rendezvous with a comet€¦ · •how do comets work? -development of activity, in particular jets...
TRANSCRIPT
Picture: Comet McNaught, Akira Fujii
Rosetta Rendezvous with a comet
Harald Krüger
Max-Planck-Institut für Sonnensystemforschung Göttingen
Outline
1. What do we know about comets? Composition, orbits, origin and evolution
!2. Why do we study comets? !3. Rosetta mission overview and target comet
Spacecraft, scientific instruments, orbit, target comet 67P/Churyumov-Gerasimenko
!4. Philae’s landing on comet 67P/C-G on 12 November 2014 !5. First Philae science results !6. Summary and Outlook
1. What do we know about comets?
!Image: Comet Hale-Bopp, MPIA/Calar Alto
The “pieces” of a comet…
Light and particles from the Sun
Coma (100.000 km)
Gas(Ions)-tail(~ 50 Mio. km)
!Dust tail
Invisible nucleus (1-10 km)
Borelly (Deep Space 1)
Halley (Giotto)
Tempel 1 (Deep Impact, Stardust-NExT)
Wild 2 (Stardust)
Hartley 2 (Deep Impact)
!Image: Science
Inventory of cometary nuclei
67P/Churyumov-Gerasimenko (Rosetta)
Orbits and origin of comets
3 types of orbits: - Jupiter family comets
orbital period < 20 years; Origin: Kuiper belt
- Short-period comets orbital period 20 to 200 years; Origin: Kuiper belt
- Long-period comets orbital period > 200 years Origin: Oort cloud
!Comets spend most of their time far from the Sun ➞ Little evolution since their formation (“deep-frozen in the fridge of the solar system”)
Long-period
Short-period
Jupiter family
Some facts about comets (before Rosetta)
• ‘Dirty snowball’ (or ‘icy mudball’?): ~ 85% water ice, 4% CO, 3% CO2, 1% N2, rest minerals and organic compounds
• Cometary activity driven by sublimation of volatiles (water, CO, CO2) when the nucleus approaches the Sun
• Nucleus loses ~ 1% of its mass per revolution about the Sun
• Very dark surface, albedo ~ 4 %
• Very porous on average (ρ ~ 400 kg/m3). A comet nucleus would swim on an Earth ocean like an iceberg
• Comets are the most pristine material left over from the formation of the solar system
• Origin: Kuiper belt (short-period and Jupiter family comets) and Oort cloud (long-period comets)
• How do comets work? - Development of activity, in particular jets - Surface structure and evolution, distribution of activity regions on the surface - Life time of comets !
• How did comets and the solar system form? - Internal structure of the nucleus and nucleus material - Composition of cometary material
!• Did comets bring water and the building blocks of life to Earth?
- Organic and isotopic composition
2. Why do we study comets?
Astronomical observations In-situ investigations by spacecraft
Rosetta at Churyumov-GerasimenkoComet Hale-Bopp
How do we investigate comets?
3. The Rosetta Mission
Pic
ture
s: E
SA
/Ast
rium
2 March 2004
Pictures: ESA/Astrium
Rosetta orbiter instruments
Name Instrument PI Institute, Country
OSIRIS Optical camera MPS, Germany
ALICE UV spectrometer SRI, USA
VIRTIS Optical and NIR spectrometer IAS-CNR, Italy
MIRO Microwave spectrometer JPL, USA
ROSINA Gas mass analyser University Bern, Switzerland
COSIMA Dust mass spectrometer MPS, Germany
MIDAS Atomic force microscope Dust particle morphology
IWF, Austria
CONSERT Nucleus sounding with radio waves LPG, CNRS, France
GIADA Dust particle detector INAF, Italy
RPC
Plasma instruments: Ion and electron sensor (IES), Ion composition analyser (ICA),
Langmuir probe (LAP), Mutual Impedance Probe (MIP), Magnetometer (MAG)
IRF, Sweden; SRI, USA; TU Braunschweig, D; Imperial College, GB; LPCE/CNRS,
France
RSI Radio wave experiment University Köln, Germany
The lander Philae
Picture: ESA/ATG
ROMAP
SESAME sensor
CASSE/PP
CONSERT antenna
SESAME sensor DIM
SD2CIVA
cameraCIVA
camera
MUPUS hammer
APXS
SD2 drill
MUPUS sensors
SESAME sensor
CASSE/PP
SESAME sensor
CASSE/PP
COSAC and PTOLEMY gas
analyzers
ROLIS camera
10 years interplanetary cruise
Erde
Mars Sonne
Animation: Thomas Albin, MPS
Jupiter
The target comet 67P/Churyumov-Gerasimenko
Discovery 1969
Nucleus size ca. 4 km
Rotation period ca. 12.4 h (12.5 h until early 2014)
Orbital period 6,45 yr
Perihelion distance 1,24 AU
Aphelion distance 5,68 AU
Orbit inclination 7º
Present orbitsince 1959
(perihelion at 3.5 AU before)
Next perihelion Aug. 2015
Jupiter-family comet
ESA/Rosetta NAVCAM Sept 2014
