SPACE ROCKS!

and ice.

A steroids?

You tell me.

The Asteroid Belt

Where they are:

Red = NEOsBlue dot: J TrojansGreen = A. BeltBlue square = cometsCircles = 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

Phobos

Eros

Asteroids got moons!

Sylvia, orbited by Romulus and Remus

90 Antiope – 50km asteroids separated by 100km

Ida and Dactyl

Taken by Galileo on its way to Jupiter

36 km

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 CometsHalley’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 9This comet broke up and crashed into Jupiter in July 1994.

Multiple observations were made from ground-based 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 Oortcloud, 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, 2005 impactor

The Impactor:

370-kg copper slug, traveling at 10 km/sec (relative to nucleus).

“X-ray” view

Under the Hood

JxsmkgmvKE 1022 109.1)/000,10)(370(212/1 ===

(For comparison, a typical nuclear warhead would yield about 4x1012 J.)

"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