WASHINGTON — The director of NASA’s Jet Propulsion Laboratory said his center is pressing ahead with work on current and proposed missions to Mars and Europa despite ongoing debates on Capitol Hill about funding some of those missions and the impact they could have on the lab’s capabilities and workforce.

In a July 13 presentation at a Space Transportation Association luncheon here, Michael Watkins said that work is going well on two flagship-class planetary science missions under development at JPL, the Mars 2020 rover and the Europa Clipper multiple-flyby mission.

However, Congress and NASA are offering mixed messages about follow-on missions to those two worlds. In the case of Mars, NASA has approved no missions beyond Mars 2020, despite growing alarm from scientists that existing spacecraft there are aging.

NASA requested just $2.9 million for “Future Mars Missions” in its 2018 budget request, an amount Mars advocates say is insufficient to support development of a communications and reconnaissance orbiter for a 2022 launch. A spending bill approved by the House Appropriations Committee July 13, though, would provide $62 million for that program, which could support early development of a 2022 orbiter.

Watkins did not address that debate directly in his talk. His slides did include a notional “Mars Exploration Orbiter” spacecraft after Mars 2020, as well as a lander that could be used to collect samples cached by the Mars 2020 rover to launch into orbit for later return to Earth.

“There is some concern” about the effect that uncertainty has on the lab’s workforce and capabilities, he acknowledged. Any future missions to Mars in the 2020s, he said, should be devoted to carrying out the rest of the sample return work started by Mars 2020. “That’s something we’re in a lot of discussions with NASA and folks in the scientific community about how to make that mission affordable, and what’s the right time to do that.”

“We’re likely to see another orbiter,” he added, to provide that communications relay and high-resolution imaging capability provided by the current Mars Reconnaissance Orbiter, but didn’t specify if he thought it would be ready to fly in 2022.

Similarly, plans for a lander mission to Europa, the icy moon of Jupiter thought to have a subsurface liquid water ocean, are also unclear. NASA’s 2018 budget request included no money for work on the lander, which has received some initial development funding.

The House spending bill, though, provides additional funding for the lander, and directs NASA to launch it by 2024. The chairman of the appropriations subcommittee that funds NASA, Rep. John Culberson (R-Texas), is a highly vocal advocate for exploration of Europa to look for evidence of life there.

The Europa lander mission, Watkins said, just completed a mission concept review. A science definition team also released a report earlier this year identifying the science goals of the mission and the instruments that the lander could carry to achieve them.

“I think we’re still looking at whether those [instruments] are accommodatable,” he said. “We’re in discussions about the next steps forward with the agency.”

Watkins said after the talk that those discussions include whether the current lander concept is the right one, and if so how to pursue it. “I think where we are now, studying this concept, is the right thing,” he said. An announcement of opportunity for instruments to fly on the lander, he said, will likely be released later this year, given the long lead times needed to develop those instruments.

Both Mars 2020 and Europa Clipper — NASA’s two largest planetary missions currently under development — remain on track, Watkins said. Mars 2020 is on schedule, while Europa Clipper could launch as soon as 2022, although the mission is not mature enough to have a formal cost and schedule. The status of those missions is the subject of a July 18 hearing by the House space subcommittee.