NASA on Tuesday said it would announce final concepts for a future robotic mission to explore the solar system during a media teleconference on Wednesday.The mission, targeted to launch in the mid-2020s, would be the fourth in NASA's New Frontiers portfolio - a series of cost-capped missions led by a principal investigator. Current New Frontiers missions are New Horizons to Pluto and the Kuiper Belt, Juno at Jupiter, and the OSIRIS-REx asteroid sample return mission, now heading to the asteroid Bennu for arrival in 2018.The mission concepts were chosen from 12 proposals submitted in May to address top solar system exploration goals, as identified by the planetary science community. Investigations were limited to six mission themes - comet surface sample return, lunar south pole-Aitken Basin sample return, ocean worlds (Titan and/or Enceladus), Saturn probe, Trojan tour and rendezvous, and Venus in Situ explorer to help us understand the climate change processes that led to the extreme conditions on Venus today.