A piece of Mars will be heading home in 2020. Sayh al Uhaymir 008 (SaU008), a meteorite that originated from the surface of Mars, will be a passenger onboard NASA’s Mars 2020 rover mission. This sample of the Red Planet will serve as target practice for a high-precision laser on the rover’s arm, which will intensely study the geology and chemistry of Mars’ harsh environment.
The primary aim for NASA’s Mars 2020 rover is to collect samples of the dry and damaged surface. Information from these samples could potentially help a future mission return these samples to Earth. Although this aim is difficult, it is still plausible. For this to work the rover needs to carefully study a variety of rocks, this is why the rover’s tools will be able to examine rock features as small as a human hair.
In order to accomplish such a high level of precision, the rover needs the correct calibration target to optimise the laser’s settings. Previous Mars rovers have included calibration targets onboard, but it is dependant on the type of instrument. Target materials can include objects such as rocks, metals or glass, which also happen to strike an uncanny resemblance to a painter’s palette.
The scientists at NASA’s Jet Propulsion Laboratory in Pasadena, California, United States, working on the instrument then came across the ingenious idea of using an actual piece of Mars for the calibration tool. Unfortunately, we are not blessed with large amounts of Martian meteorites. Also, they aren’t as unique as the samples the 2020 rover will collect, since they haven’t been apart of the Red Planet in millions of years and have altered significantly. Besides this, they are still the most ideal objects for target practice.
“We’re studying things on such a fine scale that slight misalignments, caused by changes in temperature or even the rover settling into sand, can require us to correct our aim,” says Luther Beegle of JPL. Beegle is principal investigator for a laser instrument called SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals). “By studying how the instrument sees a fixed target, we can understand how it will see a piece of the Martian surface.”
SHERLOC is an incredibly special piece of equipment, as it will be the first instrument on Mars to use Raman and fluorescence spectroscopies. These techniques are best known among forensics experts. The two types of spectroscopy include shining ultraviolet light over certain carbon-based chemicals, giving off a similar glow to when black light is shown on a surface.
By analysing the glow, scientists will be able to deduce the chemicals that form. SHERLOC will image the rocks it has studied, whilst also mapping the chemicals it discovers on the face of each rock. This will add spatial context to the layers of data Mars 2020 will collect.
“This kind of science requires texture and organic chemicals – two things that our target meteorite will provide,” says Rohit Bhartia of JPL, SHERLOC’s deputy principal investigator.
As Martian samples are rare to find on Earth, JPL scientists had only about 200 meteorites to choose from, as confirmed by the Meteoritic Society. Of these small selection, JPL scientists asked for the help of NASA’s Johnson Space Centre in Houston, Texas, United States, as well as the Natural History Museum of London, United Kingdom, to find the right one.
There was a particular screening process, in order to weed out of the weak samples. This sample had to solid enough to survive the intensity of the launch and landing. To test this, experts gathered several samples and cut off thin bits to see if it would crumble. If the sample was “flaky”, it would jeopardise the entire meteorite, and therefore the mission. Not only that, but the sample had to possess certain chemical features to test SHERLOC’s sensitivity. These features have to be easily detectable, as it would be done several times during the calibration process.
The SHERLOC team came to the conclusion that SaU008, a meteorite found in Oman in 1999, will return home. Besides being more rugged than other samples, a piece was available thanks to Caroline Smith, principal curator of meteorites at the Natural History Museum of London. “Every year, we provide hundreds of meteorite specimens to scientists all over the world for study,” Smith said. “This is a first for us: sending one of our samples back home for the benefit of science.”
SaU0008 will be the first Martian meteorite to have a snippet returned to the planet’s surface. However, it’s not the first piece that has made the trip back to Mars. NASA’s Mars Global Surveyor, now defunct, included some of the meteorite Zagami. It has since remained in orbit around the Red Planet, never quite making the descent to the surface from where it once came. More Martian meteorites will be onboard the 2020 rover, as the SuperCam will have its own sample for its own calibration target.
SHERLOC will also have great implications for future human spaceflight. It will include scientific samples that can be used to make fabric, gloves and a visor for a helmet. By seeing how these materials survive the harsh terrain of Mars, NASA can determine what materials should be used for future Mars missions.
“The SHERLOC instrument is a valuable opportunity to prepare for human spaceflight as well as to perform fundamental scientific investigations of the Martian surface,” says Marc Fries, a SHERLOC co-investigator and curator of extraterrestrial materials at Johnson Space Centre. “It gives us a convenient way to test material that will keep future astronauts safe when they get to Mars.”
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