A rover that recently landed on the surface of Mars uses the same processor that powered the 1998 iMac. NASA built Perseverance around a chip from decades ago because reliability is more important than being cutting edge when the computer is 130 million miles away.
This single-core processor runs 110 MHz to 200 MHz — vastly slower than what’s in Macs today. It went into a Mars probe because it’s proved its reliability time and again. The same chip is in the Curiosity rover, the Kepler space telescope, the Juno probe to Jupiter and over 100 other spacecraft.
Perseverance needs extra radiation protection
But it’s not precisely the same processor as went into an iMac because Perseverance employs a version that’s been hardened against radiation. A 1990s Mac didn’t need to worry about solar flares, but the modified version — dubbed the RAD750 — can withstand 100,000 rads. And it doesn’t blink at temperature ranges between -67 degrees (–55 °C) and 158 degrees (70 °C). As an extra benefit, the chip requires just 10 watts of power.
Reliability is critical. While it’s inconvenient if your iMac develops a problem and has to be taken in for repair, it’ll be many years before we have the technology to put a technician in Jezero crater on Mars where they could service Perseverance.
Which isn’t to say Macs don’t go into space. In fact, the first email sent from orbit came from a Mac.