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SALT LAKE CITY — One revealing clue about how long NASA's Voyager probes have been traveling through space can be found in the "high-tech" storage device both exploration craft use to store data — an eight-track tape.

While readers of a certain age will remember the jarring, mid-song-clunks of the first popular portable music medium, those who missed that particular joy were probably not around on Aug. 20, 1977, when the first of the twin Voyager probes launched from Cape Canaveral, Florida.

Voyager 2 launched that day, followed two weeks later by the lift-off of Voyager 1. Since that time, the two probes have captured stunning images in planetary flybys and are now venturing through interstellar space, still gathering and transmitting new information back to their home planet.

Exploring on borrowed time: No one is more stunned than NASA engineers that the Voyagers, originally expected to have a lifespan of five years, are still operational, albeit at a scaled-down capacity to reserve their dwindling power supplies. Back in 2012, the Voyager program broke the record as NASA's longest-lived space mission.

Operated by NASA's Jet Propulsion Laboratory, the first destinations for both probes was Jupiter and Saturn after which Voyager 1 headed for the heliosphere and Voyager 2 went on to record close encounters with Uranus and Neptune. Both crafts are now in interstellar space — a region where the Sun's constant flow of material and magnetic field stop affecting its surroundings — and transmitting data that's solving some scientific mysteries and unveiling new ones. As of January of this year, Voyager 1 was 14.5 billion miles from Terra Prime, also called the planet Earth.

"Today, as both Voyagers explore interstellar space, they are providing humanity with observations of uncharted territory," said Linda Spilker, Voyager's deputy project scientist at JPL in a report posted to the lab's website this week. "This is the first time we've been able to directly study how a star, our Sun, interacts with the particles and magnetic fields outside our heliosphere, helping scientists understand the local neighborhood between the stars, upending some of the theories about this region, and providing key information for future missions."

In case of alien encounters, drop the needle on this: Sounding a bit like the proud parents of over-achieving children, JPL points out that the Voyagers' eight-track tape storage systems have about 3 million times less memory than modern cellphones and transmit data about 38,000 times slower than a 5G internet connection.

While the technology behind the probes' data storage may sound a bit dusty, their on-board "message in a bottle," should either of the probes encounter extraterrestrial life on their journeys, can be found on an even more aged relic of recording.

Each Voyager is carrying a golden record containing images of life on Earth, diagrams of basic scientific principles and audio that includes sounds from nature, greetings in multiple languages and music, according to JPL. The gold-coated records serve as a cosmic handshake for anyone (or anything) that might encounter the space probes and include "how to play" instructions. JPL says at the rate gold decays in space and is eroded by cosmic radiation, the records will last more than a billion years.

The sound of silence approaches: The Voyager probes are powered by a radioisotope thermoelectric generator containing plutonium, which gives off heat that is converted to electricity, according to JPL. As the plutonium decays, the heat output decreases and the Voyagers lose electricity. To compensate, the Voyager team turned off all nonessential systems and some once considered essential, including heaters that protect the still-operating instruments from the frigid temperatures of space. JPL says all five of the instruments that have had their heaters turned off since 2019 are still working, despite being well below the lowest temperatures they were ever tested at.

NASA expects Voyager 1 and Voyager 2 to run out of power — officially ending their decades-long missions — sometime in the mid-2020s, according to UPI.

Once the probes go silent, NASA says the Voyager crafts will begin their final mission — venturing deeper into space and serving as Earth "ambassadors" should they ever encounter another life form.