At 50,000 mph, here’s the travel time at their closest approach. According to World Atlas, the New Horizons spacecraft reached a maximum speed of 50,000 mph and was the first to explore Pluto up close. Mercury and Venus are the closest to Earth, so they would take the shortest time to reach. Mars is the third-closest planet to Earth, and while humans have yet to land, space agencies have sent numerous rovers and satellites to the Red Planet. Jupiter and Saturn are even farther away; even at their closest, it would take 306 days to reach Jupiter and just over a year and a half to reach Saturn. Uranus and Neptune are so far away that you often need a telescope to view them. At their closest approach, at 1.7 and 2.7 billion miles, it would take thousands of days to reach either planet.