Deep Impact - Stony Brook Astronomy · 2007. 3. 30. · Deep Impact - July 3, 2005! Comet consists...
Transcript of Deep Impact - Stony Brook Astronomy · 2007. 3. 30. · Deep Impact - July 3, 2005! Comet consists...
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Deep Impact
Open Night
October 28, 2005
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Terminology
! Albedo - % of sunlight reflected
! Volatiles - ices, material that is liquid or gas at
moderate temperatures but form solids/crystals at
low temperatures (e.g. water, carbon dioxide,
methane)
! Rock - objects such as silicates
! Organic materials - hydrocarbons (C-H-X)
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Formation of Comet
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Comets & the Early Solar System
! Formation far from Sun
- Not much processing
by solar radiation
! Small - not much
alteration of
composition by
compression
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Connection to other planetary news
of the summer -
Kuiper Belt Object
UB313 - aka the “10th
planet”
The Kuiper Belt is
the reservoir from
which comets come
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Anatomy of a Comet
! Nucleus - core of the
comet ~ 10 km in size
comprised of rock and
ices
! Coma - the
“atmosphere” of the
nucleus
! Dust & gas tail
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The appearance cometary nuclei
from close flybly missions
Comet Halley
(Giotto -
March 1986)
Comet Borrelly
(Deepspace 1 -
September 2001)
Comet Wild 2
(Stardust -
January 2004)
" Observations of the Nucleus which is typical
obscured by coma
" Collection of samples of dust and volatiles
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Deep Impact - July 3, 2005
! Comet consists ofunprocessed materialfrom theprotoplanetary disk
! Dig deep into cometnucleus to view materialunheated by the Sun
! And to determinephysical properties (e.g.material strength) ofnucleus
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Comet Tempel 1
! Discovered in 1867 byWilhelm Tempel
! Orbital Period ~ 5.5 yr
! Perihelion ~ 1.6 AU
! Size ~ 11x4x4 km(9x2x2 miles)
! Albedo ~ 4%
! Spin period ~ 2 days
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The Spacecraft! Impactor mass ~ 370 kg (~
820 lb on Earth) + 6.5 kg of
fuel (hydrazine ~ N2H4)
! Relative velocity ~ 10 km/s
(22,800 mph)
! Late stage self-navigation
! 4500 images returned
! Best resolution ~ 4 m (13 ft)
! Flyby closest approach ~
500km (300 miles)
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Trajectory of Deep Impact
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Simulation - close-up of encounter
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Impact as Seen from Impactor
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Impact Trajectory Maneuver
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Impact as Seen from Flyby Spacecraft
Expansion rate ~ 5 km/s (3.1 miles per second)
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Impact as Seen from Flyby Spacecraft
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Brightening of Comet Tempel 1 as
seen from Earth
Mount Laguna Observatory - 1m telescope (San Diego St.)
R-band
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Impact Ejecta Fan
-1 day impact +1 day
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See for detailed reading of mission
& discoveries - Oct 14 ‘05
! Surface
! Ejecta & Shadow
! Spectra from Deep
Impact
! Spectra from Spitzer
Space Telescope
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The Surface
! Outgassing observed during approach
! ~329 K (135O F) at “noon” & ~ 260 K (10O F) in shadow- Today’s high & low on L.I. ~ 35O F & 51O F
! Surface temperature, albedo, & spectra are indicativeof no ice on the surface
! Craters - prior impacts with solar system debris
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Ejecta & Shadow
! Gas = steam + CO2! Fine Dust ~ 1-1000 µm
in size (human hair is ~70-180 µm in size)
! Lots of material inejecta even 13 minutesafter impact
! Surface is weak &powdery
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DI Spectral Data
Green curve - 0.6
sec after impact -
water, carbon
dioxide &
hydrocarbons
Red Curve -
Before Impact
Blue curve - H20, CO2, & continuum model
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Off-nuclear spectra - Hydrocarbons
below surface of Comet
Preimpact ~ -10 min Postimpact ~ +4 min
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Recipe for a Comet - What the
Spitzer Space Telescope Observed
! Silicates of Olivine (found on Hawaii’s Green Sand Beach)
! Clay & Carbonates (thought to require liquid water to form)
! Iron compounds
! hydrocarbons (found in car exhaust & BBQ pits)
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Summary - What have we learned
thus far?
! Craters observed on surface
! Surface is powdery
! No ice on surface, but there isice just below the surface
! Organic molecules, water ice,and silicate dust composition &abundances indicate that someof the comets originated closeto or within giant planet region
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Acknowledgements
! Thanks to Dave Jewitt
! http://deepimpact.jpl.nasa.gov/home/index.html &
Science Magazine (Oct 14 ‘05)