Credit: NASA
Credit: NASA
Credit: Wordpress
Credit: Lowell
Credit: NSS L5
Credit: Chuck Jones
Credit: NASA
Rob Hunt Oct 2011
By Rob Hunt. June, 2012
The Potential
For Observing
Methane on Mars
Using
Earth-based
Extremely Large
Telescopes
1
• Recent detections of seasonal, large volumes of atmospheric CH4 have re-fuelled the
‘life-on-Mars’ discussion
• CH4 strongest vibrational frequency is at 3.3 μm in the Near Infra Red (NIR) L Band,
and is readily detectable in the Martian atmosphere from ground-based spectrographs at
high, dry locations such as Hawaii and Chile
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• Resolution and origin of specific spectral absorption lines which identify CH4 are
disputed in the literature
• Could proposed Extremely Large Telescopes (ELTs) supplement, or even replace
space-based instruments trained on Martian CH4?
• A review of immediate-past, present, and future NIR spectrometers revealed a wide
range of capabilities and limitations
• Spatial, spectral, radiometric, and temporal resolutions were all considered and found
to be complex, inter-related and highly instrument-specific
• The Giant Magellan Telescope, the Thirty Meter Telescope, and the European
Extremely Large Telescope will each have at least one L Band NIR spectrometer
supported by adaptive optics, capable of extreme spatial, spectral and radiometric
resolution
• Replicating observations over time will provide a critical constraint to theoretical
considerations about the origins of CH4 on Mars
2
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• to document the relevant capabilities and limitations of the three proposed ELTs,
• to summarize the capabilities of instruments at other locations, and
• to recommend future Mars science drivers for the ELTs
3
• Astronomers have been doing remote sensing at least since Galileo
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U
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D
• Three new 30 – 40 m diameter optical/NIR telescopes in design phase
• The Giant Magellan Telescope (GMT) will be built high in the Atacama desert of
Chile (with significant Australian involvement)
• The Thirty Meter Telescope (TMT) will be built on Mt Maunakea in Hawaii
• The European Extremely Large Telescope (E-ELT) is also planned for high in the
Atacama, Chile
• Space Agency budget cuts mean ELTs may step in to do some science
• Modern spectrometers on ground-based telescopes can detect many chemical
species on Mars and can subtract the effects of Earth’s intervening ‘telluric’ spectral
lines
• Temporal (over time), radiometric (bit data), spatial (over distance), and spectral
resolution (across wavelengths) all reveal important information about a target, usually
with trade-offs between each
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The Giant Magellan Telescope (GMT)
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Ground broken 23rd March, 2012
7 primary mirrors each 8.4 m diameter
368 m2 light collecting area
10x spatial resolution of HST
spectral resolution up to 120,000
2,516 m altitude in Atacama Desert, Chile
The Thirty Meter Telescope (TMT)
•
•
•
•
•
•
Area E, North Plateau, Maunakea
single mirror with 492 segments
707 m2 light collecting area
spatial resolution 0.007 arcsec @ 1μm
4,050 m altitude
spectral resolution up to 100,000
The European Extremely Large Telescope (E-ELT)
•
•
•
•
•
Budgetary approval to begin ground works
39.3 m diameter primary of 798 segments
978 m2 light collecting area
spectral resolution up to 100,000
3,060 m altitude in Atacama Desert, Chile
5
Secondary mirror
Primary
mirror
A = π r2
Optimal light collection
Cassegrain
Prism, grism, grating etc
Small, elongated or none
CCD array
The spectrograph
6
Credit: Kilkenny
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Credit: MiViM
NIR bands in astronomy (μm)
R&I
J
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N
Q
Z
0.65 – 1
1.1 – 1.4
1.5 – 1.8
2 – 2.4
3–4
4.6 – 5.0
7.5 – 14.5
17 - 25
28 - 40
7
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• spectroscope = spectrometer = spectrograph
• original and common diffraction component is prism (a la Newton or Pink Floyd)
• diffraction gratings now used, esp. Echelle type
• combo grating and prism called Grism - permits specific wavelength to pass
• spectral resolving power of disperser: R = λ (70,000 is v. good)
Δλ
• but overall spectral resolution depends on slit parameters, optics & magnification
• telescope nods on and off target, within slit to ‘zero’ telluric components (HITRAN)
• spatial and spectral data obtained simultaneously using Doppler shift
