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NASA's hefty Martian rover will use an AI brain on a robot arm to map out signs of ancient life on Red Planet

The tiny X-ray bullets are only the size of a grain of sand. Pew! Pew! Pew!

Perseverance, NASA's latest Martian rover, will extend its two-metre robotic arm and use an AI-powered control system to carefully aim X-ray beams at ancient rock samples that might contain fossilised microbes.

The instrument known as PIXL, which stands for Planetary Instrument for X-Ray Lithochemistry, shoots X-rays to analyse chemical compounds on the Red Planet. The spectrometer's beam has been designed to be narrow enough to detect features that are as small as a grain of salt, and it will map out detailed textures in soil and rocks.

The heightened precision means that PIXL has to have excellent aim to target the tiny grooves in a sample. Engineers at NASA have fitted the instrument to a hexapod, a stand with six legs that connects PIXL to Perseverance's robotic arm. It uses AI technology to automatically swivel the instrument to adjust the direction of the X-ray beam.

"The hexapod figures out on its own how to point and extend its legs even closer to a rock target," said Abigail Allwood, PIXL's principal investigator at NASA's Jet Propulsion Laboratory. "It's kind of like a little robot who has made itself at home on the end of the rover's arm."

NASA did not divulge what kind of AI algorithm the hexapod uses to aim its PIXL beam. The Register has asked for more details.

The device is sensitive enough to shift by a distance of just 100 microns – about twice the width of a human hair – to carefully direct the X-ray spectrometer to analyse the chemical components in a specimen.

Illustration of NASA's Perseverance rover

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PIXL zaps the rock every 10 seconds before its position is adjusted by the hexapod and it shoots from a slightly different angle. It's a fiddly procedure that's repeated thousands of times, which means it can take up to nine hours just to analyse a sample the size of a postage stamp.

During the day, the temperature on the Red Planet can fluctuate by up to 38°C. The added heat can cause the metal on Perseverance's robotic arm to expand and contract by up to 13 millimetres, making it more difficult for the hexapod to aim PIXL's X-rays effectively.

"PIXL is a night owl," Allwood said. "The temperature is more stable at night, and that also lets us work at a time when there's less activity on the rover."

Perseverance is looking for tiny textural changes in rocks resembling stromatolites on Earth. Stromatolites are produced by ancient cyanobacteria that secrete compounds that cause layers of sand to stack on top of one another, and they grow over time.

Astronomers believe that Mars might have these stromatolite-like fossils too. Confirmation would provide direct evidence that alien life once existed on the Red Planet. If Perseverance detects a particularly promising sample, it will drill into the rock and insert the specimen into a metallic tube that can be collected in future missions and brought back to Earth.

The chunky rover was launched earlier this year in July, and is expected to land on Mars on 18 February next year. ®

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