By Joel Achenbach — But there's a problem with the harder stuff: Often it's just too hard.
Just about everyone in the space community wants to go to Mars. Rovers are great, but they're sluggish, and scientists fantasize about a human geologist being able to decide where to dig into the Martian soil for clues about the planet's history and possible signs of life.
Many people feel strongly that societies that don't explore the frontier will invariably go into decline. The fourth rock from the sun haunts the imagination of people from the third rock. Mars has as much land area as the Earth. Someone like Elon Musk, the visionary founder of SpaceX, isn't necessarily going to wait for a NASA mission; he talks of establishing a Mars colony, and says he wants to die there — just not while attempting to land.
A private venture called Inspiration Mars hopes to send two astronauts on a fly-by mission of Mars in 2018. And a Dutch reality show, "Mars One," is lining up thousands of volunteers for a Mars colony that supposedly — and implausibly — will begin with landings in 2023.
NASA, however, is not an entrepreneurial outfit. Its plans have to pass multiple layers of technical, political and budgetary review. A fundamental presumption of NASA missions is that the astronauts will come back alive.
A journey to Mars would take about two years and expose astronauts to extremely high levels of radiation. The Martian atmosphere is a nightmare, just thick enough to cause problems but too thin to be of much use in braking a speeding spacecraft. NASA last year landed a one-ton rover on Mars, but to put humans there, engineers think they would need to land a 40-ton payload, including a habitat, fuel and food. To scale up by a factor of 40 is not as simple as, for example, making a parachute 40 times as big, because physics and aerodynamics don't work that way.