• multi-object spectrographs use optic fibre bundles feeding CCDs
• integral field spectrographs use complex combo of lenslets, fibres and processing
• tuneable laser and Raman spectrographs compare beam and energy states
• Volume Phase Holographic gratings use sandwiched gel of varying refractive index
• detector usually a CCD with physical and electronic specs matched to target λ
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CRIRES at VLTA (Credit: ESO)
NSFCAM2 at IRTF (Credit: IRTF)
Phoenix (Credit: NOAO)
FLITECAM on SOFIA (Credit: Mike Wall)
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NICMOS on HST (Credit: Astro4u.net)
WISE (Credit: NASA)
CRISM on MRO (Credit: NASA)
VIRTIS on Rosetta (Credit: ESA)
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TLS on MSL (Credit: NASA)
Gone With The Wind On Mars (Credit: Caltech)
TES on MGS (Credit: NASA)
11
• sub-atomic, atomic, and molecular species all have quantised energy states
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• moving into, and out of these states, or passage through an intervening medium,
results in discrete and specific energies being absorbed or emitted
• these transitions, energy states, or absorptions can be used as a fingerprint to
identify the target species in a spectrograph
• peaks or troughs in a spectrograph reveal the existence of target species
percentage atmospheric absorption of
various species by the Earth’s atmosphere
(Credit: Valley)
• molecules have 3N – 6 modes of vibration, where N = number of atoms
• CH4 has 9 modes, some with the same energy
12
• CH4 vibrational energies are around 1.7 μm, 2.3 μm, 3.3 μm, 6.3 μm, and 7.7 μm
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• overall instrument sensitivity is a complex area constrained by parameters
affecting the various types of resolution
• temporal resolution is a function of mission design and/or access
• spatial, spectral, and radiometric resolution are inter-related and constrained by
CCD design, software, target wavelength, SNR, optics, and structural engineering
• CCD performance depends on pixel number and size, FWC, DN, gain, software,
and SNR
• optics is affected by size, design, and engineering quality
• advanced Adaptive Optics systems minimize the distorting effects of
atmosphere and instrument movement
• these multiple parameters are optimised for a particular target species,
wavelength, and science outcome
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ν1 vibration of CH4
ν2 vibration of CH4
Only
these
two
absorb
IR light
This one has strongest line
ν3 vibration of CH4
ν4 vibration of CH4
14
Credit: UCLA
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• mid 1800s: spectroscopy of Mars begins
• 1947: Kuiper believed ‘green spots’ on Mars explained using spectroscopy
• 1957: Sinton Bands controversially thought to be CH4
• 1969: first false positive detected by Mariner 7 (actually CO 2)
• 1977: Mariner 9 detections corroborated telescopically in 1997
• 2003: Mumma et al detected large amounts CH4 with two Hawaiian telescopes
• 2004: Formisano et al (using Mars Express) and Krasnopolsky et al (using Canada-FranceHawaii Telescope) confirm Mumma detections
• 2008: Oliva and Origlia regard NIR spectroscopy as new and instruments poor
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• 2008: Encrenaz casts doubt over the detections, calls for more evidence
• 2009: Mumma et al publish data showing thousands of tons of CH 4 on Mars (see next
slide)
• 2010: Fonti & Marzo regard Mumma’s results as telluric isotopologues
• 2011: Zahnle criticises results on several grounds, calls for better science from ground and
space
• 2012: Mumma and Formisano defend their results
15
Credit: NASA (Mumma et al, 2009)
16
Problem #1
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• Martian and telluric lines
coincide, so must subtract using
HITRAN
• can use blue-shifted Martian
lines, but….
• telluric 13C form of methane is in
blue wing of telluric 12C methane
and easily confused with the blue
shifted Martian 12C methane
detection
• need instrument with greater
spectral resolution
17
Credit: Zahnle
Problem #2
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• atmospheric CH4 on Mars is well understood to need
several hundred years to dissipate chemically
• but recently detected large volumes disappear after a
few weeks
• there is no known chemistry which could oxidise or
condense out, these volumes without measurable byproducts
• methanogens would re-supply atmospheric CH4, while
consuming CO – but there is plenty of CO in the
atmosphere
18
1.
W
H
E
R
E
2.
3.
A
R
E
T
H
E
Y
?
4.
5.
6.
7.
