Remember the iMac computers produced in the late 1990s? NASA’s brand-new Perseverance rover, the most advanced machine that’s ever landed on Mars, uses the same processor that powered those 1990 iMacs. When it comes to rovers, “state of the art” is a subjective term.
Perseverance is running on none other than a PowerPC 750 that’s most famous for powering the original “Bondi blue” iMac from 1998; it consists of a single-core, 233MHz processor with just 6 million transistors. NASA’s Curiosity rover uses the same type of processor. Even affordable smartphones now have more than 1000 times the transistors in these rovers.
Why is such old technology being used in a cutting-edge space exploration mission?
Even with the difficulty of buying computer parts these days, surely somewhere in the $2.7 billion costs of Perseverance, NASA could have found the $500 budget for something like Intel’s Core i9-10900K CPU (with 10 cores and a max clock speed of 5.3GHz). But as a report by New Scientist explains, such an advanced chip is actually not good for the unique operating conditions of Mars.
Earth’s atmosphere provides protection from harmful radiation and charged particles much more than Mars’ atmosphere. A bad burst of radiation can destroy the sensitive electronics of a modern processor — and there is a possibility of more going wrong with the increased complexity of the chip.
Plus, at 138 million miles away, NASA cannot just swap out the processor if things go sideways. Because of those conditions, two computing modules are present in Perseverance: one is a backup just in case something goes wrong. (A third copy of the module is also on board for image analysis.)
The PowerPC 750 chip in Perseverance is not exactly like the one in the old iMacs to increase durability. It’s technically a RAD750 chip, a special variant that’s hardened against radiation, costing upwards of $200,000. The chip is popular for spacecraft, too: in addition to Perseverance and Curiosity, it also powers the Lunar Reconnaissance Orbiter, the Kepler telescope, the Fermi Space Telescope, and the Deep Impact comet-hunting spacecraft, among others.
Compared to a modern smartphone or gaming PC, the processor may be weak. NASA’s spec sheet for Perseverance notes that it’s far more powerful than earlier rovers like Opportunity or Spirit. According to The Verge, “its 200MHz clock speed is 10 times faster than those older rovers, and with 2GB of flash memory, it offers eight times the storage. (Rounding things out, Perseverance also has 256MB of RAM in case you were looking to build your own rover.)”
Perseverance features some new computer technology: Linux is debuting on Mars, it powers the Ingenuity helicopter, and will attempt to fly autonomously on Mars as part of Perseverance’s mission.