28.2 – the inner planets - okanagan mission...
TRANSCRIPT
MAIN IDEA
• Mercury, Venus, Earth, and marks have high densities and rocky surfaces
• Just as in a family in which brothers and sisters share a strong resemblance, the
inner planets share many characteristics
TERRESTRIAL PLANETS
• The four inner planets are called terrestrial planets because they are similar in density to
Earth
• They have solid rocky surfaces
• Density is important because it indicates the internal conditions of these planets are
compressed
MERCURY
• Mercury is the closest planet to the sun, for this reason it
is difficult to see from Earth
• Is about 1/3 of the size of Earth
• Easily seen at sunrise and sunset
• Very slow spin – it takes 1407.6 hours to spin
• In one orbit, Mercury spins one and one-half times
• This means Mercury’s years equal three complete
Mercury days!
• No moons!
MERCURY’S ATMOSPHERE
• The atmosphere in Mercury is mostly made up of oxygen and sodium
• The daytime temperature is 427°C while temperatures at night fall to -173°C
• This is the largest day-night temperature difference among the planets
SURFACE OF MERCURY
• A U.S. space probe passed the surface of the moon in 1974 and 1975 and it found the
surface is similar to the moon with craters and plains
• Maria on the surface formed like the ones on the moon
• The gravity of Mercury is much greater than the moon, resulting in small ejecta and rays
• Planetwide system of cliffs called scarps
INTERIOR OF MERCURY
• Has a high density made up of nickel-iron core
• Small magnetic field
• Core is molten
• Mercury’s size was much larger but outer layers may have been lost with a collision with
other celestial bodies early in history
VENUS
• Brightest planet in the sky – albedo is 0.75 therefore known as the bright ‘star’
• Aka ‘evening or morning star’
• Very thick clouds make it difficult to observe
• In 1989 Magellan spacecraft was able to map 98% of the surface using radio-telescopes
• In 2006 – Venus express gathered atmospheric data for 1.5 yrs
VENUS’ ROTATION
• Slow rotation – one day is equivalent to 243 Earth days
• Spins clockwise, unlike other planets which spin counter-clockwise
• Sunrise in the west and sets in the east
• Collision with another body may have caused this
VENUS’ ATMOSPHERE
• Most similar to the Earth
• Physical properties like diameter, mass, and density
• Venus is 92 atmospheres (atm) – 915m of water
• Clouds of sulphuric acid
• Hottest planet because of high levels of carbon dioxide
• So hot (464°C) that liquid water cannot exist
SURFACE AND INTERIOR
• Venus has a smooth surface
from lava flow however no
crustal plates or impact
craters
• Because of its size and
density, scientists believe
the internal structure is very
similar to that of Earth
• Liquid core
• No measurable
magnetic field because
of its slow rotation
EARTH
• Allows water to exist as solid, liquid and
gas
• Dense atmosphere of nitrogen and
oxygen allows for life
• Only planet where plate tectonics occurs
MARS
• The red planet
• Smaller and less dense than Earth
• Has two irregularly shaped moons – Phobos and Deimos
• Lots of exploration
• Historic Log at NASA
MARS’ ATMOSPHERE
• Mars is very similar to Venus
• Density and pressure is much lower, there greenhouse effect is not as strong
• Constant winds and dust storms can last for weeks because of thin atmosphere
MARS’ SURFACE
• Northern and southern hemisphere vary greatly
• Southern hemisphere is heavily cratered
• Lots of highlands
• Northern hemisphere has sparsely cratered plains
MARS’ SURFACE
• Four gigantic shield volcanoes are located near the equator called the Tharsis Plateau
• Largest volcano is called Olympic Mons
• 3 times higher than Mount Everest
TECTONICS
• Valles Marineris is an enormous canyon
stretching 400km long
• 10 times longer than the grand canyon
and 3 times deeper
• Formed by a fracture 3 bya
EROSIONAL FEATURES
• Dried river and lake beds
• Outflow channels and runoff channels
• Astronomers think the atmosphere was once much warmer, thicker, and richer in carbon
dioxide allowing liquid water to flow on Mars
• Small amount of Ice at the poles
ICE CAPS
• Caps grow and shrink with the
seasons
• Seasons caused by tilt and orbit
• Carbon dioxide ice
• Interior
• The interior remains unknown of
Mars as it is hypothsized that
there is a core of iron, nickel, and
sulfur
• No magnetic field
• Snow Falls