On Earth
• Keck
• VLTA
• Gemini
• IRTF
• GMT
• TMT
• E-ELT
(3)
(2)
(2)
(6)
(2)
(4)
(1)
NIRC, NIRC2, NIRSPEC
CRIRES, ISAAC
GNIRS, Phoenix
SPeX, NSFCAM2, CSHELL, iSHELL, BASS, MIRIS
GMTNIRS, MIISE
IRIS, NIRES, WIRC, PFI
METIS
In Flight
• SOFIA
• FISTA
(1)
(1)
FLITECAM (2.7 m aperture, from stratosphere)
SAIRS (USAF - unknown resolution, security targets)
In Earth Orbit
• Akari
• ISO
• HST
• Spitzer
• WISE
• Arkyd 101
(1)
(3)
(1)
(1)
(1)
(1)
IRC/NIR
ISOCAM, ISOPHOT, SWS
NICMOS (methane 1.7 μm)
IRAC (centred on 3.6 μm)
dedicated whole sky
dedicated to asteroid observation
In Solar Orbit
• Rosetta
(1)
VIRTIS (possible Mars flyby 2015)
In L2 Orbit
• JWST
(3)
NIRCam, NIRSpec, NIRISS
In Mars Orbit
• MGS
• Mars Express
• MRO
• MAVEN
• ExoMars
(1)
(2)
(1)
(1)
(2)
TES (above 6 μm)
OMEGA, PFS
CRISM (100 mm aperture)
NGIMS
MicrOmega, Raman Spectrometer
On Mars
• MSL
(1)
• GOne with the Wind ON Mars
• Biological Oxidant and Life Detection
completed
existing
proposed
TLS (ppt sensitivity)
GOWON
multiple Moballs distributed by wind
BOLD
multiple detectors dropped to surface 19
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Field
(arcseconds)
Spectral Res.
(R)
Spatial Res.
(arcsec/pixel)
Instrument
Location
Wavelength (μm)
CCD
NIRC2
Hawaii
0.9 – 5.3
1024 x 1024
NIRSPEC
Hawaii
0.95 – 5.5
1024 x 1024
25,000
CRIRES
Chile
0.92 – 5.2
1024 x 1024
100,000
0.086
ISAAC
Chile
2.5 – 5.0
1024 x 1024
10,000
0.071
GNIRS
Hawaii
0.9 – 5.5
1024 x 1024
18,000
Phoenix
Arizona
1.0 – 5.0
1024 x 1024
70,000
SPeX
Hawaii
2.3 – 5.5
1024 x 1024
30 x 30
2,000
0.12
NSFCAM2
Hawaii
1.0 – 5.5
2048 x 2048
80 x 80
low
0.04
CSHELL
Hawaii
1.08 – 5.5
256 x 256
30 x 30
40,000
0.2
iSHELL
Hawaii
1.15 – 5.4
2048 x 2048
30 x 30
67,000
0.06
BASS
Hawaii/SOFIA
2.9 – 13.5
2 x 58
MIRIS
USA/SOFIA
3.0 – 5.5
FLITECAM
SOFIA
3.0 – 5.5
2048 x 2048
SAIRS
USAF
1.3 – 5.0
12 bit
NICMOS
Earth orbit
0.8 – 2.5
256 x 256
IRAC
Earth orbit
3.6
256 x 256
WISE
Earth orbit
3.4
1024 x 1024
OMEGA
Mars orbit
1.0 – 5.2
13 – 20 nm
PFS
Mars orbit
1.2 – 5.0
8,000
CRISM
Mars orbit
1.0 – 3.92
TLS
On Mars
3.27
GMTNIRS
Chile
1.0 – 5.0
2048 x 2048
2x2
120,000
0.2 – 0.3 @ 0.5 μm
MIISE
Chile
3.0 – 5.0
2048 x 2048
120 x 120
2,000
0.2 – 0.3 @ 0.5 μm
IRIS
Hawaii
1.7 and 2.3
4096 x 4096
17 x 17
NIRES
Hawaii
1.0 – 5.0
4096 x 4096
PFI
Hawaii
1.0 – 4.0
4096 x 4096
WIRC
Hawaii
0.6 – 5.0
4096 x 4096
METIS
Chile
3.0 – 5.3
highest (?)
70 x 70
120
0.02 μm
1.0 mrad
moderate
?
?
?
