The ExoMars Rosalind Franklin rover.
ESA’s ExoMars rover will join an orbiter launched in 2016 on a mission to search for evidence of past life on Mars. Credit: ESA

WASHINGTON — While the European Space Agency has secured funding to continue the ExoMars mission for a 2028 launch, that plan requires cooperation with NASA that has yet to be finalized.

At a Nov. 23 press conference at the end of a two-day ministerial council meeting, ESA Director General Josef Aschbacher said the agency had secured funding from its member states to continue the ExoMars mission, which had been stranded after ESA terminated cooperation with Russia in the aftermath of Russia’s invasion of Ukraine just months before its planned September 2022 launch.

ESA went into the meeting looking for about half of the 700 million euros ($725 million) needed to replace components of the mission Russia was originally to provide, including the landing platform that would deliver ESA’s Rosalind Franklin rover to the surface of Mars.

“There were different options that have been discussed, all the way to putting the Rosalind Franklin rover in a museum,” Aschbacher said. “I am very glad to say that we have found a very positive way forward.” He did not disclose how much funding ESA member states contributed to ExoMars.

The mission, now slated for launch in 2028, will primarily replace the Russian components with European ones, with several exceptions. “We have expectations that the U.S. will also contribute to this, with a launcher, a braking engine and the RHUs, the radioisotope heating units,” he said. “But the majority of the future ExoMars mission is European.”

Those NASA contributions are in line with past comments by project officials. In May, Jorge Vago, ExoMars project scientist at ESA, said the agency would likely need thrusters for the new landing system like those Aerojet Rocketdyne produced for NASA Mars landers because there are no similar thrusters available from European sources.

Europe also lacks the plutonium-238 used for RHUs, devices about the size of a C-cell battery that provide heating through radioactive decay. NASA’s solar-powered Spirit and Opportunity Mars rovers, for example, each used eight RHUs to keep the spacecraft warm without using electrical power. Supplying the RHUs would, in turn, require launch on a U.S. vehicle because the RHUs cannot be exported.

An industry source, speaking on background, said the launch will be the most expensive contribution, with the overall NASA contribution likely on the order of a couple hundred million dollars. NASA is expected, in turn, to seek opportunities for U.S. scientists to participate on ExoMars in exchange for that contribution.

Both ESA and NASA officials have hinted for months about a role for the NASA along those lines to support the ExoMars mission but have been reticent to go into details. Aschbacher and NASA Administrator Bill Nelson met in June, and Aschbacher said at a briefing that he received a “very strong” letter of support regarding ExoMars from Nelson, but no firm commitment.

Aschbacher said at the briefing that those planned NASA contributions were pending an agreement yet to be finalized between the agencies. “Their contribution still needs to be confirmed because they waited for our decision today,” he said.

NASA has not publicly commented on its plans for ExoMars since the ministerial meeting, and an agency spokesperson did not respond to questions Nov. 23 about NASA’s plans for the mission.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...