A leading scientist slammed a NASA plan to lasso a giant space rock to use it as a launch pad for missions to Mars, calling it a “multimillion-dollar stunt.”

Richard Binzel, planetary scientist at the Massacusetts Institute of Technology (MIT), said in commentary in the journal Nature that the NASA plan is a distraction from the overall Mars effort, according to the Los Angeles Times. He was responding to a National Research Council report in June that suggested a number of routes to Mars, including grabbing an asteroid, although that report didn’t make any recommendations.

Binzel has examined the behavior of near-Earth asteroids for years and said that NASA should focus on an asteroid survey in its upcoming 2015 budget as its main priority for developing future crewed missions.

The Obama administration’s goal is to put austronauts on an asteroid by 2025, and then to Mars in the mid-2030s. However, Binzel said trying to grab part of the asteroid is a mistake because it will require an ancillary spacecraft towing a giant capture bag or arcade-game-like claw, which are not useful technologies for the ultimate goal: getting to Mars.

Instead, Binzel believes NASA should be using asteroids near the Earth as “stepping stones” to Mars, as thousands of such rocks pass by each year. He said it makes more sense to wait for them to come to Earth rather than bring one near Earth.

NASA likely will gradually build up its ability to travel great distances by starting with a few short trips that last a few weeks before building up to missions that would last months and send humans deeper into space than ever before. Throughout the process, NASA could test the technology used for sending humans to Mars.

Binzel said it would cost $200 million per year to find 90 percent of asteroids near earth, which would be far less than it would cost for hte Asteroid Redirect Mission (ARM).