This proximity interprets that the Earth is in "opposition" with Mars - meaning that it is sitting directly between the Sun and the planet.
A map of the sky that shows Mars and Saturn, as they can be seen from NY on July 31 at 11 pm.
The nearest point to Earth in Mars´ elliptical orbit came at around 1100 GMT on Tuesday, NASA said. With Mars and the Sun on either sides and Earth in the middle, the three celestial bodies will be in a straight line on Tuesday.
The red planet comes close enough for viewing only once or twice every 15 or 17 years.
Last week, Mars was already brighter than usual and will shine even more - and appear bigger - on Tuesday. You can use a high powered telescope with a large lens to watch it.
According to NASA, the Red Planet will be at a distance of 57.6 million kilometres.
Griffith Observatory in Los Angeles, Calif. will livestream the close approach, from 1 to 4 a.m. It will be 38.6 million miles (62 million kilometers) apart then, according to NASA. And if you miss it this time around, you'll have to wait another 269 years before it comes around again.
Although people viewing Mars from low latitudes and from the Southern Hemisphere will have the clearest view of the the Red Planet, Mars will be visible worldwide. He continued, saying that "we need to occupy the moon while we are preparing with those lessons to begin to land and stay on Mars".
Observatories across the U.S. are hosting Mars-viewing events.
Mars will start to dim by around mid-August and return to its normal magnitude of brightness around the start of September.
"There's one very bright orange-coloured star in the sky". Additionally, gravitational pull of the planets within our solar system constantly affects the shape of their orbits, moving Mars' orbit even closer to the Earth.
Scientists said mankind can no longer think of Mars as a "safety valve" in case things go wrong on our planet.
Saturn also made a close approach to Earth this summer, and the ringed planet remains especially visible for anyone scouring the sky for the best sights.