Perseverance's SuperCam detects chromium-in-corundum luminescence in a light-toned rock at Jezero crater
SuperCam recorded narrow luminescence peaks at 692.7 and 694.1 nm from chromium in corundum, a mineral not expected on a planet without plate tectonics.
The SuperCam instrument on the Perseverance rover recorded strong, narrow luminescence peaks at 692.7 and 694.1 nanometers when its laser hit a light-colored rock near the rim of Jezero crater. This is described in a post by SuperCam principal investigator Roger C. Wiens of Purdue University, published by NASA science.nasa.gov
NASAscience.nasa.govOpen source ↗. The emission comes from chromium atoms in a corundum mineral structure. The gemstone form of chromium-bearing corundum is ruby, but no collectable rubies have been found on Mars yet.
How SuperCam sees luminescence
SuperCam, SHERLOC and PIXL detect minerals with several techniques, including X-ray fluorescence, Raman and infrared spectroscopies. Because of the way SuperCam performs its Raman spectroscopy, it can also study time-resolved luminescence. Luminescence normally spreads over a broad wavelength range, so the team was startled by such narrow peaks about two years before the post.
The peaks come from delayed atomic transitions in chromium. SuperCam can time the delay through the resulting photons, which let the team verify that the emission came from chromium in corundum. The results were published in Geophysical Research Letters by a team led by Ann Ollila. Before SuperCam was installed on the rover, the team placed a ruby in the laser beam, and the whole room pulsed a bright red.
Corundum and impact metamorphism
Corundum is a metamorphic and pegmatitic mineral. It would not be expected on Mars, a planet that lacks plate tectonics science.nasa.gov
NASAscience.nasa.govOpen source ↗. Large meteor and asteroid impacts, however, can cause local metamorphism through long-term heating from the impact.
Perseverance is working in a very ancient terrain near the Jezero rim, so some evidence of localized metamorphism can be expected, according to Wiens. Early in the mission the team used the technique only rarely. Lately it has carried out time-resolved luminescence observations frequently on light-toned rocks to look for more evidence of impact effects. The small corundum crystals are helping the team learn more about the past of Mars.
