Back when I was in high school and a little later when I started university, NASA launched a series of exploratory probes. The ones I remember best were the last of the Pioneer missions (10 and 11) and the Voyagers 1 and 2. All were slated for some form of outer planetary exploration which they went on to successfully complete. Beyond these assignments was an eventual encounter with deep space, journeys forever into our galaxy.

As of a few weeks ago, both of the Voyagers had passed beyond the heliosheath (the Sun's protective bubble or furthest boundary of the solar wind) and were now in interstellar space. The Pioneers I mentioned will one day achieve the same feat, all four craft then being outside the influence of their home star.

I often ponder what will be left when humans are gone, what artefacts of our presence will remain for distant and alien explorers to discover. The most obvious ones are those that we have sent from the Earth, creations upon which some form of rough immortality has been conferred. Of course, the chances of stumbling upon an artificial space probe must be very tiny indeed, as are the chances of intelligent life, elsewhere.

Still, getting out of the solar system at all is a remarkable achievement. I think its a time for deep reflection upon human potential - we may or may not make it a lot further - but these are shining moments.

A NASA graphic on the relative status of Voyager's 1 and 2.



A NASA gif showing the remarkable moment when the solar rubicon was passed by Voyager 2.