In 10 million years, will any signs of humanity remain on Earth’s surface? Nobody knows; possibly all the evidence will have been erased or buried. But there are some artifacts of our technology that should still be intact, in good condition, even in 100 million years! These are the spacecraft that we humans have launched to explore the outer reaches of the Solar System. Successful beyond our wildest dreams, they have visited the farthest planets, passing near Jupiter, Saturn, Uranus, Neptune and Pluto, sending back amazing pictures and valuable data.
On January 1, the New Horizons spacecraft sped within 2,200 miles (3,500 kilometers) of Ultima Thule. A billion miles further than Pluto, photographs showed two balls of rock, each about 10 miles across. They collided slowly and stuck together, so it looks like a snowman. “Ultima Thule” means “beyond the known world,” the name chosen after a public vote, more poetic than 2014 MU69. It is in the vast Kuiper Belt, with trillions of other rocks.
Launched in 2006, New Horizons passed Pluto in 2015, and is traveling at 32,000 miles per hour. At that speed it would take only 80 seconds to go from Chicago to New York!
It took six hours for the radio signals to reach Earth from Ultima Thule. The song “New Horizons” by Brian May, guitarist of Queen and astrophysicist (how cool is that?), was beamed there on January 1 and took six hours to arrive.
Two spacecraft called Voyagers, launched in 1977 and carrying recordings of Earth sounds (thanks to Carl Sagan) are three times farther away and even faster. But it would take about 6,000 years for them to reach the nearest star, if they were going in that direction (they are not). Robots are OK with that, humans not so much!
Our intrepid Voyagers have a good chance of emerging unscathed into deep interstellar space, unless they crash into something. Much farther from the sun than Ultima Thule there are trillions of objects in the Oort Cloud. Some, like dirty snowballs, can be kicked gravitationally in a close encounter towards the sun, becoming comets.
Far beyond the Solar System the spacecraft will streak through a bath of cosmic rays, and relatively harmless neutrinos, dark matter and dark energy. At nearby Fermilab, we are trying to understand these mysteries. These are exciting times exploring the universe, from the tiniest particles to the whole enchilada.