SuperCam sits on the top of the mast of NASA’s Perseverance rover, which landed on the surface of Mars on Feb. 18, At a news conference on March 10, SuperCam scientists and engineers reported on the first data from the instrument. Photo Courtesy NASA/JPL-Caltech
BY MAIRE O’NEILL
The SuperCam instrument on the Perseverance rover in the Jezero Crater on the planet Mars continues to instill excitement around the world as evidenced by last week’s international press conference hosted by the French National Centre for Space Studies (CNES) featuring members of the SuperCam operations teams in France and at Los Alamos National Laboratory.
Clearly delighted with the work of the SuperCam to date, LANL’s SuperCam Principal investigator Roger Wiens talked about the instrument’s initial exploration of the Jezero Crater. Wiens noted that SuperCam is a geological observatory on the mast of the rover.
“We usually think of observatories as telescopes that study the stars. SuperChem trains its 108 mm diameter telescopes on rocks and soils near the rover, using a laser for interrogation in some cases to study their composition. SuperCam uses three optical spectroscopy techniques that a camera and a microphone to determine the surface texture, the chemistry, the mineralogy and the physical properties of the rocks around Jezero Crater. We’re looking for a time when water was abundant on the Red Planet and when life may have developed there,” he said.
The operations team will also be supporting the sample caching of the rover with SuperCam, which will help find the most relevant samples for collection and will document comprehensively their geological setting.
“We designed this instrument as a greatly augmented version of the ChemCam instrument that is on the Curiosity rover. ChemCam used a pulse laser projected through its telescope to oblate small amounts of rock or soil up to 7 meters or 25 feet away from the rover. This material, which is at high energy, creates a ball of plasma – it’s bright – and that allows us to see the atomic emission from the elements that are present in the rock and that reveals its chemistry,” Wiens said.
He added that the nice thing about this technique on Mars is that the shockwave from the laser blows the dust off the rock which really helps on a dusty planet.
“ChemCam also has the highest resolution remote imager on the Curiosity rover, so like ChemCam, SuperCam uses the same laser chemistry and also a color micro-imager which we started using on Day 4 of the mission,” Wiens said. “The images we’ve taken reveal that its resolution is really impressive. It’s able to see a human hair from eye level to the ground. It’s also able to look at long distances. For example it could spot a soccer ball from a mile away.”
Of course those objects don’t exist on Mars, Wiens said, as he showed several Remote Micron-Imager (RMI) images of SuperCam’s calibration targets on the back of the rover.
“SuperCam’s RMI has a characteristic spyglass round field of view which makes you know that it’s from a telescope with high magnification. We can see specks of dust on the target that are four-thousandths of an inch or 100 microns in diameter. The imager is normally used to provide the context for our spectral observations,” he said.
Wiens noted that SuperCam’s chemical spectrum, which is generated by an infrared laser, is very similar to ChemCam’s and the optical resolution is just slightly better in some spectral regions than its predecessor.
“The laser spot is a little bit smaller too – about one-hundredth of an inch – on the target. On Day 12 of the mission, we tested it on the first named target of Perseverance’s mission. We named this rock after the Navajo word for the planet Mars – Máaz. We are using these Navajo names and we’re proud of it and that’s because the rover is in a quadrangle named Canyon de Chelly after the national monument on Navajo tribal lands in Arizona,” he said.
Wiens said SuperCam’s target analysis revealed that the target Máaz is basaltic in composition.
“The basalt refers to an igneous rock type that is common on earth in the mid-ocean or ocean regions and in some places on earth’s continents. Basalts are also common on Mars and we don’t know yet if this rock is igneous (volcanic) or perhaps if it is sedimentary rock made up of igneous grains that were washed downriver into Jezero Lake and cemented together. So we’ll have to use more of our techniques and study the surrounding area to understand those details some more. We’ll be doing that in the near future,”
Also presenting during the press conference was LANL Scientist Ann Ollila who explained that beyond chemistry, SuperCam will provide information on mineralogy, which refers to the way that atoms are organized in a crystalline structure.
