The next medium-class New Frontiers mission to explore the solar system will land on Venus or return samples from the moon or an asteroid, NASA announced Tuesday.

NASA is evaluating mission proposals to the moon, Venus and an asteroid. Credit: NASA

The concepts are finalists for the third member of NASA's New Frontiers program.

Two of the candidates would return samples from the moon or an asteroid, and another mission would dispatch a lander to the surface of Venus.

"These are projects that inspire and excite young scientists, engineers and the public," said Ed Weiler, associate administrator for NASA's science mission directorate. "These three proposals provide the best science value among eight submitted to NASA this year."

The three mission teams will each receive $3.3 million next year to conduct year-long studies on implementation feasibility, cost, management and technical plans, according to NASA.

NASA officials will select one mission for development in mid-2011, and launch must occur before the end of 2018. The mission's cost must be less than $650 million, exluding the launch vehicle.

The New Frontiers program includes the New Horizons probe on the way to Pluto and the Juno spacecraft scheduled for launch to Jupiter in 2011.

The Surface and Atmospheric Geochemical Explorer, or SAGE, would deploy a robust spacecraft capable of withstanding the smothering heat and pressure of Venus' atmosphere.

"It has been 25 years since a spacecraft last landed on Venus, and our curiosity and scientific capabilities have increased dramatically," said Larry Esposito, SAGE principal investigator at the University of Colorado at Boulder. "This mission will be a big step forward in understanding planetary evolution both in our own solar system and in planetary systems around other stars."

SAGE would measure the atmosphere of Venus during descent, then land at the edge of a massive volcano, dig about four inches into the surface and analyze the planet's composition and texture.

"It would be the first lander NASA has ever done for the planet Venus," said Paul Hertz, the science mission directorate's chief scientist. "It's going to spend an hour descending through the Venusian atmosphere, sampling it and taking weather measurements, helping us to understand the chemical composition of the atmosphere of Venus."

According to scientists, the lander would be built to survive the harsh surface environment for at least three hours. A series of Soviet landers reached the surface and operated for up to two hours, most recently in 1985.

"During these three hours, we'll get a lot of pictures, but most excitingly we're going to take spectral measurements of the rocks at the surface of Venus," Hertz said. "We'll take some measurements of the weathered surface, and then we'll scrape off the top layer and we'll take measurements underneath."

"Venus has gone terribly bad since it first formed," Esposito said. "The surface pressure is 100 times that of Earth and its temperature is similar to that of a self-cleaning oven. We are very interested in what sent Venus down this hellish path, including its runaway global warming."

SAGE would be managed by the Jet Propulsion Laboratory and Canada would provide a robot arm for the lander.

Another candidate New Frontiers mission is the Origins Spectral Interpretation Resource Identification Security Regolith Explorer, or Osiris-Rex.

The probe would rendezvous with and enter orbit around a primitive carbon-rich asteroid to conduct extensive measurements. A sampler aboard the spacecraft would collect more than two ounces of material from the asteroid for return to Earth.

The Osiris-Rex concept was proposed for the Discovery program in 2004 and 2006. Although the mission scored high on science, engineering and management metrics, NASA judged Osiris-Rex too expensive for the lower-cost Discovery program, which was cost-capped at $425 million.

Scientists say Osiris-Rex comfortably fits into the cost envelope for a New Frontiers mission.

"This mission will spend a year orbiting the asteroid, mapping it, taking pictures of the rocks, measuring the reflection of the sunlight off of it so we understand something about the mineralogy, and picking the very best place on the asteroid to go down and do a touch-and-go, kind of a rendezvous, not a landing," Hertz said.

Osiris-Rex would return a pristine sample to Earth, giving researchers a valuable specimen that could hold clues about the formation of the solar system and the origin of life.

Other objectives of the mission would include mapping the asteroid, identifying resources that could be used in human exploration, and studying the potential for asteroids to impact Earth.

Michael Drake of the University of Arizona in Tucson leads the Osiris-Rex science team.

The third mission selected for further study is called MoonRise. The concept consists of a probe to land near the moon's south pole, gather two pounds of soil and return to Earth.

MoonRise is led by Bradley Jolliff of Washington University of St. Louis.

The spacecraft would touch down in the moon's expansive South Pole-Aitken basin, an ancient impact crater more than 1,500 miles wide. The violent impact that formed the basin is believed to have excavated rocks from deep inside the moon.

If such rocks were returned to Earth, they could hold information on the history of the Earth-moon system.

"It's going to bring back several pounds of rocks for study on Earth, and from those rocks, especially the deep ones from the mantle, we'll be able to understand about the formation of the Earth-moon system," Hertz said.

This is the second time MoonRise has reached the final round of a New Frontiers competition. The new MoonRise mission has been modified from an original proposal for the second New Frontiers mission in 2004.