SPACE ROCKS!

SPACE ROCKS!
and ice.
A steroids?
You tell me.
The Asteroid Belt
Where they are:
Red = NEOs
Blue dot: J Trojans
Green = A. Belt
Blue square = comets
Circles = planet orbits
What are asteroids?
• Two main kinds:
– C type (carbonaceous, 75% of all known)
• Make up most of outer belt (near Jupiter)
• Contain carbonates (MgCO3, CaCO3, etc)
• dark
– S type (silicaceous, 17%)
• Make up most of inner belt (near Mars)
• Contain nickel, iron, and iron/magnesium silicates
• Bright
– M type (metallic, the rest)
• Found in inner belt
• Metallic, with some stony content
• Oops. Did I say 2?
• Did I say 2? I meant 14 (A, B, C, D, E, F,
G, P, Q, R, T, V)
– Based on spectral class (light reflected from
surface)
– B, F, G are subclasses of C. Others are
distinguished by small differences in the UV
spectrum
• Problem is…
– Class now is based on spectrum, not
composition. Some carbonaceous asteroids
may not be; they may just look carbonaceous
How much material?
• Whole amount (all rocks >= 1m) of
asteroid belt matter is about 1/1000 Me.
• 1/3 of all mass is in Ceres
• All asteroids more than 200km in diameter
are known.
Asteroids on Parade!
Itokawa: coming your way in the next 500 million years! Note the smooth spot.
Hayabusa
Itokawa – 600m long. Hayabusa landed there in Sept. 2005.
Gravelball? That’s one theory as to why it has no craters.
The Shadow of Hayabusa!
NEAR at Eros
Eros in stereo?
NEAR lands
6 m!
Stereo Asteroids
Eros
Phobos
Asteroids got moons!
90 Antiope – 50km asteroids
separated by 100km
Sylvia, orbited by Romulus and Remus
Ida and Dactyl
36 km
Taken by Galileo on its way to Jupiter
Comets
• Observed throughout history; thought to be bad
omens. They represented change in the perfect
heavens, which bugged people.
• Other bad examples: assassination of Caesar
(J), conquest of Peru, Black Plague
• Mark Twain both born and died in a Halley
appearance year
• Halley’s comet was excommunicated by Pope
Calixtus III* (1450’s)
*OK, not really. But people thought he had done it.
Halley’s Comet - 1066
“Yo. What’s that hairy thing in the sky?”
“I don’t know, but it can’t be good for King Harold.”
Famous Comets
Halley’s Comet (disc. antiq): appears
every 76 years (next in 2061). Most
famous, recorded through history
Hyukatake: disc. (1/30/96): very long tail;
studied by Hubble. Won’t be back for
14,000 years.
Shoemaker-Levy 9: (disc. 1993): broke apart and collided with Jupiter (image later).
Hale-Bopp: (disc. 7/23/95), 40 km nucleus (VERY
large). It was visible even through bright city skies, and
may have been the most viewed comet in recorded
history. Comet Hale-Bopp holds the record for the
longest period of naked-eye visibility: an astonishing 19
months. It will not appear again for another 2,400
years. It hid the spaceship that was coming for the
Heaven’s Gate cultists.
Switft-Tuttle (disc. 1862): reappears every 120 years and leaves dust in the
earth’s path. This causes the Perseid meteor shower (many meteor showers are
the result of comet debris)
Sheryl Swoopes,
Houston Comets:
2003 WNBA
defensive player of
the year; 2x WNBA
MVP
What are comets?
Comets are frozen chunks of ice mixed up with the
occasional rock, dust, and other elements, including
trapped gases.
These gases sublime as the comet approaches the
sun, creating the tails of the comet.
Elements and compounds observed in various
comets include:
Hydrogen, methane, water (mostly), CO, CH3OH,
HCN, H2CO, H2S, CS, C2H6
Why do they look like that?
•Ion tail is created when the charged solar wind repels charged particles from the
comet. It ALWAYS points away from the sun
•Dust tail is uncharged material pushed away by the solar wind but the result of the
motion of the comet. It points away from the comet’s direction of motion (Drag and
all that)
•The H envelope is invisible except to radio waves
•Fluorescence causes the color of the ion trail; reflected sunlight the dust tail
Shoemaker-Levy 9
This comet broke up and crashed into Jupiter
in July 1994.
Multiple observations were made from groundbased telescopes and Hubble in many different
wavelengths.
Comet bits moving toward Jupiter
Comet breaking up
Impact sites are in a line due to
Jupiter’s rotation and the
fragments hitting sequentially.
Origin?
Thought to come from the Oort
cloud, a proposed region WAY out
from the sun. Long period (200+
year orbits) comets come from this
area and are drawn in by the
gravitational influence of other
nearby stars and objects.
Short period (also Jupiter-type)
comets are thought to come from
the Kupier belt/inner Oort cloud,
pulled out by the influence of
Neptune and Uranus.
It doesn’t take a big pull to get a
comet moving; then the sun’s
gravity takes over and it assumes
a stable orbit.
Launched 2004, impacted
comet Tempel 1 on July 4,
impactor
2005
The Impactor:
370-kg copper slug, traveling at 10
km/sec (relative to nucleus).
KE = 1 / 2mv 2 =
1
(370kg )(10,000m / s ) 2 = 1.9 x1010 J
2
(For comparison, a typical nuclear warhead would yield
about 4x1012 J.)
“X-ray” view
Under the Hood
"You can not help but get a big flash when
objects meet at 23,000 miles per hour," said
Deep Impact co-investigator Dr. Pete Schultz
of Brown University, Providence, R.I. "The heat
produced by impact was at least several
thousand degrees Kelvin and at that extreme
temperature just about any material begins to
glow. Essentially, we generated our own
incandescent photo flash for less than a
second."
13 million km away….
Tempel 1 Nucleus
Impactor site
Pull up! Pull up!
13 seconds after impact
Impactor Results