- The Surface and Atmosphere Geochemical Explorer, or SAGE, mission to Venus would release a probe to descend through the planet's atmosphere. During descent, instruments would conduct extensive measurements of the atmosphere's composition and obtain meteorological data. The probe then would land on the surface of Venus, where its abrading tool would expose both a weathered and a pristine surface area to measure its composition and mineralogy. Scientists hope to understand the origin of Venus and why it is so different from Earth. Larry Esposito of the University of Colorado in Boulder, is the principal investigator.
- The Origins Spectral Interpretation Resource Identification Security Regolith Explorer spacecraft, called Osiris-Rex, would rendezvous and orbit a primitive asteroid. After extensive measurements, instruments would collect more than two ounces of material from the asteriod's surface for return to Earth. The returned samples would help scientists better understand and answer long-held questions about the formation of our solar system and the origin of complex molecules necessary for life. Michael Drake, of the University of Arizona in Tucson, is the principal investigator.
- MoonRise: Lunar South Pole-Aitken Basin Sample Return Mission would place a lander in a broad basin near the moon's south pole and return approximately two pounds of lunar materials for study. This region of the lunar surface is believed to harbor rocks excavated from the moon's mantle. The samples would provide new insight into the early history of the Earth-moon system. Bradley Jolliff, of Washington University in St. Louis, is the principal investigator
Out of these three potential missions, I would really like to see the SAGE mission approved. No spacecraft has landed on Venus since before I was born (I am excluding the VEGA balloons here since they were primarily atmospheric probes). And the descent imaging could be some of the most dramatic images that we could expect for the next decade.
Check out Van Kane's post on this subject for more information.
Link: NASA Chooses Three Finalists for Future Space Science Mission to Venus, an Asteroid or the Moon [www.nasa.gov]
EDIT: As Ted points out in the comments, the VEGA probes did land on the surface, but they didn't return images of the surface, so they still don't count. I am still looking forward to the descent images from SAGE.