A state-of-the-art Thales laser is performing a vital function onboard NASA’s Mars Perseverance rover. Melissa Bradshaw reports
On 18 February 2021, the world watched with fascination as NASA’s Perseverance Rover landed successfully on the surface of Mars following its launch in July 2020 from Cape Canaveral Air Force Station in Florida. Captured by the rover’s onboard cameras (of which there are 23 in total) making its descent to the 28 mile wide Jezero Crater, located just north of the Martian equator in the Isidis Planitia region, Perseverance is now on a mission to explore the site for the next two years seeking signs of previous microbial life.
Earlier studies have provided scientists with evidence that the area was once filled with water, home to an ancient river delta believed to have long ago been a habitable environment. By analysing samples of rock and soil in the exploration site that are more than three billion years old, scientists will aim to delve deeper into whether life really did exist at some point on the Red Planet — and what that may have looked like.
Instrumental to the Mars 2020 mission, and to the 7ft tall 1,025kg Perseverance rover, is the SuperCam. One of seven instruments onboard, the system has been described as the ‘eyes of the rover’. Featuring a combination of advanced technologies, its development has involved close collaboration between Los Alamos National Laboratory (LANL) in the US and the IRAP astrophysics and planetology research institute in France, alongside contributions from the universities of Hawaii and Valladolid, Spain.
SuperCam is being used to provide imaging, chemical composition analysis and mineralogy at a distance of up to 20 feet away. This is being achieved through use of a high-power laser, designed and developed by a team of experts from aerospace and defence tech giant Thales, led by the group’s managing director of laser solutions, Franck Leibreich.
The laser for the SuperCam instrument was developed through a partnership between Thales’ team in Paris and CNES, the National Centre for Space Studies based in Toulouse, France. It forms part of the device’s ‘Mast Unit’, located at the top of the rover’s mast.
Thales’ partnership with CNES is a long-standing one — the laser developed for SuperCam has joined another Thales laser on Mars, which has been up and running since the launch of the Curiosity rover in August 2012. This laser formed part of the ChemCam instrument, which has already fired more than 855,000 shots onboard Curiosity over the last nine years, helping to provide crucial information about the signs of previous life on Mars.
Thales began work on the SuperCam project with CNES in 2013 to develop a more advanced and powerful laser which would aim to take the exploration to the next level.
“We were working very closely with them since the beginning, and we had everything designed and tested as it was required by the specification of CNES and the rover itself,” Leibreich said. “The main difference between the ChemCam and the SuperCam was that ChemCam was designed to use only one wavelength — a red wavelength, used for LIBS (Laser Induced Breakdown Spectroscopy).”
Leibreich explained that the LIBS process works by launching the infrared laser beam at a distance to create a plasma on the rocks, which excites the atoms. When the atoms break down to a stable state they emit photons, and with a telescope the light from the rocks can be analysed for presence of spectral signatures of different components like carbons and nitrogens.
“This [aimed] to understand if it was at one point habitable,” Leibreich said, explaining the importance of the LIBS process in discovering that ancient Mars could once have supported microbial life. “What CNES asked us to do was to go one step further and in the same volume, and the same weight, we were tasked to include two lasers in one. Two wavelengths, one red micro beam, and a visible green one which would be used to do Raman spectroscopy.”
Raman spectroscopy gives a better idea of the presence of links between different atoms, Leibreich added, allowing for presence of molecules which are representative of traces of life to be detected. The process is a technique of spectroscopic analysis, involving the use of scattered light to provide structural and chemical information of a substance. The green laser beam excites the chemical bonds in samples, and produces a different signal according to their various linked components. It will also be used to induce fluorescence in mineral and organic compounds.
“We couldn’t afford extra weight, so we had to reduce the size of the red laser by 30 per cent,” Leibreich said, highlighting some of the challenges in upgrading the laser from that of the ChemCam. Optics and electronics were used to keep the green and red lasers easily interchangeable on the same axis, and thermal shock testing was conducted to ensure that the laser could survive both the rocket launch and landing. All components of the lasers were selected carefully to provide the range of temperatures that were needed.
It is the first time that Raman spectroscopy has been demonstrated on Mars, and as of Tuesday 23 March, Leibreich confirmed that the process had been tested and was running smoothly as part of the instrument with around 620 shots of the lasers already achieved.
The goal now is for the rover to select some rock and sediment samples from Mars and store them in its sample caching system, before later depositing them in a location where they can be retrieved by a Mars Sample Return mission and eventually brought back down to Earth. By using SuperCam and its lasers, more precise selections are able to be made based on which rocks will be most interesting and suitable for further analysis.
SuperCam also includes a microphone, which is able to record the sounds of the laser hitting its targets as well as of the wind. Sound clips from the instrument have been made available to listen to via YouTube alongside sound captured from another microphone onboard affixed to the side of the rover, which was able to capture the sounds of the rover landing for the first time.
In addition to allowing for a better understanding of the geology and climate of Mars, the mission will allow us to know more about planet Earth and aims to eventually arm astronauts with the knowledge and technologies required for human exploration of the Red Planet.
The Properties of Perseverance
In addition to the SuperCam, there are six other key instruments onboard the Perseverance rover, each with their own important role to play. These are:
- MastCam-Z: an advanced camera system with panoramic and stereoscopic imaging and zoom capabilities
- Planetary Instrument for X-Ray Lithochemistry (PIXL): an X-Ray fluorescence spectrometer and high-res imager to map fine-scale elemental composition of Martian surface materials
- Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals (SHERLOC): a spectrometer that uses a UV laser to map mineralogy and organic compounds, includes a high-res colour camera for microscopic imaging
- The Mars Oxygen In-Situ Resource Utilisation Experiment (MOXIE): a technology demonstration to provide oxygen from Martian atmospheric CO2
- Mars Environmental Dynamics Analyser (MEDA): a set of sensors that will provide measurements of temperature, wind speed and direction, pressure, relative humidity and dust size and shape
- The Radar Imager for Mars’ Subsurface Experiment (RIMFAX): a ground-penetrating radar to provide centimetre-scale resolution of the subsurface’s geologic structure