Transcript Slide 1

Science Background
The Big Idea
Asteroids and comets are
messengers from space that have
had a significant impact on Earth’s
history and are likely to influence
the future as well.
The Questions Behind the Exhibit
How did our Solar System form?
What are asteroids & comets like?
What impact have space
rocks had on our planet?
Are we at risk?
Our Solar System
KEY QUESTION:
What is gravity?
Gravity Rules
Gravity is the attractive force between objects
that have mass. In space, this means that a swarm
of small objects eventually collects into a big one
under the influence of gravity. This is how moons,
rings, planets, and stars form.
Can You Fill in the Blanks?
Click for Answers
Exploring the Structure of the Universe
Before entering the exhibit, fill in the blanks using the following key words.
galaxy
Universe
100 billion
orbit
Earth
solar system
Jupiter
moon
planets
star
Sun
The Sun is a _________
Our
star located at the center of our __________________.
solar system
home, called __________,
Earth is one of 8 planets that orbit around the _________.
Sun
Earth has one _________
moon that orbits around it each month, showing different
phases. Some planets have many moons that ___________
orbit around them.
________________
is the largest planet in the Solar System and has 64 moons!
Jupiter
Our sun is one of about _______________
100 billion stars contained in the spiral
_____________
we call the Milky Way. Astronomers are now discovering
galaxy
Jupiter-sized ____________
planets that orbit around some of those distant stars. Outer
space is even bigger yet because the Milky Way is only one of an estimated 100
billion (100,000,000,000) galaxies in the ______________!
Universe
Copyright 2000 Cherilynn Morrow – Used with permission
A. Solar System Formation
1. Something (perhaps a supernova) triggers the gravitational collapse of a nearby
interstellar cloud.
2. The cloud naturally heats up and spins faster as it collapses. Collisions between
particles flatten the cloud into a disk. The Sun and planets start to form in
this spinning, flattened disk (proto-planetary disk), with the Sun at the
hottest central part.
3. In our Solar System, Earth formed in the inner region of the disk where rocky &
metallic material could condense in the greater heat. Ices & hydrocarbons
settled in the outer regions where gas giants like Jupiter form.
Crash Course
•
The largest planet, Jupiter, exerted
a powerful gravitational influence. If
Jupiter had formed closer to the
Sun, Earth and some of the other
inner planets might have been
thrown out of the Solar System!
•
Jupiter, Saturn, Uranus, and
Neptune formed amid a blizzard of
icy particles. They swept up much of
this frozen material. But much also
collected into huge “iceballs.” The
powerful gravity of the giant worlds
flung most of the iceballs into the
outskirts of the Solar System.
•
However some were diverted
toward Earth, where they crashed
and deposited vast amounts of
water—maybe enough to fill our
oceans. Since life probably started
in the oceans, we may owe our
existence to these snowballs from
afar.
Our Place in the Solar System
Earth is one of 8 PLANETS in our SOLAR SYSTEM.
The planets orbit a central STAR we call the SUN.
Jupiter
Mercury
Saturn
Mars
Venus
Earth
Neptune
Uranus
Can you name the other planets?
Hit <RETURN> for answers
Rocky terrestrial planets
of the inner Solar System.
Gas & ice giant planets
of the outer Solar System.
Influenced by the gravity of Jupiter & Neptune, icy
comets from the outer solar system likely delivered
important ingredients for life to the young Earth
environment (e.g. water and carbon compounds).
How do we explore our Solar System?
Ground-based Telescopes
The most readily available tools for exploring the
giant worlds are ground-based telescopes. These
include mammoth instruments such as the 110foot, 500-ton Goldstone Apple Valley Radio
Telescope located in California.
Space Telescopes
One advantage of launching telescopes into space
is that they have a view unobstructed by Earth’s
atmosphere. Orbiting several hundred kilometers
above Earth is the Hubble Space Telescope, which
has captured detailed views of the giant planets
and their moons.
