What’s New on the Planets?

Small Bodies of the Solar System Asteroids: within the orbit of Jupiter Centaurs: Between Jupiter and Neptune Kuiper Belt Objects (KBO’s): Beyond Neptune Scattered Disk: Extreme KBO’s Comets: Icy bodies with elongated orbits Meteoroids: Small objects Meteors: vaporize in Earth’s atmosphere Meteorites: survive to reach surface

The Asteroid Belt, 2001

The Asteroid Belt, 2010

Asteroid Discoveries Asteroids Year 1 1801 100 1867 500 1902 1,000 1921 2,000 1942 5,000 1972 10,000 1981 20,000 1993 50,000 1999 100,000 2000 200,000 2003

Recent Progress 2010 September 2 2013 February 1 535789 Minor planets catalogued 251651 Officially numbered 16154 Named 2013 February 1 604344 Minor planets catalogued 353926 Officially numbered 17698 Named

Can we predict impacts? Incomplete inventory of objects May be a million km-sized objects Initial observations don't permit completely accurate predictions Comets vent gases and change orbits The meaning of probability of impact Planets don’t “wander” Observational uncertainty

Example, Measuring A Lot You measure the lot 5 times, getting 99.7, 99.9, 100.1, 100.0 and 100.3 feet. Average = 100 Best estimate but might not be true value Any random measurement has even odds of being too high or low P All 5 too high or low = (1/2)5 = 1/32 P 4 too high or low = 5/32 P 3 too high or low = (5*4/2)/32 = 10/32

Impact Probability

Impact Probability

Meteorite Peekskill, NY 1992

Chondrite

Stony-Iron Meteorite

Iron Meteorite

Meteo-Wrongs Meteorites Never: Have internal cavities Have layers Have veins Flatten on impact Mold around objects Almost never light in color outside If you “think” it’s magnetic, it’s not magnetic

Nope

Nope

Uh-uh

No Way

Nope

Nope

Nope

Tunguska, 1908

Tunguska, 1908

Sikhote-Alin Fall, February 12, 1947 Mass = 100,000 Kg

Sikhote-Alin Crater

Sikhote-Alin Crater

Sikhote-Alin Crater

Near Miss, August 10, 1972

1972 Near Miss Object was about the size of a bus Entered Atmosphere over Utah, travelling north, exited over Canada Velocity 15 km/sec Missed by 58 km

Returning to Space

Carangas, Peru, 2007

Carangas, Peru, 2007

Averting Impact Hazards Simplest Strategy: Detection + Diversion Destruction too unpredictable Can object be destroyed? “Cookie crumbs have no calories” In real life, the pieces matter The longer the lead time, the easier diversion becomes Only need a close miss Detection is cheap and off-the shelf

Diversion “The question is: how to do it? These things must be done … delicately.” Nukes? Thrusters? Space tug? Gravitational? Solar Sail Laser?

Asteroid Itokawa

Space Tug

What is a Planet? Ancient: 7 (including sun and moon) Copernicus: Sun and moon out, Earth in (6) Uranus, 1781 (7) Ceres 1801 (8); 12 by 1850 Asteroids Out, back to 7 Neptune 1846 (8) Pluto 1930 (9) Kuiper Belt, 1990’s; Pluto out This is not over yet.

What is a Planet? Current Definition: Hydrostatic Equilibrium Clears its vicinity Will certainly need adjustment in the future

Hydrostatic Equilibrium

Hydrostatic Equilibrium

Clearing the Vicinity

Two Coming Comets PANSTARRS ISON Comets are like cats; they have tails, and they do precisely what they want. –David Levy PANSTARRS March-April 2013 Near Moon on March 12 Faintly visible to unaided eye? ISON 800,000 miles from Sun in November 2013 May be very bright in December January 8, 2014, only 2° from Polaris

Ceres and Vesta

Dawn to Vesta and Ceres First Mission to use ion propulsion First Mission to main belt asteroids First Mission to orbit two different bodies

Getting There

Vesta’s Huge Crater

Rocket Science

Dropping the Heat Shield

Curiosity Landing

Where Things Landed

Mount Sharp

Layeerd Rocks

Conglomerate

Layered Rocks

Self Portrait

Drill Holes

Meteorite from Mercury?

Finding Other Solar Systems

The Sample Bias Problem

The Exoplanet Zoo Hot Jupiters Highly eccentric orbits Super-Earths Must have migrated inward Highly eccentric orbits Super-Earths Waterworlds? 861 as of February 19, 2013

Kepler Monitor 100,000 stars continuously for 4+ years Views an area about 10 degrees across Detects transits Star dims by 1/10,000