The twin probes, Voyager 1 and Voyager 2, left Earth in 1977 and have been sending our planet very important information about the largest planets in the Solar System ever since. It seems unbelievable, yet after 47 years radioactive isotope batteries continue to power the detection systems carried by the probes. Of the twin probes, perhaps the second one is the most famous because it observed Jupiter and Saturn, like Voyager 1, and then also Uranus and Neptune by taking advantage of the peculiar position taken by the giant planets reciprocally in the late 1970s. Throughout this long journey through time and space, the probes almost never lost contact with NASA, the US space agency. Everything was fine until a few weeks ago, when Voyager 1 started sending strange messages back to Earth. Today, the first probe is 24 billion kilometres away, the farthest a man-made object has travelled so far.
The Voyager probes communicate with NASA scientists using a binary code, i.e. a sequence of 0s and 1s just like all our electronic devices do, from computers to mobile phones. It takes about 22 hours for a message to reach Earth and another 22 for a command to reach the probes. Communication is definitely slow but has always worked well. But for some time now, Voyager 1 has been sending out nonsensical sequences, all the same and repetitive, as if it had jammed. Scientists are trying to reprogramme the probe but there is little hope of recovering it. The probes have worked very well, beyond expectations, but, according to calculations, we will lose contact with them by 2025. From then on, the probes will truly be alone and adrift in deep space.