Space Probes
The best views of the giant worlds are from up
close. Several space probes have made the
journey to the realm of giants for “quick-look” flyby
missions or for long-duration orbiting missions.
Cassini-Huygens is a spacecraft that arrived in
orbit around Saturn in 2004.
Asteroid/Comet
Locations
Asteroid & Comet Sizes
B. The Story of Asteroids
Lutetia
The Asteroid Belt
Asteroid Facts
• Color: Grey to slightly reddish. Asteroids turn redder and darker as
they age.
• Material: Most are similar to ordinary rocks. A small number are
nearly pure iron. Still others contain substantial amounts of carbon.
• Surface: Pock-marked. Asteroids are covered with impact craters
from collisions with smaller asteroids.
• Temperature: Asteroid temperatures vary a lot depending on how
fast they spin and whether you measure the side facing the Sun.
Temperatures range from -100ºC to 100ºC.
• Size: Asteroids can be almost any size from tens of meters across
to nearly 1/4 the diameter of our moon.
• Hidden Asteroids: We know the most about larger asteroids
because we can see them. There are countless asteroids smaller
than a kilometer (0.6 miles) that we can’t observe directly.
C. The Story of Comets
What are Comets?
Ion tail: ions created
by sunlight (blue color
Caused by CO2+).
Points away from Sun.
• Chunks of Ice and Rock:
“Dirty Snowballs”
• The most visible part (tail) is less
dense than best lab vacuum.
Dust tail: Dust particles
scatter (reflect) sunlight.
Direction due to motion.
Nucleus: Ice with
intermixed ‘gravel.’
.
Cometary Orbital Activity Cycle
Why are Comets Interesting??
• Relatively “pristine” materials from
the formation of the solar system.
• Used as proxies to study other
parts of the solar system (Kuiper
belt, Oort cloud).
• Occasional impacts that also can
deliver water to the inner solar
system.
A Jupiter Collision: Shoemaker-Levy 9
SL9 broke into pieces during a
close encounter with Jupiter in
1992 and collided with Jupiter
in July 1994.
Impacts by disrupted objects
can make crater chains like
this one on Ganymede
The same impact scar transposed onto
Earth from Fragment G
CC. Space Rock Impacts & Risk
Moon & Mars: Impact Craters?
What about Earth?
Identified impact structures on the Earth
The Inner Solar System
Main-belt
asteroids are
shown in green.
Near-Earth
asteroids are
shown in red.
Trojan asteroids
are shown as small
blue dots.
Comets are shown
as blue open
squares.
Positions as of 2
May, 2007.
NEOs: where do they come from?
• Main Belt Asteroids (MBAs) – between
Mars and Jupiter
• Kuiper Belt – at or beyond the orbit of
Neptune
• Oort Cloud Comets (may also include
larger bodies and some asteroids) –
long orbits extending out >10,000 AU,
106-yr periods
Tunguska Impact, Siberia,
30 June, 1908; Airburst, no crater
Barringer Crater, Arizona
1.2 km diameter
50,000 years ago
Manicouagan, Canada, 100 km diameter crater
214 million years ago
Chicxulub,Mexico, 180 km diameter crater
K-T
Boundary
The impact of a comet or
asteroid ~10 km in diameter is
now believed to be the cause
of the extinction of ~2/3 of
the species of life on the
Earth, including the dinosaurs,
65 million years ago. Thus, we
probably owe our very
existence to impacts.
CONCLUSION
Re-visiting the Big Ideas
We study asteroids and comets
because they tell us about the
formation of solar systems, our
planet, and the conditions
necessary for life. Someday we may
answer the age-old question of
whether there is life beyond Earth.
Asteroids and comets come in a
variety of shapes and sizes. They
are truly space messengers that
have had a significant impact on
Earth’s history and are likely to
influence our future as well.
http://www.killerasteroids
http://dawn.jpl.nasa.gov