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

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.

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.

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

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

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

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

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

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

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

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.

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

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 106.7 nm 　Pink: He 58.4 nm Red: 0-order 25mm x 25mm x 62.5mm　 < 105 g w/o Pulse Laser

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

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.

Optical design of Telescope FOV: φ10mm Spectral range: 360-1064nm

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

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