It is interesting, even if a little maudlin, to wonder how long the mark of humans will remain after our extinction. As a tool using and now technological species, humans have come to dominate the Earth with all manner of artificially created objects. Look around.

But most of what has been made or built will be gone in a million years and an intelligent life-form visiting the planet in a billion years would find nothing to show that once mighty civilisations lived here.

However there are at least five objects, currently speeding through or beyond the Kuiper belt, that may live for billions of years. These are the two Pioneer and Voyager probes and the New Horizons spacecraft. They are hurtling in different directions and without meeting some calamity, carry the best hope to show that humans once existed. Sure their power will give out long before that, but they will be intact creations shuttling through the darkness, nevertheless. And all, bar New Horizons, carry some kind of message about their creators.

Hoping that one will be captured by an advanced alien species, should one exist, is a very long bet indeed. Imagine being stranded on that proverbial desert island and sending a message in a bottle on the tide with the hope that it will be found and read by one specific person someday. Similar odds, I think.

Bon Voyage!

Courtesy of NASA.