200/pixel
6.0
300m
18 m/pixel
ppt
0.007 @ 1 μm
100,000
0.004
2x2
100
0.007 @ 1 μm
30 x 30
100
0.007 @ 1 μm
0.4 x 1.5
100,000
0.001 –20
0.65
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Giant Magellan Telescope Near InfraRed
Spectrometer (GMTNIRS)
• 1 – 3 μm channel (R = 100,000)
• 3 – 5 μm channel (R = 120,000)
• narrow field of 2 arcseconds
• 2048 x 2048 pixel CCD
• will detect three CH4 lines (1.7, 2.3 & 3.3 μm)
Mid-IR Imaging Spectrograph (MIISE)
• one channel in 3 – 5 μm range
• R = 2,000
• large field of 2 arcminutes
21
Credit: GMTO
Infra Red Imaging Spectrograph (IRIS)
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•
•
•
•
•
integral field with multiplexed fibre optics
detect 1.7 μm and 2.3 μm lines
4096 x 4096 pixel CCD
17 arcsecond field of view
spatial resolution 10x HST
Planetary Formation Instrument (PFI)
Near Infra Red Echelle Spectrometer
(NIRES)
•
•
•
•
•
conventional Echelle spectrometer
1 – 2.5 μm channel
2.9 – 5.0 μm channel
spectral resolution up to 100,000
spatial resolution to 4 milliarcseconds
Wide Field Adaptive Optics Imager
(WIRC)
?
•
•
•
•
designed for exoplanet atmospheres
1 – 4 μm range
low spectral resolution around 100
2 arcseconds field of view
•
•
•
•
if built, will have:
30 arcsecond field of view
low spectral resolution around 100
0.6 – 5 μm range
22
Credit: TMTO
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Mid InfraRed Imager and Spectrograph (METIS)
Credit: ESO
• 3 – 5.3 μm range
• high spectral resolution up to 100,000
• field of view 0.4 x 1.5 arcseconds
• laser guide star for telluric subtraction
23
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• The range of capabilities of NIR instruments at other terrestrial, and off-Earth,
locations is large and powerful and offers great opportunities to further the study
of Martian methane
• NIRC2, CRIRES and iSHELL will doubtless contribute high spatial and
spectral resolution results in the near future
• FLITECAM shows particular promise with relatively cost-effective, high
sensitivity observations from above the Earth’s atmosphere
• Notwithstanding highly advanced equipment being readied, or currently
enroute to Mars, existing spacecraft have valuable contributions to make
• Mars Express and MRO instruments will provide time-dependent detections
which will further the cause greatly
• Curiosity Rover will hopefully provide ppt on-Mars data points
• Space/Mars-borne missions suffer the usual constraints of any launched
mission with a payload – efficacy versus cost. However, the particular
advantages of their location complements Earth-based facilities.
24
• over 40 (past, present & future) NIR instruments capable of detecting 3.3 μm CH4
• design and specifications vary widely wrt location, science and operation
C
O
N
C
L
U
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I
O
N
S
• comparisons very difficult, esp. wrt radiometric resolution
• main constraint is signal-to-noise-ratio, which has many contributing factors
• ground-based instruments can/will rival space-based for spatial resolution
• ground-based instruments have better spectral resolution
• ground-based instruments have good opportunity for synoptic observations
• all 3 ELTs will have twice spectral resolution of current best instruments
• all 3 ELTs will have spatial resolution of a few mas - better than Mars spacecraft
• telluric subtraction is still problematic
• access time for Mars science on big scopes is an issue
• existing on-ground & in-flight instruments are complimented by Mars missions
25
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• that a more thorough, and exhaustive investigation be carried out
into the specific capabilities of all existing NIR instruments with
respect to their detection of methane on Mars
• that datasets from previous missions and facilities be mined for
intrinsic or corroborating detections of Martian methane, at all of it’s
vibrational frequencies
• that the Martian atmosphere science cases for the three ELTs be
given strong support
• that collaboration networks between telescope projects, and Mars
mission teams, be strongly encouraged
26
A
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N
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W
L
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D
G
E
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T
S
• Res. Assoc. Prof. Dr Scott Madry, University of North Carolina
• Assoc. Prof. Dr David Bruce, University of South Australia
• Dr Jonathan Clarke, Geoscience Australia and Australian Centre for Astrobiology
•
•
•
•
•
•
•
•
•
•
•
Dr Máté Ádámkovics, Post Doctoral researcher, University of California, Berkeley
Assoc. Prof. Dr Jeremy Bailey, University of New South Wales
Assoc. Prof. Dr Bernard Brandl, Leiden University, The Netherlands
Prof. Dr Gary Da Costa, Australian National University
Dr Chis Flynn, Swinburne University, Victoria
Dr Hans-Ulrich Kaufl, European Southern Observatory, Chile
Dr Michael Kueppers, Rosetta Science Operations, ESA Directorate of Science
Joshua Nelson, Mars Desert Research Station, Utah
Dr Stuart Ryder, Australian Gemini Scientist, Australian Astronomical Observatory
Dr Michael Smith, NASA Goddard Space Flight Center
Prof. Dr Chris Tinney, University of New South Wales
thanks
27
• Encrenaz, T. 2008. Search for methane on Mars: Observations, interpretation and future work. Advances in Space Research, 42, (1), p.
