rendezvous with a comet€¦ · •how do comets work? -development of activity, in particular jets...

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

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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

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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

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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

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• Generally smooth terrain covered with gravel

• Gravel and blocks with varying frequency

• Features resembling pits

• Partially buried blocks

Dust raised at landing…

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Dust cloud raised from surface

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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

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At the final landing site

“Cliff” with linear fractures

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At the final landing site

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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 ???

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Thank you!

67P/C-G and the skyline of Frankfurt