When it comes to exploring Mars, human-made robots have, literally and figuratively, only scratched the surface. To date, rovers on Mars have driven less than 65 km on the Red Planet. The surface of Mars is almost 145 million square km, and while satellites orbiting the planet like the Mars Reconnaissance Orbiter have helped, there is still a lot of ground left to cover up close. One faster way to do that is a plane, and NASA has a concept for a Martian flyer that might work.

Again and again these days, we're seeing evidence that our solar system is awash in H₂O. Now, after numerous major revelations of liquid oceans throughout our celestial home, it looks as though Mars may have liquid water close to its surface as well.