1-5.
• Fonti, S., & Marzo, G. 2010. Mapping the Methane on Mars. Astronomy and Astrophysics, 512, A51. DOI: 10.1051/0004-6361/200913178
• Formisano, V., Atreya, S., Encrenaz, T., Ignatiev, N., & Giuranna, M. 2004. Detection of Methane in the Atmosphere of Mars. Science,
306, 1758.
R
E
F
E
R
E
N
C
E
S
• Kilkennyweb, 2012. South African National Astrophysics and Space Science Program website [online]. Available from:
<http://www.star.ac.za/course-resources/local/david-buckley/spec1.pdf> [Accessed 12th March, 2012].
• Krasnopolsky, V. A., Bjoraker, G. L., Mumma, M. J., & Jennings, D. E., 1997. High-resolution spectroscopy of Mars at 3.7 and 8μm: A
sensitive search of <formula>H2O2, <formula>H2CO, HCl, and <formula>CH4, and detection of HDO. Journal of Geophysical Research,
102(E3), pp. 6525-6534.
• Kuiper, G. P., Wilson, W., & Cashman, R. J., 1947. An infrared stellar spectrometer. Astronomical Journal, 52, p. 154.
• Mumma, M. J., Novak, R. E., DiSanti, M. A., & Bonev, B. P., 2003. A Sensitive Search for Methane on Mars. Bulletin of the American
Astronomical Society, 35, p.937.
• Mumma, M. J., Villanueva, G. L., Novak, R. E., Hewagama, T., Bonev, B. P., DiSanti, M. A., Mandell, A. M., & Smith, M. D. 2009, Strong
Release of Methane on Mars in Northern Summer 2003. Science, 323, pp 1041-1054.
• Oliva, E. & Origlia, L., 2008. High-resolution near-IR spectroscopy: from 4m to 40m class telescopes. In: I. S. McLean: M. M. Casali, ed.
Proc. SPIE Ground-based and Airborne Instrumentation for Astronomy II, Vol 7014.
• Sinton, W. M. 1957. Spectroscopic evidence of vegetation on Mars. Astrophysical Journal, 126, 231.
• Zahnle, K., Freedman, R. S., & Catling, D. C. 2011. Is there Methane on Mars? Icarus, 212 (2), pp 493-503.
• Giant Magellan Telescope website
http://www.gmto.org/
• Thirty Meter Telescope website
http://www.tmt.org/
• European Extremely Large Telescope website
http://www.eso.org/public/teles-instr/e-elt.html
28
18 METRES
FLIGHT
DECK
CABIN
MESS/GALLEY
CABIN
AIR LOCK
LAB
EXIT
STAIRS
-
2
3
-
-
REMOVABLE TRUCK
PIN FRAME
SECTION 1
STORE
GALLEY
BEDROOM 7
BEDROOM 6
BEDROOM 5
STAIRS
4530
FLOOR WIDTH
WATER
TANK
FLIGHT
DECK
LADDER
WATER
TANK
DINING
TABLE
LOUNGE
AREA
2100
SWITCHBOARD
FLIGHT DECK
SEATS
STORE
BEDROOM BEDROOM BEDROOM
4
3
2
BEDROOM
1
STAIRS
EXERCISE
AREA
HEALTH
CENTRE
2100
ELEVATION
1
SECTION 2
FIRE ESCAPE
AIR
CON
AIR DUCT
WORK DESK
STAIRS
WASH
EXERCISE
EVA SUIT
BASIN
AREA
STORAGE
TOILET
SHOWER
AIRLOCK
EXIT
STAIR
LADDER
WASH
BASIN
AIR
CON
MAIN DOOR
LAB
WORK DESK
HEALTH
CENTRE
TOILET
AIR DUCT
WASHER & SUIT CLEAN UP &
SURFACE EQUIPMENT DOUBLE DOOR HATCH
DRYER
AND COLLAR
5500
UPPER FLOOR PLAN
1950
FLOOR WIDTH
Q
U
E
S
T
I
O
N
S
WET
EXERCISE
ROOM
AREA &
MEDICAL CENTRE
LADDER
AIRLOCK
CABIN
DETACHABLE LEG
SECTION 3
LOWER FLOOR PLAN
29