NASA is considering five investigations for its third – and cheapest – tier of missions, known as their Discovery Program. The missions, which must cost no more than $500 million (£330 million), excluding launch costs, are each being given $3 million (£2 million) of funding to conduct concept design studies. One, or maybe two, will be selected for full funding.

Of the five missions, whittled down from an initial list of 27, one is a new mission to Venus called the Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy mission (VERITAS). Managed by NASA’s Jet Propulsion Laboratory (JPL), the spacecraft would be the first to produce maps of the surface composition of Venus, in addition to imaging the entire surface in high-resolution.

The Psyche mission, also managed by JPL, would send a spacecraft to study the intriguing metallic asteroid known as Psyche. It is one of the 10 most massive asteroids in the asteroid belt, over 200 kilometres (120 miles) in diameter, and is thought to be the exposed iron core of a protoplanet – the beginnings of a fully fledged planet.

Another JPL proposal, the Near Earth Object Camera (NEOCam), would be capable of finding 10 times more near-Earth objects have been found to date, to better understand the trajectory of objects near us, and identify any potential future threats.

NASA’s Goddard Space Flight Center has proposed another Venus mission, called the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI), which would actually plunge into the atmosphere of Venus. During the 63 minute descent, it would study the chemical composition of the atmosphere, and look for signs of active volcanoes on the surface – the presence of which remains unknown.

Finally, a second Goddard proposal called Lucy would send the first spacecraft to one of Jupiter’s Trojan asteroids, which trail the gas giant in its orbit and may hold clues to the formation of the early Solar System.

^{The Psyche mission (illustrated) would study an intriguing object in the asteroid belt. NASA/JPL-Caltech.}

Previous Discovery Program proposals include MESSENGER, which orbited Mercury from March 2011 to April 2015; Dawn, which is currently in orbit around the dwarf planet Ceres; and InSight, a stationary lander that is scheduled to launch to Mars in March 2016.

On this occasion, NASA has not ruled out the possibility of funding more than one of the proposals. “We are not committing to selecting two, but we are stating that we may choose either one or two,” David Schurr, NASA’s deputy director for planetary science, told SpaceNews.

The winning mission – or missions – of this 13th Discovery program contest will be announced in September 2016, with a tentative launch date in 2021 on the agenda.