In September 2015, NASA chose five potential space exploration missions to fund and awarded them each US$3 million to take their concepts further. Now the space agency has narrowed the field down to two winners – Lucy, which is scheduled to launch in 2021, and Psyche, set to blast off in 2023. The missions will see robotic spacecraft probing parts of our Solar System that could give us deeper insights into its formation and evolution.

Both missions were proposed under NASA's Discovery Program, which has seen such successful projects as Dawn, Kepler and MESSENGER launched previously. Missions under this program have a low cost point compared to larger ventures, with development capped at approximately US$450 million.

Lucy, scheduled for launch in October 2021, will zoom out to study six of the "Trojan" asteroids that both lead and follow Jupiter in orbit around the sun thanks to the gas giant's gravitational influence upon them. The asteroids are believed to be composed of the very stuff of formation of our Solar System, so visiting them is akin to visiting our galactic neighborhood when it was first getting started.

"This is a unique opportunity," said Harold F. Levison, principal investigator of the Lucy mission from the Southwest Research Institute in Boulder, Colorado. "Because the Trojans are remnants of the primordial material that formed the outer planets, they hold vital clues to deciphering the history of the solar system. Lucy, like the human fossil for which it is named, will revolutionize the understanding of our origins."

Lucy is scheduled to arrive at its first Trojan in 2025.

The second mission – Psyche – is also slated for an October takeoff, although two years after Lucy's, in 2023. After launch, the spacecraft will get a gravity boost from Earth and pass by Mars before arriving in 2030 at the asteroid that's its namesake, 16 Psyche.

Located in the asteroid belt between Mars and Jupiter the asteroid is a massive specimen, measuring about 130 miles (210 kilometers) in diameter, which places it among the ten largest asteroids in the belt. 16 Pysche was chosen because of its strange composition. Unlike other asteroids which consist of ice or rock, this one is mostly metal, being comprised primarily of iron and nickel. This has led scientists to believe it could be the leftover core of a planet, considering that Earth's core has a similar composition.

"This is an opportunity to explore a new type of world - not one of rock or ice, but of metal," said Psyche Principal Investigator Lindy Elkins-Tanton of Arizona State University in Tempe. "16 Psyche is the only known object of its kind in the solar system, and this is the only way humans will ever visit a core. We learn about inner space by visiting outer space."

The video below provides further insight on the missions: