Deep Impact the MovieDeep Impact the MovieScience Fact vs. FictionScience Fact vs. Fiction

Karen J. Karen J. MeechMeech, Astronomer, AstronomerInstitute for AstronomyInstitute for AstronomySession 34 Session 34 –– 1/19/05 1/19/05

Science Fact vs. FictionScience Fact vs. Fiction Deep Impact, the MovieDeep Impact, the Movie ArmageddonArmageddon Themes:Themes:

comet/asteroid is about to impact Earthcomet/asteroid is about to impact Earth What we can to What we can to toto avert disaster avert disaster

Deep Impact FactsDeep Impact Facts

Nucleus Split in twoNucleus Split in two DiamDiam11 = 1 mi = 1 mi r = 0.8km r = 0.8km DiamDiam22 = 6 mi = 6 mi r = 4.8km r = 4.8km

Rotation period 14 hrRotation period 14 hr Earth collision Earth collision rr = 1AU = 1AU

What the Movie Got RightWhat the Movie Got Right

Comet AppearanceComet Appearance Impact Impact EnergeticsEnergetics

E = 0.5 m vE = 0.5 m v22

vv2 2 = GM(2/r = GM(2/r –– 1/a) 1/a) Global consequencesGlobal consequences

1 km radius major1 km radius major 4.8 km catastrophic4.8 km catastrophic

690,900690,9004.1x104.1x1021214.7x104.7x1014144.84.8320032001.9x101.9x1019192.2 x 102.2 x 1012120.80.8

KE [KE [MtonMton TNT] TNT]KE [J]KE [J]Mass [kg]Mass [kg]Radius [km]Radius [km]

Historical ImpactsHistorical Impacts

Lunar evidenceLunar evidence BarringerBarringer crater, AZ ~ crater, AZ ~

50,000 yr50,000 yr 1972 Fireball, 1972 Fireball, TetonsTetons

Historical ImpactsHistorical Impacts Tunguska (1908)Tunguska (1908)

30m radius30m radius 8 km explosion area8 km explosion area

KT Impact (65 KT Impact (65 MyrMyr)) Crater 10-15 x meteorite sizeCrater 10-15 x meteorite size Extinction of 50% of speciesExtinction of 50% of species Storms and firesStorms and fires Atmospheric dust Atmospheric dust months to months to

clearclear

ChicxulubChicxulub Crater Crater –– Yucatan Yucatan

Crater discovered 1950Crater discovered 1950’’s oils oilsurvey drillingsurvey drilling Ground water seeping Ground water seeping limestone limestone

CenotesCenotes DiamDiam 145-180 km 145-180 km 10 km 10 km diamdiam; 10; 108 8 ton TNTton TNT

Global EffectsGlobal Effects Debris into AtmosphereDebris into Atmosphere

Greenhouse gases (CaCOGreenhouse gases (CaCO33 = limestone) = limestone) Forest fires & Forest fires & ““Nuclear WinterNuclear Winter””

Yucatan during Cretaceous Yucatan during Cretaceous shallow sea shallow sea Tsunami Tsunami –– 100m high wave 100m high wave

Craters on EarthCraters on Earth

What the Movie Got WrongWhat the Movie Got Wrong

Observing with lights onObserving with lights on Orbit determined fromOrbit determined from

single data pointsingle data point

What the movie got WrongWhat the movie got Wrong Boulders in TailBoulders in Tail

Largest: cm-sizedLargest: cm-sizedaacritcrit = c Q = c Q vvthth / / ρρgg ρρnucnuc R R33

nucnuc

OutgassingOutgassing at sunrise at sunrise Heat slowly penetratesHeat slowly penetrates No instantaneous jetsNo instantaneous jets

What theWhat themovie gotmovie got

wrongwrong The tidal waveThe tidal wave

Impact velocity 70000mphImpact velocity 70000mph Tsunami 500-1000 km/hrTsunami 500-1000 km/hr Deepwater Deepwater wavehtwaveht 1km: 1km:

6-35m (10x @ 100 km)6-35m (10x @ 100 km) ““runuprunup”” height greater height greater

Factor of 2-3Factor of 2-3(conservative)(conservative)

Factor 25-40 HawaiiFactor 25-40 Hawaii

Empire state: 443.2mEmpire state: 443.2m

ArmageddonArmageddon Right:Right:

Thrusters for gravityThrusters for gravity Impact in ParisImpact in Paris

Wrong: All elseWrong: All else Discovery TX-sizedDiscovery TX-sized Comet or Asteroid?Comet or Asteroid? Scheduling HSTScheduling HST Meteor stream Meteor stream radiantsradiants Particle size DistributionParticle size Distribution Asteroid Asteroid ““CompositionComposition””

Armageddon (Armageddon (contdcontd).).

Composition:Composition: If asteroid (metal): Ni or FeIf asteroid (metal): Ni or Fe Density 7000 kg/mDensity 7000 kg/m33

Easy to drillEasy to drill Form from differentiationForm from differentiation No volatiles! CHNo volatiles! CH44