Space. Voyager 1, NASA's indestructible probe 25 billion kilometers away

When it left Earth, Jimmy Carter had just arrived at the White House and Star Wars had not yet been released in French cinemas. Having left in 1977, would the Voyager 1 probe recognize the planet it left behind? It doesn't matter, since it has already reached the outskirts of the solar system and is now heading towards the constellation of Giraffe. In about ten days, it will be 25 billion kilometers from Earth —a barely imaginable distance, corresponding to more than 160 times the distance between the Sun and Earth. Since 2012, the American probe has left the Heliosphere, the bubble of plasma that protects the solar system from cosmic radiation, and is now traveling through interstellar space.

Originally, its mission was only supposed to last five years: the time it took to fly one way to Jupiter and Saturn, thanks to an alignment of the planets that occurs less than once a century. In 1979, Voyager 1 unlocked some of Jupiter's secrets. Transmitted via its parabolic antenna, its images revealed with unprecedented precision the cloud bands of the giant planet, as well as previously unnoticed rings.

The probe also detected, for the first time, volcanic activity on a body other than Earth, namely on Io, one of four Galilean satellites. In November 1980, Voyager 1 flew by Saturn and brushed past its moon Titan, whose methane-rich atmosphere intrigued NASA scientists.

Its flirtation with Titan catapulted the probe out of the ecliptic plane, while its twin continued its journey toward the outer reaches of the solar system. Launched three weeks earlier, Voyager 2 reached Uranus in 1986 and Neptune in 1989, discovering some twenty moons and Neptune's ring system along the way. To date, it is the only probe to have ventured close to the two ice giants. In 1990, Voyager 1 also took a final symbolic photo of Earth: a pale blue dot lost in the immensity.

This cascade of scientific feats was followed by a series of technical miracles. Once the objectives were accomplished, as the two probes sped toward the outer reaches of the solar system, NASA decided to continue the Voyager program. To save energy, some instruments were disconnected, starting with the cameras, which were useless as the probes plunged into darkness. Others showed signs of degradation. In 2017, to correct Voyager 1's orientation, thrusters that had not worked since 1980 were restarted—a test that put the nerves of NASA engineers to the test: the signal took more than 19 hours to reach the probe, and the same amount for the return. At the end of 2023, Voyager 1 began to spout nonsense. Engineers diagnosed memory corruption, which an update to its computer code allowed them to bypass. Last May, another thruster that had been shut down for more than 20 years was restarted.

21 billion kilometers from Earth, Voyager 2 is subject to the same ravages of time. In August 2023, NASA believes it has lost contact for good, but the probe automatically realigns itself a few days later .

While indestructible, Voyager 1 isn't eternal. The probe still has 20% of its hydrazine reserves, a fuel it uses sparingly to realign itself with Earth: enough to last a good ten years. But its engines are largely clogged with deposits. On the electrical side, the probe's plutonium battery has lost more than half of its initial 470 W of power. It must juggle powering the instruments with the heating required to operate the engines, with the constant fear that one or the other won't restart.

But ironically, it's the election of a new American president that could put paid to the oldest of the current programs. By the end of June, NASA had already closed the social media accounts of around twenty missions, including Voyager. And Voyager could be among the programs sacrificed by the American agency, on the altar of budget cuts and the war on science decreed by Donald Trump .

The end of the probe's journey? Not necessarily. In a few centuries, Voyager 1 will cross the Oort cloud that marks the boundary of the solar system. And in 40,000 years, cold and long extinct, it will arrive near the star Gliese 445, carrier of the famous golden disc bound for a hypothetical extraterrestrial civilization. It contains anatomical charts, photographs of Earth and its inhabitants, recordings of Mozart, Chuck Berry, and birdsong. Released too late, Star Wars is not on it. Neither is Donald Trump.