Transcript presentation

DEEP IMPACT and ROSETTA –
Cometary Science
Today and
in 7 Years from Now
Hermann Boehnhardt
Max-Planck Institute for Solar System Research
Max-Planck Institute for
Solar System Research
(until 2005 MPI for
Aeronomy)
• Solar Physics
• Planetary Sciences
• Spacecraft & balloon
instrumentation
• Earth-based observations
Content of the Talk
• Why Cometary Research?
• DEEP IMPACT: Comet Crash 2005
• ROSETTA: Comet Exploration 2014/15
Comets & Solar System Formation
• Comets are dirty iceballs or icy
dirtballs (gas/dust ratio varies)
 evolution result?!
• Ices of supervolatiles (CO, CO2, CH4)
 comets were deeply frozen over
their whole lifetime
 formation region = outer planetary
disk (Jupiter and beyond)
 supervolatiles (& ortho-para ratio of
H2O and others) are T tracers of
evolution history of comets back to
formation era
• Small in size (m – km)
Irregular shape (potato)
 primordial planetesimals
(how primordial are they?)
Komet Borrelly von
DEEPSPACE 1
IR spectrum
Mumma
Weidenschilling
C/1999 S4 (Mumma etal. 2000)
Comets of 1-50km size have “typical”
planetesimal masses
Weidenschilling 2000
Run-away growth of planet embryos
produces planets at random distances
Cometary Orbits &
Comet Reservoirs
• Members of the solar system in
very eccentric orbits
- Oort Cloud comet
- long-periodic comet
- short-periodic comet
 no interstellar comet
• Comet reservoirs
- Oort Cloud
- Kuiper Belt (+Centaurs)
with “graveyards” for
- Jupiter family comets
- dormant comets
- main belt comets ?
Oort Cloud
Dormant comets
Tisserand constant of orbit as
invariance parameter
aj/a + 2 (a/aj (1-e-2))1/2 cos i =
C
Kuiper Belt
The Main Belt Comet Asteroids
Making the Oort Cloud from the Planetary Disk
Comets & Earth Ocean Water
• Earth after formation: hot, hence
no water on Earth
• Clean-up of formation disk
produced bombardment
(most likely in 2 phases)
 import of water on terrestrial
surface
Problem: D/H ratio of ocean
water differs from (barely
known) D/H ratio of comets
 way-around: mixing of 2 or
more sources with different
D/H ratio, cometary source
would have contributed
about 30%
early bombardment
late bombardment
(comets?)
Organics in Comets
• Comets contain organic
compounds both in volatile
ices (simple organics) and
solid dust (CHON, most
likely more complex
organics)
 long-term storage facility
• CI chondrite meteorites are
most likely related to
comets
2 CI chondrites had amino
acids with preference for
left-handed enantiomer
 contribution to life formation
on Earth (if cometary
material can reach Earth
surface reasonably intact)
GIOTTO
CHON dust in Halley
POM in comet Halley??
Import channels of cometary material to
Earth surface
• impacts (large pieces, discontinuous)
• gentle “rain” (micron size,
continuous)
 cometary material has reached and
still reaches terrestrial surface
SL9 impact at Jupiter in 1994
IDP from U2 in-flight collection
Comets and the Formation of the
Planetary System – Series of
(Hypo)Theses
• Comets are building blocks of planets in the
outer solar system
• Most primordial & widely unaltered material
(deeply frozen)
• Reflect the conditions in the formation
environment of the planets
(exo-planets)
• Important for early history of the Earth
(ocean water)
• Bringer of life (pre-biotic material)?
