WASHINGTON — NASA may decide to launch its own Mars mission in 2016 if ongoing negotiations over a European-led robotic expedition fall apart, the lead scientist for NASA’s Mars Exploration Program said.

NASA officials see collaboration with as a way to bolster a Mars exploration program struggling to pay for the two-year delay of the Mars Science Laboratory (MSL). Before postponing the launch of MSL to 2011, NASA had been planning to launch another rover to the red planet around 2016.

NASA has been discussing with the European Space Agency (ESA) possible participation in Europe’s estimated $1.6 billion ExoMarslander and rover mission, scheduled for launch in 2016, or possibly identifying less expensive joint Mars missions NASA and ESA could pursue in that timeframe.

Both ESA and NASA are having trouble coming up with the money for ExoMars, said Michael Meyers, NASA’s lead scientist for the Mars program.

NASA is considering contributing a launch vehicle and an orbiter to provide a communications link for the ExoMars rover at an estimated cost to the space agency of about $900 million.

“[ESA is] short $400 million and when we come up with what we can contribute, we come up short about $200 million. So I’m not sure how this is going to go but there’s going to have to be some major compromise to either get ExoMars to go or get a joint program going,” Meyers told the Space Studies Board’s Committee on the Origins and Evolution of Life meeting Feb. Washington.

As a backup, NASA is looking at doing a competitively selected Mars Scout mission in 2016.

Meyers said NASA has about $700 million available for a 2016 mission, more than what NASA would likely have to spend on a cost-capped Mars Scout. NASA’s next Mars Scout, Maven, was cost capped at $475 million, but that was before its launch was postponed two years to 2013.

“Right now with the budget that we have, we can afford something a little bit better than a Scout in 2016. Part of our discussions with the Europeans is that if we’re not going to get together and do what we both want to do, then we can just go and do a Scout mission,” Meyers said.

NASA’s first Mars Scout mission was the Phoenix lander that spent five months studying the planet’s arctic plains and scooping up soil samples before shutting down in November due to a lack of sunlight to power the spacecraft. The atmosphere-probing Maven orbiter would be NASA’s second Mars Scout.

ESA is in the process of scaling back ExoMars, , to fit within budget constraints expected to be imposed by ESA governments when they meet later this year. ESA governments refused in November to approve spending $1.6 billion on ExoMars, and directed ESA to seek international cooperation from , the and other nations. One option discussed is asking to provide a Proton rocket free of charge to launch the ExoMarslander and the NASA orbiter.

Meyers said a launch contribution from would make the mission far more affordable by saving ESA or NASA from having to pay $150 million or more for a launch vehicle.

But questions remain over ‘s willingness to contribute a Proton and whether the workhorse rocket could handle the combined mass of the orbiter, lander and rover.

“They want to go into orbit before landing their lander, which adds a lot of mass, so it would need a large launch vehicle,” Meyers said.