Perseverance’s Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) Investigation

The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is an arm-mounted instrument on NASA’s Perseverance rover. SHERLOC has two primary boresights, the Spectroscopy boresight generates spatially resolved chemical maps using fluorescence and Raman spectroscopy coupled to microscopic images (10.1 microns/pixel) and the second boresight is a Wide Angle Topographic Sensor for Operations and eNgineering (WATSON); a reflight of the MAHLI camera on Mars Science Laboratory (MSL) which obtains color imaging from microscopic scales (~13 micron/pixel) to infinity. SHERLOC Spectroscopy focuses a deep UV, 248.6 nm, Neon-Copper, 40 µs pulsed laser source to a ~100 micron spot onto a target at a working distance of ~48 mm. Fluorescence emissions from organics and Raman scattered photons from organics and minerals are spectrally resolved with a single diffractive grating spectrograph with a spectral range from 250 to ~370 nm. Since the fluorescence and Raman regions are naturally separated with deep UV excitation (<250 nm), the Raman region ~ 800 – 4000 cm-1 (250 to 273 nm) and the fluorescence region (274 to ~370 nm) are acquired simultaneously without time gating or additional mechanisms. SHERLOC science is enabled using an Autofocus Context Imager (ACI) to obtain focus and acquire 10.1 micron/pixel greyscale images. Chemical maps of organic and mineral signatures are enabled using an internal scanning mirror that moves the focused laser spot across the target surface. The high resolution images, and the <100 micron chemical maps will enable the first in situ view of the distribution and interaction between organics, minerals, and chemicals to assess potential biogenicity. Single arm placement chemical maps can be up to 7x7 mm in area and with the < 10 min acquisition time per map, larger mosaics are possible with arm movements. This microscopic view of the organic geochemistry of a sample at the Perseverance landing site, when combined with the other instruments, such as Mastcam-Z, PIXL and SuperCam, will enable unprecedented analysis of surface targets for both scientific research and for identifying samples that should be cached for sample return.