In a keynote speech titled "Making Humans a Multiplanetary Species" at the 67th International Astronautical Congress (in Guadalajara, Mexico), SpaceX founder and CEO Elon Musk said a city will be built in Mars in the future. Although he didn't mention a time frame as such, he did share significant pointers from the plans he has for the times to come.

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A view of the Noctis Labyrinthus region of Mars, perched high on the Tharsis rise in the upper reaches of the Valles Marineris canyon system.Reuters

 Musk revealed that there would be airline-like flights that would shuttle between the Red Planet and the Earth, with each course taking six months or more to complete. He projected that for his ideas to take shape, he would at least need a $10 billion investment.

"What I really want to try to achieve here is to make Mars seem possible – like it's something we can achieve in our lifetimes," he further added. In his speech, Musk feared that there's an inevitable extinction of human life fast approaching and there are two ways to deal with — vanish or become a "spacefaring civilization, and a multi-planetary species."

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The base of Mars' Mount Sharp.Reuters
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A view of Ophir Chasma on the northern portion of the vast Mars canyon system, Vallles Marineris, taken by NASA's Mars Reconnaissance Orbiter.Reuters
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Nili Patera, one of the most active dune fields on the planet Mars.Reuters
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Rough spherical features in an area called Yellowknife Bay. These features are interpreted as concretions, implying they formed in water that percolated through pores in the sediment. Spherical concretions have previously been discovered in other rocks on Mars.Reuters
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An impact crater on Mars is seen in an image taken by Orbiter.Reuters
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A location on Mars associated with the best-selling novel and Hollywood movie, "The Martian" This area is in the Acidalia Planitia region and in the novel and the movie, it is the landing site of a crewed mission named Ares 3.Reuters
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Curiosity appears as a bluish dot near the lower right corner of this enhanced-color view from Orbiter taken June 2013.Reuters
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A rock outcrop called Link pops out from a Martian surface. Rounded gravel fragments, or clasts, up to a couple inches in size are in a matrix of white material. The outcrop characteristics are consistent with a sedimentary conglomerate, or a rock that was formed by the deposition of water and is composed of many smaller rounded rocks cemented together. Scientists enhanced the color in this version to show the Martian scene as it would appear under the lighting conditions we have on Earth.Reuters
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Portions of the Martian surface showing many channels from 1 meter to 10 meters wide on a scarp in the Hellas impact basin.Reuters
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The northern-most sand dunes are seen as they begin to emerge from their winter cover of seasonal carbon dioxide (dry) ice.Reuters
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Mars' Victoria Crater at Meridiani Planum.Reuters