1. In-situ K-Ar dating using LIBS in the VUV range
Shingo Kameda1, Yuichiro Cho2,
Yasuhito Sekine2, Seiji Sugita2
1 Rikkyo University, 2 The University of Tokyo

2. K–Ar dating Rock: Ar degassing occurs before solidified
40Ca Ca Ca
β ~90%
40K
40K/K ~10-4
40Ar
Half-life
~1.8 By
EC ~10%
Rock:
Ar degassing occurs before solidified
The dominant source of 40Ar is 40K decay.
Ca is abundant  Difficulty to estimate the amount of 40K originated Ca.

3. K–Ar dating
Ice:
K has a high solubility in water
Ar degassing also occurs before frozen.
The dominant source of 40Ar in ice should be also 40K decay.
・Possibility of K-Ar dating on Europa [Swindle et al., 2005]
Europa’s surface: tens of My.
Ganymede’s surface: hundreds of My.

4. LIBS: Laser Induced Breakdown Spectroscopy
Optical elemental analysis technique
Ablation: a high intensity pulse laser
Pulse laser
Ablation

5. LIBS: Laser Induced Breakdown Spectroscopy
Optical elemental analysis technique
Ablation: a high intensity pulse laser
Plasma emission spectroscopy: spectrometer
Spectrometer
Plasma emission

6. K-Ar dating using LIBS (MSL/ChemCam)
LIBS in UV-Vis-IR range
K emission lines: 767nm, 770nm
MSL/Chemcam NASA

7. K-Ar dating using LIBS (MSL)
LIBS in UV-Vis-IR range
K emission lines: 767nm, 770nm Ar
・Vacuum chamber and mass spectrometer
Measuring the mass of the sample and the amount of outgassing Ar with heating.
target
Spectrometer
Pulse Laser

8. K-Ar dating using LIBS (MSL)
LIBS in UV-Vis-IR range
K emission lines: 767nm, 770nm Ar
Vacuum chamber, mass spectrometer,…
Measuring the mass of the sample and the amount of outgassing Ar with heating.
robotic
arm
Spectrometer
Vacuum
Chamber
Q Mass
Pulse Laser

9. Determination of quantity of Ar using LIBS
New idea to observe Ar emission line.
Ar emission lines: 104.8nm and 106.7nm
・ Vacuum chamber is not necessary on the airless body.  Less mass
robotic
target
arm
Spectrometer
Vacuum
Chamber
Q Mass
Pulse Laser

10. Determination of quantity of Ar using LIBS
New idea to observe Ar emission line.
Ar emission lines: 104.8nm and 106.7nm
・ Vacuum chamber is not necessary on the airless body.  Less mass
・Remote Sensing (1m TBC)
No experiment for Ar in rocks yet.
(LIBS experiment for Ar atmosphere was performed.)
target
Spectrometer
Pulse Laser

11. Determination of quantity of Ar using LIBS
MCP with Phosphor
Grating
Sample
Nd:YAG
K-feldspar
(Age and composition are unknown..)
Ar Lamp
Rikkyo Univ.

12. Preliminary result K-feldspar Still in preparation.
←Spectrum of Ar Lamp
FWHM is 0.3 nm.
Preliminary result
K-feldspar

13. Optical Design 25mm x 25mm x 62.5mm  < 105 g w/o Pulse Laser
Toroidal grating
4800gr/mm
Banpass filter for K
~767nm
62.5mm
100mm
Detector
MCP+multi anord Or
MCP+Phosphor+CCD
25mm
Blue: Ar nm 　Pink: He 58.4 nm
Red: 0-order
25mm x 25mm x 62.5mm　 < 105 g w/o Pulse Laser

14. Ganymede Lander & Orbiter (JUICE)
Lander: In-situ K-Ar
Absolute age
One point
JUICE: Crater-count
Global Map
Relative age
Complementary
NASA

15. Another activity on LIBS SELENE-2 (Lunar Rover, ‘Pre’-Project)
ChemCam-like LIBS is too big (9-11kg) to install on the gimbal on the mast unit of the SELENE-2 rover.Install LIB-S2 on the body to reduce the total mass. (Fiber becomes unnecessary.)3.5 kg
Closer to the ground Distance range can be reduced.

16. Optical design of Telescope
FOV: φ10mm Spectral range: nm

17. Interface point (Optics)
Spain Dr. F. Rull
France
Dr. O. Ganault
Dr. S. Maurice
Install Visible LD in Japan on the base plate.
Align Laser & Spectrograph with Vis. LD in France & Spain.
Fix them on the B/P.
Movement
Movable telescope
Automatic focus adjustment

18. Specification Distance: 1.0 – 1.5 m Spectral range: 360 – 1064 nm
Laser intensity: ~10 mJ/pulse
(Nd:KGW, almost the same as ChemCam)
Laser spot diameter: < 300 um
FOV: φ10mm at the target plane
Spatial resolution of
the imager: 30um/pix
Scanning gap: ~300um
Mass: 3.52kg
Power: 7W(max)
3 movement systems:
#1 wide-range vertical movement,
#2 short-range horizontal scanning,
#3 focus adjustment