For the past decade, NASA's Mars exploration strategy was to follow the water.
Signs of water have been found in weathered rocks, mineral deposits and the arctic plains. Now, scientists say it's time to search for life again - something the space agency hasn't done directly since 1976 when the Viking mission turned up empty-handed.
This time, there's a push to bring Martian rock and soil samples back to Earth. Here, they could be analyzed for fossilized traces of alien bacteria, or chemical or biological clues that could only be explained by something that was alive.
NASA can't afford such a mission on its own, so it recently joined the European Space Agency to map out a shared project.
Space policy experts think the timing is right despite the risks and hefty price tag, which can cost as much as $10 billion.
Do you think that this expense is worthwhile?
