Nearby asteroids could be stepping-stones on a trip to Mars, says a planetary scientist calling for an ambitious effort to map them while calling a NASA plan to capture and retrieve one a waste of time and energy.
The debate has been ignited as NASA contemplates a trip to Mars for either a fly-by or a landing on the surface of the Red Planet sometime after 2030.
Richard Binzel, a planetary scientist at the Massachusetts Institute of Technology, says mapping of large asteroids that approach the Earth as close as the Moon's orbit could provide candidate targets for visits by astronauts.
"Thousands of shipping-container-sized and larger asteroids pass almost as close as the Moon each year," Binzel wrote in the journal Nature.
Trips to such large asteroids, each one perhaps longer in duration than the previous one, would yield the experience and confidence necessary to embark on the years-in-duration voyage to Mars itself, he says.
Binzel is critical of a NASA plan, dubbed "Asteroid Redirection Mission" and intended to capture a space rock and bring into a lunar orbit, which the agency is also promoting as a way to develop the technologies and techniques needed for a trip to Mars.
The ARM mission, Binzel maintains, would just be an expensive distraction that would contribute little to the goal of putting humans on the Red Planet.
"The principal reason that ARM makes no sense is that it is a misstep off the path to Mars," Binzel told Space.com. "There's nothing about sending humans to Mars that requires us to capture an asteroid in a baggie. That's a multibillion-dollar expenditure that has nothing to do with getting humans to Mars."
Such a "one-off costly stunt" involving developing hardware and procedures to corral and move an asteroid would make no contribution to learning how best to conduct long-duration crewed space mission, he wrote in his Nature article.
"There is a better way," he wrote.
The space agency should scrap its ARM proposal, he says, and devote its resources to a survey to map near-Earth asteroids that crewed missions could visit in the space rocks' normal orbits, going further and further into space with each such mission.
"Asteroid retrieval gets you one object; a survey will get you thousands, at a fraction of the cost," Binzel says. "Knowing that those objects are there is like a gateway toward human exploration and eventual commercialization."
Binzel's position has its supporters.
In May, Congressman Steven Palazzo from Mississippi, chairman of the space subcommittee of the House Committee on Science, Space, and Technology, called NASA's asteroid-retrieval proposal a "detour for a Mars mission."