“This information is critical for planetary scientists because the structure tells us about the processes that led to the formation and evolution of the geological formations we see in Jezero Crater today,” she said.
Ollila said to do this, SuperCam used two techniques – Raman and VISIR spectroscopy.
“Raman is a technique that’s based on a scattering phenomenon that occurs when a laser interacts with a sample. A small fraction of the laser light will actually change its energy after interacting with the target. You can think of it as a change in color. The extent of these energy changes reflects the energies of the vibration between bonded atoms inside the host mineral structure. The Raman signal is weak and the SuperCam team had to overcome numerous challenges in terms of designing an instrument that can detect these subtle changes at distance,” she said.
SuperCam has checked the performance of the Raman system by collecting the first extraterrestrial Raman spectrum which is a spectrum of the diamond calibration target, Ollila said. The short peak is due to the vibrations of carbon atoms in the diamond structure. The continuous background is due to fluorescence of the glue used to affix the diamond to the target holder. Organics on Mars may be also detected in the same type of fluorescence, Ollila said.
“The second type of mineralogy technique used by SuperCam is called visible and infrared reflectance (VISIR) spectroscopy. Here the reflection of the sunlight on a sample is analyzed by a spectrometer. When reflected, the spectrum of the sunlight is altered slightly as some energies are absorbed by molecular vibrations in the sample. This provides some information on the bonds between atoms in the sample as well as on the atmosphere that it passes through,” she said.
Ollila noted that VISIR spectroscopy has been used on Mars for a long time, for example on the CHRISM instrument on NASA’s Mars Reconnaissance orbiter as well as by the European Omega instrument on Mars Express.
“These are orbital instruments that have provided global information on the mineralogical composition of the Mars surface. SuperCam is working at a much higher spatial resolution as it analyzes individual rocks on the surface. SuperCam has already collected its first infrared spectrum on the surface of Mars,” she said.
Ollila said the raw data contains a strong contribution from the carbon dioxide rich atmosphere.
“After preliminary processing and correction of this atmosphere contribution, we observed some features that are related to the minerals in the target, which are currently being investigated,” she said.
She noted that SuperCam’s Raman and VISIR techniques are working very well and it is be;oeved that the two techniques will be useful for detecting minerals like carbonates, phosphates and silicates and maybe some organic compounds in the Martian surface.
“This information will be key to understanding the geologic history of Jezero Crater and potentially to help identify possible traces of past life. These techniques will also be used to study the atmosphere of Mars,” Ollila said.
Institut Supérieurde l’Aéronautique et de l’Espace Professor Naomi Murdoch spoke about the SuperCam’s space-qualified Martian microphone for completing laser measurements.
“Using its microphone, the SuperCam team has recorded for the first time, the sounds of Mars. The main scientific goal of the SuperCam microphone is to support the laser-induced breakdown spectroscopy (LIBS) investigation by giving unique measurements of physical properties of Martian rocks and soils. The other part to the SuperCam instrument that you just heard about gives really important information about both the chemical and mineralogical composition of the targets,” Murdoch said. “Our microphone will complement these measurements by listening to the amplitude of the acoustic sound produced during the laser shots.”
She said this is a very important technique in order to determine the hardness of the samples.
“For example, if we tap on a surface that is hard, we will not hear the same sound as if we fire on a surface that is soft. Take for example, chalk and marble. These two materials have an identical chemical composition but very different physical properties. By listening with our microphone when we fire with the laser we are going to be able to distinguish between these two, otherwise identical targets,” Murdoch said.
What’s so special about a microphone on Mars? Murdoch said, first of all, on the surface of Mars there is very low atmospheric pressure – 150 times lower than on earth.
“In addition the atmosphere is made up of carbon dioxide and these two factors together mean that sound doesn’t propagate in the same way on the surface of Mars as it does on earth. What this means is that two people standing several meters apart on Mars will actually have a hard time hearing each other,” she said. “For that reason the SuperCam microphone is particularly sensitive and this allows us to record sounds despite the strong attenuation in the Martian atmosphere.”
