WASHINGTON – President Barack Obama’s proposed 2017 budget would reduce NASA spending nearly $300 million from 2016 – but those cuts face staunch opposition from a space-friendly Congress.

The $19 billion NASA budget, which the White House released Tuesday, included major cuts to two of the space agency’s signature projects: the Space Launch System, the rocket that would take astronauts to Mars, and a satellite mission to Europa, a moon orbiting Jupiter which some scientists say may harbor microbial life.

Under the president’s budget, the Space Launch System would receive $1.3 billion in 2017, down from $2 billion in 2016. The Europa mission would get $50 million, down from $175 million the year before. Obama made similarly modest requests in his 2016 spending plan, but Congress boosted NASA’s total budget by $1.3 billion in the omnibus bill it passed in December.

This budgetary tug-of-war between the president and Congress is “business as usual” according to Casey Dreier, director of space policy for the Planetary Society.

“They cut planetary science (the budget area including the Europa mission) and they cut the SLS program. They’ve been doing that every year, and Congress every year so far has added money back to those programs,” Dreier said.

It didn’t take long for Rep. Lamar Smith, the Republican chair of the House Science, Space, and Technology Committee, to condemn the president’s cuts to the Space Launch System.

“This administration cannot continue to tout plans to send astronauts to Mars while strangling the programs that will take us there,” Smith, R-Texas, said in a statement.

Dreier said Europa cuts are unlikely to find backing in Congress either, especially since Europa’s “strongest supporter,” Rep. John Culberson, R-Texas, is the chairman of the House Appropriations Subcommittee on Commerce, Justice, and Science, which will ultimately determine funding for the Europa mission.

While the administration delivered no major surprises in Obama’s final NASA budget, bigger shake-ups may follow the 2016 election.

When Obama took office, he ended Constellation, the Bush administration’s Mars program and replaced it with a plan to reach the red planet by developing the Space Launch System rocket and Orion crew capsule. The first manned test of the Space Launch System, however, is slated for 2021 – four years into the next administration.

“The truth is that the only thing we can hope to know for certain about our future is that it’s uncertain,” said NASA administrator Charles Bolden in his State of NASA address on Tuesday. “When it comes to aeronautics and space, President Obama has set us on a visionary course. It’s my sincere hope that future leaders from all sides of the political spectrum will see it through.”

Casey Dreier said it’s unlikely that space will be a high enough priority for the next president to justify a showdown with Congress in a bid to start yet another new mission from scratch. “It’ll be very variable and very dependent on external factors,” Dreier said of future political wrangling in Washington. “NASA’s just kind of along for the ride.”