 Mars is our second-closest neighbor next to Venus, and our spacecraft and landers have explored it in great detail. Iron oxide in the dirt and rocks gives the planet a reddish color. It's tilted like the earth, giving it seasons. Olympus Mons, its biggest mountain, is three times higher than Mount Everest. And Valus Marineris, its giant gorge, is three times longer than the Grand Canyon. On May 12, 2016, the Hubble Space Telescope captured this striking image of Mars. The planet was 80.5 million kilometers from Earth. This observation was made just a few days before Mars' opposition on May 22, when the Sun and Mars were on exact opposite sides of the Earth. This phenomenon is a result of the difference in orbital periods between Earth's and Mars' orbit. While Earth takes 365 days to travel once around the Sun, Mars takes 687. As a result, Earth makes almost two full orbits in the time it takes Mars to make just one, resulting in a Martian opposition about every 26 months. The next one will be on July 27, 2018. Given that the orbits of Mars and Earth are ellipses, and their orbital velocities are different, the distance between the two can vary from 55 to 402 million kilometers. That's 34 to 250 million miles. Back in 2003, the two planets reached a near-minimum distance of 56 million kilometers. The last time that they were that close was over 50,000 years ago.