As "Star Trek" marks its 45th anniversary, space exploration is less about the voyages of the starship Enterprise and more about robots that boldly go where no man has gone before. But surely even Lieutenant Commander Data would approve the slate of robotic missions looking out beyond Earth orbit toward extraterrestrial destinations both familiar and mysterious.

Possible candidates for robotic planetary exploration missions include Venus, Mars, asteroids, comets and even Saturn's moon Titan. Such ambitious targets have appeared in proposals for NASA Discovery-class missions that have budget caps of roughly half a billion dollars — a testament to how planetary scientists have balanced risk and innovation while searching for new science frontiers.

"No one ever expected to be able to get out there to one of the Saturn moons with the Discovery missions, but the imagination of the scientific community is pretty unbounded," said Bruce Banerdt, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "More and more destinations will open up."

Several planetary scientists shared their thoughts with InnovationNewsDaily on the hottest targets for unmanned flights during the International Academy of Astronautics' ninth Low-Cost Planetary Missions Conference, held in June in Laurel, Md.

Her mysterious face
Banerdt is shepherding his own Discovery-class proposal for a Mars mission cobbled together, Frankenstein-style, from past spacecraft. But he also points to another neighbor of Earth's as a destination overdue for a visit.

"Venus has really been on the short end of the stick so many times, and I don't think it's a concerted effort to snub it. It's just been pretty consistent bad fortune along the way," Banerdt told InnovationNewsDaily.

That includes Japan's Akatsuki mission, which inadvertently overshot Venus in December 2010.

The Venus Express orbiter launched by the European Space Agency has done great work studying the veiled planet's atmosphere, but it's time for a closer look, said Ralph Lorenz, a planetary scientist in Laurel at the Johns Hopkins University Applied Physics Laboratory.

"It does really seem it's Venus' turn again," Lorenz said. "In particular, we need to study the planet's lower atmosphere and surface."

Lorenz was chosen by NASA as a participating scientist for the Akatsuki mission. That spacecraft may get a second chance to enter Venus orbit sometime between December 2016 and January 2017.

Shooting for space rocks
Several scientists also pointed to smaller targets, notably comets and asteroids, as a high priority in new missions. Japan's Hayabusa probe returned to Earth last year with a sample from the Itokawa asteroid, and the NASA Dawn spacecraft has begun its approach to the asteroid Vesta.

NASA's upcoming OSIRIS-REx mission plans take a sample from another asteroid, called 1999 RQ36. That space rock represents the greatest known current threat to Earth, said Joe Nuth, OSIRIS-REx project scientist at NASA's Goddard Spaceflight Center in Greenbelt, Md.

"With small bodies, we thought we knew everything about comets and asteroids initially, and then we went to one and it was completely different," Nuth said. "So with those kinds of results, you need to keep going back to see what the range of small bodies actually is."

Era of planetary exploration
Whatever the destination, scientists agree they have enjoyed a rich run of planetary exploration missions — a run they hope won't falter under tightening budgets.

"Things certainly are pretty grim right now in terms of the healthy planetary exploration program we've had for the past decade and a half," Banerdt said. "If you look 15 years before, in the 1980s and starting out in the 1990s, it was pretty thin pickings. The last 15 years have been pretty nice."

Lorenz also described this as a "privileged era of planetary exploration" for NASA and its international partners.

"Now there's a spacecraft at Venus, another one maybe coming back to Venus, one at Mercury, three working orbiters at Mars, one working rover, another rover just about to go, a couple of things at the moon, and Cassini is still going great" at Saturn, Lorenz said. "There's a lot going on; it's great."

The adventures of such robotic explorers may not fully satisfy Trekkies who long to see the adventures of a Captain Kirk and his crew happening today. But they might be surprised to see what astronauts and robonauts are doing two centuries from now.

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