In November Ars revealed exclusive details about a daring mission to land on Jupiter’s moon Europa, and now it has become the law of the land. The Congressional budget deal to fund NASA for the fiscal year 2016 includes $1.63 billion for planetary science, of which $175 million is designated for the “Jupiter Europa clipper mission.” It has a target launch date of 2022.

But the new budget legislation does not stop there. It further stipulates, “This mission shall include an orbiter with a lander that will include competitively selected instruments and that funds shall be used to finalize the mission design concept.” In other words, it's against the law to fly the mission to Europa without a lander.

The overall budget for NASA provides $19.2 billion for NASA in fiscal year 2016, about $700 million more than President Obama requested. “This number, this year, is the largest vote of confidence that Congress has ever given NASA,” Texas Congressman John Culberson, who chairs the House Appropriations subcommittee with jurisdiction over the space agency, told Ars. “There’s enough money to do everything on their plate.”

Of NASA’s activities, none has had a higher priority for Culberson than Europa, Jupiter’s ice-encrusted moon. In championing the mission, Culberson has the backing of the scientific community, which in its most recent “decadal survey” cited a mission to return a sample Martian soil and a Europa orbiter as its two highest priorities. Culberson believes sampling the icy surface of Europa, and landing near a vent to its oceans below, offers the best possibility to find life elsewhere in the solar system.

“Until now Europa has had no advocate,” he said. “NASA headquarters was prepared to let the Europa mission die. But I have always believed there is life on other worlds, and I have wanted to have a hand in helping to discover life on other worlds.”

NASA’s administrator, Charles Bolden, has accepted the Europa mission only grudgingly. When NASA didn’t ask for Europa funding in its 2013 or 2014 budgets, Culberson gave it a total of more than $120 million. Finally, in its fiscal year 2015 budget request, NASA acquiesced and created a Europa program. The president’s budget called for $15 million to begin preliminary studies. Culberson appropriated $100 million. For fiscal year 2016, NASA requested $30 million. It got nearly six times that.

Now that NASA has accepted an orbital mission to Europa, the biggest point of contention has been a lander. During a November interview with Ars, Bolden explained why he didn’t want to tackle such an ambitious mission.

“My scientific community, the people who do mission planning, say we need to go and do a little research with the first mission to Europa to determine whether that’s a place we want to send a lander,” Bolden said. “That’s the point of our big disagreement with Congressman Culberson right now. He wants a multibillion dollar Europa mission that has a lander on the first flight and everything. Our belief is that that is imprudent from a scientific perspective.”

But Culberson has not been deterred. This year he became chairman of the House Appropriations subcommittee, the group that sets the budgets for Commerce, Justice, and Science, which includes NASA. He has twice made weekend visits to the California-based Jet Propulsion Laboratory to meet with key scientists and engineers there who landed Curiosity and other probes safely on Mars. They have enthusiastically told them they can do the same on Europa even though its frigid, radiation inundated surface would be a nightmare to land on. Their plan would be to fly a “Clipper” that makes dozens of flybys of Europa before identifying the best location to send a lander to the surface.

During these meetings with the scientists, Culberson asked how much money they needed now to begin developing key scientific instruments for the Europa lander. Their responses are reflected in this year’s budget appropriation. If the spacecraft is to be ready to go by 2022, there’s much work to be done, they told him.

And just to make sure Bolden and others at NASA headquarters got the message, he wrote the requirement right into the law.