Shape model 67P/C-G Aug 2014
ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Comet 67P/Churyumov-Gerasimenko An irregularly shaped object
Das Ziel der Reise:Der Komet 67P/Churyumov-Gerasimenko
ESA/Rosetta NAVCAM Sept 2014
Bild
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Comet activity
10 Sept 2014
ESA/Rosetta NAVCAM Sept 2014
4. Philae’s landing on 12 Nov 2014
Der Landeplatz
Roter Kreis: 500m Durchmesser
Rosetta: Close orbits to Philae deployment
Animation: ESA
Philae’s descent as seen from the orbiter
ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
First touchdownTouchdown time: 12 Nov 2014; 15:34 UTC
Bild
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The nominal landing site
Red circle: 500 m radius
First touchdown ~100m away from targeted landing site
Nominal landing site from 40 meters altitude
ES
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hila
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10 m
• Generally smooth terrain covered with gravel
• Gravel and blocks with varying frequency
• Features resembling pits
• Partially buried blocks
Dust raised at landing…
ES
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ta N
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Dust cloud raised from surface
ES
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At the final landing site
20 years old
4.567 billion years old
The oldest object where a man-made spacecraft has ever landed
ES
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ta/P
hila
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At the final landing site
“Cliff” with linear fractures
ES
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/CN
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At the final landing site
ES
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At the final landing site
5. First Philae science results
Structure of the cometary soil(?) (As seen before Philae landing)
Drawing: DLR
• Soil sampling with drill (SD2)
• Thermal treatment (pyrolysis) of sample in dedicated ovens
• Chromatography of released gases
• Electron ionisation and time-of-flight mass spectra of released gases
Cometary Sampling and Composition Experiment (COSAC)
The Lander Philae
Image: DLR
ROMAP
SESAMESensor
SESAMESensor
SESAMESensor
CONSERTAntenna
SESAMESensor
SD2CIVA
CameraCIVA
Camera
MUPUS
APXS
SD2Drill
MUPUSSensorMUPUS
Sensor
Dienstag, 29. Oktober 13
Mumma & Charnley, 2011
AcetyleneMethane
Ethane
MethanolFormaldehyde
Ethylene glycolFormic acid
Methyl formateAcetaldehyde
Formamide
AmmoniaHydrogen cyanide
Isocyanic acidHydrogen isocyanide
AcetonitrileCyanoacetylene
Hydrogen sulfideCarbonyl sulfide
Sulfur dioxideThioformaldehyde
Sulfur
Water
Carbon dioxideCarbon monoxide
Glycine: smallest amino acid found in proteins was identified in dust samples retruned to Earth from comet Wild 2 by Stardust mission (Elsila et al., 2009)
Abundances of cometary volatiles
6. Summary and Outlook• Comets:
- Most pristine material left over from the formation of our solar system - “Dirty snowball”: mostly porous water ice with contributions by rocky material (?) - Sublimation of volatiles from nucleus surface due to heating by solar radiation;
leads to formation of gas and dust coma surrounding the nucleus; material from the coma forms the tails due to solar radiation and solar wind pressure
!• 67P/C-G:
- Much more irregularly shaped than expected (two bodies sticking together?); rugged terrain with pits, landslides, boulders and a dust layer above a hard surface
- Localized activity; comet more active at large heliocentric distance than expected !• Rosetta: first landing on a cometary nucleus
- So far very successful long-term investigation of the comet nucleus and its environment with many different measurement techniques
May 2014 to mid 2016 Rosetta orbiter mission at the comet
12 Nov 2014 Philae landing at 3 AU heliocentric distance
July 2015 to Sept 2015 Philae extended mission ???
Bild
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M/D
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A;
Mon
tage
: Axe
l M. Q
uetz
, Ste
rne
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Wel
trau
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Thank you!
67P/C-G and the skyline of Frankfurt