Transcript Slide 1

Journal 11/7/16
Tell me everything you know about asteroids.
Objective
Tonight’s Homework
To learn about some of the
other, smaller objects in the
solar system.
p 358: review 5, 7, 9, 18
Notes on Pluto and the Asteroid Belt
It’s only very recently that we sent a mission to
Pluto and got to see it up close for the first
time. We expected to find a simple frozen ball of
ice with no surface features. What we’ve found
instead is quite different and very mysterious.
To start, the mountains seen in the picture
below are about 11,000 feet high. How did they
get there? We don’t know.
Notes on Pluto and the Asteroid Belt
Pluto has a large, heart shaped area that’s also
very interesting because it’s smooth. We care
because smooth means there’s been recent
geological activity that erased
craters. Pluto is way too
small to have
tectonics.
Everything
should be
frozen!
Notes on Pluto and the Asteroid Belt
Pluto also has a very tilted orbit that’s very
elliptical. When Pluto is at its farthest, it gets so
cold that its atmosphere freezes and snows onto
the surface, leaving Pluto with no atmosphere
for a while.
Notes on Pluto and the Asteroid Belt
Pluto’s biggest moon, Charon is also very
mysterious. Charon has a canyon that goes so
deep you could fit all of Mount Everest inside!
Other than that,
Pluto and Charon
remain mostly
a mystery.
We still have a
lot of data to
go through to
uncover more
secrets.
Notes on Pluto and the Asteroid Belt
There’s more stuff floating around the solar
system than just planets. The previous slide
showed comet 67P. This comet is still far from
the sun, so right now it’s just a dirty ice ball.
The whole thing is about as big as L.A.
The European
Space Agency
actually landed
on this comet
and is taking
data for the next
several years.
Notes on Pluto and the Asteroid Belt
Why do we care about comets? Most comets are
literally left over chunks of ice and rock from the
beginning of the solar system. We care about
them because samples from them can tell us
what the solar system was like right when it
formed.
One thing we’ve already learned is that the ice
comets are made from is chemically different
from the water on Earth. This means Earth
couldn’t have gotten its oceans from a bunch of
comets hitting it, which is what our current
theory proposed.
Notes on Pluto and the Asteroid Belt
Comets are interesting because they also have
very elliptical orbits. As a comet gets closer to
the sun, the ice heats up and starts to melt.
This is a pretty violent process, causing tons of
water and gas to stream off the comet in a
direction opposite the sun.
Each time a comet
goes around the sun
it loses a bit more
material.
Eventually a comet
will get “used up”
and disappear.
Notes on Pluto and the Asteroid Belt
In 1994, a comet got caught by Jupiter’s
gravity, broke apart, and slammed into Jupiter
in about 20 pieces. Each piece hitting released
way more energy than a nuclear bomb and left
scars that stayed on Jupiter for months.
Notes on Pluto and the Asteroid Belt
The last major thing is the asteroid belt. This is
a large collection of asteroids orbiting the sun
between Mars and Jupiter.
Notes on Pluto and the Asteroid Belt
We originally thought that the asteroid belt was
the remains of a planet that got ripped apart or
maybe never formed, but there’s just not
enough stuff.
If we gather up all the material in the asteroid
belt into one big ball, its still not even as big as
the Moon.
In fact, stuff here is so spread out that you’d
have trouble seeing one asteroid if you were
standing on the surface of another. They’re just
too small and far apart.
Notes on Pluto and the Asteroid Belt
The two largest asteroids - Ceres and Vesta –
were once considered planets, but are now
dwarf planets like Pluto. Ceres is even big
enough to form into a sphere.
Notes on Pluto and the Asteroid Belt
A number of years back, we sent a lander to an
asteroid named 433 Eros. For scale, this
asteroid would cover about 1/3 of Denver. Even
though it’s small, it still has enough gravity for
craters to form.
Notes on Pluto and the Asteroid Belt
Asteroids come in 3 types – C, S, and M.
C (carbon) asteroids are mostly made of ice,
carbon, and some organic compounds like tar.
There’s a lot of gravel and rock here, too.
S (silicon) asteroids are mostly made of metals
like nickel and silicon. This makes them the
most rocky of the asteroids. A lot of their
surface is covered in dust and gravel.
M (metal) asteroids are mostly made of pure
nickel and iron. These are usually smaller but
more dense.
Exit Question
Why do comets emit gas and dust as they get near the
sun?
a) They start moving fast enough to break apart
b) Their unstable orbit causes them to shake apart
c) Because the sun’s heat is causing them to evaporate
d) We don’t know why
e) Because God loves gassy comets.