?
No life has yet been discovered on Mars.
Self-Check
1: Compare and contrast the atmospheres of the terrestrial planets in
terms of temperature, pressure, and chemical composition.
2: List the properties that Mercury has in common with the other
terrestrial planets with the Moon.
3: Compare and contrast the surfaces of Mercury, Mars, and Venus with
that of the Earth in terms of geologic structures and evidence
regarding tectonic activity.
4: Describe plausible explanations for the absence of water vapor in the
Venusian and Martian atmospheres.
5: Discuss the contributions of the various spacecraft missions to our
understanding of the terrestrial planets.
6: Discuss the evidence for the existence of water on Mars surface in the
past and the location and form of that water today.
7: Compare the magnetic fields of Mercury, Venus, and Mars with that of
Earth.