Bucking their Republican counterparts and the Obama White House, Democrats on the House Science Committee are offering an “alternative” NASA reauthorization that sets a 15-year goal of landing humans on Mars.

The Democratic alternative pumps NASA spending up to $18.1 billion in fiscal 2014, and keeps it there with out-year adjustments for inflation. Funding for the heavy-lift Space Launch System (SLS) is gradually increased until it reaches $1.8 billion in fiscal 2016. Initiated under the 2010 NASA reauthorization, the big rocket and the Orion multipurpose crew vehicle are recognized “as the highest priorities for carrying out the Mars goal,” according to a Democratic fact sheet.

“We have a choice,” says Rep. Donna Edwards of Maryland, ranking Democrat on the House Science space subcommittee. “We can either hold onto and reminisce about past accomplishments and missions, or we can chart a bold new vision for 21st century space exploration and innovation. I want to choose the latter. We don’t need another report or another commission. It’s time now that we commit — I mean really commit — to a manned Mars mission.”

Edwards is leading the charge on the alternative approach, which she presented at a well-attended — and well-received — forum at the Center for International and Strategic Studies in Washington. While the Republican reauthorization draft specifically prohibits use of federal funds to develop the asteroid-capture mission that is the latest centerpiece of NASA’s human-exploration program, the Democratic version leaves it up to NASA to decide how to get to Mars.

“We’ve had discussions with the White House, and obviously we’ve had discussions with them as they’ve appeared before the committee,” Edwards told Aviation Week. “I think one of the things that our authorization speaks to is this question of do we go to an asteroid, do we go to the Moon, and those things. What we spell out in our authorization is that it’s not our job to spell out those things. It’s a scientific determination. But what we need to make sure is that the vision has an ultimate destination.”

That destination is Mars, which Edwards said is challenging enough to spark job-creating innovation and inspire students to study the math, science and engineering subjects that will help make the U.S. economy more competitive. Despite the constrained economic environment that shapes this year’s budget debates on Capitol Hill, Edwards argued that an investment in space exploration is worthwhile because of its long-term returns in jobs.

“What we’ve done is that we want to see a funding profile that enables us to build a stepping-stone approach over the next 15 years,” she said.

In addition to the increases in the SLS, the Democratic alternative boosts planetary science spending to $1.5 billion annually, and sets spending on NASA’s effort to seed a commercial crew transport industry at $700 million, less than NASA wants but more than it has been getting.

The measure, which may get its first debate during a reauthorization markup in the House science panel on July 10, also calls for keeping the International Space Station flying through 2020, and to begin definitive work on deciding how much longer after that it should be funded. It also “encourages the president to invite partners to participate in a U.S.-led international initiative to achieve the goal of a successful crewed mission to Mars,” according to the Democratic fact sheet.