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 — A key official for Europe’s ExoMars mission believes that the rover’s launch will be pushed back until at least 2028 to accommodate changes after ending cooperation with Russia.

ExoMars was to launch in September on a Proton rocket through a partnership between Roscosmos and the European Space Agency. Roscosmos also provided the landing platform for the ESA-built Rosalind Franklin rover.

However, ESA announced March 17 it was suspending cooperation with Russia on ExoMars in response to Russia’s invasion of Ukraine. That requires ESA to find not just a new launch for the mission but also replacing the landing platform. That meant pushing the launch back to at least 2026, ESA Director General Josef Aschbacher said at the time, adding that “even that is very challenging.”

Speaking at a May 3 meeting of NASA’s Mars Exploration Program Analysis Group (MEPAG), Jorge Vago, ExoMars project scientist at ESA, said he doubted a new lander could be ready by 2026. “It is theoretically possible, but in practice we think it would be very difficult to reconfigure ourselves and produce our own lander for 2026,” he said. “Realistically, we would be looking at a launch in 2028.”

Launching in 2028 could pose technical challenges for ExoMars. One trajectory would get the rover to Mars relatively quickly, but have it arrive just a month before dust storm seasons starts at the preferred landing site. An alternative trajectory would require traveling for more than two years to each Mars, but get the rover there six months before dust storms start.

“We have been trying very hard to convince the engineering team that the dust storm season is not death,” Vago said. “We should concentrate on making the rover more robust and able to weather a dust storm.”

A 2028 launch, he added, would require assistance from NASA. Specifically, he said ESA would need descent engines similar to those produced by Aerojet Rocketdyne for NASA Mars missions like Curiosity and Perseverance, because there are not European models the right size for ExoMars.

A second item is radioisotope heating units, or RHUs, which use the heat produced from the radioactive decay of plutonium to keep the rover warm. Russia had provided RHUs for the rover, and there is no European replacement. Using American RHUs would likely also require that ExoMars launch from the United States, he said.

Aschbacher said in an April 6 interview that ESA was working with NASA on potential cooperation with ExoMars while also looking at replacing Russian components of the mission with European alternatives. That will lead to a decision in July on a path forward for ExoMars, which would likely require additional funding that would be requested at ESA’s next ministerial meeting late this year.

A delay to 2028 would mean ExoMars would be launching at the same time as the two landers for the revised Mars Sample Return (MSR) campaign that NASA and ESA are jointly conducting. ESA’s contributions include a rover that would go on one of the landers to pick up samples cached by Perseverance, placing them into a rocket on the other lander that would place the samples in Mars orbit to be picked up and returned to Earth by an ESA orbiter.

That’s led to some speculation in the Mars exploration community that the Rosalind Franklin rover could be repurposed to support the Mars Sample Return effort. Vago said he expected some kind of “quid pro quo” arrangement between NASA and ESA if NASA assisted ESA on ExoMars. That could mean, he said, to “look at both MSR and ExoMars in sort of a holistic way, if you like, and see if we can find solutions that work for both missions.”

A unique aspect of the Rosalind Franklin rover is a drill that can collect samples from up to two meters below the surface. A similar drill is proposed for Mars Life Explorer, a Mars lander concept endorsed by the recent planetary science decadal survey for launch no earlier than the mid-2030s to look for signs of life in subsurface ice deposits. During MEPAG discussions May 2, some suggested a rover-mounted drill, like that for ExoMars, would be more effective than a drill mounted on a stationary lander.

Vago confirmed that the ExoMars drill can handle ice as well as rock, although he said the mixture of ice and rock could complicate processing of the sample.

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...