Comet Halley by GIOTTO
Cometary Science –
In Praxi
• Telescopes: Ground & Orbit
- remote sensing through light
• Space missions
- fly-bys (10x)
remote sensing through light & insitu lab experiments
 short duration (~h)
 rendez-vous: much better & longer
 landing: “touching a comet”
The Latest Coup: Deep Impact Live Impact & Cratering Experiment
• NASA mission to 9P/Tempel 1
- impact: 4 July 2005, 05:52UT
- impactor: 360kg
– speed: 10 km/s
– vis. camera
– fly-by S/C: vis. cameras
& IR spectrometer
– impact site visibility:
14min
Deep Impact: Learning by Doing
• impact: shot in the blind
• shape of ejecta cloud indicates
low strength dominated
impact regime
• DI impact crater not found
 cratering science suffers
(now to be imaged by
STARDUST in 2011)
• surface: many natural craters
 occurence frequency
consistent with expected
cratering rate of inactive
body
 but impact craters should not
survive cometary activity for
very long (erosion rate
~ 1 m/rev)
DI: The Expected & the Unexpected
• low bulk density 0.6 g/cm3
 Kuiper Belt objects are
heavier (Pluto: 2 g/cm3)
• low thermal conductivity
(100 W/K/m2/s1/2)
 very porous material
• comet: very weak (~300 Pa)
(weaker than powder snow)
 loosely bound, signature of
soft aggregation process
during formation, unclear
whether planetesimal or
impact formation
1km
DI: The Expected & the Unexpected
• water ice exists on surface at < 1%
surface coverage
 most of water production is
subsurface
 surface must be rejuvenated
quickly (no deep layering
zones in cometary nuclei)
• dust ejecta: micron size &
partially crystalline
silicates (heated > 1000K)
(already known from HB)
 hot & cold phase are
intimately mixed in
nucleus (and even on grain
level  from STARDUST)
 radial mixing of crystalline
and amorphous dust in
formation disk to large
distances
• phyllosilicates are interesting!
ESA’s ROSETTA
Mission
Goal:
rendez-vous
with a comet
(orbiting)
surface samples
(landing)
Start:
1993
Launch:
2 March 2004
(1 year delay)
Target:
67P/CG
Arrival:
May 2014
67P/Churyumov-Gerasimenko
ARIANE 5 & ROSETTA
The ROSETTA S/C
• ROSETTA Orbiter (ESA)
Dimensions:
Weight:
2.8 x 2.1 x 2.0 m
3000 kg
1600 kg fuel
165 kg experiments
Instrumente:
11
- close sensing (~ telescopes)
- in-situ experiments (~ lab)
• PHILAE Lander (DLR/CNES/ASI)
Dimensions:
Weight:
0.7 x 0.7 x 0.9 m
100kg
15kg experiments
Instruments:
10
(telescope & lab & samples)
The Flight Schedule
Duration:
~ 10 years
 4x planet swing-bys
(Earth, Mars)
Cruise science:
2 x asteroids
Earth/Mars fly-bys
Science at comet:
> 1 ½ years in orbit
lander delivery
1 Launch Earth
02.03.2004
2 Swing-by 1/Earth
04.03.2005
3 Swing-by 2/Mars
25.02.2007
4 Swing-by 3/Earth
13.11.2007
5 Fly-by Steins
05.09.2008
6 Swing-by 4/Earth
13.11.2009
7 Fly-by Lutetia
10.07.2010
8 Rendez-vous comet
22.05.2014
9 Landing on comet
10.11.2014
OSIRIS - The
ROSETTA Eyes
© OSIRIS team
(close sensing)
2 cameras (wide & narrow
angle + stereo) for vis. + UV
wavelength region
Science: nucleus mapping
geology, activity
(backbone inst.)
Orion nebula
© DLR
© NASA
Resolution: 1 cm/pixel
 100 x better than any
existing comet image
Komet Wild2 mit STARDUST
Farbe
100x
1x
ROSINA – COSIMA
The Comet
Chemistry Labs
ROSETTA
(in-situ)
Science goal: original gas and
dust chemistry
cometary organics
Isotope ratio in comets
(ocean water from
comets?)
Instrument type: mass
spectrometers (lab exp.)
GIOTTO
CONSERT- The
Nucleus Tomograph
(close sensing)
Science goals: inner
constitution of the nucleus
building blocks
Instrument type: radio sounder
with sender/receiver
onboard
orbiter and repeater onboard
lander
Life Science: COSAC @ PHILAE
(sampling & lab exp.)
Science goals: chemistry of
cometary soil
organics in particular
amino acids
Instrument type:drill and sample
device (SD2)
mass spectrometer
gas chromatograph
clou: determination of
chirality of material
life on Earth: left
handed chirality
 each result will have important
consequences on scenarios of life
formation on Earth
 bitings are still accepted
... more in 2014/2015