NASA may be in some significan trouble is things keep going the way that they’ve been going in recent years. While the space agency has big plans in the future, like sending a new rover to Mars in 2020 and a manned mission to the Red Planet in the coming decades, there’s concerns that there’s no intermediary step between the two missions, which could threaten future exploration by the space agency.

The Mars 2020 rover would be the first step toward a “Mars sample return,” but there’s no second step planned that would involve getting the samples off of Mars and then back to Earth. That’s why the Planetary Society has released a white paper titled “Mars in Retrograde” that suggests that because of cutbacks in the last decade, NASA’s exploration of Mars may come to a halt after the rover.

The Planetary Society says that officials need to start developing some new missions if work is going to continue toward a manned mission, including a new orbiter to provide communication capabilities, and a way to pull samples from Mars and come back to Earth. But based on the president’s 2018 budget request, it doesn’t appear there’s any intention to do that.