Forget a mission to Mars, scientists are now looking at a massive asteroid.
Known as 16 Psyche, it is thought to be the molten core of a planet once the size of Mars that was stripped of its rocky mantle by a series of massive collisions and since slowly cooled into a solid mass of iron and nickel.
The asteroid is so unusual that NASA is considering sending a spaceship to study it.
"Psyche is by far the largest metal object in the solar system," said Benjamin Weiss, professor of planetary sciences at the Massachusetts Institute of Technology.
"Psyche would be the first and only metal world to be visited by humanity. This is true exploration."
In an interview with The Times, Linda Elkins-Tanton, Director of Arizona State University's School of Earth and Space Exploration, said: "If Psyche has a magnetic field then it was the molten core of a little planet that was stripped of its rocky exterior. Its original body might have been as small as Vesta, or as large as Mars."
Earlier this year, Prof. Elkins-Tanton said: "Every world explored so far has a surface of ice, rock or gas. Now imagine a world made of iron and nickel. How alien it must be. But deep below Earth's surface, unreachable to us, is a metal core resembling asteroid Psyche.
"A mission to this metal world would be the equivalent to a mission deep below the surface of any of the terrestrial planets to examine their cores."
16 Psyche has a diameter of approximately 150 miles (241 km) and is made almost completely of iron and nickel. With our current technology, it is probably the only planetary core that we will be able to examine directly .
If NASA approves the $500 million mission, the probe would be launched at the end of 2020, and would reach its destination in 2026.