In addition the microphone can resist the low temperatures and the high levels of radiation.
“We will be recording the LIB signs but we can also do atmospheric science and we can listen to the sounds coming from the rover itself, from other instruments or when we’re driving or even during drilling operations,” Murdoch said.
Over the years many wonderful images have been received from the surface of Mars, but until the Perseverance mission, had never been heard.
“Now, thanks to the SuperCam microphone, we have been able to record for the first time sounds from the planet Mars. During our very first day on Mars, we turned on the microphone – the sound was a little bit muffled because the mast was still stowed but could still hear the sounds of the wind,” she said. “The second recording was with mast deployed.”
Murdoch said the recordings are fascinating in themselves but they also allow the team to do atmospheric science.
“We can listen to them, we can determine the wind speed, the wind direction and even study the turbulence in the Martian atmosphere. In fact, the measurements we are making are at a frequency range higher than any other meteorological instruments from about 50 Hz to 10 kHz. This means that we are actually accessing regimes of Martian atmospheric science that until now have never been explored,” she said. “These sounds are exactly as you would hear them with your own ears if you were standing on the surface of the planet.”
Murdoch said the recordings of the laser shots on Mars demonstrate not only that the microphone is functioning well but that there is a very high quality signal.
“In the SuperCam team, we’re extremely excited about the prospectus and the science investigations we’re going to be able to do with the microphone data,” she said.
SuperCam Instrument Manager Scott Robinson said a great instrument comes with great challenges, and that to succeed, above all else it requires a team of dedicated engineers such as he has had the privilege to lead.
“SuperCam was developed by an international consortium just like ChemCam was 15 years ago. In the U.S., Los Alamos National Laboratory in New Mexico leads the effort. In France, under the authority of the French Space Agency CNES, numerous laboratories, universities and research institutes were involved. Altogether more than 500 people contributed to this instrument,” he said.
Robinson noted that SuperCam is made up of three parts and that the mast unit with the laser, telescope camera, microphone, infrared spectrometer and control electronics are French, assembled in Toulouse. The body unit with three spectrometers and the main control electronics was built in Los Alamos. The calibration targets were assembled in Spain with targets contributed by France, Denmark, Canada and the U.S.
“SuperCam’s multiple techniques represent extraordinary advances in technology. It encompasses more than 60 optical pieces integrated in subsystems such as lasers and spectrometers. In the body unit, for instance, we have a high-transmission spectrometer incorporating an image intensifier similar to what’s used in night vision goggles. This allows us to detect the very few photons that arrive at the modulated wavelengths to reveal the targets’ mineral structure with Raman spectroscopy. In the mast unit, the infrared spectrometer uses radiofrequency stimulation of a crystal to bend the light one wavelength at a time to determine the infrared color spectrum,” he said.
Robinson said that in proposing the SuperCam instrument to NASA back in 2014, engineers were worried that they were being way too ambitious.
“We are grateful to NASA for accepting our challenge. One of the roughest challenges along the way was when the mast unit optics were destroyed in a freak accident just four months before delivery,” he said. He went on to describe how the team scrambled to pull together spare parts to rebuild the telescope from scratch, working days, nights and weekends.
“In the process, we discovered a Hubble-like flaw in the original mirror which we were able to correct. As the results show, we have made our delivery date with an even better instrument than we had originally,” Robinson said.
Now that Perseverance has landed on Mars, SuperCam is operated jointly with operation centers in Toulouse and Los Alamos.
“We have been trading off operational responsibilities every two or three days in the early part of the mission with plans to go to operations of every other week later in the month. SuperCam has required unusually close collaborations across international boundaries and this collaboration has been a very enriching experience,” Robinson said. SuperCam represents a pinnacle of achievement in remote-sensing technology. We are excited to use it in NASA’s greatest challenge on Mars. Representing the engineers in charge of the construction of SuperCam, I am pleased to hand this instrument over to our fellow scientists for them to explore Mars and to search for traces of past life”.